Review Article The Biosynthesis of the Molybdenum Cofactor...

Review ArticleThe Biosynthesis of the Molybdenum Cofactor inEscherichia coli and Its Connection to FeS ClusterAssembly and the Thiolation of tRNA

Silke Leimkuumlhler

Department of Molecular Enzymology Institute of Biochemistry and Biology University of Potsdam Karl-Liebknecht-Straszlige 24-2514476 Potsdam Germany

Correspondence should be addressed to Silke Leimkuhler sleimuni-potsdamde

Received 16 January 2014 Accepted 28 March 2014 Published 29 April 2014

Academic Editor Paul Rosch

Copyright copy 2014 Silke Leimkuhler This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The thiolation of biomolecules is a complex process that involves the activation of sulfur The L-cysteine desulfurase IscS is themain sulfur mobilizing protein in Escherichia coli that provides the sulfur from L-cysteine to several important biomolecules in thecell such as iron sulfur (FeS) clusters molybdopterin (MPT) thiamine and thionucleosides of tRNA Various proteins mediate thetransfer of sulfur from IscS to various biomolecules using different interaction partners A direct connection between the sulfur-containing molecules FeS clusters thiolated tRNA and the molybdenum cofactor (Moco) has been identified The first step ofMoco biosynthesis involves the conversion of 51015840GTP to cyclic pyranopterin monophosphate (cPMP) a reaction catalyzed by a FeScluster containing protein Formed cPMP is further converted toMPT by insertion of two sulfur atomsThe sulfur for this reactionis provided by the L-cysteine desulfurase IscS in addition to the involvement of the TusA protein TusA is also involved in the sulfurtransfer for the thiolation of tRNA This review will describe the biosynthesis of Moco in E coli in detail and dissects the sulfurtransfer pathways for Moco and tRNA and their connection to FeS cluster biosynthesis

1 An Introduction to the Importance ofMolybdenum and Molybdoenzymes inBacteria

Molybdenum is the only second row transition metal essen-tial for biological systems which is biologically available asmolybdate ion [1] Molybdenum has a chemical versatilitythat is useful to biological systems it is redox-active underphysiological conditions (ranging between the oxidationstates VI and IV) since theV oxidation state is also accessiblethe metal can act as transducer between obligatory two-electron and one-electron oxidation-reduction systems andit can exist over a wide range of redox potentials [2 3]The metal forms the active site of molybdoenzymes whichexecute key transformations in the metabolism of nitrogensulfur and carbon compounds [3] The catalyzed reactionsare in most cases oxo-transfer reactions for example thehydroxylation of carbon centers and the physiological role are

fundamental since the reactions include the catalysis of keysteps in carbon nitrogen and sulfur metabolism

There are two distinct types of molybdoenzymes molyb-denum nitrogenase has a unique molybdenum-iron-sulfurcluster the [Fe

4S3]-(bridging-S)

3-[MoFe

3S3] center called

FeMoco [4] Nitrogenase catalyzes the reduction of atmo-spheric dinitrogen to ammonia All other molybdoenzymescontain the molybdenum cofactor (Moco) In Moco themolybdenum atom is coordinated to a dithiolene group onthe 6-alkyl side chain of a pterin calledmolybdopterin (MPT)[3 5] The chemical nature of Moco has been determinedby Rajagopalan and coworkers in 1982 [5] They postulateda structure of the cofactor consisting of a pterin deriva-tive with the pterin ring substituted at position 6 with aphosphorylated dihydroxybutyl side chain containing a cis-dithiolene bond (Figure 1)The sulfur atoms of the dithiolenegroup were proposed to coordinate the molybdenum atomwith a stoichiometry of one MPT per Mo Moco is present

Hindawi Publishing CorporationAdvances in BiologyVolume 2014 Article ID 808569 21 pageshttpdxdoiorg1011552014808569

2 Advances in Biology

OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN

Ominus

S

O O O

OH

OHOH

P

Ominus

O OP

H HH H

O

Cytosine

O

H2N

S

S

Mo

O

ON

NN

H

H

HNCys

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

Ominus

S

X

S

O O O

O

OOOOOO

OS

OHOH

P

P P

Ominus

O OP

H HH H

O

Guanine

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

OminusOminusOHOH

HHH H

O

Guanine

Molybdenum cofactor (Moco)Mo-MPT

Xanthine oxidase familySulfurated MCD

Aldehyde oxidoreductase(PaoABC)

Xanthine dehydrogenase(XdhABC XdhD)

Sulfite oxidase familydi-oxo Moco

Sulfite oxidase (YedY)bis-MGD

TMAO reductase A (TorA)TMAO reductase Z (TorZ)

DMSO reductase (DmsABC)Nitrate reductase A (NarGHI)Nitrate reductase Z (NarZYV)

Peripl Nitrate reductase (NapA)Biotin sulfoxide reductase (BisC)

Formate dehydrogenase N (FdnGHI)Formate dehydrogenase O (FdoGHI)

Formate dehydrogenase H (FdhF)

DMSO reductase family

Figure 1 The different structures of Moco in E coli The basic form of Moco is a 5678-tetrahydropyranopterin with a unique dithiolenegroup coordinating the molybdenum atom named Mo-MPT Mo-MPT (shown in the tri-oxo structure [25]) can be further modified andin E coli three different molybdenum-containing enzyme families exist classified according to their coordination at the molybdenum atomthe xanthine oxidase sulfite oxidase and DMSO reductase families In E coli the xanthine oxidase family contains the sulfurated MCDcofactor The sulfite oxidase family is characterized by a di-oxo Moco with an additional protein ligand which usually is a cysteine TheDMSO reductase family contains two MGDs ligated to one molybdenum atom with additional ligands being an OS and a sixth ligand Xwhich can be a serine a cysteine a selenocysteine an aspartate or a hydroxide andor water molecule The characterized molybdoenzymesin E coli are shown in blue for each family

in more than fifty enzymes in bacteria including nitratereductases sulfite dehydrogenase xanthine oxidoreductasealdehyde oxidoreductase DMSO reductase formate dehy-drogenase CO dehydrogenase and various other enzymes[3] In the redox reactions catalyzed by molybdoenzymeselectron transfer is mediated by additional redox centerspresent in the protein or on other protein domains like FeScenters cytochromes or FADFMN cofactors [6] Duringthese redox reactions the molybdenum atom can exist invarious oxidation states and couple oxide or proton transferwith electron transfer [2]

The different enzymes contain different forms of Mocoand were historically categorized into three families based onthe ligands at themolybdenum atomwhich are characteristicfor each family (Figure 1) the xanthine oxidase (XO) familythe sulfite oxidase (SO) family and the dimethyl sulfoxide(DMSO) reductase family [3 7] The XO family is charac-terized by an MPT-MoVIOS(OH) core in the oxidized state

with one MPT equivalent coordinated to the molybdenumatom one oxo-group one sulfido-group and one hydroxo-group [3] (Figure 1) The sulfido-group is cyanide labile [8ndash10] and removal of the sulfido group results in formation ofan inactive desulfo-enzyme with an oxygen ligand replacingthe sulfur at the Mo active site [10] The enzymes of thisfamily are involved in two-electron transfer hydroxylationand oxo-transfer reactions with water as the source of oxygen[7 11] Among themembers of the XO family in E coli are thexanthine dehydrogenase XdhABC the periplasmic aldehydeoxidoreductase PaoABC and the so far uncharacterizedxanthine dehydrogenase homologue XdhD (Figure 1 Table 1)[6 12]

Enzymes of the SO family coordinate a single equivalentof the pterin cofactor with an MPT-MoVIO

2core in its

oxidized state and usually an additional cysteine ligandwhichis provided by the polypeptide [3] Members of this familycatalyze the transfer of an oxygen atom either to or from

Advances in Biology 3

Table 1 Overview on the E colimolybdoenzymes and the involvedchaperones required for maturationcofactor insertion

Mo-enzyme Subunits Chaperone MocoDMSO reductase familyNitrate reductase A NarGHI NarJ bis-MGDNitrate reductase Z NarZYV NarW bis-MGDPeripl nitrate reductase NapABCGH NapD bis-MGDTMAO reductase A TorAC TorD bis-MGDTMAO reductase Z TorZY bis-MGDDMSO reductase DmsABC DmsD bis-MGDFormate dehydrogenase N FdnGHI FdhD bis-MGDFormate dehydrogenase O FdoGHI FdhD bis-MGDFormate dehydrogenase H FdhF FdhD bis-MGDBiotin sulfoxide reductase BisC mdash bis-MGDSelenate reductase YnfEFGH DmsD bis-MGD YdhYVWXUT YdeP Xanthine oxidase familyAldehyde oxidoreductase PaoABC PaoD MCDXanthine dehydrogenase XdhABC YqeB MCD XdhD (YgfM) YqeB Sulfite oxidase familySulfite oxidase YedYZ mdash Mo-MPT YcbX mdash YiiM mdash mdash no chaperone identified function unknown or not clear which chaperone is involved inmaturationform of Moco not characterized

the substrate [13] Among the members of this family in Ecoli is the YedY protein (Figure 1 and Table 1) for which thephysiological role is unknown so far [14]

The DMSO reductase family is diverse in both structureand function but all members have two equivalents of thepterin cofactor bound to the metal [3] The molybdenumcoordination sphere is usually completed by a single Mo=Ogroup with a sixth ligand in the MPT

2-MoVIO(X) core

however a sulfido ligand has been recently described toreplace the oxo-group in formate dehydrogenase-H from Ecoli [15] The sixth ligand X can be a serine a cysteinea selenocysteine an aspartate or a hydroxide andor watermolecule [16] The reactions catalyzed by members of thisfamily frequently involve oxygen-atom transfer but dehy-drogenation reactions also occur Members of the DMSOreductase family are not present in eukaryotes and includeamong other enzymes the dissimilatory nitrate reductasesformate dehydrogenases trimethylamine-N-oxide (TMAO)reductases DMSO reductase and biotin sulfoxide reductasesof E coli (Figure 1 and Table 1)

This review will give in the first part an overview onthe recent discoveries in Moco biosynthesis in E coli SinceMPT is a sulfur-containing cofactor the biosynthesis ofMocois linked to the sulfur mobilization in the cell Two sulfursare present in MPT which coordinate the molybdenum

atom This sulfur is mobilized from L-cysteine in the cellby a general pathway which links Moco biosynthesis to thesynthesis of other sulfur-containing biomolecules like FeScluster assembly and the thiolation of tRNAAdditionally FeScluster containing proteins are required for the biosynthesisof the first intermediate in Moco biosynthesis Thus we willdissect the sulfur transfer pathway for the biosynthesis ofMoco and FeS clusters and their connection to the thiolationof tRNA in the second part of the review The biosynthesisof the molybdenum cofactor in eukaryotes has been addi-tionally studied and is also highly conserved Since thereare numerous reviews available in the literature describingMoco biosynthesis in humans and plants [17ndash20] we focusonly on the biosynthesis in bacteria and the newly discoveredconnection to other biosynthetic pathways

2 The Biosynthesis of the MolybdenumCofactor in E coli

Using a combination of biochemical genetic and structuralapproaches Moco biosynthesis has been extensively stud-ied for decades In all bacteria Moco is synthesized by aconserved biosynthetic pathway that can be divided intofour steps according to the stable biosynthetic interme-diates which can be isolated and were intensively studiedin Escherichia coli (Figure 2) [21] the synthesis of cyclicpyranopterin monophosphate (cPMP) [22] conversion ofcPMP into MPT by introduction of two sulfur atoms [23]and insertion of molybdate to form Moco [24] In bacteriaMoco is further modified by the attachment of GMP or CMPto the phosphate group of MPT forming the dinucleotidevariants of Moco MPT-guanine dinucleotide (MGD) [25ndash27] andMPT-cytosine dinucleotide (MCD) [28] AfterMocobiosynthesis the different forms of Moco are inserted intothe specific target enzymes by the help of molecular Moco-binding chaperones

In E coli five gene loci were identified which are directlyinvolved in the biosynthesis of Moco moa mob moc moeand mog comprising 11 genes in total [21 29] (Figure 3)The moa locus contains the genes moaABCDE whose geneproducts are involved in cPMP formation from 51015840GTP and inthe formation ofMPT [30]Themob locus contains the genesmobAB whose gene products are involved in the synthesisof bis-Mo-MPT and bis-MGD from Mo-MPT [31] The moclocus contains the gene mocA and the MocA protein isinvolved in MCD synthesis from Mo-MPT [28] The moelocus contains themoeA andmoeB genes [32]WhileMoeA isinvolved inMo-MPT formation fromMPT-AMP [33] MoeBis involved in the activation ofMoaDby adenylation [34]Themog locus contains the mogA gene whose gene product isinvolved in the formation of MPT-AMP [33 35] Additionalessential reactions are the transport of molybdate [36] andthe mobilization of sulfur [37] The proteins and biochemicalreactions involved in the four steps of Moco biosynthesis aredescribed in detail below

21 Conversion of 51015840GTP to cPMP The biosynthesis of Mocostarts from 51015840-GTP which results in the formation of cPMP


+Mg-GTP

cPMP

MPT

Mo-MPT MCD

bis-Mo-MPT

bis-MGD Sulfurated MCD

MPT-AMP

MoaA

MoaC

MoaDMoaEMoeB

+SAM

+ATP +L-cysteine IscSTusA(YnjESufS)

MogA

MoeA

+ATP

MobA

MobA

MocA

+Mg-CTP

+L-cysteine IscS

+MoO42minus

Ominus

OO

O

OOOHOH

P

Ominus Ominus

OminusOP

OP

O

N

NN

HN

H2NO

O

OH2N

Ominus

O

O ON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

H2N

SH

SH

O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

N

NH2

N

NN

Ominus

Ominus

S

S

O

O

O

OO

O

O

P

P

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

minusOminusO

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HNH2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

OO

S

S

Mo

Ominus

S

S

O

O

O

O

OO

O

O

O

O

O

P

P P

Ominus

O

OP

Guanine

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

OHOH

O

minusOminusOGuanine

OHOH

O

H2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

O

S

S

SMo

5998400GTP

OH

OH

Ominus

Figure 2The biosynthesis of Moco in E coli Shown is a scheme of the biosynthetic pathway forMoco biosynthesis in E coli and the proteinsinvolved in this pathway Mo-MPT is formed from 51015840GTP with cPMP MPT and MPT-AMP as intermediates Mo-MPT is directly insertedinto enzymes of the sulfite oxidase family For enzymes of the DMSO reductase family Moco is further modified by formation of a bis-Mo-MPT intermediate and further addition of a GMP molecule to each MPT unit forming the bis-MGD cofactor Both reactions are catalyzedby the MobA protein For enzymes of the xanthine oxidase family in E coli Mo-MPT is further modified by the addition of CMP to form theMCD form of the cofactor Additionally a terminal sulfur ligand is added to the molybdenum site generating sulfuratedMCD An additionalligand at the Mo-center usually is a hydroxo-group The names of the proteins involved in the reactions are colored in red and additionalmolecules required for the reactions are shown in blue


moa

mob

moc

moe

mog

moaA

mobB

mocA

moeB

mogA

moaB

mobA

moeA

moaCmoaD moaE

1000 bp

Figure 3 Organization of the genes involved in the biosynthesis ofMoco in E coli In total 11 genes are involved in the biosynthesis ofMoco in E coliThese are organized into 5 different gene loci termedmoamobmocmoe andmog Genes of known function are coloredin white Black dots indicate promotor regionsThe genes are drawnapproximately to scale Additional operons with a role for in Mocobiosynthesis such as the isc operon or themod operon formolybdatetransport are not shown

the first stable intermediate of Moco biosynthesis (Figure 4)[22]The cPMPmolecule is an oxygen-sensitive 6-alkyl pterinwith a cyclic phosphate group at the C21015840 and C41015840 atoms[38 39] In E coli the moaA and moaC gene products areresponsible for the complicated chemical reactions requiredto generate cPMP [32 40ndash42] An in vitro system for cPMPsynthesis containing the MoaA and MoaC proteins purifiedfrom Staphylococcus aureus showed that 51015840-GTP is the specificinitial substrate for cPMP biosynthesis [43] In this reactionthe C8 of GTP is inserted between the C21015840 and C31015840 carbonsof the GTP ribose MoaA belongs to the superfamily of S-adenosyl methionine- (SAM-) dependent radical enzymes[44]Members of this family catalyze the formation of proteinandor substrate radicals by reductive cleavage of SAM by[4Fe4S] cluster [45] MoaA is a protein containing twooxygen-sensitive FeS clusters each of which is coordinatedby only three cysteine residues The N-terminal [4Fe4S]cluster present in all radical SAM proteins binds SAM andcarries out the reductive cleavage of SAM to generate the51015840-deoxyadenosyl radical which subsequently initiates thetransformation of 51015840-GTP bound through the C-terminal[4Fe4S] cluster [44 46 47] Experiments with GTP isotopesshowed that the ribose C31015840 hydrogen atom is abstracted bythe 51015840-deoxyadenosyl radical ofMoaA [48] Further reactionsinvolve the attack of the C8 in the guanine ring by theformed C31015840 radical resulting in the formation of (8S)-310158408-cyclo-78-dihydroguanosine 51015840triphosphate (310158408-cH

2GTP)

intermediate (Figure 4) [40 41] The additional reducingequivalents required for this stepmight be provided by the C-terminal [4Fe4S] cluster inMoaAThe intermediate serves asa substrate for MoaC which converts 310158408-cH

2GTP to cPMP

including pyrophosphate cleavage and formation of the cyclicphosphate group by general acidbase catalysis [40]

22 Conversion of cPMP to MPT The next step involves theconversion of cPMP to MPT in which two sulfur atoms areincorporated in the C11015840 and C21015840 positions of cPMP [23 3849] (Figure 5) This reaction is catalyzed by MPT synthasea protein consisting of two small (sim10 kDa) and two large

subunits (sim21 kDa) encoded by moaD and moaE respec-tively [50 51] It was shown that MPT synthase carries thesulfur in form of a thiocarboxylate at the C-terminal glycineof MoaD [52] The central dimer is formed by two MoaEsubunits containing oneMoaD at each end as revealed by thecrystal structure [53] It was shown that the twoMoaDMoaEdimers act independently Thus for the insertion of twosulfurs into cPMP two MoaD proteins are required at eachend of the MPT synthase tetramer [54] The first sulfur isadded by one MoaD molecule at the C21015840 position of cPMP(Figure 5) a reaction which is coupled to the hydrolysis ofthe cPMP cyclic phosphate [55] During the course of thisreaction a hemisulfurated intermediate is formed in whichthe MoaD C-terminus is covalently linked to the substratevia a thioester linkage which subsequently is hydrolyzed bya water molecule After the transfer of its thiocarboxylatesulfur to cPMP the first MoaD subunit dissociates from theMPT synthase complex [54 55] During the reaction of thefirst sulfur transfer the opening of the cyclic phosphate isproposed to shift the location of the intermediate withinthe protein so that the C11015840 position now becomes moreaccessible to the attack by the second MoaD thiocarboxylate(Figure 4)This results in a second covalent intermediate thatis converted to MPT via the elimination of a water moleculeand hydrolysis of the thioester intermediate During thereaction cPMP and the hemisulfurated intermediate remainbound to one MoaE subunit [56]

The regeneration of sulfur at the C-terminal glycine ofMoaD is catalyzed by MoeB [32 57] and resembles thefirst step of the ubiquitin-dependent protein degradationsystem [58] (Figure 4) It was determined that in E coli L-cysteine serves as the origin of the MPT dithiolene sulfursand that the cysteine sulfur is transferred to the activatedMoaD acyl-adenylate by the action of a persulfide-containingprotein [37] After the reaction MoaD-SH dissociates fromthe complex and reassociates with MoaE to form activeMPT synthase (Figure 5) The binding constants within thedifferent complexes of MoaD were shown to follow theorder (MoaD-SH-MoaE)

2gt (MoaD-MoeB)

2gt (MoaD-

MoaE)2[56 59] This order is mechanistically logical given

that during the course of MPT biosynthesis MoaD-SH firstbinds to MoaE to form the active MPT synthase complexwhere transfer of the MoaD-SH thiocarboxylate to cPMPoccurs yielding MPT and inactive MPT synthase MoaDmust then dissociate from this inactive complex to form anew complex with MoeB a prerequisite for the regenerationof MoaD-SH In addition the (MoaD-MoeB)

2complex is

stabilized by ATP addition and the subsequent formation ofthe acyl-adenylate on MoaD [34] In this form the sulfurtransfer to MoaD occurs generating MoaD-SH In the sulfurtransfer reactions the proteins IscS and TusA are involvedforming a sulfur relay system [60] However under anaerobicconditions TusA can be replaced by YnjE and SufS [61]The exact mechanism of sulfur mobilization and transfer isfurther described below After the formation of the (MoaD-SH-MoaE)

2complex introduction of the dithiolene moiety

in MPT completes the formation of the chemical backbonenecessary for binding and coordination of the molybdenumatom in Moco (Figure 2)


N

N

OHOH

O

O

NOPPP

1998400

29984003998400 4

998400

5998400

876 5432

19

H2N

HN

NH2

O

O

HOOH

O

N

NPPPN8

H

HN

N

NH2

N

NN

OHOH

O

HH

N

O O

6 5432

1

H2N

HN

N

N

H

H

O

O

O

O

19984002998400

3998400

4998400

5998400

87

9Ominus

P

[4Fe4S]+

[4Fe4S]2+

SAM

eminus

+L-Met

MoaAMoaA

MoaC

cPMP

dA∙

8-cH2GTP

5998400GTP

3998400

∙

Figure 4 Synthesis of cPMP from 51015840GTP All carbon atoms of the 51015840GTP are found within cPMP The C8 atom from the guanine ring isinserted between the C21015840 and C31015840 atoms of the ribose This reaction is catalyzed by the MoaA protein an S-adenosylmethionine- (SAM-)dependent enzymeMoaA forms a dimer with two [4Fe4S] clusters bound to eachmonomerThe trimericMoaC protein is suggested to cleavethe pyrophosphate group of the cyclic intermediate cPMP is shown in the tetrahydropyrano form with a keto group at the C11015840 position assuggested from the crystal structure [55]

23 Insertion of Molybdate into MPT In E coli insertion ofthe metal into MPT is accomplished by the moeA and mogAgene products (Figure 2) [24 32] The structure showed thatMogA is a trimer in solution with each monomer folded intoa single compact domain and MogA binds MPT with highaffinity [62]The crystal structures for E coliMoeA showed adimeric structure with an elongated monomer consisting offour distinct domains one ofwhichwas structurally related toMogA [63 64] It was shown that the proteins have differentfunctions in the molybdenum chelation reaction [33 65]MoeA appeared to mediate molybdenum ligation to newlysynthesized MPT in vitro at low concentrations of MoO

4

2minusThis reaction was strongly inhibited by MogA in the absenceof ATP but in the presence of ATP MogA doubled the rateof molybdenum ligation [65] Later the catalytic formationof anMPT-AMP intermediate during the reaction was shownby the crystal structure of the homologous protein Cnx1 fromArabidopsis thaliana with boundMPT-AMP [35 66 67]Theaccumulation of a comparable MPT-AMP intermediate in Ecoli moeAminus extracts was verified later (Figure 2 unpublisheddata) After in vitro incubation of MoeA with Mo-MPTEXAFS studies showed that Mo-MPT is bound in its tri-oxostructure to MoeA [25]

It was shown that under physiological molybdate concen-trations (1ndash10 120583M) MogA is required in E coli to form anMPT-AMP intermediate that facilitates molybdate insertionon the dithiolene sulfurs However this reaction is not

absolutely required under high molybdenum concentrationsin vivo since mogAminus cells were rescued for molybdoenzymeactivities by the addition of highmolybdate concentrations tothe medium [68] This suggested that under high molybdateconcentrations (gt1mM) in the cell MPT-AMP formation byMogA is not required and molybdate can be directly insertedintoMPTwith the aid of theMoeAprotein [69] Additionallyit was shown that bivalent copper and cadmium ions as wellas trivalent arsenite ions could all be inserted nonspecificallyinto MPT without the presence of either MoeA or MogA andthat copper had a higher affinity for the dithiolene groupof MPT than molybdate [69] Thus bivalent metal ions inhigh concentrations might inhibit Moco biosynthesis in Ecoli After its formation theMo-MPT cofactor can be directlyinserted into enzymes from the sulfite oxidase family withoutfurther modification [68] like into the E coli YedY protein(Figure 1) [70]

24 Further Modification of Moco

241 bis-Mo-MPT and bis-MGD Formation for Enzymes ofthe DMSO Reductase Family The proteins of the DMSOreductase family in E coli contain a dinucleotide derivativeof Moco the MPT-guanine dinucleotide (MGD) cofactor[3] Additionally the molybdenum atom is ligated by twodithiolene groups of two MGD moieties forming the bis-MGD cofactor [27] The synthesis of the bis-MGD cofactor


O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N

Hemisulfurated intermediate

C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP

Sulfur transferIscSTusA

C1998400

C2998400

C1998400

C2998400

C1998400

C2998400

Figure 5 The biosynthesis of MPT from cPMP In the MPT synthase mechanism cPMP is bound to the MoaE subunit The initial attackand transfer of the first thiocarboxylated MoaD-SH sulfur atom occurs at the C21015840 position of cPMP coupled to the hydrolysis of the cPMPcyclic phosphate An intermediate is formed in which the MoaD C-terminus is covalently linked to the substrate via a thioester linkage thatis subsequently hydrolyzed by a water molecule to generate a hemisulfurated intermediate at C21015840 Opening of the cyclic phosphate shifts thelocation of the intermediate within the complex to a position where C11015840 becomes more accessible A new MoaD-SH thiocarboxylate attacksthe C11015840 resulting in a second covalent intermediate which is converted to MPT via the elimination of a water molecule and hydrolysis of thethioester intermediate During the reaction cPMP remains bound to the MoaE molecule The MPT synthase tetramer is built of two MoaEand twoMoaD subunits TheMoaD-SH thiocarboxylate is formed on MoeB where MoaD is first activated under ATP consumption to forman activated MoaD acyl-adenylate Further sulfur is transferred from a sulfur relay system by an L-cysteine desulfurase in conjunction witheither TusA or YnjE to MoaD The mechanism was adapted from the one proposed in [55]

occurs in a stepwise reaction which only requires Mo-MPT(which was previously formed by theMogAMoeA reaction)MobA and Mg-GTP [25] In the first reaction the bis-Mo-MPT intermediate is formed on MobA (Figure 2) In thesecond reaction two GMP moieties from GTP are added tothe C41015840 phosphate of each MPT via a pyrophosphate bondleading to release of the 120573- and 120574-phosphates of GTP aspyrophosphate [71] However the molecular mechanism ofbis-Mo-MPT formation as well as its binding mode to MobAis not clear so far The crystal structure of MobA showed thatthe protein is a monomer with an overall 120572120573 architecturein which the N-terminal domain of the molecule adoptsa Rossmann fold and a possible MPT binding site that islocalized to the C-terminal half of the protein [72 73] Sincefor bis-Mo-MPT formation two MPT moieties have to bebound to monomeric MobA this might occur by using theMPT and predicted GTP-binding sites (Figure 6) During

this reaction one molecule of molybdate has to be releasedwhen two Mo-MPT molecules are combined however theunderlying chemistry remains elusive and the release ofmolybdate has not been proven so far It also remains possiblethat MobA binds one Mo-MPT molecule and one MPTmolecule from which the bis-Mo-MPT could be formedAfter the attachment of two GMP molecules to the bis-Mo-MPT intermediate bis-MGD is formed [25] Facilitatedrelease of bis-MGD from MobA in the presence of GTP wasobserved which suggested that GTPmight compete with thesame binding site occupied by the MPT units thus resultingin the release of formed bis-MGDWe propose that twoMPTmoieties bind to both the predicted GTP-binding sites inaddition to the predicted MPT binding site on MobA thusenabling bis-Mo-MPT and bisMGD synthesis by monomericMobA (Figure 5) The favourable release only of the finalproduct may then be induced by a different binding mode of


bis-MGD compared to bis-Mo-MPT to MobA Both bindingmodes can bemodeled onMobA which is shown in Figure 6

While the role of MobA in MGD formation of Moco wasalready discovered in 1991 [74] the role of MobB the secondprotein encoded by the mob locus [31] remains uncertain[75] Based on its crystal structure it was postulated thatMobB could be an adapter protein acting in concert withMobA to achieve the efficient biosynthesis and utilizationof MGD [75] Another possible role might be that MobBprotects formed bis-MGD or prevents its release fromMobAuntil an acceptor protein is present A docking model ofMobA and MobB suggested that GTP is bound to a sharedbinding site at the interface between both proteins [75 76]However conditions under which MobB is essential for bis-MGD synthesis were not reported so far However in somebacteria like Rhodobacter capsulatus MobB is not presentand thus is not essential for bis-MGD formation [77]After bis-MGD biosynthesis the cofactor is released fromMobA and either is bound to Moco-binding chaperones oris inserted into the target molybdoenzymes of the DMSOreductase family [71 78]

242Molecular Chaperones for bis-MGD Insertion into TargetEnzymes The last step of Moco modification including theformation of bis-MGD prepares the cofactor for insertioninto the specific apo-enzymes Until now it is not completelyunderstood how Moco is inserted into the folded proteinThe crystal structures of several molybdoenzymes revealedthat Moco is deeply buried inside the proteins at the end ofa funnel-shaped passage giving access only to the substrate[79] The insertion step is catalyzed by Moco-binding molec-ular chaperones which bind the respective Moco variantand insert it into the target molybdoenzyme [78] With afew exceptions most of the molybdoenzymes of the DMSOreductase family in E coli have a specific chaperone forMoco insertion (Table 1) [6] NarJ is the chaperone fornitrate reductase A NarGHI [80] NarW is the chaperone fornitrate reductase Z NarZYV [81] DmsD is the chaperone forDmsABC [82] and YnfEF [83] and FdhD is the chaperonefor FdhF [84] One well-studied example is the TorDTorAsystem for TMAO reductase in E coli TorD was shown tobe the specific chaperone for TorA [85] and plays a directrole in the insertion of Moco into apoTorA [86] Duringthis reaction TorD interacts with both MobA and apoTorAand further stabilizes apoTorA for Moco insertion to avoida proteolytic attack of the latter This is consistent with itsrole as ldquofacilitatorrdquo of the bis-MGD insertion and maturationof the apo-enzyme [6 78 87] For the chaperone TorD itwas described that it is able to bind to the signal peptideof apo-TMAO reductase until the bis-MGD is inserted andTMAO reductase is correctly folded [87] Pre-TorA is thentranslocated to the periplasm where the active TorA enzymeis finally generated after cleavage of the signal peptide [6]

Recently it was shown that these chaperones not onlyfacilitate the insertion of bis-MGD into the target enzymebut also directly bind bis-MGD [88] This was shown by theFdsC-FdsA system for maturation of R capsulatus formate

dehydrogenase (FDH) R capsulatus FDH consists of (120572120573120574)2

heterotrimer in which the large 120572-subunit FdsA (105 kDa)harbors the bis-MGD cofactor and a set of four [Fe

4S4]

clusters and one [Fe2S2] cluster (Figure 7) FdsA is linked

to the 120573-subunit FdsB (52 kDa) that binds one additional[Fe4S4] cluster and the FMN cofactor [89] The 120574-subunit

FdsG (15 kDa) binds [Fe2S2] cluster The terminal electron

acceptor was shown to be NAD+ For R capsulatus FDHso far two proteins named FdsC and FdsD were identifiedto be essential for the production of an active FDH butare not subunits of the mature enzyme [89] While FdsDhas only counterparts in some oxygen-tolerant FDHs FdsCshares high amino acid sequence homologies to E coli FdhDthe chaperone for the membrane-bound FDH (FdhF) [84]FdsC was directly copurified with bound bis-MGD [88] Thedefinitive proof that bis-MGD was bound to FsdC and notonly MGD was given by the reconstitution of E coli TMAOreductase activity in a system solely consisting of FdsC andapo-TMAO reductase It also was concluded that in additionto bis-MGD binding FdsC might have a similar role in thematuration of FDH like TorD for TMAO reductase ForTorD it was shown that it interacts with MobA and TorA[78 87] For FdsC an interaction with MobA FdsD andFdsA was shown Thus FdsC might also act as a platformconnecting bis-MGD biosynthesis and its insertion into thetarget protein (Figure 7) FdsC binds directly bis-MGD andthereforemight protect the bis-MGDcofactor fromoxidationbefore its insertion into FdsA Alternatively it might be thefactor that determines the specificity for bis-MGD insertioninto FDHTheFdsDprotein seems to be additionally essentialin this reaction Since FdsD was only identified in organismswhich contain an oxygen-tolerant FDH its role might alsoserve to protect the bis-MGD cofactor specifically in thepresence of oxygen

Additionally it was reported that the bis-MGD cofactorcan be further modified by sulfuration [15 16 90 91] Rein-terpretation of the original crystal data of FdhF suggestedthat at the molybdenum site the apical ligand is rathera sulfur ligand instead of an oxygen ligand [15] In theoxidized state the enzyme contains the four pterin sulfurligands at the Mo site a selenocysteine ligand and a minusSHligand The chaperone involved in sulfuration of the Mocofor FdhF was shown to be the FdhD protein [84] Forthe E coli FdhD protein it was reported that it acts as asulfurtransferase between the L-cysteine desulfurase IscS andFdhF a mechanism which is essential to yield active FdhF[84] Conclusively the additional role of bis-MGD bindingchaperones might be the further modification of Moco bysulfuration In addition to FDHs theDMSO reductase familyincludes othermembers for which an additional sulfur ligandof the molybdenum atom has been reported at the catalyticsite The X-ray crystal structure of the periplasmic nitratereductase (Nap) of Cupriavidus necator showed the presenceof a terminal sulfur ligand at the molybdenum coordinationsphere [90] Similar data were obtained for the homologousNapA protein from Desulfovibrio desulfuricans ATCC 27774for which the crystal structure showed a unique coordinationsphere of six sulfur ligands bound to the molybdenumatom [91] These observations might suggest that sulfuration


OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD

Figure 6 Model of the formation of bis-Mo-MPT and bis-MGD by MobA It is proposed that two Mo-MPT moieties bind to the proposedMPTandGTP-binding sites on theMobAmonomer thus enabling first bis-Mo-MPTand then bisMGDsynthesis by the addition of twoGMPmolecules to bis-Mo-MPT bis-Mo-MPT and bis-MGD are believed to have different binding modes on MobA resulting in the favourablerelease of bis-MGD as final product The structures of MobA were modeled using the coordinates from the Protein Data Bank (1FRW) andthe figure was adapted from the one shown in [25]

N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+

Figure 7 Model for the role of FdsC in bis-MGD insertion into R capsulatus FDH Shown is a scheme for bis-MGD biosynthesis from twoMo-MPT molecules via a bis-Mo-MPT intermediate MobA binds Mo-MPT and catalyzes first the synthesis of bis-Mo-MPT and then thesynthesis of bis-MGD by ligation of two GMP molecules to each MPT moiety in bis-Mo-MPT Further bis-MGD is transferred fromMobAto FdsC FdsC FdsD and MobA were shown to form a complex and are believed to protect the bis-MGD cofactor from oxidation before itsinsertion into the FdsA subunit of R capsulatus FDH Additionally FdsC is believed to contribute to the specificity for bis-MGD insertioninto FDHThe role of FdsD in the reaction is not completely resolved so far


of bis-MGD is more common of this group of enzymesthan previously expected In total we believe that bis-MGDbinding to chaperones for enzymes of the DMSO reductasefamily might be a common feature which might serve asa platform for further modification of Moco or the specificinteraction with target enzymes for bis-MGD insertion

243 MCD Formation and FurtherModification byMCD Sul-furation for Enzymes of the Xanthine Oxidase Family Morerecently three enzymes were identified in E coli belonging tothe xanthine oxidase family (XdhABC XdhD and PaoABC)which bind theMCD form of the cofactor (Figure 1) [92ndash94]MCD formation is catalyzed by a protein which was namedMocA for molybdopterin cytosine dinucleotide synthesis(Figures 2 and 3) [28] MocA was identified by amino acidsequence comparison toMobA since they exhibit 22 aminoacid sequence identity [28 95] The catalytic reaction ofMocA is similar to the reaction of MobA in that it acts as aCTPmolybdopterin cytidylyltransferase and covalently linksMPT and CMP with the concomitant release of the 120573- and120574-phosphates of CTP as pyrophosphate [28] However bis-MCD is not the end product of the reaction instead onlyone MCD moiety is ligated to the molybdenum atom in thiscofactor variantTherefore the end product ofMocAmust bea monopterin MCD cofactor Instead the MCD cofactor forenzymes of the xanthine oxidase family is furthermodified inE coli and contains an equatorial sulfido ligand at its activesite [12] Thus MCD sulfuration might prevent bis-MCDformation

Comparison of the two MPT nucleotidyl transferasesshowed that MobA is highly specific for binding of thepurine nucleotide GTP while MocA is specific for bindingof the pyrimidine nucleotide CTP [28] The most significantsequence differences between the two proteins were observedin two conserved motifs at their N-terminal domain Thecrystal structure of MobA with bound GTP showed thatthe guanine moiety is mainly bound by the 12LAGG15and 78GPLAG82 amino acid sequence segments [72 96]In MocA these sequences are altered to 12TAAG15 and78GLLTS82 [95] Site directed mutagenesis studies showedthat the introduction of only 5 amino acid exchanges inthe two N-terminal regions of either MobA or MocA wassufficient to cause loss of specificity for the pyrimidine orpurine nucleotides so that both proteins were able to bindeither CTP or GTP to almost the same extent In addition theC-terminal domains of MocA andMobA have been found toplay an important role in determining the specificity of theirinteraction with the target molybdoenzymes [95]

After MCD formation the cofactor is handed over toMCD binding chaperones which are PaoD or YqeB in Ecoli (Table 1) PaoD is the specific Moco-binding chaperonefor the periplasmic aldehyde oxidoreductase PaoABC in Ecoli [6] PaoD belongs to the XdhC family of Moco-bindingchaperones [12] The best characterized chaperone from thisfamily is the R capsulatus XdhC protein which is essentialfor the maturation of R capsulatus xanthine dehydrogenase(XDH) [12] Investigation of R capsulatus XdhC showed thatit binds the Moco produced by MoeAMogA and protects

it from oxidation until the terminal molybdenum sulfurligand is inserted [97 98] XdhC also interacts with theR capsulatus L-cysteine desulfurase NifS4 the protein thatactually replaces the cofactor equatorial oxygen ligand witha sulfido ligand [99] The sulfur for this reaction originatesfrom L-cysteine andNifS4 persulfide group is formed duringthe course of the reaction After the sulfuration reaction it isbelieved that XdhC with its bound sulfurated Moco dissoci-ates from NifS4 and forms a new interaction with the XdhBsubunits of the R capsulatus (120572120573)

2XDH heterotetramer [98

100] Thus it appears from the R capsulatus studies thatXdhC-like proteins perform a number of functions includingstabilization of the newly formed Moco and interaction withan L-cysteine desulfurase to ensure that Moco sulfurationoccurs [99] as well as interaction with their specific targetproteins for insertion of the sulfurated Moco [12] BecauseMoco is deeply buried in the protein it is also believed thatthe XdhC proteins may act as chaperones to facilitate theproper folding of the target proteins after Moco insertion[101]Thismodel implies thatmolybdoenzymes requiring thesulfurated form of Moco exist in a Moco competent ldquoopenrdquoapo-molybdoenzyme conformation until the insertion ofsulfurated Moco After insertion the protein adapts the finalactive ldquoclosedrdquo conformation that can no longer accept Moco[101]

Since PaoD belongs to the XdhC family it is expected toplay a role similar to that of XdhC with the only differencebeing that PaoD binds theMCD cofactor rather than anMPTcofactor (Figure 8) [102] The specific L-cysteine desulfuraseinvolved in the sulfuration of PaoD-bound MCD has notbeen identified in E coli to date but it is expected that IscSperforms this role in E coliThe only other XdhC-like proteinthat is present in E coli is the YqeB protein (Table 1) YqeB isexpected to play a similar and shared role for both XdhABCand XdhD since it is located in the vicinity of both generegions in the E coli genome [12] YqeB is a little larger insize than other members of the XdhC family and it containsan NAD(P) binding Rossman fold So far no further data areavailable for YqeB

3 The Distribution of Sulfur for Sulfur-Containing Biomolecules in Bacteria

L-Cysteine is the source for the biosynthesis of Moco anda variety of other biomolecules such as thiamin iron-sulfur(FeS) clusters and thionucleosides in transfer RNA (tRNA)(Figure 8) [103] In E coli the L-cysteine sulfur for thesebiomolecules is initially mobilized by the house-keeping L-cysteine desulfurase IscS [104] The enzyme is a pyridoxal51015840-phosphate-containing homodimer that decomposes L-cysteine to L-alanine and sulfane sulfur via the formationof an enzyme-bound persulfide intermediate [104ndash106] Thepersulfide sulfur from the L-cysteine desulfurase is furtherincorporated either directly or via sulfur relay systems intothe biosynthetic pathways of several sulfur-containing bio-factors thus providing an elegant mechanism for makingsulfur atoms available without releasing them in solution[107 108] IscS is encoded by a gene that is part of a larger


L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation

FeS cluster biosynthesis

TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U

Uthiamine biosynthesis

Cms2i6A

IscS-SSminus

s2

s4

s2

Figure 8 Sulfur transfer to sulfur-containing biomolecules involving the IscS-bound persulfide A protein-bound persulfide group is formedon the L-cysteine desulfurase IscS which is further transferred to proteins like IscU TusA or ThiI CyaY and IscX were also shown to bindto IscS IscU is the primary scaffold for the assembly of FeS clustersThe IscS sulfur can also be further transferred for the thiolation of tRNAIn E coli tRNA modification can be divided into an FeS cluster independent pathway and into a pathway which requires FeS clusters Thesynthesis of s2C by TtcA and ms2i6A by MiaB require sulfur from the FeS clusters initially formed on IscU ThiI can transfer sulfur either forthe formation of thiamine or for the formation of s4U in tRNA TusA can transfer sulfur for a sulfur relay system involving TusBCD TusEandMnmA for the formation of s2U in tRNA or additionally TusA is involved in sulfur transfer forMoco biosynthesis Persulfide-containingproteins are highlighted in red and names of the final sulfur-containing molecules are colored in blue

operon iscRSUA-hscBA-fdx-iscX in which the other geneproducts are involved in the biosynthesis of FeS clustersin E coli (Figure 9) [104] For FeS cluster biosynthesis IscSinteracts with IscU which serves as a scaffold protein forFeS cluster assembly [109 110] However IscU is not theonly interaction partner of IscS since IscS was shown tointeract with a number of other proteins for delivery of sulfurto other sulfur-containing molecules such as CyaY IscXTusA andThiI (Figure 8) [107 110]While CyaY and IscX arealso involved in FeS cluster biosynthesis [110ndash112] ThiI andTusA are involved in tRNA thiolation (ThiI and TusA) [113114] thiamine biosynthesis (ThiI) [115] or Moco biosynthesis(TusA) [60] Thus the persulfide sulfur from IscS can betransferred in a relay flow to the conserved cysteine residuesof acceptor proteins [116] This chapter will describe how thesulfur transfer pathways for FeS clusters tRNA andMoco areconnected and which factors determine the direction of thesulfur transfer mechanism to the various biomolecules

31 The Biosynthesis of FeS Clusters FeS clusters are amongthe earliest catalysts in the evolution of biomolecules andserve as electron carriers in redox reactions regulatorysensors stabilizers of protein structure and chemical cat-alysts [103] The most abundant types are [2Fe2S] clustersand [4Fe4S] clusters Although FeS clusters can be formedspontaneously in vitro with inorganic iron and sulfide [117]the in vivo synthesis is a complex process which is highlyregulated in the cell [118]

The isc operon encodes for IscS the scaffold protein IscUferredoxin (Fdx) the scaffold protein IscA the twomolecularchaperones HscA and HscB and IscX a protein of unknown

function (Figure 9) [104] The isc operon is controlled byIscR FeS cluster binding transcriptional repressor [119] Thescaffold protein IscU is the central protein in FeS clusterbiosynthesis and is responsible for the assembly of [2Fe2S]and [4Fe4S] clusters [109] IscS provides the inorganic sulfurfor FeS clusters [120] In the presence of L-cysteine and Fe2+IscS and IscU form a transient macromolecular complex andform sequentially [2Fe2S] clusters and then from two [2Fe2S]a [4Fe4S] cluster on IscU [121] The sulfur is bound on IscSas a persulfide on Cys-328 and is subsequently transferredto the scaffold IscU The crystal structure of the IscU-IscScomplex showed that each IscU molecule interacts with oneIscS molecule in a 1 1 stoichiometry [110] In an intermediatestructure the Cys-328 residue of IscS is used as a ligand of thetransient [2Fe2S] cluster together with the three cysteines onIscU [121] Further ferredoxin was proposed to participate inthe reductive coupling of two [2Fe2S] clusters to form a single[4Fe4S] cluster on IscU [122]The cluster is then subsequentlytransferred to a recipient apoprotein which can be facilitatedby the help of IscA [123] The two chaperones HscA andHscB help in the formation and transfer of the [4Fe4S] cluster[124] CyaY the E coli frataxin homologue has also a rolein FeS cluster biosynthesis and was shown to regulate thebiosynthesis by competing about the binding site of IscSwith other proteins like IscX [110 112 125] Upon bindingto IscS CyaY was shown to inhibit FeS cluster biosynthesisIt has been suggested that CyaY binding may induce aconformational change in the IscS-IscU complex that doesnot significantly affect the IscS L-cysteine desulfurase activitybut abolishes FeS cluster synthesis [126] This might occur bystabilizing a conformation on the flexible loop of IscS whichdisfavors FeS cluster assembly The role of CyaY as an iron


SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA

iscR iscS iscU iscA hscB hscA fdx iscX

IscXCyaY

SSminus SSminusFe2+

Figure 9 General scheme for FeS cluster biosynthesis in E coli Shown is the isc operon containing the genes iscR-iscSUA-hscAB-fdx-iscXIscR is the regulator for expression of the operon by sensing the FeS status of the cell FeS clusters assemble on the scaffold protein IscU whichreceives the sulfur from the L-cysteine desulfurase IscS The iron donor in this reaction is not identified so far CyaY is believed to stabilizea conformation of the IscS-IscU complex The role of IscX is unclear Ferredoxin is proposed to participate in the reductive coupling of two[2Fe2S] clusters to form a single [4Fe4S] cluster on IscU Release of the clusters is catalyzed by the chaperones HscAB The carrier proteinIscA delivers the formed FeS clusters to the final target proteins

donor in this process is not completely resolved so far [127]During stress conditions such as iron starvation and oxidativeor heavy metal stress the SufS protein is rather involved inbiosynthesis of FeS clusters replacing IscS in some functions[128 129]

In total FeS clusters are found to participate in diversebiological processes such as respiration central metabolismDNA or gene regulation FeS clusters can act as catalystsor redox sensors and are predicted to be used by over 150proteins in E coli [118] Among the FeS cluster containingmolybdoenzymes are nitrate reductase DMSO reductase andformate dehydrogenase involved for example in anaerobicrespiration [6]

32 The Thiolation of tRNA TusA and ThiI are two proteinswhich are involved in the posttranscriptional modificationof tRNA by producing thiolated nucleoside species at spe-cific positions in the tRNA (Figure 8) [114 130] Thiolatednucleosides are found in several tRNAs In E coli these ares4U8 s2C32 ms2i(o)6A37 and mnm5s2U34 which with theexception of s4U8 are located within the anticodon loop andare crucial for proper mRNA decoding (Figure 10) [107] Thebase thiolations are mediated by several acceptor proteinswhich are divided into an FeS cluster dependent and anindependent pathway In the iron-sulfur cluster independentpathway direct transfer of sulfur from IscS to the acceptorThiI leads to the s4U8 modification at position 8 in bacterialtRNAs (Figure 10) [113 131] The s4U serves as a near UV-photosensor since it undergoes photocrosslinking with acytidine at position 13 which causes a growth delay sincecross-linked tRNAs are inefficient aminoacylation substratesHowever ThiI has a dual role and also participates inthiamine biosynthesis by providing the sulfur of the thiazolespecies in thiamine pyrophosphate (Figure 12) [115]

In contrast the TusA protein was identified to functionas a sulfur mediator for the synthesis of 2-thiouridine of themodified wobble base 5-methylaminomethyl (mnm)5s2U in

tRNA (Figure 10) [114] It interacts with IscS and stimulates itsL-cysteine desulfurase activity 3-fold [114] TusA transfers thesulfur from Cys19 to Cys78 of TusD in the TusBCD complexin a TusE-dependent manner TusE is likely to accept thesulfur fromTusD to form a persulfide of Cys108 Finally TusEtransfers the sulfur to MnmA which directly incorporatessulfur into the tRNA wobble position MnmA has a P-loopin its active site that recognizes tRNA and activates the C2position of the uracil ring at position 34 by forming anadenylate intermediate [132ndash134] In total little is knownabout the function of the modification of 2-thiouridine Itis proposed that in E coli thio-modified tRNALys confersefficient ribosome binding and 2-thio-modified tRNAGlu isrequired for specific recognition by glutaminyl-tRNA syn-thetase It also assists proper codon-anticodon base pairingat the ribosome A site and prevents frameshifting duringtranslationThus the 2-thio-modification of uridine 34 playsa critical role in the decoding mechanism [135]

The modification of tRNA also seems to affect lambdaphage infection in E coli [136 137] The process of phagedevelopment is dependent on tRNA thiolation It was shownthat a ΔtusA mutant is more resistant to lambda phageinfection because of a reduced tRNA modification efficiencyand as a consequence has a defect in an associated frame-shift reprogramming control In contrast E coli ΔhscAΔhscB or ΔiscU mutants were shown to be hypersensitiveto lambda phage infection [137] Inactivation of the FeSassemblymachinery increases sulfur flux toTusA resulting inan increased tRNA thiolation and as a consequence a ldquophagehypersensitivityrdquo phenotype Thus tRNA modification andFeS cluster biosynthesis seem to be linked by the control ofthe sulfur flux to each pathway which influence each other

33 Sulfur Transfer for Moco Biosynthesis The first stepin Moco biosynthesis the conversion of 51015840GTP to cPMPdirectly depends on the availability of FeS clusters [43] TheMoaA protein belongs to the class of radical SAM enzymes


HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD

Figure 10 Chemical structure of thio-containing tRNA modifications Shown are the secondary structure and the positions of thiolatednucleosides in tRNA Abbreviations s4U 4-thiouridine s2U 2-thiocytidine mnm5s2U 5-methylaminomethyl-2-thiouridine ms2i6A 2-methylthio-N6-isopentenyladenosinems2io6AN6-(4-hydroxyisopentenyl)-2-methylthioadenosine Eachnumber represents the nucleosideposition in the tRNA On the left-hand side the sulfur transfer pathway for the formation of s2U is shown The sulfur transfer involves theinitial sulfur mobilization by IscS sulfur transfer to TusA-C19 and further transfer via TusD in the TusBCD complex TusE to MnmA whichbinds and activates the tRNA by adenylation After formation s2U is further modified to form cmnm5s2U and mnm5s2U

and contains two [4Fe4S] clusters which are essential forits activity (Figure 4) [45] Thus when no FeS clusters arepresent in the cell cPMP is not formed Further for the for-mation ofMPT from cPMP two sulfurmolecules are inserted[53] The primary sulfur for the dithiolene group of the MPTbackbone of Moco was shown to be the IscS protein [37]Further studies suggested that TusA is additionally involvedin sulfur transfer for the synthesis of MPT by a balancedregulation of the availability of IscS to various biomoleculesin E coli (Figure 5) [60] It was shown that deletion of tusAin E coli affected the activity of molybdoenzymes underaerobic and anaerobic conditions Characterization of theΔtusA strain under aerobic conditions showed an overalllow MPT content and an accumulation of cPMP Underanaerobic conditions the activity of nitrate reductase wasonly 50 reduced showing that TusA is not essential forMoco biosynthesis and can be replaced by other proteinsOne sulfur-carrier is the rhodanese-like protein YnjE which

was shown to be preferentially sulfurated by IscS [61] Theexpression of ynjE is increased under anaerobic conditionsand in the absence of TusA thus making it more available forsulfur transfer under these conditions Additionally SufS canreplace IscS in its role in providing the sulfur under certainconditions [60]

However overexpression of IscU reduced the level ofactive molybdoenzymes in E coli (Figure 11) When IscUis present in high amounts it forms a complex with IscSmaking it unavailable for the interaction with TusA thusresulting in a lack of sulfur transfer for the conversion ofcPMP to MPT A similar situation was obtained when TusAwas overexpressed in E coli (Figure 11) Here the levelsof FeS clusters are decreased which further result in aninactive MoaA protein and thus in a decreased activity ofmolybdoenzymes

Conclusively the pleiotropic effects of a tusA deletionmight be caused by changes in the FeS cluster concentration


IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS

FeS MolybdoenzymesreduceddecreasedIscU

TusA

TusA

TusA

No sulfur for MPT

No FeS cluster for MoaA

MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA

Figure 11 Model for the effect of elevated concentrations of TusA or IscU on Moco biosynthesis IscS interacts with IscU TusA and ThiIfor sulfur transfer to FeS clusters tRNA Moco biosynthesis and thiaminetRNA respectively FeS clusters are inserted into target proteinsAmong these proteins is MoaA involved in Moco biosynthesis (conversion of 51015840GTP to cPMP) TusA is involved in the sulfur transfer forthe conversion of cPMP to MPT Increased levels of IscU reduce the level of active molybdoenzymes in E coli When IscU is present in highamounts it forms a complex with IscS making it unavailable for the interaction with TusA thus resulting in a lack of sulfur transfer forthe conversion of cPMP to MPT When the amount of TusA is increased the levels of FeS clusters are decreased which further result in aninactive MoaA protein and thus in a decreased activity of molybdoenzymes Detailed descriptions are given in the text

leading to differences in the sulfur transfer to tRNA and forMoco biosynthesis It was proposed that TusA is involvedin regulating the IscS pool and shifting it away from IscUthereby making IscS available for sulfur transfer for thebiosynthesis of MPT Additionally major changes in the generegulation were observed

34 The Complex Network of Sulfur Transfer to VariousBiomolecules It seems that a lot of pathways are regulatedby the availability of FeS clusters in the cell since either theyrequire directly FeS clusters or their synthesis is indirectlyregulated by transcriptional regulators that depend on FeSclusters in the cell [138 139] Under these conditions whenFeS clusters are required the isc operon is induced and IscSthen forms a complex with IscU for FeS cluster biogenesismaking it unavailable for the synthesis of other sulfur-containing biomolecules [138] However the other interac-tion partners of IscS like TusA andThiI also direct the sulfurfor important cellular processes like thiamine biosynthesistRNA thiolation and Moco biosynthesis (Figure 12) [110] Itthus seems likely that within the cell the relative affinitiesof the interaction partners of IscS in addition to theirconcentration will determine which is the preferred partnerprotein that interacts with IscS It was shown that IscU andTusA are not able to bind simultaneously to IscS due to stericclashes of both proteins upon binding [110] Since IscU binds

with higher affinity to IscS than TusA this would support thesynthesis of FeS clusters under sulfur limitation in the cell[125] Since the binding sites of ThiI and TusA also overlapthis would suggest that tRNA modification for s4U and s2Uformation is a competitive process [110]

Conclusively changes in the concentration of the inter-action partners of IscS in the cell globally affect path-ways requiring sulfur Microarray analysis of a ΔtusAstrain showed that the expression of genes regulated byFNR (hypABCDE narGHJI moaABCDE soxS cyoABCDEsdhAB tdcABCDEFG and feoB) was increased [60] Thesame effect was observed after overexpression of FNR in Ecoli under aerobiosis which led to the induction of the iscoperon due to a higher FeS cluster demand in the cell [138] Ahigher level of FeS clusters in the cell stabilizes holoFNR thusstimulating the transcription of FNR regulated genes (likethe genes for NR) [138] Conclusively the absence of TusAchanges the level of IscS which is available for FeS clusterbiosynthesis However a higher level of FeS clusters in thecell reduces the sulfur transfer of IscS to other biosyntheticpathways like Moco thiamine or thiolated tRNA This wasshown by an overexpression of the isc operon which resultedin a decreased activity of molybdoenzymes [60] The sameeffect was obtained after overexpression of IscU alone orthe absence of TusA in the cell which both decreased theamount of active nitrate reductase or TMAO reductaseThus


O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD

YedY(sulfite oxidase homologue)

PaoABCaldehyde oxidoreductase

Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA

Thiamine pyrophsphate

S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)

Molybdenum cofactor (Moco)

S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )

Figure 12Model for the connection ofMoco biosynthesis FeS cluster assembly thiamine biosynthesis and tRNA thiolation in E coli Shownis a general scheme for the sulfur mobilization by IscS the interaction partners of IscS and the pathways for the synthesis of s4U and thiamineinvolving ThiI FeS clusters assembly involving IscU Moco biosynthesis involving TusA and YnjE and s2U formation involving TusA FeSclusters are also required for Moco biosynthesis connecting both pathways The acceptor proteins for Moco are shown in addition to theirlocalization in the cell Detailed descriptions are given in the text


the availability and amount of IscS have an effect on variouspathways in the cell

Since FeS clusters are very important for cellular pro-cesses it is conclusively suggested that one part of IscSin the cell is mostly in complex with IscU for FeS clusterbiosynthesis and the other part might be available for theother interaction partners like TusA orThiI (Figure 12)Thusduring FeS cluster formation a portion of IscS would not beavailable for acceptor proteins like TusA or ThiI When theconcentration of one of the interaction partners is changed(as tested for IscU and TusA) the IscS pool is shifted toone or the other direction with a drastic effect on generegulation Conclusively our studies show that the pleiotropiceffect of a tusA deletion might be caused by changes inthe FeS cluster concentration in the cell leading to majordifferences in gene regulation [138] It is proposed that TusA isinvolved in regulating the IscS pool and shifting it away fromIscU thereby making IscS available for sulfur transfer for thebiosynthesis of MPT thiamine and thiolated tRNA

However TusA might have additional roles in the cellsince Ishii et al [140] showed that the FtsZ-ring formationappeared to be severely impaired in tusA-deficient E coli cellsresulting in formation of a nondivided filamentous cellTheseeffects need to be clarified in future studies

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The author thanks all current and former members of theresearch group in addition to collaboration partners whowere involved in this work over the past years and decadesSpecial thanks go to K V Rajagopalan the founder of thefield of Moco biosynthesis for his support over the years andthe helpful discussions The work was mainly supported bycontinuous grants of the Deutsche Forschungsgemeinschaft

References

[1] M P Coughlan ldquoThe role of molybdenum in human biologyrdquoJournal of Inherited Metabolic Disease vol 6 supplement 1 pp70ndash77 1983

[2] R Hille ldquoMolybdenum and tungsten in biologyrdquo Trends inBiochemical Sciences vol 27 no 7 pp 360ndash367 2002

[3] R Hille ldquoThe mononuclear molybdenum enzymesrdquo ChemicalReviews vol 96 no 7 pp 2757ndash2816 1996

[4] G Schwarz R R Mendel and M W Ribbe ldquoMolybdenumcofactors enzymes and pathwaysrdquo Nature vol 460 no 7257pp 839ndash847 2009

[5] K V Rajagopalan J L Johnson and B E Hainline ldquoThe pterinof the molybdenum cofactorrdquo Federation Proceedings vol 41no 9 pp 2608ndash2612 1982

[6] C Iobbi-Nivol and S Leimkuhler ldquoMolybdenum enzymestheir maturation and molybdenum cofactor biosynthesis inEscherichia colirdquo Biochimica et Biophysica Acta vol 1827 pp1086ndash1101 2013

[7] R Hille T Nishino and F Bittner ldquoMolybdenum enzymes inhigher organismsrdquo Coordination Chemistry Reviews vol 255no 9-10 pp 1179ndash1205 2011

[8] S Gutteridge S J Tanner and R C Bray ldquoComparison of themolybdenum centres of native and desulpho xanthine oxidaseThe nature of the cyanide-labile Sulphur atom and the nature ofthe proton-accepting grouprdquo Biochemical Journal vol 175 no3 pp 887ndash897 1978

[9] M P Coughlan J L Johnson and K V Rajagopalan ldquoMech-anisms of inactivation of molybdoenzymes by cyaniderdquo TheJournal of Biological Chemistry vol 255 no 7 pp 2694ndash26991980

[10] R C Wahl and K V Rajagopalan ldquoEvidence for the inorganicnature of the cyanolyzable Sulfur of molybdenum hydroxy-lasesrdquo The Journal of Biological Chemistry vol 257 no 3 pp1354ndash1359 1982

[11] R Hille and R F Anderson ldquoCoupled electronproton transferin complex flavoproteins solvent kinetic isotope effect studiesof electron transfer in xanthine oxidase and trimethylaminedehydrogenaserdquo The Journal of Biological Chemistry vol 276no 33 pp 31193ndash31201 2001

[12] S Leimkuhler and M Neumann ldquoThe role of system-specificmolecular chaperones in thematuration ofmolybdoenzymes inbacteriardquo Biochemistry Research International vol 2011 ArticleID 850924 13 pages 2011

[13] M S Brody and R Hille ldquoThe kinetic behavior of chicken liversulfite oxidaserdquo Biochemistry vol 38 no 20 pp 6668ndash66771999

[14] S J Brokx R A Rothery G Zhang D P Ng and J HWeiner ldquoCharacterization of an Escherichia coli sulfite oxidasehomologue reveals the role of a conserved active site cysteine inassembly and functionrdquo Biochemistry vol 44 no 30 pp 10339ndash10348 2005

[15] H C A Raaijmakers and M J Romao ldquoFormate-reducedE coli formate dehydrogenase H the reinterpretation of thecrystal structure suggests a new reactionmechanismrdquo Journal ofBiological Inorganic Chemistry vol 11 no 7 pp 849ndash854 2006

[16] S Grimaldi B Schoepp-Cothenet P Ceccaldi B Guigliarelliand A Magalon ldquoThe prokaryotic MoW-bisPGD enzymesfamily a catalytic workhorse in bioenergeticrdquo Biochimica etBiophysica Acta vol 1827 pp 1048ndash1085 2013

[17] F Bittner ldquoMolybdenum metabolism in plants and crosstalk toIronrdquo Frontiers in Plant Science vol 5 article 28 2014

[18] R R Mendel and T Kruse ldquoCell biology of molybdenum inplants and humansrdquo Biochimica et Biophysica ActamdashMolecularCell Research vol 1823 no 9 pp 1568ndash1579 2012


[20] R R Mendel ldquoThe molybdenum cofactorrdquo The Journal ofBiological Chemistry vol 288 pp 13165ndash13172 2013

[21] K V Rajagopalan ldquoBiosynthesis of the molybdenum cofactorrdquoin Escherichia Coli and Salmonella Cellular and Molecular Biol-ogy F C Neidhardt Ed pp 674ndash679 ASM Press WashingtonDC USA 1996

[22] M M Wuebbens and K V Rajagopalan ldquoStructural character-ization of a molybdopterin precursorrdquoThe Journal of BiologicalChemistry vol 268 no 18 pp 13493ndash13498 1993

[23] D M Pitterle J L Johnson and K V Rajagopalan ldquoIn vitrosynthesis of molybdopterin from precursor Z using purifiedconverting factor Role of protein-bound Sulfur in formation of


the dithiolenerdquoThe Journal of Biological Chemistry vol 268 no18 pp 13506ndash13509 1993

[24] M S Joshi J L Johnson and K V Rajagopalan ldquoMolybdenumcofactor biosynthesis inEscherichia colimod andmogmutantsrdquoJournal of Bacteriology vol 178 no 14 pp 4310ndash4312 1996

[25] S Reschke K G Sigfridsson P Kaufmann et al ldquoIdentificationof a Bis-molybdopterin intermediate in molybdenum cofactorbiosynthesis in Escherichia colirdquoThe Journal of Biological Chem-istry vol 288 pp 29736ndash29745 2013

[26] T Palmer A Vasishta P WWhitty and D H Boxer ldquoIsolationof protein FA a product of themob locus required formolybde-num cofactor biosynthesis in Escherichia colirdquo European Journalof Biochemistry vol 222 no 2 pp 687ndash692 1994

[27] J C Hilton and K V Rajagopalan ldquoIdentification of the molyb-denum cofactor of dimethyl sulfoxide reductase from Rho-dobacter sphaeroides f sp denitrificans as bis(molybdopteringuanine dinucleotide)molybdenumrdquo Archives of Biochemistryand Biophysics vol 325 no 1 pp 139ndash143 1996

[28] M Neumann G Mittelstadt F Seduk C Iobbi-Nivol and SLeimkuhler ldquoMocA is a specific cytidylyltransferase involvedin molybdopterin cytosine dinucleotide biosynthesis in Escher-ichia colirdquo The Journal of Biological Chemistry vol 284 no 33pp 21891ndash21898 2009

[29] K T Shanmugam V Stewart R P Gunsalus et al ldquoPro-posed nomenclature for the genes involved in molybdenummetabolism in Escherichia coli and Salmonella typhimuriumrdquoMolecular Microbiology vol 6 no 22 pp 3452ndash3454 1992

[30] S L Rivers E McNairn F Blasco G Giordano and DH Boxer ldquoMolecular genetic analysis of the moa operonof Escherichia coli K-12 required for molybdenum cofactorbiosynthesisrdquo Molecular Microbiology vol 8 no 6 pp 1071ndash1081 1993

[31] C Lobbi-Nivol T Palmer P W Whitty E McNairn and DH Boxer ldquoThe mob locus of Escherichia coli K12 required formolybdenum cofactor biosynthesis is expressed at very lowlevelsrdquoMicrobiology vol 141 no 7 pp 1663ndash1671 1995

[32] M E Johnson and K V Rajagopalan ldquoInvolvement of chlA EM and N loci in Escherichia coli molybdopterin biosynthesisrdquoJournal of Bacteriology vol 169 no 1 pp 117ndash125 1987

[33] J Nichols and K V Rajagopalan ldquoEscherichia coli MoeA andMogA function in metal incorporation step of molybdenumcofactor biosynthesisrdquo The Journal of Biological Chemistry vol277 no 28 pp 24995ndash25000 2002

[34] S Leimkuhler M MWuebbens and K V Rajagopalan ldquoChar-acterization of Escherichia coliMoeB and its involvement in theactivation ofmolybdopterin synthase for the biosynthesis of themolybdenum cofactorrdquoThe Journal of Biological Chemistry vol276 no 37 pp 34695ndash34701 2001

[35] J Kuper A Llamas H-J Hecht R R Mendel and G SchwarzldquoStructure of the molybdopterin-bound Cnx1G domain linksmolybdenum and copper metabolismrdquo Nature vol 430 no7001 pp 803ndash806 2004

[36] J A Maupin-Furlow J K Rosentel J H Lee U DeppenmeierR P Gunsalus and K T Shanmugam ldquoGenetic analysis of themodABCD (molybdate transport) operon of Escherichia colirdquoJournal of Bacteriology vol 177 no 17 pp 4851ndash4856 1995

[37] S Leimkuhler and K V Rajagopalan ldquoA sulfurtransferaseis required in the transfer of cysteine Sulfur in the in vitrosynthesis of molybdopterin from precursor Z in Escherichiacolirdquo The Journal of Biological Chemistry vol 276 no 25 pp22024ndash22031 2001

[38] S Leimkuhler M M Wuebbens and K V Rajagopalan ldquoThehistory of the discovery of the molybdenum cofactor and novelaspects of its biosynthesis in bacteriardquo Coordination ChemistryReviews vol 255 no 9-10 pp 1129ndash1144 2011

[39] J A Santamaria-Araujo B Fischer T Otte et al ldquoThe tetrahy-dropyranopterin structure of the Sulfur- and metal-free molyb-denum cofactor precursorrdquoThe Journal of Biological Chemistryvol 279 no 16 pp 15994ndash15999 2004

[40] B M Hover A Loksztejn A A Ribeiro and K YokoyamaldquoIdentification of a cyclic nucleotide as a cryptic intermediatein molybdenum cofactor biosynthesisrdquo Journal of the AmericanChemical Society vol 135 pp 7019ndash7032 2013

[41] A PMehta SHAbdelwahed andT P Begley ldquoMolybdopterinbiosynthesis trapping an unusual purine ribose adduct in theMoaA-catalyzed reactionrdquo Journal of the American ChemicalSociety vol 135 pp 10883ndash10885 2013

[42] M M Wuebbens M T Liu K V Rajagopalan and HSchindelin ldquoInsight into molybdenum cofactor deficiency pro-vided by the crystal structure of the molybdenum cofactorbiosynthesis proteinMoaCrdquo Structure vol 8 no 7 pp 709ndash7182000

[43] P Hanzelmann and H Schindelin ldquoCrystal structure of the S-adenosylmethionine-dependent enzymeMoaA and its implica-tions for molybdenum cofactor deficiency in humansrdquo Proceed-ings of the National Academy of Sciences of the United States ofAmerica vol 101 no 35 pp 12870ndash12875 2004

[44] P Hanzelmann H L Hernandez C Menzel et al ldquoCharacter-ization of MOCS1A an Oxygen-sensitive Iron-Sulfur proteininvolved in human molybdenum cofactor biosynthesisrdquo TheJournal of Biological Chemistry vol 279 no 33 pp 34721ndash347322004

[45] H J Sofia G Chen B G Hetzler J F Reyes-Spindola and NE Miller ldquoRadical SAM a novel protein superfamily linkingunresolved steps in familiar biosynthetic pathways with radicalmechanisms functional characterization using new analysisand information visualizationmethodsrdquoNucleic Acids Researchvol 29 no 5 pp 1097ndash1106 2001

[46] N S Lees P Hanzelmann H L Hernandez et al ldquoENDORspectroscopy shows that guanine N1 binds to [4Fe-4S] clusterII of the S-adenosylmethionine-dependent enzyme MoaAmechanistic implicationsrdquo Journal of the American ChemicalSociety vol 131 no 26 pp 9184ndash9185 2009

[47] P Hanzelmann and H Schindelin ldquoBinding of 51015840-GTP to theC-terminal FeS cluster of the radical S-adenosylmethionineenzyme MoaA provides insights into its mechanismrdquo Proceed-ings of the National Academy of Sciences of the United States ofAmerica vol 103 no 18 pp 6829ndash6834 2006

[48] A P Mehta J W Hanes S H Abdelwahed D G HilmeyP Hanzelmann and T P Begley ldquoCatalysis of a newribose Carbon-insertion reaction by the molybdenum cofactorbiosynthetic enzyme MoaArdquo Biochemistry vol 52 pp 1134ndash1136 2013

[49] D M Pitterle and K V Rajagopalan ldquoThe biosynthesis ofmolybdopterin in Escherichia coli Purification and charac-terization of the converting factorrdquo The Journal of BiologicalChemistry vol 268 no 18 pp 13499ndash13505 1993

[50] D M Pitterle J L Johnson and K V Rajagopalan ldquoMolyb-dopterin formation by converting factor of E coli chlA1rdquo TheFASEB Journal vol 4 p A1957 1990

[51] D M Pitterle and K V Rajagopalan ldquoTwo proteins encodedat the chlA locus constitute the converting factor of Escherichia


coli chlA1rdquo Journal of Bacteriology vol 171 no 6 pp 3373ndash33781989

[52] G Gutzke B Fischer R R Mendel and G Schwarz ldquoThiocar-boxylation ofmolybdopterin synthase provides evidence for themechanism of dithiolene formation in metal-binding pterinsrdquoThe Journal of Biological Chemistry vol 276 no 39 pp 36268ndash36274 2001

[53] M J Rudolph M M Wuebbens K V Rajagopalan and HSchindelin ldquoCrystal structure of molybdopterin synthase andits evolutionary relationship to ubiquitin activationrdquo NatureStructural Biology vol 8 no 1 pp 42ndash46 2001

[54] M M Wuebbens and K V Rajagopalan ldquoMechanistic andmutational studies of Escherichia coli molybdopterin synthaseclarify the final step ofmolybdopterin biosynthesisrdquoThe Journalof Biological Chemistry vol 278 no 16 pp 14523ndash14532 2003

[55] J N Daniels M M Wuebbens K V Rajagopalan and HSchindelin ldquoCrystal structure of a molybdopterin synthase-precursor Z complex insight into its Sulfur transfer mechanismand its role in molybdenum cofactor deficiencyrdquo Biochemistryvol 47 no 2 pp 615ndash626 2008 Erratum in Biochemistry vol47 no 10 pp 3315 2008

[56] J Schmitz M M Wuebbens K V Rajagopalan and SLeimkuhler ldquoRole of the C-terminal Gly-Gly motif of Escher-ichia coli MoaD a molybdenum cofactor biosynthesis proteinwith a ubiquitin foldrdquo Biochemistry vol 46 no 3 pp 909ndash9162007

[57] K V Rajagopalan ldquoBiosynthesis and processing of the molyb-denum cofactorsrdquo Biochemical Society Transactions vol 25 no3 pp 757ndash761 1997

[58] M W Lake M M Wuebbens K V Rajagopalan and HSchindelin ldquoMechanism of ubiquitin activation revealed by thestructure of a bacterial MoeB-MoaD complexrdquoNature vol 414no 6861 pp 325ndash329 2001

[59] Y Tong M M Wuebbens K V Rajagopalan and M CFitzgerald ldquoThermodynamic analysis of subunit interactions inEscherichia colimolybdopterin synthaserdquo Biochemistry vol 44no 7 pp 2595ndash2601 2005

[60] J U Dahl C Radon M Buhning et al ldquoThe Sulfur carrierprotein TusA has a pleiotropic role in Escherichia coli thatalso affects molybdenum cofactor biosynthesisrdquo The Journal ofBiological Chemistry vol 288 pp 5426ndash5442 2013

[61] J-U Dahl A Urban A Bolte et al ldquoThe identification of anovel protein involved in molybdenum cofactor biosynthesis inEscherichia colirdquo The Journal of Biological Chemistry vol 286no 41 pp 35801ndash35812 2011

[62] M TW LiuMMWuebbens K V Rajagopalan andH Schin-delin ldquoCrystal structure of the gephyrin-related molybdenumcofactor biosynthesis protein MogA from Escherichia colirdquoTheJournal of Biological Chemistry vol 275 no 3 pp 1814ndash18222000

[63] S Xiang J Nichols K V Rajagopalan and H Schindelin ldquoThecrystal structure of Escherichia coli MoeA and its relationshipto the multifunctional protein gephyrinrdquo Structure vol 9 no 4pp 299ndash310 2001

[64] J D SchragWHuang J Sivaraman et al ldquoThe crystal structureof Escherichia coli MoeA a protein from the molybdopterinsynthesis pathwayrdquo Journal of Molecular Biology vol 310 no 2pp 419ndash431 2001

[65] J D Nichols and K V Rajagopalan ldquoIn vitro molybdenumligation to molybdopterin using purified componentsrdquo TheJournal of Biological Chemistry vol 280 no 9 pp 7817ndash78222005

[66] A Llamas R R Mendel and G Schwarz ldquoSynthesis ofadenylated molybdopterin an essential step for molybdenuminsertionrdquo The Journal of Biological Chemistry vol 279 no 53pp 55241ndash55246 2004

[67] A Llamas T Otte G Multhaup R R Mendel and G SchwarzldquoThe mechanism of nucleotide-assisted molybdenum insertionintomolybdopterin a novel route towardmetal cofactor assem-blyrdquo The Journal of Biological Chemistry vol 281 no 27 pp18343ndash18350 2006

[68] S Leimkuhler and K V Rajagopalan ldquoIn vitro incorporation ofnascent molybdenum cofactor into human sulfite oxidaserdquoTheJournal of Biological Chemistry vol 276 no 3 pp 1837ndash18442001

[69] M Neumann and S Leimkuhler ldquoHeavy metal ions inhibitmolybdoenzyme activity by binding to the dithiolene moiety ofmolybdopterin in Escherichia colirdquo The FEBS Journal vol 275no 22 pp 5678ndash5689 2008

[70] L Loschi S J Brokx T L Hills et al ldquoStructural andbiochemical identification of a novel bacterial oxidoreductaserdquoThe Journal of Biological Chemistry vol 279 no 48 pp 50391ndash50400 2004

[71] C A Temple and K V Rajagopalan ldquoMechanism of assemblyof the bis(molybdopterin guanine dinucleotide)molybdenumcofactor in Rhodobacter sphaeroides dimethyl sulfoxide reduc-taserdquo The Journal of Biological Chemistry vol 275 no 51 pp40202ndash40210 2000

[72] MW Lake C A Temple K V Rajagopalan andH SchindelinldquoThe crystal structure of the Escherichia coli MobA proteinprovides insight into molybdopterin guanine dinucleotidebiosynthesisrdquo The Journal of Biological Chemistry vol 275 no51 pp 40211ndash40217 2000

[73] C E M Stevenson F Sargent G Buchanan T Palmer andD M Lawson ldquoCrystal structure of the molybdenum cofactorbiosynthesis proteinMobA from Escherichia coli at near-atomicresolutionrdquo Structure vol 8 no 11 pp 1115ndash1125 2000

[74] J L Johnson L W Indermaur and K V Rajagopalan ldquoMolyb-denum cofactor biosynthesis in Escherichia coli requirementof the chlB gene product for the formation of molybdopteringuanine dinucleotiderdquo The Journal of Biological Chemistry vol266 no 19 pp 12140ndash12145 1991

[75] K McLuskey J A Harrison A W Schuttelkopf D H Boxerand W N Hunter ldquoInsight into the role of Escherichia coliMobB in molybdenum cofactor biosynthesis based on the highresolution crystal structurerdquoTheJournal of Biological Chemistryvol 278 no 26 pp 23706ndash23713 2003

[76] D J Eaves T Palmer and D H Boxer ldquoThe product of themolybdenum cofactor gene mobB of Escherichia coli is a GTP-binding proteinrdquo European Journal of Biochemistry vol 246 no3 pp 690ndash697 1997

[77] S Leimkuhler and W Klipp ldquoThe molybdenum cofactorbiosynthesis protein MobA from Rhodobacter capsulatus isrequired for the activity of molybdenum enzymes containingMGD but not for xanthine dehydrogenase harboring the MPTcofactorrdquo FEMS Microbiology Letters vol 174 no 2 pp 239ndash246 1999

[78] O Genest V Mejean and C Iobbi-Nivol ldquoMultiple roles ofTorD-like chaperones in the biogenesis of molybdoenzymesrdquoFEMS Microbiology Letters vol 297 no 1 pp 1ndash9 2009

[79] C Kisker H Schindelin and D C Rees ldquoMolybdenum-cofactor-containing enzymes structure and mechanismrdquoAnnual Review of Biochemistry vol 66 pp 233ndash267 1997


[80] F Blasco J-P Dos Santos A Magalon et al ldquoNarJ is a specificchaperone required for molybdenum cofactor assembly innitrate reductase A of Escherichia colirdquoMolecular Microbiologyvol 28 no 3 pp 435ndash447 1998

[81] F Blasco J Pommier V AugierM Chippaux andG GiordanoldquoInvolvement of the narJ or narWgene product in the formationof active nitrate reductase in Escherichia colirdquoMolecular Micro-biology vol 6 no 2 pp 221ndash230 1992

[82] N Ray J Oates R J Turner and C Robinson ldquoDmsD isrequired for the biogenesis of DMSO reductase in Escherichiacoli but not for the interaction of the DmsA signal peptide withthe Tat apparatusrdquo FEBS Letters vol 534 no 1-3 pp 156ndash1602003

[83] D Guymer J Maillard and F Sargent ldquoA genetic analysisof in vivo selenate reduction by Salmonella enterica serovarTyphimurium LT2 and Escherichia coli K12rdquo Archives of Micro-biology vol 191 no 6 pp 519ndash528 2009

[84] RThome A Gust R Toci et al ldquoA sulfurtransferase is essentialfor activity of formate dehydrogenases in Escherichia colirdquo TheJournal of Biological Chemistry vol 287 no 7 pp 4671ndash46782012

[85] O Genest M Ilbert V Mejean and C Iobbi-Nivol ldquoTorD anessential chaperone for TorA molybdoenzyme maturation athigh temperaturerdquoThe Journal of Biological Chemistry vol 280no 16 pp 15644ndash15648 2005

[86] OGenest F Seduk LTheraulazVMejean andC Iobbi-NivolldquoChaperone protection of immature molybdoenzyme duringmolybdenum cofactor limitationrdquo FEMS Microbiology Lettersvol 265 no 1 pp 51ndash55 2006

[87] O Genest M Neumann F Seduk et al ldquoDedicated metal-lochaperone connects apoenzyme and molybdenum cofactorbiosynthesis componentsrdquo The Journal of Biological Chemistryvol 283 no 31 pp 21433ndash21440 2008

[88] N Bohmer T Hartmann and S Leimkuhler ldquoThe chaperoneFdsC for Rhodobacter capsulatus formate dehydrogenase bindsthe bis-molybdopterin guanine dinucleotide cofactorrdquo FEBSLetters vol 588 no 4 pp 531ndash537 2014

[89] T Hartmann and S Leimkuhler ldquoThe Oxygen-tolerant andNAD(+) -dependent formate dehydrogenase from Rhodobactercapsulatus is able to catalyze the reduction of CO

2to formaterdquo

The FEBS Journal vol 280 pp 6083ndash6096 2013[90] C Coelho P J Gonzalez J G Moura I Moura J Trincao

and M Joao Romao ldquoThe crystal structure of cupriavidusnecator nitrate reductase in oxidized and partially reducedstatesrdquo Journal ofMolecular Biology vol 408 no 5 pp 932ndash9482011

[91] S Najmudin P J Gonzalez J Trincao et al ldquoPeriplasmicnitrate reductase revisited a Sulfur atom completes the sixthcoordination of the catalyticmolybdenumrdquo Journal of BiologicalInorganic Chemistry vol 13 no 5 pp 737ndash753 2008

[92] H Xi B L Schneider and L Reitzer ldquoPurine catabolism inEscherichia coli and function of xanthine dehydrogenase inpurine salvagerdquo Journal of Bacteriology vol 182 no 19 pp 5332ndash5341 2000

[93] S G Kozmin and R M Schaaper ldquoMolybdenum cofactor-dependent resistance to N-hydroxylated base analogs inEscherichia coli is independent of MobA functionrdquo MutationResearchmdashFundamental and Molecular Mechanisms of Mutage-nesis vol 619 no 1-2 pp 9ndash15 2007

[94] M Neumann G Mittelstadt C Iobbi-Nivol et al ldquoA periplas-mic aldehyde oxidoreductase represents the first molyb-dopterin cytosine dinucleotide cofactor containing molybdo-flavoenzyme from Escherichia colirdquoThe FEBS Journal vol 276no 10 pp 2762ndash2774 2009

[95] M Neumann F Seduk C Iobbi-Nivol and S LeimkuhlerldquoMolybdopterin dinucleotide biosynthesis in Escherichia coliidentification of amino acid residues of molybdopterin din-ucleotide transferases that determine specificity for bindingof guanine or cytosine nucleotidesrdquo The Journal of BiologicalChemistry vol 286 no 2 pp 1400ndash1408 2011

[96] A Guse C E M Stevenson J Kuper et al ldquoBiochemical andstructural analysis of the molybdenum cofactor biosynthesisproteinMobArdquoThe Journal of Biological Chemistry vol 278 no28 pp 25302ndash25307 2003

[97] S Leimkuhler S Angermuller G Schwarz R R Mendel andW Klipp ldquoActivity of the molybdopterin-containing xanthinedehydrogenase of Rhodobacter capsulatus can be restored byhigh molybdenum concentrations in a moeA mutant defectivein molybdenum cofactor biosynthesisrdquo Journal of Bacteriologyvol 181 no 19 pp 5930ndash5939 1999

[98] M NeumannW Stocklein and S Leimkuhler ldquoTransfer of themolybdenum cofactor synthesized by Rhodobacter capsulatusMoeA to XdhC andMobArdquoThe Journal of Biological Chemistryvol 282 no 39 pp 28493ndash28500 2007

[99] M Neumann W Stocklein A Walburger A Magalon andS Leimkuhler ldquoIdentification of a Rhodobacter capsulatus L-cysteine desulfurase that sulfurates the molybdenum cofactorwhen bound to XdhC and before its insertion into xanthinedehydrogenaserdquo Biochemistry vol 46 no 33 pp 9586ndash95952007

[100] M Neumann M Schulte N Junemann W Stocklein andS Leimkuhler ldquoRhodobacter capsulatus XdhC is involved inmolybdenum cofactor binding and insertion into xanthinedehydrogenaserdquoTheJournal of Biological Chemistry vol 281 no23 pp 15701ndash15708 2006

[101] S Leimkuhler and W Klipp ldquoRole of XDHC in molybdenumcofactor insertion into xanthine dehydrogenase of Rhodobactercapsulatusrdquo Journal of Bacteriology vol 181 no 9 pp 2745ndash27511999

[102] A R Otrelo-Cardoso V Schwuchow D Rodrigues et alldquoBiochemical stabilization and crystallization studies on amolecular chaperone (PaoD) involved in the maturation ofmolybdoenzymesrdquo PLoS ONE vol 9 no 1 Article ID e872952014

[103] H Beinert ldquoA tribute to Sulfurrdquo European Journal of Biochem-istry vol 267 no 18 pp 5657ndash5664 2000

[104] L Zheng V L Cash D H Flint and D R Dean ldquoAssemblyof Iron-Sulfur clusters Identification of an iscSUA-hscBA-fdx gene cluster from Azotobacter vinelandiirdquo The Journal ofBiological Chemistry vol 273 no 21 pp 13264ndash13272 1998

[105] L Zheng R HWhite V L Cash and D R Dean ldquoMechanismfor the desulfurization of L-cysteine catalyzed by the NIFs geneproductrdquo Biochemistry vol 33 no 15 pp 4714ndash4720 1994

[106] L Zheng R H White V L Cash R F Jack and D RDean ldquoCysteine desulfurase activity indicates a role for NIFSin metallocluster biosynthesisrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 90 no7 pp 2754ndash2758 1993


[107] R Hidese H Mihara and N Esaki ldquoBacterial cysteine desul-furases versatile key players in biosynthetic pathways of Sulfur-containing biofactorsrdquo Applied Microbiology and Biotechnologyvol 91 no 1 pp 47ndash61 2011

[108] E G Mueller ldquoTrafficking in persulfides delivering Sulfur inbiosynthetic pathwaysrdquo Nature Chemical Biology vol 2 no 4pp 185ndash194 2006

[109] HDUrbina J J Silberg KGHoff and L EVickery ldquoTransferof Sulfur from IscS to IscU during FeS cluster assemblyrdquo TheJournal of Biological Chemistry vol 276 no 48 pp 44521ndash44526 2001

[110] R Shi A Proteau M Villarroya et al ldquoStructural basis forFe-S cluster assembly and tRNA thiolation mediated by IscSprotein-protein interactionsrdquo PLoS Biology vol 8 no 4 ArticleID e1000354 2010

[111] C Iannuzzi S Adinolfi B D Howes et al ldquoThe role of cyay inIron Sulfur cluster assembly on the E coli iscu scaffold proteinrdquoPLoS ONE vol 6 no 7 Article ID e21992 2011

[112] S Adinolfi C Iannuzzi F Prischi et al ldquoBacterial frataxinCyaYis the gatekeeper of Iron-Sulfur cluster formation catalyzed byIscSrdquo Nature Structural amp Molecular Biology vol 16 no 4 pp390ndash396 2009

[113] E G Mueller C J Buck P M Palenchar L E Barnhart and JL Paulson ldquoIdentification of a gene involved in the generationof 4-thiouridine in tRNArdquo Nucleic Acids Research vol 26 no11 pp 2606ndash2610 1998

[114] Y Ikeuchi N Shigi J-I Kato A Nishimura and T SuzukildquoMechanistic insights into Sulfur relay by multiple Sulfurmediators involved in thiouridine biosynthesis at tRNA wobblepositionsrdquoMolecular Cell vol 21 no 1 pp 97ndash108 2006

[115] T P Begley D M Downs S E Ealick et al ldquoThiaminbiosynthesis in prokaryotesrdquo Archives of Microbiology vol 171no 5 pp 293ndash300 1999

[116] D Bordo and P Bork ldquoThe rhodaneseCdc25 phosphatasesuperfamily Sequence-structure-function relationsrdquo EMBOReports vol 3 no 8 pp 741ndash746 2002

[117] R Malkin and J C Rabinowitz ldquoThe reconstitution ofclostridial ferredoxinrdquo Biochemical and Biophysical ResearchCommunications vol 23 no 6 pp 822ndash827 1966

[118] B Roche L Aussel B Ezraty P Mandin B Py and F BarrasldquoIronSulfur proteins biogenesis in prokaryotes formationregulation and diversityrdquo Biochimica et Biophysica Acta vol1827 pp 455ndash469 2013

[119] C J Schwartz J L Giel T Patschkowski et al ldquoIscR an Fe-Scluster-containing transcription factor represses expression ofEscherichia coli genes encoding Fe-S cluster assembly proteinsrdquoProceedings of the National Academy of Sciences of the UnitedStates of America vol 98 no 26 pp 14895ndash14900 2001

[120] C J Schwartz O Djaman J A Imlay and P J Kiley ldquoThecysteine desulfurase IscS has a major role in in vivo Fe-Scluster formation inEscherichia colirdquoProceedings of theNationalAcademy of Sciences of the United States of America vol 97 no16 pp 9009ndash9014 2000

[121] E N Marinoni J S de Oliveira Y Nicolet et al ldquo(IscS-IscU)2

complex structures provide insights into Fe2S2biogenesis and

transferrdquo Angewandte Chemie vol 51 no 22 pp 5439ndash54422012

[122] K Chandramouli M-C Unciuleac S Naik D R Dean H HBoi and M K Johnson ldquoFormation and properties of [4Fe-4S]clusters on the IscU scaffold proteinrdquo Biochemistry vol 46 no23 pp 6804ndash6811 2007

[123] S Ollagnier-De-Choudens T Mattioli Y Takahashi and MFontecave ldquoIron-Sulfur cluster assembly Characterization ofIscA and evidence for a specific and functional complex withferredoxinrdquoThe Journal of Biological Chemistry vol 276 no 25pp 22604ndash22607 2001

[124] J H Kim M Tonelli R O Frederick D C Chow and J LMarkley ldquoSpecialized Hsp70 chaperone (HscA) binds preferen-tially to the disordered form whereas J-protein (HscB) bindspreferentially to the structured form of the Iron-Sulfur clusterscaffold protein (IscU)rdquoThe Journal of Biological Chemistry vol287 pp 31406ndash31413 2012

[125] F Prischi P V Konarev C Iannuzzi et al ldquoStructural basesfor the interaction of frataxin with the central components ofIron-Sulphur cluster assemblyrdquo Nature Communications vol 1article 95 2010

[126] J Bridwell-Rabb C Iannuzzi A Pastore and D P BarondeauldquoEffector role reversal during evolution the case of frataxin inFe-S cluster biosynthesisrdquoBiochemistry vol 51 no 12 pp 2506ndash2514 2012

[127] F Bou-Abdallah S Adinolfi A Pastore T M Laue andN Dennis Chasteen ldquoIron binding and oxidation kinetics infrataxin CyaY of Escherichia colirdquo Journal of Molecular Biologyvol 341 no 2 pp 605ndash615 2004

[128] L Loiseau S Ollagnier-de-Choudens L NachinM Fontecaveand F Barras ldquoBiogenesis of Fe-S cluster by the bacterial sufsystem SufS and SufE form a new type of cysteine desulfuraserdquoThe Journal of Biological Chemistry vol 278 no 40 pp 38352ndash38359 2003

[129] F W Outten O Djaman and G Storz ldquoA suf operon require-ment for Fe-S cluster assembly during Iron starvation inEscherichia colirdquoMolecular Microbiology vol 52 no 3 pp 861ndash872 2004

[130] R Kambampati and C T Lauhon ldquoEvidence for the transfer ofsulfane Sulfur from IscS toThiI during the in vitro biosynthesisof 4-thiouridine in Escherichia coli tRNArdquo The Journal ofBiological Chemistry vol 275 no 15 pp 10727ndash10730 2000

[131] P M Palenchar C J Buck H Cheng T J Larson and E GMueller ldquoEvidence that ThiI an enzyme shared between thi-amin and 4-thiouridine biosynthesismay be a sulfurtransferasethat proceeds through a persulfide intermediaterdquoThe Journal ofBiological Chemistry vol 275 no 12 pp 8283ndash8286 2000

[132] R Kambampati and C T Lauhon ldquoMnma and IscS are requiredfor in vitro 2-thiouridine biosynthesis in Escherichia colirdquoBiochemistry vol 42 no 4 pp 1109ndash1117 2003

[133] T Numata Y Ikeuchi S Fukai T Suzuki andONureki ldquoSnap-shots of tRNA Sulphuration via an adenylated intermediaterdquoNature vol 442 no 7101 pp 419ndash424 2006

[134] T Numata Y Ikeuchi S Fukai et al ldquoCrystallization andpreliminary X-ray analysis of the tRNA thiolation enzymeMnmA from Escherichia coli complexed with tRNAGlurdquo ActaCrystallographica F Structural Biology and Crystallization Com-munications vol 62 no 4 pp 368ndash371 2006

[135] I Moukadiri M J Garzon G R Bjork and M E ArmengodldquoThe output of the tRNA modification pathways controlled bythe Escherichia coli MnmEG and MnmC enzymes depends onthe growth conditions and the tRNA speciesrdquo Nucleic AcidsResearch vol 42 no 4 pp 2602ndash2623 2013

[136] N D Maynard E W Birch J C Sanghvi L Chen M VGutschow and M W Covert ldquoA forward-genetic screen anddynamic analysis of lambda phage host-dependencies revealsan extensive interaction network and a new anti-viral strategyrdquoPLoS Genetics vol 6 no 7 Article ID e1001017 2010


[137] N D Maynard D N MacKlin K Kirkegaard and M WCovert ldquoCompeting pathways control host resistance to virusvia tRNAmodification and programmed ribosomal frameshift-ingrdquoMolecular Systems Biology vol 8 article 567 2012

[138] J L Giel A D Nesbit E L Mettert A S Fleischhacker BT Wanta and P J Kiley ldquoRegulation of Iron-Sulphur clusterhomeostasis through transcriptional control of the Isc pathwayby [2Fe-2S]-IscR in Escherichia colirdquo Molecular Microbiologyvol 87 pp 478ndash492 2013

[139] K S Myers H Yan I M Ong et al ldquoGenome-scale analysis ofEscherichia coli FNR reveals complex features of transcriptionfactor bindingrdquo PLoS Genetics vol 9 Article ID e1003565 2013

[140] Y Ishii H Yamada T Yamashino et al ldquoDeletion of the yhhPgene results in filamentous cell morphology in Escherichia colirdquoBioscience Biotechnology and Biochemistry vol 64 no 4 pp799ndash807 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology


Molecular Biology International

GenomicsInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


BioinformaticsAdvances in

Marine BiologyJournal of



Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Genetics Research International


Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN

Ominus

S

O O O

OH

OHOH

P

Ominus

O OP

H HH H

O

Cytosine

O

H2N

S

S

Mo

O

ON

NN

H

H

HNCys

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

Ominus

S

X

S

O O O

O

OOOOOO

OS

OHOH

P

P P

Ominus

O OP

H HH H

O

Guanine

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

OminusOminusOHOH

HHH H

O

Guanine

Molybdenum cofactor (Moco)Mo-MPT

Xanthine oxidase familySulfurated MCD

Aldehyde oxidoreductase(PaoABC)

Xanthine dehydrogenase(XdhABC XdhD)

Sulfite oxidase familydi-oxo Moco

Sulfite oxidase (YedY)bis-MGD

TMAO reductase A (TorA)TMAO reductase Z (TorZ)

DMSO reductase (DmsABC)Nitrate reductase A (NarGHI)Nitrate reductase Z (NarZYV)

Peripl Nitrate reductase (NapA)Biotin sulfoxide reductase (BisC)

Formate dehydrogenase N (FdnGHI)Formate dehydrogenase O (FdoGHI)

Formate dehydrogenase H (FdhF)

DMSO reductase family

Figure 1 The different structures of Moco in E coli The basic form of Moco is a 5678-tetrahydropyranopterin with a unique dithiolenegroup coordinating the molybdenum atom named Mo-MPT Mo-MPT (shown in the tri-oxo structure [25]) can be further modified andin E coli three different molybdenum-containing enzyme families exist classified according to their coordination at the molybdenum atomthe xanthine oxidase sulfite oxidase and DMSO reductase families In E coli the xanthine oxidase family contains the sulfurated MCDcofactor The sulfite oxidase family is characterized by a di-oxo Moco with an additional protein ligand which usually is a cysteine TheDMSO reductase family contains two MGDs ligated to one molybdenum atom with additional ligands being an OS and a sixth ligand Xwhich can be a serine a cysteine a selenocysteine an aspartate or a hydroxide andor water molecule The characterized molybdoenzymesin E coli are shown in blue for each family

in more than fifty enzymes in bacteria including nitratereductases sulfite dehydrogenase xanthine oxidoreductasealdehyde oxidoreductase DMSO reductase formate dehy-drogenase CO dehydrogenase and various other enzymes[3] In the redox reactions catalyzed by molybdoenzymeselectron transfer is mediated by additional redox centerspresent in the protein or on other protein domains like FeScenters cytochromes or FADFMN cofactors [6] Duringthese redox reactions the molybdenum atom can exist invarious oxidation states and couple oxide or proton transferwith electron transfer [2]

The different enzymes contain different forms of Mocoand were historically categorized into three families based onthe ligands at themolybdenum atomwhich are characteristicfor each family (Figure 1) the xanthine oxidase (XO) familythe sulfite oxidase (SO) family and the dimethyl sulfoxide(DMSO) reductase family [3 7] The XO family is charac-terized by an MPT-MoVIOS(OH) core in the oxidized state

with one MPT equivalent coordinated to the molybdenumatom one oxo-group one sulfido-group and one hydroxo-group [3] (Figure 1) The sulfido-group is cyanide labile [8ndash10] and removal of the sulfido group results in formation ofan inactive desulfo-enzyme with an oxygen ligand replacingthe sulfur at the Mo active site [10] The enzymes of thisfamily are involved in two-electron transfer hydroxylationand oxo-transfer reactions with water as the source of oxygen[7 11] Among themembers of the XO family in E coli are thexanthine dehydrogenase XdhABC the periplasmic aldehydeoxidoreductase PaoABC and the so far uncharacterizedxanthine dehydrogenase homologue XdhD (Figure 1 Table 1)[6 12]

Enzymes of the SO family coordinate a single equivalentof the pterin cofactor with an MPT-MoVIO

2core in its

oxidized state and usually an additional cysteine ligandwhichis provided by the polypeptide [3] Members of this familycatalyze the transfer of an oxygen atom either to or from






2-MoVIO(X) core









+Mg-GTP

cPMP

MPT

Mo-MPT MCD

bis-Mo-MPT


MPT-AMP

MoaA

MoaC

MoaDMoaEMoeB

+SAM


MogA

MoeA

+ATP

MobA

MobA

MocA

+Mg-CTP

+L-cysteine IscS

+MoO42minus

Ominus

OO

O

OOOHOH

P

Ominus Ominus

OminusOP

OP

O

N

NN

HN

H2NO

O

OH2N

Ominus

O

O ON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

H2N

SH

SH

O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

N

NH2

N

NN

Ominus

Ominus

S

S

O

O

O

OO

O

O

P

P

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

minusOminusO

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HNH2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

OO

S

S

Mo

Ominus

S

S

O

O

O

O

OO

O

O

O

O

O

P

P P

Ominus

O

OP

Guanine

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

OHOH

O

minusOminusOGuanine

OHOH

O

H2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

O

S

S

SMo

5998400GTP

OH

OH

Ominus



moa

mob

moc

moe

mog

moaA

mobB

mocA

moeB

mogA

moaB

mobA

moeA

moaCmoaD moaE

1000 bp



2GTP)


2GTP to cPMP





2gt (MoaD-MoeB)

2gt (MoaD-



2complex is





N

N

OHOH

O

O

NOPPP

1998400

29984003998400 4

998400

5998400

876 5432

19

H2N

HN

NH2

O

O

HOOH

O

N

NPPPN8

H

HN

N

NH2

N

NN

OHOH

O

HH

N

O O

6 5432

1

H2N

HN

N

N

H

H

O

O

O

O

19984002998400

3998400

4998400

5998400

87

9Ominus

P

[4Fe4S]+

[4Fe4S]2+

SAM

eminus

+L-Met

MoaAMoaA

MoaC

cPMP

dA∙

8-cH2GTP

5998400GTP

3998400

∙



4







O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N


C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP


C1998400

C2998400

C1998400

C2998400

C1998400

C2998400











4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology






2-MoVIO(X) core









+Mg-GTP

cPMP

MPT

Mo-MPT MCD

bis-Mo-MPT


MPT-AMP

MoaA

MoaC

MoaDMoaEMoeB

+SAM


MogA

MoeA

+ATP

MobA

MobA

MocA

+Mg-CTP

+L-cysteine IscS

+MoO42minus

Ominus

OO

O

OOOHOH

P

Ominus Ominus

OminusOP

OP

O

N

NN

HN

H2NO

O

OH2N

Ominus

O

O ON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

H2N

SH

SH

O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

N

NH2

N

NN

Ominus

Ominus

S

S

O

O

O

OO

O

O

P

P

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

minusOminusO

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HNH2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

OO

S

S

Mo

Ominus

S

S

O

O

O

O

OO

O

O

O

O

O

P

P P

Ominus

O

OP

Guanine

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

OHOH

O

minusOminusOGuanine

OHOH

O

H2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

O

S

S

SMo

5998400GTP

OH

OH

Ominus



moa

mob

moc

moe

mog

moaA

mobB

mocA

moeB

mogA

moaB

mobA

moeA

moaCmoaD moaE

1000 bp



2GTP)


2GTP to cPMP





2gt (MoaD-MoeB)

2gt (MoaD-



2complex is





N

N

OHOH

O

O

NOPPP

1998400

29984003998400 4

998400

5998400

876 5432

19

H2N

HN

NH2

O

O

HOOH

O

N

NPPPN8

H

HN

N

NH2

N

NN

OHOH

O

HH

N

O O

6 5432

1

H2N

HN

N

N

H

H

O

O

O

O

19984002998400

3998400

4998400

5998400

87

9Ominus

P

[4Fe4S]+

[4Fe4S]2+

SAM

eminus

+L-Met

MoaAMoaA

MoaC

cPMP

dA∙

8-cH2GTP

5998400GTP

3998400

∙



4







O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N


C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP


C1998400

C2998400

C1998400

C2998400

C1998400

C2998400











4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


+Mg-GTP

cPMP

MPT

Mo-MPT MCD

bis-Mo-MPT


MPT-AMP

MoaA

MoaC

MoaDMoaEMoeB

+SAM


MogA

MoeA

+ATP

MobA

MobA

MocA

+Mg-CTP

+L-cysteine IscS

+MoO42minus

Ominus

OO

O

OOOHOH

P

Ominus Ominus

OminusOP

OP

O

N

NN

HN

H2NO

O

OH2N

Ominus

O

O ON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

H2N

SH

SH

O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

N

NH2

N

NN

Ominus

Ominus

S

S

O

O

O

OO

O

O

P

P

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

minusOminusO

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HNH2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

OO

S

S

Mo

Ominus

S

S

O

O

O

O

OO

O

O

O

O

O

P

P P

Ominus

O

OP

Guanine

H2N

S

S

Mo

O

O

N

NN

N

H

NH

H

NH

HN

NH

NH2

OHOH

O

minusOminusOGuanine

OHOH

O

H2N O

ON

NN

H

H

HNOminus

OO

OO

OHOH

P

Ominus

OP O

Cytosine

O

S

S

SMo

5998400GTP

OH

OH

Ominus



moa

mob

moc

moe

mog

moaA

mobB

mocA

moeB

mogA

moaB

mobA

moeA

moaCmoaD moaE

1000 bp



2GTP)


2GTP to cPMP





2gt (MoaD-MoeB)

2gt (MoaD-



2complex is





N

N

OHOH

O

O

NOPPP

1998400

29984003998400 4

998400

5998400

876 5432

19

H2N

HN

NH2

O

O

HOOH

O

N

NPPPN8

H

HN

N

NH2

N

NN

OHOH

O

HH

N

O O

6 5432

1

H2N

HN

N

N

H

H

O

O

O

O

19984002998400

3998400

4998400

5998400

87

9Ominus

P

[4Fe4S]+

[4Fe4S]2+

SAM

eminus

+L-Met

MoaAMoaA

MoaC

cPMP

dA∙

8-cH2GTP

5998400GTP

3998400

∙



4







O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N


C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP


C1998400

C2998400

C1998400

C2998400

C1998400

C2998400











4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


moa

mob

moc

moe

mog

moaA

mobB

mocA

moeB

mogA

moaB

mobA

moeA

moaCmoaD moaE

1000 bp



2GTP)


2GTP to cPMP





2gt (MoaD-MoeB)

2gt (MoaD-



2complex is





N

N

OHOH

O

O

NOPPP

1998400

29984003998400 4

998400

5998400

876 5432

19

H2N

HN

NH2

O

O

HOOH

O

N

NPPPN8

H

HN

N

NH2

N

NN

OHOH

O

HH

N

O O

6 5432

1

H2N

HN

N

N

H

H

O

O

O

O

19984002998400

3998400

4998400

5998400

87

9Ominus

P

[4Fe4S]+

[4Fe4S]2+

SAM

eminus

+L-Met

MoaAMoaA

MoaC

cPMP

dA∙

8-cH2GTP

5998400GTP

3998400

∙



4







O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N


C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP


C1998400

C2998400

C1998400

C2998400

C1998400

C2998400











4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


N

N

OHOH

O

O

NOPPP

1998400

29984003998400 4

998400

5998400

876 5432

19

H2N

HN

NH2

O

O

HOOH

O

N

NPPPN8

H

HN

N

NH2

N

NN

OHOH

O

HH

N

O O

6 5432

1

H2N

HN

N

N

H

H

O

O

O

O

19984002998400

3998400

4998400

5998400

87

9Ominus

P

[4Fe4S]+

[4Fe4S]2+

SAM

eminus

+L-Met

MoaAMoaA

MoaC

cPMP

dA∙

8-cH2GTP

5998400GTP

3998400

∙



4







O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N


C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP


C1998400

C2998400

C1998400

C2998400

C1998400

C2998400











4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


O O

C SH HS

HNN

NN

H

HO

O

OO

O

O

C

O

O

P

O O

HNN

NN

H

HO

S

MoaD

MoaD

MoaD

MoaD

MoeB

MoaE

MoaD-SH

MPT

MPT synthase

O

O O

HNN

NN

H

H O

H2O

H2O

H2N

G81G

G81G

G81G

G81G

Ominus

Sminus

OPO2minus3

OPO2minus3

HO C

O

H2N

H2N

Sminus

Sminus

O

O

HNN

NN

H

H OOPO2minus

3

OPO2minus3

H2N

S

SminusSminus

SminusO

HNN

NN

H

H OH2N


C

C C

SH

AMP AMP

O

O O

CHO

O+Mg-ATP

cPMP


C1998400

C2998400

C1998400

C2998400

C1998400

C2998400











4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








4S4]







OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


OO

H2N

S

S

MoOminus

OPO32minus

O

ON

NN

H

H

HN2x

Mo-MPT

MobA +2Mg-GTP

bis-Mo-MPT bis-MGD


N

NH

O

NHN

NH

O

SMo S

O

O

S

S

OO

N

NH

HHN

N

O

H N P

O

P

OH

2

2

Ominus

Ominus

N

NH

O

NHN

NH

O

SMo S

O

OS

S

OO

N

NH

H

HN

N

O

H N P

O

PO

H

2

2

O

Ominus

O

P

OOHOH

Guanine OO

Guanine

OP

O

Ominus

O

OHOH

minusO minusO

N

NH

O

NHN

NH

O

SMo S

O OO

S

S

OO

N

NH

H

HN

N

O

H N P

O

P

OH

2

2

Ominus

O

P

OOHOH

GuanineO

OHOH

Guanine

OP

O

Ominus

O

minusOminusO

Fe2S2

Fe2S2

Fe4S4

Fe4S4

Fe4S4Fe4S4Fe4S4

HCOOminus CO2

bis-MGD

FdsA

105 kDa

52kDa

15kDaFdsB

FdsG

FMN

NAD+ NAD

2 Mo-MPT

MobA

MobA

FDH

bis-Mo-MPT

bis-MGDbis-MGD

FdsD

FdsC

FdsC+2Mg-GTP

minusOminusO

O

H + H+














L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology













L-cysteine

L-alanine

TusA

TusA

ThiI

IscU

TusBCD TusE MnmA

Moco biosynthesis

IscUCyaYIscX

tRNA thiolation


TtcA[Fes]

MiaB[Fes]IscU[Fes]

mnm5 U


Cms2i6A

IscS-SSminus

s2

s4

s2







SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


SS

S SFeFeFe

FeTarget proteins

IscU IscU

Fe FeS

S

HscA HscBIscS

L-cysL-ala

IscS

Fdx

IscA


IscXCyaY

SSminus SSminusFe2+










HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


HNN N

NO N

OH

HO

CH2

SCH3

3

3CH

CH

CHC

OHHNN N

NO N

OHOH

OH

HO

CH2

SCH3

3

2CH

CH

CHC

NH

O

O

N

OHOH

HO S

H3CHNH2C

NH

O

O

O

N

HO

HO S

H2CHNH2C

C

OHOH

8

NH

O

S

N

OHOH

HO O

32

3437

ms2i6A

ms2io6Amnm5s2U

cmnm5s2U

N

O

NH2

N

OHOH

HO Ss2C

s4U

tRNA(s2U34)

MnmA

TusA

SSminus

SSminusSSminus

SSminus

SSminus

SSminus

C19

TusE

L-cysL-ala

IscS

IscS

Tus

B

B

C

C

DD







IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


IscS

IscU

IscS

FeSMolybdoenzymes

reduced

IscSIscU IscS

IscU

IscSIscU

IscS

IscSIscS

IscS

IscS

FeS

Moco biosynthesis

cPMP

MPT

Biotin Lipoic acid

Thiamine

Target proteins

TusA

ThiI

[S]

increasedIscU

IscU

IscS

IscS


TusA

TusA

TusA

No sulfur for MPT


MoaA

IscX

CyaY

[S]

[S]

+

S4mnm5S2

minus

minus

+

TusA

TusA

ThiI

IscU

TusA

IscU

TusA

IscU

5998400GTP

U8 tRNAU34 tRNA







O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


O

H2N

Ominus

O

O

O

OON

NN

H

H

HN P

H2N

SH

SH

OPO32minus

O

ON

NN

H

H

HN

OO

H2N

S

S

Mo

OPO32minus

O

ON

NN

H

H

HN

GTPMoaAMoaC

MoaD

MoaD

MoaDcPMP

MoaE

MoaE

MoeB

MoeB

RLD

MnmA

MogA

MocAMobA

MoeA

MCDbis-MGD



Nitrate reductase

TorATMAO reductase

Tat-translocation

Target proteinsIscA


S

HN

O N

tRNA

tRNA (s4

Periplasm

Cytosol

S

SS

S

S SFe

FeFeSS FeFeS

S FeFeFe

FeFe

SS

S SFeFe

FeFe

ATP

ATP

ThiS GG

GG

O

OO

O

Sminus

SminusSminus

Sminus

SSminus

+

N

N

N NH2

3minusO6P2O

S

IscS

IscU

IscU

IscU

ThiI

SSminus

ThiI

ThiI

IscS

SSminusIscS

SSminus

SSminus SSminus

IscS

IscS

IscX

CyaY

HscA HscB

L-cys L-ala

TusA

TusE

TusA

YnjE

C19

Molybdopterin (MPT)


S

HN

O

N

tRNA

tRNA (s2

[S]

[S]

[S]MPT synthase

SSminus SSminus

SSminus

SSminus

SSminus

SSminus

IscS

TusAC19

Thiosulfate Sulfite

TusB

B

C

CD

D

[S] ThiF

U8)

U34 )








Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology







Acknowledgments


References































































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








































































2to formaterdquo
































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology














































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

Review Article The Biosynthesis of the Molybdenum Cofactor...

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