Type III secretion effectors in Type III secretion effectors in bacterial genomebacterial genome

5 May 20105 May 2010

Sūn Guăng Wén Sūn Guăng Wén

Biochemistry, NUSBiochemistry, NUS

MelioidosisMelioidosis Causative agent: Causative agent: Burkholderia Burkholderia

pseudomalleipseudomallei Endemic area: SEA; northern AustraliaEndemic area: SEA; northern Australia Symptom: variableSymptom: variable Diagnosis: Serum test, culture of bacteria, Diagnosis: Serum test, culture of bacteria,

PCRPCR Risk factor: Type II diabetes and kidney Risk factor: Type II diabetes and kidney

failurefailure Treatment: CeftazidimeTreatment: Ceftazidime Vaccine: not available Vaccine: not available

Burkholderia pseudomalleiBurkholderia pseudomallei

• Facultative anaerobic,

in soil and surface water• Opportunistic pathogen• Resistant to many antibiotics• Huge genome: 4.1Mb +3.2Mb

• Many virulence factors: siderophore, flagella, T3SSs, T6SSs

• Able to invade cells and survive intracellularly

Type III secretion system Type III secretion system (T3SS)(T3SS)

SPI I of Salmonella

T3SS and flagellaT3SS and flagella

Distribution of T3SSs among pathogenic bacteria

Nat rev MCB 3:743

T3 Effectors modify host signaling T3 Effectors modify host signaling pathwayspathways

Effectors mimic host protein Effectors mimic host protein functionfunction

Effectors can introduce Effectors can introduce covalent-modificationcovalent-modification

Effectors are less conservedEffectors are less conserved

N-terminal of effector contains N-terminal of effector contains secretion signalsecretion signal

Fusion assay N-ter signal reporter

Determination of secretion signalDetermination of secretion signal

PLoS Pathogens April 2009 | Volume 5 | Issue 4 | e1000376

http://www.effectors.org/ ---very high false positive rate!

Signal is more defined within a Signal is more defined within a speciesspecies

Inv/mxi/spa-like T3S3 ofInv/mxi/spa-like T3S3 of B. B. pseudomalleipseudomallei

Base and inner membrane complex

TransloconsSecreted effectors

Molecular Microbiology (2002) 46(3), 649–659

Molecular Microbiology (2010) 76(3), 677–689

Regulator

Chaperone

Burkholderia pseudomalleiBurkholderia pseudomallei genomegenome

Burkholderia pseudomallei K96243: NC_006350; NC_006351 ,

http://www.ncbi.nlm.nih.gov/sutils/genom_table.cgihttp://www.sanger.ac.uk/cgi-bin/blast/submitblast/b_pseudomallei

The challenge: To identify T3S3 The challenge: To identify T3S3 effectors ineffectors in bp bp genomes genomes

Define training sets, collect effector Define training sets, collect effector sequencessequences

Find patterns in N-terminalsFind patterns in N-terminals Search Search Burkholderia pseudomalleiBurkholderia pseudomallei

genomesgenomes Blast top hits in protein databasesBlast top hits in protein databases Verify through experimentsVerify through experiments

Assembly of T3S needleAssembly of T3S needle