Lodish Chptr. 13 & 14; Folding, Vesicular Traffic ... · PDF fileFigure 14.11 Vescle-mediated...
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Copyright © 2013 by W. H. Freeman and Company Molecular Cell Biology, 7th Edition Lodish et al.
Lodish Chptr. 13 & 14; Folding, Vesicular Traffic,
Secretion, and Endocytosis
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Chapter Opener
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Figure 14.1
Overview of the secretory and endocytic pathways of protein sorting.
Proteins that are for
secretory vescicles,
lysosome or having
posted receptors on pm
than will bind specific
ligands for endocyotic
vescicles to bring them
into cell and digest them
in an endosome.
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Figure 13.5
Structure of the signal-
recognition particle
(SRP).
In targeting protein to the
ER ‘secretory pathway’ has two
components, the SRP and the
SRP receptor on the ER
membrane.
The SRP is made up of 6
proteins and a 300 nucl. RNA.
SRP p54 binds to the signal
seq. It arrests elongation. It has
GTPase binding and hydrolysis
activity. Hydrolysis causes the
release of ribosome to
translocon.
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Figure 13.6
Cotranslational translocation.
• The SRP receptor binds the SRP bound to the ribosome. This
is then transfered to the Translocon, which the nascent
protein grow chain will enter the ER through.
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Experimental Figure 13.7 Sec61a is a translocon component.
• Sec 61 is the
Translocon protein
that is the transport
for the nascent
chain to enter the
ER through. Signal
peptidase
associated with
sec61 removes the
signal sequence as
it enters the lumen
of the ER.
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Experimental Figure 13.8 Structure of a bacterial Sec61 complex.
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Figure 13.9 Post-translational translocation.
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Chaperone
mediated folding
There are 3 bacterial
equivalent proteins
DnaK, HscA, HscC. It
has an N-terminal
ATPase domain,
substr binding
domain, C-terminal
domain that acts as a
lid to binding domain.
There is mito version
mtHsp 70.
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The bacterial
equivalent of Hsp90
protein is HtpG. It
is found in both
cytosol, ER and
mitochondrial
matrix.
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Figure 13.10 ER membrane proteins.
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Figure 13.11 Positioning type I single-pass proteins.
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Figure 13.13 Insertion of tail-anchored proteins.
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Figure 13.17 Biosynthesis of the oligosaccharide precursor.
Biosynthesis of oligosacch for protein.
• DoliholPO4 is a polyisoprenoid lipid in the ER membrane
that the oligo sacch are built attached to the
pyrophosphate. First added sugar is GlNAc.
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Figure 13.18 Addition and initial processing of N–linked oligosaccharides.
The finished oligosacch is transferred to specific N
on an aspparagine in the sequence asn-X-Ser(Thr).
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Figure 13.22 Modifications of N-linked oligosaccharides are used to monitor folding and quality
control.
• After removing terminal 3Glc residues from N-linked
oligosacch then a glc can be re-added to bind CXN/CRT
for retention in ER.
• Tailoring to remove mannose residue is then recognized
by EDEM,or OS-9 leads to misfolded unfolded protien
removal from ER.
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Figure 13.19 Action of protein disulfide isomerase (PDI).
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Figure 13.20 Hemagglutinin folding and assembly.
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Figure 13.24 Protein import into the mitochondrial matrix.
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Experimental Figure 13.25 Experiments with chimeric proteins elucidate mitochondrial protein
import.
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Figure 13.27 Three pathways to the inner mitochondrial membrane from the cytosol.
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Figure 13.28 Two pathways to the mitochondrial intermembrane space.
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Experimental Figure 14.2 Protein transport through the secretory pathway can be visualized by
fluorescence microscopy of cells producing a GFP-tagged membrane protein.
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Experimental Figure 14.3 Transport of a membrane glycoprotein from the ER to the Golgi can be
assayed based on sensitivity to cleavage by endoglycosidase D.
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Figure 14.6 Overview of vesicle budding and fusion with a target membrane.
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Experimental Figure 14.7 Vesicle buds can be visualized during in vitro budding reactions.
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Figure 14.8 Model for the role of Sar1 in the assembly and disassembly of COPII coats.
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Experimental Figure 14.9 Coated vesicles accumulate during in vitro budding reactions in the
presence of a nonhydrolyzable analog of GTP.
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Figure 14.10 Model for docking and fusion of transport vesicles with their target membranes.
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Figure 14.11 Vescle-mediated protein trafficking between the ER and cis-Golgi.
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Figure 14.12
Three-dimensional structure of the ternary complex comprising the COPII coat proteins Sec23 and Sec24 and Sar1·GTP.
Sar1 is the locator that
binds Sec23 /24
forming the coat
complex.
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Figure 14.13 Role of the KDEL receptor in retrieval of ER-resident luminal proteins from the Golgi.
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Figure 14.14 Processing of N-linked oligosaccharide chains on glycoproteins within cis-, medial-, and trans-Golgi
cisternae in vertebrate cells.
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Experimental Figure 14.15 Electron micrograph of the Golgi complex in an exocrine pancreatic cell reveals
secretory and retrograde transport vesicles.
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Figure 14.17 Vesicle-mediated protein trafficking from the trans-Golgi network.
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Figure 14.18 Structure of clathrin coats.
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Figure 14.19 Model for dynamin-mediated pinching off of clathrin/AP-coated vesicles.
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Experimental Figure 14.20 GTP hydrolysis by dynamin is required for pinching off of clathrin-coated
vesicles in cell-free extracts.
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Figure 14.21 Formation of mannose 6-phosphate (M6P) residues that target soluble enzymes to
lysosomes.
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Figure 14.22
• Newly synthesized
protein for the lysosome
acquire a man 6PO4
residue, which is
necessary to pakg into
vescile for lysosome
Trafficking of soluble lysosomal enzymes from the trans-Golgi network and cell surface to lysosomes.
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Experimental Figure 14.23 Proteolytic cleavage of proinsulin occurs in secretory vesicles after they
have budded from the trans-Golgi network.
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Figure 14.24 Proteolytic processing of proproteins in the constitutive and regulated secretion
pathways.
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Figure 14.25 Sorting of proteins destined for the apical and basolateral plasma membranes of
polarized cells.
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Experimental Figure 14.26 The initial stages of receptor-mediated endocytosis of low-density
lipoprotein (LDL) particles are revealed by electron microscopy.
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Figure 14.27 Model of low-density lipoprotein (LDL).
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Experimental Figure 14.28 Pulse-chase experiment demonstrates precursor-product relations in
cellular uptake of LDL.
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Figure 14.29 Endocytic pathway for internalizing low-density lipoprotein (LDL).
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Figure 14.30 Model for pH-dependent binding of LDL particles by the LDL receptor.
• This is the pH
dependent LDL receptor
for lipoprotien particles
carrying FA and
cholesterol to cells that
display the LDL
recerptor on its cell
membrane.
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Figure 14.31 The transferrin cycle, which operates in all growing mammalian cells.