lodish chptr. 13 & 14; folding, vesicular traffic ... · pdf filefigure 14.11...

Lodish Chptr. 13 & 14; Folding, Vesicular Traffic,

Secretion, and Endocytosis

Chapter Opener

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.

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.

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.

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.

Experimental Figure 13.8 Structure of a bacterial Sec61 complex.

Figure 13.9 Post-translational translocation.

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.

The bacterial

equivalent of Hsp90

protein is HtpG. It

is found in both

cytosol, ER and

mitochondrial

matrix.

Figure 13.10 ER membrane proteins.

Figure 13.11 Positioning type I single-pass proteins.

Figure 13.13 Insertion of tail-anchored proteins.

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.

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).

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.

Figure 13.19 Action of protein disulfide isomerase (PDI).

Figure 13.20 Hemagglutinin folding and assembly.

Figure 13.24 Protein import into the mitochondrial matrix.

Experimental Figure 13.25 Experiments with chimeric proteins elucidate mitochondrial protein

import.

Figure 13.27 Three pathways to the inner mitochondrial membrane from the cytosol.

Figure 13.28 Two pathways to the mitochondrial intermembrane space.

Experimental Figure 14.2 Protein transport through the secretory pathway can be visualized by

fluorescence microscopy of cells producing a GFP-tagged membrane protein.

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.

Figure 14.6 Overview of vesicle budding and fusion with a target membrane.

Experimental Figure 14.7 Vesicle buds can be visualized during in vitro budding reactions.

Figure 14.8 Model for the role of Sar1 in the assembly and disassembly of COPII coats.

Experimental Figure 14.9 Coated vesicles accumulate during in vitro budding reactions in the

presence of a nonhydrolyzable analog of GTP.

Figure 14.10 Model for docking and fusion of transport vesicles with their target membranes.

Figure 14.11 Vescle-mediated protein trafficking between the ER and cis-Golgi.

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.

Figure 14.13 Role of the KDEL receptor in retrieval of ER-resident luminal proteins from the Golgi.

Figure 14.14 Processing of N-linked oligosaccharide chains on glycoproteins within cis-, medial-, and trans-Golgi

cisternae in vertebrate cells.

Experimental Figure 14.15 Electron micrograph of the Golgi complex in an exocrine pancreatic cell reveals

secretory and retrograde transport vesicles.

Figure 14.17 Vesicle-mediated protein trafficking from the trans-Golgi network.

Figure 14.18 Structure of clathrin coats.

Figure 14.19 Model for dynamin-mediated pinching off of clathrin/AP-coated vesicles.

Experimental Figure 14.20 GTP hydrolysis by dynamin is required for pinching off of clathrin-coated

vesicles in cell-free extracts.

Figure 14.21 Formation of mannose 6-phosphate (M6P) residues that target soluble enzymes to

lysosomes.

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.

Experimental Figure 14.23 Proteolytic cleavage of proinsulin occurs in secretory vesicles after they

have budded from the trans-Golgi network.

Figure 14.24 Proteolytic processing of proproteins in the constitutive and regulated secretion

pathways.

Figure 14.25 Sorting of proteins destined for the apical and basolateral plasma membranes of

polarized cells.

Experimental Figure 14.26 The initial stages of receptor-mediated endocytosis of low-density

lipoprotein (LDL) particles are revealed by electron microscopy.

Figure 14.27 Model of low-density lipoprotein (LDL).

Experimental Figure 14.28 Pulse-chase experiment demonstrates precursor-product relations in

cellular uptake of LDL.

Figure 14.29 Endocytic pathway for internalizing low-density lipoprotein (LDL).

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.

Figure 14.31 The transferrin cycle, which operates in all growing mammalian cells.

lodish chptr. 13 & 14; folding, vesicular traffic ... · pdf filefigure 14.11...

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