Lecture 10 (Sept 16)

Lecture 10 (Sept 16) - Biological S nce 110A: I ntroduction...

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Lecture 10: Protein transport between organelles Transport vesicles move membrane and protein Vesicle coat proteins (COPs, Clathrin) Vesicle trafficking specificity (SNARE proteins) Mechanism of vesicle membrane fusion (SNAREs) Sorting proteins in the Golgi (Lysosomal targeting) Direct (non-vesicular) protein trafficking mechanisms Targeting proteins to mitochondria/chloroplasts Biological Sciences 110A: Introduction to Biology Kendal Broadie Reading Chapter 8: 298-320 Karp
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The Golgi is a primary sorting station for proteins destined for the plasma membrane and other organelles Proteins enter in transport vesicles fusing with the cis-Golgi network Proteins exit in transport vesicles budding from the trans-Golgi network How do transport vesicles do their job? The Golgi apparatus
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Transport between ER and Golgi compartments occurs via COP-coated transport vesicles ER-to-Golgi transport vesicles are formed by vesicle coat proteins called “Coatomers” or “COPs” : deform the membrane into spheres COP-coated vesicles function in transport between: ER and Golgi Golgi and ER (retrieval) intra-Golgi (cis, medial, trans) TGN and plasma membrane See Fig. 8.25 Karp
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Vesicle transport is a multi-step process See Fig. 8.26 Karp Vesicle coating at the starting ( donor ) membrane and vesicle uncoating prior to delivery at the end ( target ) membrane are both tightly regulated processes. Vesicle coating determine when/where a new transport vesicle will form. Vesicle uncoating is a prerequisite to membrane fusion, delivery of cargo.
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Transmembrane SNARE proteins on vesicle and target membrane proposed to provide transport specificity A specific vesicle SNARE (V-SNARE) binds a specific target SNARE (T-SNARE) This pairwise specificity assures that a vesicle is correctly targeted >20 known SNARE pairs in animals cells directing vesicle trafficking See Fig. 8.31 Karp
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T-SNARE Transmembrane SNARE function as fusion proteins Transport vesicles are first tethered to the target membrane via Rab GTPases working with unidentified “tethering proteins” The V-SNARE and T-SNARE then associate specifically in an energetically favorable (- G) conformational change that overcomes the energy cost (+ G) of membrane fusion Fig. 8.32 Karp V-SNARE
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This note was uploaded on 01/04/2010 for the course BSCI BSCI 110A taught by Professor Zwiebel during the Spring '09 term at Vanderbilt.

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Lecture 10 (Sept 16) - Biological S nce 110A: I ntroduction...

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