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Lecture 12

Biology 2382B Lecture Notes - Lecture 12: Copii, Atp Hydrolysis, Protein Targeting


Department
Biology
Course Code
BIOL 2382B
Professor
Sashko Damjanovski
Lecture
12

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Lecture 05: Vesicular Traffic of Proteins + Golgi Apparatus
Where do proteins go after ER? Golgi!
Proteins ER Golgi
Golgi Complex
- consists of flattened, dislike, cisternae w/no ribosomes
- vesicles at cisterna tips fuse or pinch off
- 3 types of cisternae (cis, medial, and trans) and 2 flanked networks of tubules (cis, medial, and trans).
Cis Golgi Network (CGN) faces RER and Trans Golgi Network (TGN) is opposite to RER.
- Processing and sorting of proteins (secreted, membrane, lysosomal)
ER Golgi is anterograde transport and Golgi ER is retrograde transport
(in both cases, protein moves via vesicles)
Transport Vesicles: Budding + Fusion
- Coat proteins promote budding of vesicles
- Snare proteins promote fusion of vesicles w/target membranes
- COPII vesicles are used for anterograde transport (ER Golgi)
- COPI vesicles are used for retrograde transport (Golgi ER)
- Clathrin vesicles move from TGN/PM to late endosomes
Budding
1 Cago ids to Cago Reepto poteis to eeal speifi sotig sigal seuee of AA o ago
2) Cargo Receptors now stick out from ER membrane to recruit GTP binding proteins which promote
COPII coat proteins to surround vesicles.
3) COPII coat proteins cause local bending of membrane until it forms a vesicle.
4) Eventually, cop II vesicle buds off donor membrane
Fusion
5) GTP binding proteins hydrolyze GTP to remove COPII coat proteins off vesicles
6) SNAREs on vesicle (v-snare) and SNAREs on target membrane (t-snare) associate together which pulls
vesicle close to target membranes and causes them to fuse together.
7) SNARE complex is broken up by ATP hydrolysis and contents of vesicles released into Golgi
Anterograde Transport (RER Cis-Golgi)
- Cop II vesicles mediate anterograde transport
- GTP-binding proteins have 2 functions:
1. Assembly and Disassembly of COPII coat proteins
2. Dock vesicles to target membranes
- Certain cargo membrane proteins use DXE (Asp-X-Glu) sorting signal recognized by COPII proteins
- ATP hydrolysis is required for dissociation of SNARE complexes
Note: COPI vesicles mediate retrograde transport between Cis-Golgi and ER
targeted
Sorted
(via vesicles)
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