Lect6_protSort

Lect6_protSort - Molecular mechanisms of vesicular...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Molecular mechanisms of vesicular trafficking Transport vesicles originate from coated regions of membranes - Coat functions: • Concentrates transport proteins into patches • Induce patches to vesicularize - Types coats: • COPII = ER to Golgi • COPI = Golgi to Golgi, Golgi back to ER • Clathrin = Trans-Golgi Network (TGN), endocytosis - Proteins essential to vesicle function: •Monomeric GTPases control coat assembly EXAMPLE: Coat-recruitment GTPases = ARFs (responsible for COPI and clathrin coat assembly) = Sar1 (responsible for COPII coat assembly) •SNARE proteins guide vesicles (mediate vesicle fusion?) •Rab proteins ensure specificity of vesicle docking 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
How are vesicles formed? (Clathrin coated) 1. Adapter proteins bind clathrin to membrane, and trap transmembrane proteins that bind to cargos inside membrane 2. Different adaptor proteins exist, that bind different cargo receptors 3. Adaptor proteins can also recruit special lipids (phosphoinositides) 4. Assembly of clathrin coat deforms membrane and forms vesicle. 5. Clathrin coat is dissasembled after vesicle formation 2 F09 D103 Cell Biology - lecture 12 © Gross- all rights reserved.
Background image of page 2
Dynamin finishes vesicle formation 3 Drosophila Shibire mutant: paralyzed No clathrin-mediated endocytosis no recycling of synaptic vesicle membranes blocked neurotransmitter release (see later in lecture) F09 D103 Cell Biology - lecture 12 © Gross- all rights reserved.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 How are COPII vesicles formed? Recruitment of Sar1(small GTPase) to donor membrane is the first step in vesicle formation Subsequent hydrolysis of GTP by Sar1 causes loss of coat. Coat and cargo recruitment vesicle buds off F09 D103 Cell Biology - lecture 12 © Gross- all rights reserved. Sar1 conformational change extends amphipathic helix into membrane
Background image of page 4
Rabs direct transport 5 Cell Biology - lecture 14 © Gross- all rights reserved. ~60 Rabs; different rabs on different cargos molecular marker for identifying membranes & guiding transport. Rabs can function on both cargo and target membrane. Inactive: in GDP-bound form, in cytosol Active: in GTP-bound form amphipathic helix released to bind membrane Rabs recruit ‘rab effectors’ Rab effectors can be molecular motors , or tethering proteins , and SNARE-interacting proteins Phosphatidylinositol (PI) phosphorylated at 3’, 4’, 5’ positions on inositol sugar to produce different Phosphoinositides (PIP)s: PIPs help organize membranes/ vesicles; different kinases/PIPs on different vesicles. Specific proteins bind specific PIPs.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Tethering of a vesicle to the target membrane 1. Rab-GTP binds the Rab effector (tethering) protein 2. SNARE proteins pair to dock vesicle and catalyze fusion of two membranes 6 Cell Biology - lecture 14 © Gross- all rights reserved.
Background image of page 6
The life cycle of a vesicle a-b. GTPase cleaves GTP to GDP: results in loss of coat and exposing V- SNARE proteins on surface of the vesicle c-d. V-SNARE finds appropriate T-SNARE: fusion occurs v-SNARE 7 Cell Biology - lecture 14 © Gross- all rights reserved.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
How do the vesicles know where to go?! How ensure specificity in vesicle targeting?
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/13/2011 for the course BIOSCI d103 taught by Professor Staff during the Fall '11 term at UC Irvine.

Page1 / 41

Lect6_protSort - Molecular mechanisms of vesicular...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online