Bio 9 part 1 - Bio 9-11-2008 Vesicular transport depends on...

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Bio 9-11-2008 Vesicular transport depends on small G-proteins Budding vesicles at the ER membrane need the existance of small G-proteins . These coat recruitment GTPases collaboration with GEFs on the surface of the ER. G-proteins are GTPases. The GTP hydrolysis induces a conformational change of the G- protein, which act as a molecular switch changing its interacting properties with other proteins. “ result in” Small G-proteins are regulated by additional proteins: GAP and GEF . - The GTPase activity of small G-proteins can be accelerated by GAP ( G TPas a ctivating p rotein). - The switch back to the GTP bound state is accelerated by GEF ( G DP- e xhange f actors). on the pic why the orange part is called Sec β it should be COPII 1
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Vesicle pinching off from the ER needs the action of coat recruitment GTPases Formation of a COPII coated vesicle at the ER-membrane . Coat recruitment GTPase - Sar1 is stimulated by a membrane bound GEF at the surface of the ER. - Sar1 exhanges GDP against GTP, which anchors the G-protein at the surface of the ER, - since a amphiphilic helix is exposed to the membrane by conformational change. - After fixation of the G-protein the assembly of coat protein starts . - Binding of the coat proteins also to specific phosphoinositides leads to deformation of the membrane and pinching off the vesicle. so we need the action of the GTPase and the PI to pinching of the vesicle o PI to identify in which part of the mem the budding off the v should occur o The GTPase to recruit the ptn needed for the formation of the V - The COPII proteins Sec24 and Sec23 act together to induce 1- bending of the membrane and 2- binding of cargo by cargo receptors . Vesicles need Rab-proteins to directed vesicles to its target compartments In addition to the 1- coat recruitment GTPases 2- an further group of small G- proteins, the Rab-proteins , Rab-proteins is needed to direct the vesicles to its target membranes. The Rab-proteins are with 60 members the largest
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Bio 9 part 1 - Bio 9-11-2008 Vesicular transport depends on...

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