749-766 - I nt racellular Vesicular Traffic THE MOLECU LAR MECHAN ISMS OF MEMBRANE TRANSPORT AND THE MA I NTENANCE OF COMPARTMENTAL DIVERSITY

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Intracellular Vesicular Traffic THE MOLECULAR MECHANISMS OF MEMBRANE TRANSPORT AND THE MAINTENANCE OF COMPARTMENTAL DIVERSITY Molecular markers displayed on the cytosolic surface of the membrane serve as guidance cues for incoming traffic to ensure that transport vesicles fuse only with the correct compartment There are various types of coated vesicles o Most transport vesicles form from coated regions of membranes, bud off as coated vesicles, have cage of proteins covering their cytosolic surface o Before vesicle fuses with target membrane it has to discard the coat o Coat concentrates membrane proteins in a specialized patch, which then gives rise to the vesicle membrane. This is how it selects the right molecules for transport o Coat proteins assemble into a curved basketlike lattice that deforms the membrane patch and thereby shapes the vesicle o 3 types of coated vesicles: clathrin-coated, COPi-coated, COPII-coated Each type used for different transport steps o Clathrin-coated Mediate transport from ER and from golgi cisternae o COPI-coated o COPII-coated The Assembly of a clathrin coat drives vesicle formation o Clathrin-coated vesicle Major protein component is clathrin Adaptor proteins = another component From second layer of coat, positioned between clathrin cage and membrane Adaptor proteins bind the clathrin coat to the membrane Adaptor proteins trap transmembrane receptors that capture soluble cargo molecules inside the vesicle (Cargo receptors) Several types of adaptor proteins – each has a different set of cargo receptors Clathrin coated vesicles budding from different membranes use different adaptor proteins and thus package different receptors and cargo molecules o COPI-coated vesicle Bud from golgi compartments o COPII-coated vesicle Bud from the ER Not all coats form basketlike structures o Retromer is a coat which assembles on endosomes and forms vesicles that return acid hydrolase receptors to
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This note was uploaded on 12/30/2010 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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749-766 - I nt racellular Vesicular Traffic THE MOLECU LAR MECHAN ISMS OF MEMBRANE TRANSPORT AND THE MA I NTENANCE OF COMPARTMENTAL DIVERSITY

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