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21 Cards in this Set
- Front
- Back
cargo
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membrane components and soluble molecules
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defining a compartment
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composition of its enclosing membrane, combination of selective markers
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coated vesicles
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transport vesicles containing distinctive cage of proteins covering their cytosolic surface
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purpose of coated vesicles - two
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- concentrates specific membrane proteins in a specialized patch, thereby selecting the appropriate molecules for transport
-molds the forming vesicle |
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three main types of coated vesicles
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clathrin - Golgi and plasma membrane
COPI and COPII - ER to Golgi, early in the secretory pathway |
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triskelion
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clathrin subunit formed by three large and small polypeptide chain
determines the geometry of the clathrin cage |
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adaptor proteins
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form a discrete second layer of the coat positioned between the clathriin cage and membrane
bind clathrin to the membrane specific for a different set of cargo receptors |
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coincidence detector - three requirments
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bind cytoplasmic tails of cargo receptors
interact directly with curved phospholipid bilayer bind specific phosphorylated PIPs |
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PI vs PIP
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phosphatidylinositol - PI
phosphoinositides - PIP interconversion is highly compartmentalized PI and PIP kinases and phosphatases recognized by protein domains that discriminate between the different phosphorylated forms, and thus recruit domains to mebrane |
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dynamin
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GTPase domain, PIP domain which tethers the protein to the membrane
recruits other proteins to site, directly distorts lipid membrane by recruitment of lipid modifying enzymes |
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Hsp70 role in uncoating
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uses ATP hydrolysis to peel off the clathrin coat
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coat recruitment GTPase
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usually found in high cytosolic concentrations in GDP inactive form
recruits coat proteins when GTP bound form is present when GTP bound is hydrolyzed = coat disassembly |
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Rab proteins
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GTPase - monomeric
direct the vesicle to the specific spots on the correct target membrane identifies membrane type and guides vesicular transport between them |
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GDI
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Rab-GDP dissociation inhibitor
keeps GDP bound Rab soluble in the cytosol |
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Rab effectors
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bound by Rap proteins once on membrane and facilitate vesicle transport, membrane tethering, and fushion
can be: motor proteins tethering proteins interact with SNARES same Rab protein can bind to multiple effectors |
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SNARE proteins
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transmembrane proteins involved in vesicle fushion, usually in complementory sets V and T
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V SNARE
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single polypeptide chain found on vesicle
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T SNARE
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two or three polypeptide chains found on target cell
often associated with inhibitory proteins which need to be released prior to proper functioning - typically released by Rab and effector proteins |
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trans-SNARE complexes
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resulting interaction of the T and V SNARE protein helices domain
uses energy of unwrapping of helices to overcome energy barrier |
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NSF protein
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cycles between the cytosol and membrane catalyzing the disassembly of stable complex of partner SNAREs allowing for repeated use
ATP hydrolysis |
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NSF requirment
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prevents membranes from fusing indiscriminately
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