3592195059001 - TA Jason Smith Email [email protected] OH W...

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TA: Jason Smith OH: W 4-5pm Sun God Lounge BICD 110 Email: [email protected] Important stuff: MIDTERM next Tuesday (5/4)! Come to the review session in lecture on Thursday!! Section and normal OH next week are CANCELLED (we won’t have learned anything ;p) EXTRA OH LECTURE 8 VESICULAR TRANSPORT Two major pathways of transport: Biosynthetic-secretory ( ER outside) and Endocytic Transport is mediated by vesicles, of which there are three major types: Clathrin: Found on plasma membrane/golgi; major mediator of COPI: Transport from golgi ER COPII: Transport from ER Golgi Clathrin Coated Vesicles – Bringing stuff the cell -Forms characteristic Process: 1. Cargo binds cargo receptor on side of PM 2. Adaptor proteins ( ) binds to cargo receptor on cytosolic side of PM 3. Clathrin binds adaptor proteins and self assembles into cage structure begins 4. Once budding is almost complete, pinches bud off from PM What would happen if dynamin couldn’t function? (Hint: Shibire mutant in Drosophila) 5. Once vesicle fully formed, clathrin coat disassembles via auxillin activated ATPase and ARF GTPase Important GTPases ARF proteins: recruit and Sar1 protein: recruit Sar1 Inactive when bound to GDP Sar1-GEF (ONLY on ) causes Sar1 to bind GTP, making amphipathic helix pop out o Allows Sar1 to attach to ER membrane Sar1 can then go on to recruit the proteins (Sec24,Sec23) that bind the cargo receptor COPII binds to complex and forms vesicle Eventually, Sar1’s GTPase function hydrolyses its GTP and causes the coat to disassemble ARF ARF-GTP recruits which then recruit clathrin o ARF-GEF only found on membrane COPI uses similar mechanism Problem: Why is it significant that Sar1-GEF and ARF-GEF are only found in specific locations? GUIDANCE OF VESICULAR TRANSPORT 1. Rab-GTPases (don’t confuse with Ran proteins!!) -Mediate the initial docking and tethering of vesicles to target membrane and matching of SNAREs -Rab proteins ensure the of the vesicle that is docking
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They make sure the right molecules are going to the right location
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3592195059001 - TA Jason Smith Email [email protected] OH W...

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