Question

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Problem 4.2.2 (tags: #COPII, #mutant analysis, #fluorescence microscopy) Explain the following experimental results: a) A mutant cell in which the COPII proteins have lost ability to interact with cargoes, all plasma membrane proteins are mislocalized to the ER. b) A population of animal cells is engineered to express a secreted protein fused to GFP. When these cells are treated with colchicine, the fluorescence accumulates in COPII-coated vesicles. (NOTE: This question will require information from Unit 6 in order to answer it).

Answer 1

a)COP II proteins mediate protein sorting and transport between ER&GA.They are also requiredfor selective export of newly syntesized proteins from ER.Thus the inability and mislocation causes problems in vesicular trafficking,apoptosis,signal transduction and lipid biosynthesis.

b)when the secreted protein fused GFP treated colchicine concentrates into COP II vesicles,which build upto form an intermediate compartment or trasport complex containing ERGIC 53 and KDEL receptor where COPII replaced by COP I.