3. ARF1 GTPase is a coat-recruitment protein, in the Golgi, similar to SAR1 GTPa

Question

3. ARF1 GTPase is a coat-recruitment protein, in the Golgi, similar to SAR1 GTPase in the ER. A. (1pt) What type of coat protein does ARF1 GTPase most likely assemble? B. (3pts) Imagine that theA GTP into GDP, regardless of its binding partners. Would you expect ARF1-initiated transport vesicles to bud off normally? How might subsequent or downstream steps in transport be affected if ARF1 cannot hydrolyze GTP into GDP? C. (3pts) What if the ARF1 protein was mutated so that it was locked in a GDP-bound state, regardless of its binding partners. How would you expect this mutation to affect ARF1-initiated transport vesicle coat formation? D. (2pts) Please identify two plausible cellular destinations of vesicles associated with ARF1 GTPase. Additionally, please predict which type of motor protein is most likely involved in vesicle transport to these destinations

Explanation / Answer

A) The ADP Ribosylation Factor 1 GTPase is required for the budding of COPI-coated vesicles and clathrin-coated vesicles containing adaptor protein complexes AP1, AP3, AP4 from Golgi membranes. The budding of vesicles from the endosomal compartments and trans-Golgi networks also require ARF1 GTPase.

B) If ARF1 GTPase protein was mutated resulting blockage in GTP to GDP hydrolysis, it will lead to coat disassembly. The downstream process will lead to oncogenic transformation. Coatomeraggregation will be inhibited and budding process will be disrupted. The number of coated vesicles will be increased compared to the wild-type and the release of uncoated products will be decreased.

C) If ARF1 protein was mutated so that it was locked in the GDP bound state, COP! dependent vesicle formation will be inhibited and nucleotide exchange will be interrupted.

D) Two plausible cellular destinations of vesicles associated with ARF1 GTPase-

1) Transport from trans-Golgi network to Endosomes and Lysosomes.

2) Golgi to Endoplasmic Reticulum. Associated motor protein: P23/24.

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