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 the ARF1 GTPase protein was mutated so that it could not hydrolyze 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 ex transport vesicle coat formation? pect this mutation to affect ARF1-initiated 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

B.

When the ARF1 cofactor is in active form that is with GTP it allows formation of coat I proteins loaded vesicles which function in transport of lipids from golgi complexes to endoplasmic reticulum.After the task is completed that GTPase protein comes into picture which hydrolyses the GTP which is bound to the ARF,making it inactive. So according to this comcept if the GTPase is mutated then there will be budding of vesicles as this mutation does not interfere in budding process.

C.

IF the ARF is locked in GDP bound state, that is in inactive form then the N terminal alpha helix of ARF 1 cannot extrude from its hydrophobic pocket to assemble to the target organelle.Extrusion of Helix is brought about by association of GTP in place of GDP by Guanidine nucleotide exchanging factor(GEF) proteins.Thus GTP cannot get replaced by GDP.So there will be no transport through vesicles and there will be no coat protein formation.

D.

Endoplasmic reticulum and plasma membrane are the destinations.

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