Question

When does GAP work on Rab?

A. When Rab is inactive
B. When Rab is bound to GTP
C. When Rab is bound to GDP
D. When Rab is undergoing phosphorylation

Answer 1

GAPs work on Rab when Rab is bound to GTP, which is part of the G-protein signaling cycle that leads to the inactivation of the Rab protein by hydrolyzing GTP to GDP.

Step-by-step explanation:

The question pertains to the G-protein signaling and the action of GTPase-activating proteins (GAPs) on small GTPases like Rab. GTPase-activating proteins, or GAPs, are able to interact with and accelerate the hydrolysis of GTP to GDP on Rab proteins when they are in their active, GTP-bound state. This action leads to the inactivation of the Rab protein, thus facilitating the 'turning off' part of the signaling cycle.The correct answer to the question 'When does GAP work on Rab?' is B. When Rab is bound to GTP. This is because GAPs function to turn off the signaling by making Rab hydrolyze the bound GTP to become inactive GDP-bound Rab.