A GAP A. stimulates the exchange of bound GDP for GTP. B. is a factor without which Ras cannot hydrolyze its GTP. C. enhances the GTP hydrolysis rate of Ras. D. enhances the GTPase activity of Ras even in the presence of mutations that maintain Ras in a permanently GTP-bound active state.

A GAP  enhances the GTP hydrolysis rate of Ras

Explanation:

The correct answer to the question is option C

ENHANCES THE GTP HYDROLYSIS RATE OF Ras

A GAP enhances the GTP hydrolysis rate of Ras

Explanation: GTPase-activating proteins (GAPs) accelerate the very slow intrinsic hydrolysis reaction of the GTP-bound Ras by several orders of varying magnitude and thereby act as presumably negative regulators of Ras action.The GTP hydrolysis of oncogenic mutants of Ras remains unaltered. GTPase-activating proteins or GTPase-accelerating proteins (GAPs) are a family of regulatory proteins whose members can bind to activated G proteins and stimulate their GTPase activity, this results in the termination of the signaling event.

GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP) while Ras on the other hand Ras is a small GTP-binding protein, Ras is an important component of the signal transduction pathway used by growth factors to initiate cell growth and differentiation. Cell activation with growth factors such as epidermal growth factor (EGF) induces Ras to move from an inactive GDP-bound state to an active GTP-bound state.

In GAP, the GTP-bound conformation is biologically active and promotes a cellular functions such as signal transduction, cytoskeleton organization, protein synthesis/translocation, or a membrane budding/fusion event. GTP hydrolysis turns off the GTPase switch by converting it to the inactive GDP-bound conformation.