Question

Please provide detail explanation. Thank you.

When a small GTP-binding protein (GBP) is in the "on" (active) state (select any/all answers that apply):

a) its Switch I and Switch II domains tilt toward one another

b) GDP is bound within the nucleotide-binding pocket of the GBP

c) the GBP is incapable of hydrolyzing its bound GTP

d) the Switch II domain is phosphorylated on multiple tyrosine residues

e) the GBP can physically interact with downstream effector molecules

Answer 1

Correct answer is C because  GTP-binding protein regulators regulate G proteins in several different ways. Small GTPases act as molecular switches in signaling pathways, which act to regulate functions of other proteins. They are active or 'ON' when it is bound to GTP and inactive or 'OFF' when bound to GDP.

GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved G domain common to many GTPases.

Difference between GTP and GDP : Their activity is regulated by factors that control their ability to bind to and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP). When they are bound to GTP, they are 'on', and, when they are bound to GDP, they are 'off'. G proteins belong to the larger group of enzymes called GTPases.

Thank You.