Question

What inactivates an active G-protein alpha subunit?

Answer 1

G proteins are membrane-associated, heterotrimeric proteins composed of three subunits such as alpha, beta, and gamma. The activated receptor facilitates the exchange of bound GDP for GTP on the G protein alpha subunit. The primary function of GPCRs in activating G proteins is to catalyze an exchange of GTP for GDP. This is the temporary switch because G proteins contain an inherent GTPase activity that is responsible to hydrolyze the bound GTP and converts the G protein back into the GDP-bound. That is the inactive state of G-protein alpha subunit.