3.(heterotrimeric)G protein molecular switch activated (on) state: has high affinity for GTP inactivated (off) state: preferentially binds GDP has three subunits: a, Band y The asubunit is frequently the "business end"of the heterotrimeric G protein3. (heterotrimeric) G protein • molecular switch activated (on) state: has high affinity for GTP inactivated (off) state: preferentially binds GDP • has three subunits: α, βand γ • The αsubunit is frequently the “business end” of the heterotrimeric G protein