REGULATION OF PURIFIED TYPE-I AND TYPE-II ADENYLYLCYCLASES BY G-PROTEIN BETA-GAMMA-SUBUNITS

Type I and type II adenylylcyclases have been purified after expression in Sf9 cells, each by application of a two-step purification protocol. The specific activities of the essentially homogeneous enzymes are approximately 7 and 2 mumol.min-1.mg-1, respectively. Each purified enzyme preparation is activated by G(salpha), but they are regulated in an opposite fashion by G protein betagamma subunits. Purified betagamma inhibits G(salpha)-stimulated type I adenylylcyclase directly, while betagamma activates type II adenylylcyclase and potentiates the G(salpha)-mediated stimulation of the enzyme. This is the first demonstration of the activation of a purified effector molecule by G protein betagamma subunits.