Regulation of purified type I and type II adenylylcyclases by G protein βγ 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 μmol · min^-1 · mg^-1, respectively. Each purified enzyme preparation is activated by G(sα), but they are regulated in an opposite fashion by G protein βγ subunits. Purified βγ inhibits G(sα)-stimulated type I adenylylcyclase directly, while βγ activates type II adenylylcyclase and potentiates the G(sα)-mediated stimulation of the enzyme. This is the first demonstration of the activation of a purified effector molecule by G protein βγ subunits.