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 Gs alpha, but they are regulated in an opposite fashion by G protein beta gamma subunits. Purified beta gamma inhibits Gs alpha-stimulated type I adenylylcyclase directly, while beta gamma activates type II adenylylcyclase and potentiates the Gs alpha-mediated stimulation of the enzyme. This is the first demonstration of the activation of a purified effector molecule by G protein beta gamma subunits.