A REGION OF ADENYLYL-CYCLASE-2 CRITICAL FOR REGULATION BY G-PROTEIN BETA-GAMMA-SUBUNITS

Receptor-mediated activation of heterotrimeric guanine nucleotide-binding proteins (G proteins) results in the dissociation of alpha from beta gamma subunits, thereby allowing both to regulate effecters. Little is known about the regions of effecters required for recognition of G beta gamma. A peptide encoding residues 956 to 982 of adenylyl cyclase 2 specifically blocked G beta gamma stimulation of adenylyl cyclase 2, phospholipase C-beta 3, potassium channels, and beta-adrenergic receptor kinase as well as inhibition of calmodulin-stimulated adenylyl cyclases, but had no effect on interactions between G beta gamma and G alpha(o). Substitutions in this peptide identified a functionally important motif, Gln-X-X-G lu-Arg, that is also conserved in regions of potassium channels and beta-adrenergic receptor kinases that participate in G beta gamma interactions, Thus, the region defined by residues 956 to 982 of adenylyl cyclase 2 may contain determinants important for receiving signals from G beta gamma.