Evidence for a dissociable protein subunit required for calmodulin stimulation of brain adenylate cyclase.

Abstract
An adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] preparation that is not stimulated by NaF, 5''-guanylyl imidodiphosphate, or Ca2+ .cntdot. calmodulin was isolated from bovine cerebral cortex by Affi-Gel Blue chromatography and calmodulin-Sepharose chromatography. Sensitivity to these effectors was restored by incubation of the adenylate cyclase preparation with detergent-solubilized protein from bovine cerebral cortex. Reconstitution of Ca2+ .cntdot. calmodulin activation required the presence of 5''-guanylyl imidodiphosphate. The factor required for restoration of Ca2+ .cntdot. calmodulin stimulation was sensitive to heat, trypsin digestion and N-ethylmaleimide. This adenylate cyclase activity probably requires the presence of 1 or more guanyl nucleotide binding subunits for calmodulin sensitivity.