Evidence that a beta-adrenergic receptor-associated guanine nucleotide regulatory protein conveys guanosine 5'-O-(3-thiotriphosphate)- dependent adenylate cyclase activity.

The guanine nucleotide regulatory protein component (N) of the frog erythrocyte membrane adenylate cyclase system appears to form a stable complex with the beta-adrenergic receptor (R) in the presence of agonist (H). This agonist-promoted ternary complex HRN can be solubilized with Lubrol. The guanine nucleotide regulatory protein associated with the solubilized complex can be adsorbed either to GTP-Sepharose directly or to wheat germ lectin-Sepharose via its interaction with the receptor which is a glycoprotein. Guanosine 5'-O-(3-thiotriphosphate)(GTP gamma S) can be used to elute the guanine nucleotide regulatory protein from either Sepharose derivative. The resulting N.GTP gamma S complex conveys nucleotide-dependent adenylate cyclase activity when combined with a Lubrol-solubilized extract of turkey erythrocyte membranes. The ability to observe GTP gamma S-dependent reconstitution of adenylate cyclase activity in the eluate from either resin required the formation of the HRN complex prior to solubilization. The N protein can be identified by its specific [32P]ADP ribosylation catalyzed by cholera toxin in the presence of [32P]NAD+. The existence of a stable HRN intermediate complex is supported by the observation that agonist pretreatment of frog erythrocyte membranes results in a 100% increase in the amount of 32P-labeled N protein eluted from the lectin-Sepharose in the presence of GTP gamma S compared to membranes pretreated with either antagonist or agonist plus GTP. Our results therefore provide evidence that the same guanine nucleotide-binding protein that associates with the beta-adrenergic receptor in the presence of agonist mediates adenylate cyclase activation.

Duke Scholars

Author Robert J. Lefkowitz Medicine, Cardiology