Guanine nucleotide binding proteins are heterotrimeric signal-transducing molecules consisting of alpha, beta, and gamma subunits. The alpha subunit binds guanine nucleotide, can hydrolyze GTP, and can interact with other proteins. The protein encoded by this gene represents the alpha subunit of an inhibitory complex. The encoded protein is part of a complex that responds to beta-adrenergic signals by inhibiting adenylate cyclase. Two transcript variants encoding different isoforms have been found for this gene.