Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) dissociate into guanosine triphosphate (GTP)-bound α subunits and a complex of β and γ subunits after interaction with receptors. The GTP-α subunit complex activates appropriate effectors, such as adenylyl cyclase, retinal phosphodiesterase, phospholipase C, and ion channels. G protein βγ subunits have been found to have regulatory effects on certain types of adenylyl cyclase. In the presence of Gsα, the α subunit of the G protein that activates adenylyl cyclase, one form of adenylyl cyclase was inhibited by βγ, some forms were activated by βγ, and some forms were not affected by βγ. These interactions suggest mechanisms for communication between distinct signal-transducing pathways.