Trimeric G protein, molecular model

Molecular model of G alpha (a trimeric G protein) in complex with adenylate cyclase, alpha helices shown as cylinders. G alpha is shown in red with the switch regions I and II in green. The trimeric guanine nucleotide-binding proteins are involved as transducers in various transmembrane signalling systems. The G alpha (s) protein is involved in hormonal regulation of adenylate cyclase: it activates the cyclase in response to beta- adrenergic stimuli.