Trimeric G protein, complex with RGS4, model

Molecular model of G alpha (a trimeric G protein) in complex with RGS4, close-up view. G alpha is shown in magenta, with the switch regions I, II and III in green, RGS4 in pink. Alpha helices are represented by cylinders. 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 cyclse: it activates the cyclase in response to beta- adrenergic stimuli, and is regulated by RGS4.