Molecular model of the trimeric G protein G alpha
in complex with (i) adenylate cyclase (PDB
code:1azs) and (ii) RGS4 (regulator of G-protein
signalling 4, PDB code:1agr), ribbon diagram. G
alpha is shown in green with the switch regions
I, I and III red. (i) the C1 and C2 subunits of
adenylate cyclase are shown in blue and violet
respectively. In (ii) RGS4 is shown blue. 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, and is regulated by RGS4.
