G protein(redirected from Gtp-binding protein alpha subunits, g12-g13)
Also found in: Encyclopedia.
A cellular protein activated by the binding of an intercellular signal to its receptor on the cell membrane; the G-protein then activates the enzyme adenyl cyclase within the cell, triggering the formation of cyclic AMP and a stereotyped response.
See also: protein
a regulatory protein which becomes activated when bound to GTP and is involved in signal transduction.
G protein coupled receptor
a member of a large class of cell-surface signaling receptors that contain seven transmembrane a helices; ligand binding results in activation of a coupled trimeric G protein that then initiates intracellular signal transduction pathways.