Main Entry: G protein

Function: noun

Etymology: guanosine triphosphate-binding protein

Date: 1967

: any of a class of cell membrane proteins that are coupled to cell surface receptors and upon stimulation of the receptor by an extracellular signaling molecule (as a hormone or neurotransmitter) bind to GTP to form an active complex which mediates an intracellular event (as activation of adenylate cyclase)