| Guanine nucleotide-binding proteins (G proteins) form a large family of signal-transducing molecules. They are found as heterotrimers made up of alpha, beta, and gamma subunits. Members of the G protein family have been characterized most extensively on the basis of the alpha subunit, which binds guanine nucleotide, is capable of hydrolyzing GTP, and interacts with specific receptor and effector molecules. The G protein family includes Gs and Gi, the stimulatory and inhibitory GTP-binding regulators of adenylate cyclase; Go, a protein abundant in brain (GNAO1); and transducin-1 (GNAT1) and transducin-2 (GNAT2), proteins involved in phototransduction in retinal rods and cones, respectively ; Bray et al., 1987 . Suki et al. concluded that the human genome contains at least 3 nonallelic genes for alpha-i-type subunits of G protein; see, e.g, GNAI2, GNAI3, and GNAIH. |
