Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. The G(o) protein function is not clear. Stimulated by RGS14 (By similarity). Interacts with RGS14 (By similarity). G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site. Histaminylated at Gln-205 residues by TGM2. Belongs to the G-alpha family. G(i/o/t/z) subfamily.