Inhibits signal transduction by increasing the GTPase activity of G protein alpha subunits thereby driving them into their inactive GDP-bound form. Binds to G-alpha subfamily 1 members, predominantly to G(i)-alpha-3. Activity on G(z)-alpha is inhibited by phosphorylation and palmitoylation of the G-protein (By similarity). Interacts with GIPC PDZ domain. Fatty acylated. Heavily palmitoylated in the cysteine string motif (By similarity). Phosphorylated, mainly on serine residues.