The function of RGS20 (regulator of G protein signaling 20, ENSG00000147509) is as follows. Inhibits signal transduction by increasing the GTPase activity of G protein alpha subunits thereby driving them into their inactive GDP-bound form. Binds selectively to G(z)-alpha and G(alpha)- i2 subunits, accelerates their GTPase activity and regulates their signaling activities. The G(z)-alpha activity is inhibited by the phosphorylation and palmitoylation of the G protein. Negatively regulates mu-opioid receptor-mediated activation of the G proteins (By similarity). .