AN INSULIN-RECEPTOR PEPTIDE (1135-1156) STIMULATES GUANOSINE 5'-[GAMMA-THIO]TRIPHOSPHATE BINDING TO THE 67-KDA G-PROTEIN ASSOCIATED WITH THE INSULIN-RECEPTOR

Peptides representing two putative G-protein-binding motifs (GPBP1 and GPBP2) derived from insulin-receptor sequences were tested for their ability to stimulate guanosine 5'-[gamma-thio]-triphosphate (GTP[S]; ' GTPgammaS') binding to a preparation containing the 41 and 67 kDa G-pr oteins that are associated with the insulin receptor [Jo, Cha, Davis a nd McDonald (1992) Endocrinology (Baltimore) 131, 2855-2861]. GPBP2 (r esidues 1135-1156) specifically stimulated GTP[S] binding, whereas GPB P1 (1319-1333) did not. Substitution of Arg-1152 with Gln in GPBP2 cor responding to a mutation site in insulin-resistant patients [Cocozza, Porcellini, Riccardi, Monticelli, Condorelli, Ferrera, Pianese, Miele, Capaldo, Beguinot and Varrone (1992) Diabetes 41, 521-526] attenuated the stimulatory potency of GPBP2. Size-exclusion chromatography and s tudies with purified 67 kDa G-protein revealed that GPBP2 stimulated G TP[S] binding only to the 67 kDa G-protein. These studies provide evid ence for a potential regulatory site for G-protein interaction with th e insulin receptor in the tyrosine kinase domain.