Hydrophobicity of residue351 of the G protein Gi1 alpha determines the extent of activation by the alpha 2A-adrenoceptor.

摘要: Cysteine351 is the site for pertussis toxin-catalyzed ADP-ribosylation in G protein Gi1 alpha. Alteration of this residue, or equivalent cysteine other Gi-family proteins, has been used to examine specific interactions between receptors and these proteins. However, no systematic analysis performed determine quantitative effect such alterations. To address we mutated cysteine351 alpha all possible amino acids. Each mutants was transiently coexpressed along with porcine 2A-adrenoceptor HEK 293/T cells. Following toxin treatment cells, membranes were prepared capacity agonist UK14304 stimulate binding [35S]GTP gamma S modified proteins measured. A spectrum function observed. The presence either a charged acid proline at position essentially attenuated regulation. wild-type did not result maximal stimulation by agonist. certain branched chain aliphatic acids bulky aromatic R groups acid351 resulted substantially greater than that achieved sequence. degree activation forms correlated strongly octanol/water partition coefficient residue351. Variation EC50 values agonist-induced mutant also coefficient. These results define central role hydrophobicity residue defining productive receptor-G interactions.