Synthetic peptides as probes for G protein function. Carboxyl-terminal G alpha s peptides mimic Gs and evoke high affinity agonist binding to beta-adrenergic receptors.

摘要: The molecular interfaces between Gs and the beta-adrenergic receptor were investigated using synthetic peptides corresponding to various regions of its alpha subunit, s. These experiments carried out on saponin-permeable C6 glioma cells in which appears tightly coupled Gs. Synthetic site-specific from s (corresponding amino acids 15-29, 354-372, 384-394) i (8-22, 315-324, 345-455) tested for their ability interfere with coupling two carboxyl-terminal blocked stimulation adenylyl cyclase permeable cells. However, only s-354-372 had this effect membranes. It is suggested that partial uncoupling Gs, occurs subsequent cell disruption, may be related a change interaction carboxyl terminus beta-adrenoreceptor. Two peptides, 354-372 384-394, could also mimic increase agonist affinity receptor. In combination, s-384-394 increased isoproterenol compete 125I-pindolol binding partially additive manner. amino-terminal no beta-agonist binding, suggesting high specificity peptide effects. findings suggest these bind directly stabilize conformation. First, GTP hydrolysis-resistant analogs did not alter presence concentrations peptides. Second, S49 lymphoma cyc- cells, lack evoked state beta-receptor. Neither an antagonist affinity, as measured by propranolol displacement 125I-pindolol. data at least subunit participate fact small holo-Gs rather surprising, suggests primary secondary structure contain much information specific receptors.