ADP-ribosylation of Gs by cholera toxin is potentiated by agonist activation of beta-adrenergic receptors in the absence of GTP

摘要: Purified Gs is a substrate for ADP-ribosylation catalyzed by cholera toxin (CTx). In S49 cyc- membranes complemented with in vitro translated alpha, the beta-adrenergic agonist isoproterenol enhanced rate. This effect was maximal if all guanyl nucleotides were suppressed but blocked antagonist alprenolol. Enhancement partially diminished addition of GDP followed that isoproterenol. When added absence agonist, GTP analogues guanosine 5‘-O-(gamma-thiotriphosphate) and 5‘-(beta, gamma-imido)triphosphate potentiated CTx-catalyzed alpha consistent their activating factors. However, this lessened when same tested presence agonist. Taken altogether, these results indicate like Gt Gi, an optimal CTx coupled to agonist-activated receptor depleted nucleotide. Therefore, coupling subsequent departure turn out be common features underlying sensitivity GTP-binding proteins ADP-ribosylation.