The beta-adrenergic stimulation of adenylyl cyclase is mediated through the stimulatory G-protein (Gs). In this study, three synthetic peptides corresponding to different regions (amino acids 3-14, 72-86 and 325-337) of the alpha subunit of Gs (Gs-alpha) have been employed in competition assays in order to examine more closely the molecular basis of receptor-Gs-alpha interaction. The direct coupling between Gs and adenylyl cyclase was not influenced by any of these peptides and only the peptide representing residues 325-337 of Gs-alpha specifically inhibited beta-adrenergic receptor-mediated activation of Gs. Essentially the same results were obtained when testing beta-1- and beta-2-adrenergic receptors, which supports the notion that both these pharmacologically distinct receptor subtypes exploit at least one identical coupling domain within Gs-alpha for its activation.

Institute of Sera and Vaccines Srobarova 48 Prague Czech Republic

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