title: A sulfhydryl group of the canine cardiac beta-adrenergic receptor observed in the absence of hormone.
abstract: Canine cardiac beta-adrenergic receptors contain a free sulfhydryl group in the adrenergic ligand binding site. [125 I]-Iodohydroxybenzylpindolol [( 125 I]-IHYP) binding to cardiac beta-receptors was inhibited 80% by treatment with 1 mM p-chloromercuribenzoic acid (pCMB). Occupation of the beta-receptors by an antagonist prior to treatment with pCMB prevented this effect suggesting that a sulfhydryl group is present in or near the ligand binding site of the cardiac beta-receptor. In the presence of agonists, the sensitivity of cardiac beta-receptors to pCMB was increased. Incubation of isoproterenol-occupied cardiac beta-receptors, resulted in a 57% inhibition of [125 I]-IHYP binding measured after extensive washing to remove bound agonist. The ability of isoproterenol to increase the reactivity of cardiac beta-adrenergic receptors supports the hypothesis that agonists produce a conformational change upon binding.
authors.forename: W L
authors.initials: WL
authors.lastname: Strauss
authors.forename: J C
authors.initials: JC
authors.lastname: Venter
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002729:Chloromercuribenzoates / Q000494:pharmacology; D004285:Dogs; D007545:Isoproterenol / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D020245:p-Chloromercuribenzoic Acid
chemical_list: D000318:Adrenergic beta-Agonists; D002729:Chloromercuribenzoates; D011943:Receptors, Adrenergic, beta; D013438:Sulfhydryl Compounds; C011878:iodohydroxybenzylpindolol; D020245:p-Chloromercuribenzoic Acid; D011433:Propranolol; D010869:Pindolol; D007545:Isoproterenol