A β-Adrenergic Receptor of the Turkey Erythrocyte: I. BINDING OF CATECHOLAMINE AND RELATIONSHIP TO ADENYLATE CYCLASE ACTIVITY

Abstract

Abstract The interaction of catecholamines with the β-adrenergic receptor and activation of adenylate cyclase were studied with plasma membranes prepared from turkey erythrocytes. The apparent affinity of isoproterenol, determined by measuring [3H]isoproterenol, for receptor was virtually identical with the apparent Km for activation of adenylate cyclase by isoproterenol. Binding of catecholamine to receptor was necessary but not sufficient for activation of adenylate cyclase. The dihydroxyphenyl function of the catecholamine molecule was required for binding as well as for activation of adenylate cyclase. The secondary alcohol function at the β-carbon, stereoconfiguration at the β-carbon, and an amine function, primary or secondary, at the α-carbon were functions essential for adenylate cyclase activation but not for specific binding at the catechol site. Those compounds that bound but did not stimulate adenylate cyclase were effective inhibitors of isoproterenol-stimulated adenylate cyclase activity. Propranolol, a β-adrenergic blocker, was a potent inhibitor of adenylate cyclase activity but a weak inhibitor of binding. It was concluded that in addition to catechol-specific binding, a further interaction between plasma membrane and hormone is necessary for activation of adenylate cyclase. This further interaction appears to involve a site specific for the ethanolamine portion of the catecholamine molecule.