BETA-ADRENERGIC-RECEPTOR OF TURKEY ERYTHROCYTE-MEMBRANES - CONFORMATIONAL MODIFICATION BY BETA-ADRENERGIC AGONISTS

The β-adrenergic receptors of turkey erythrocyte membranes have been identified by the specific binding of the radiolabeled antagonist (-)-|3H|-dihydroalprenolol. Pretreatment of these membranes with either the alkylating agent N-ethylmaleimide or with β-adrenergic agonists does not affect (-)-|3H|-dihydroalprenolol binding to the receptor sites. However, the simultaneous presence of both types of products causes a 50% decline in the number of binding sites. A less pronounced decline occurs when the membranes are pretreated with N-ethylmaleimide in presence of the partial agonist (-)-phenylephrine, and no decline in the presence of the antagonist (-)-|3H|-dihydroalprenolol. β-adrenergic agonists thus appear to induce a conformational change of their receptor, with results in an increased susceptibility to inactivation by N-ethylmaleimide. © 1979.