Tentative identification of β-adrenoreceptor subunits

MANY hormones and neurotransmitters interact with specific receptors which are coupled to the enzyme adenylate cyclase^1-4. Sutherland et al. were the first to suggest that the receptor constitutes the regulatory subunit possessing the allosteric effector site of the adenylate cyclase enzyme. Recently, two lines of experimental evidence have supported the postulate that the β-adrenoreceptor and the membrane bound enzyme adenylate cyclase are situated on separate macromolecules. Lefkowitz et al.^5,6 succeeded in separating the β-adrenoreceptor from the adenylate cyclase by molecular sieve chromatography of digitonin solubilised from erythrocyte membranes. Schramm et al.^7,8 have shown that the β-adrenoreceptor can be transferred from turkey erythrocyte cells and become coupled to adenylate cyclase of Friend erythroleukaemic cells by virus induced cell fusion. Using a tritium-labelled affinity label for the β-adrenoreceptor^9-11, we report here the tentative identification of the β-adrenoreceptor subunits from rat skeletal myoblasts grown in culture (L6P cells) and from turkey erythrocytes.