Mammalian beta-adrenoceptors: concomitant biospecific elution with protein kinase activity from Sepharose-alprenolol

The mammalian beta-adrenoceptors were solubilized from crude guinea pig lung membranes with the plant glycoside digitonin. The solubilized receptors were absorbed by affinity gels with (+/-)alprenolol as ligand and could be eluted biospecifically in good yield with either agonists or antagonists. A more than 100-fold purification can be achieved in a one-step procedure. Antagonist-eluted beta-adrenoceptors have affinities for antagonists similar to those of particulate or solubilized receptors. Their binding constants for agonists, however, are comparable to those of the particulate receptor. A cAMP-independent protein kinase activity was eluting concomitantly with the beta-adrenoceptors. The protein kinase phosphorylated endogenous substrates with 50 000 and greater than 150 000 subunit molecular weight.