The beta-adrenergic receptor binding subunits from frog erythrocytes, hamster lung and guinea pig lung have been purified to apparent homogeneity and in all cases reside on a single polypeptide. Insertion of the pure receptors into phospholipid vesicles and subsequent fusion of these vesicles with a receptor-deficient cell conveys beta-adrenergic responsiveness to the adenylate cyclase system of the acceptor cell. Such responsiveness is linearly dependent on the amount of receptor used in the fusion experiments and is independent of the receptor source. Moreover, this responsiveness displays appropriate beta-adrenergic specificity. These results indicate that the beta-adrenergic receptor polypeptide contains both the ligand binding site and the site responsible for mediating stimulation of adenylate cyclase activity, presumably via interaction with the guanine nucleotide regulatory protein.