The effect of reducing agents on the structure of mammalian beta-adrenergic receptors

Under reducing conditions (5% beta-mercaptoethanol) the mammalian beta-adrenergic receptor binding site from both beta 1 (porcine heart membranes) and beta 2 receptors (hamster lung and rat erythrocyte membranes) appears to reside on peptides of Mr 62,000-65,000 as determined by photoaffinity labeling with p-azido-m-[125I]iodobenzylcarazolol and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When similar experiments are performed in these same systems under a variety of non-reducing conditions, there are minimal changes in the apparent molecular weight of both the beta 1- and beta 2-adrenergic receptor binding subunits and no specifically labeled higher molecular weight proteins are observed suggesting that there are no disulfide linked subunits in mammalian beta-adrenergic receptors.