A monoclonal antibody to a membrane component that interacts with the beta-adrenergic receptor

A monoclonal antibody has been obtained using a combination of in vivo and in vitro immunization with a digitonin extract of purified plasma membranes from frog erythrocytes. This antibody was found to immunoprecipitate a fraction of solubilized beta-adrenergic receptor (labeled with 125I-iodohydroxybenzylpindolol) derived from frog erythrocytes and a few other sources. This immunoglobulin also significantly activated adenylate cyclase in isolated erythrocyte plasma membranes measured in the presence of GTP or GTP plus isoproterenol. Immunoprecipitation of labeled erythrocyte surface proteins and immunoblotting of the digitonin-extract of erythrocyte plasma membrane revealed that the antibody interacted with a protein with a Mr = 43,000 and pI = 6.2 32P-ADP-ribosylated alpha subunit of Ns (with Mr = 44,000) solubilized from frog erythrocyte membranes failed to be immunoprecipitated by the antibody. Thus the antigenic protein is distinct from the beta-adrenergic binding site and alpha subunit of Ns and therefore may be an unidentified component of the beta-adrenergic receptor-adenylate cyclase system. This monoclonal antibody may be a useful tool for future studies for topological and functional interactions between the beta-adrenergic receptor and other membrane components.