Monoclonal antibody to phospholamban isolated from bovine cardiac muscle

Phospholamban, a putative protein regulator of the Ca2(+)-dependent ATPase in cardiac sarcoplasmic reticulum, was isolated from bovine cardiac microsomes using a low concentration of the detergent. The phospholamban was phosphorylated by cyclic AMP-dependent protein kinase to a level of 7.55 nmol of phosphate per mg of protein. This molecular weight was found to be 20,000 dalton based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Monoclonal antibody against the bovine phospholamban was made by the hybridoma technique. The specificity of the monoclonal antibody was determined by immunoblotting experiments and the antibody was shown capable of blocking the phosphorylation of phospholamban by cyclic AMP-dependent protein kinase. The immunoglobulin subclass of the antibody was identified as IgG1. The distribution of phospholamban in muscular tissues was observed by the immunohistological method and the results showed that myocardial cells were strongly and specifically stained, while skeletal and smooth muscle cells were stained at the background level. The results showed the phospholamban in the ventricular muscle to be localized along the cellular surface and in a network over the myofilaments. The monoclonal antibody identified a reactive component in the myocardial cells of monkey, canine, mouse and man.