PHOSPHORYLATION OF ACTIVE, A-1 COMPONENT OF CHOLERA TOXIN BY PROTEIN-KINASE

Cholera toxin, an activator of adenylate cyclase in a wide variety of cells, is a substrate for the phosphotransferase reaction catalyzed by purified cyclic AMP-dependent bovine cardiac muscle protein kinase and the protein kinase associated with human erythrocyte membranes. Phosphorylation occurs when the toxin is dissociated with 5-20 mM dithiothreitol and is restricted to the A1 of adenylate cyclase activating subunit of the toxin.