This proposal described experiments to test the hypothesis that the mechanism by which insulin increases cellular seryl/threonyl protein phosphorylation is mediated, in part, by the phosphorylation and activation of a distinct protamine kinase and by the phosphorylation and inactivation of protein phosphatase 2A mediate by the protamine kinase. Specifically, immunological and biochemical experiments are described (a) to demonstrate that the rat hepatocyte insulin-stimulated protamine kinase is related to a previously characterized protamine kinase from bovine kidney cytosol, (b) to provide direct evidence that insulin stimulates the activity of the protamine kinase via increased phosphorylation of this enzyme, and (c) to examine to regulation by insulin protein phosphatase 2A. Together, these studies will establish the molecular basis, intracellular relevance and function of insulin stimulation of the protamine kinase. The information derived from these studies is critical for an understanding of the metabolic function and regulation of insulin-stimulated phosphorylation.
