Mechanism of Ca2+ and Phospholipid-Independent Protein Phosphorylation by Protein Kinase C: Protamines and Related Peptides as Substrates and Inhibitors
Ca2+ , phospholipid-dependent protein kinase (PKC) was first described as a proteolytically activated protein kinase (1). Only later its reversible activation was demonstrated to be synergistically induced by membrane acidic phospholipids in the presence of diacylglycerol (DAG) and physiological concentration of calcium (2, 3), thus implicating PCK as a mediator of the effects of a wide variety of inositol phospholipid turnover agonists (4, 5). A pivotal role for this enzyme in cell growth was further suggested by the discovery that PKC represents the major cellular receptor for tumor-promoting phorbol esters (6, 9) that can substitute for DAG as activators of the enzyme.
KeywordsProtein Kinase Phorbol Ester Aminoacid Sequence Myelin Basic Protein Peptide Synthetic Peptide Substrate
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