ACTIVATION OF PKN, A NOVEL 120-KDA PROTEIN-KINASE WITH LEUCINE ZIPPER-LIKE SEQUENCES, BY UNSATURATED FATTY-ACIDS AND BY LIMITED PROTEOLYSIS

PKN, a novel protein kinase with catalytic domain homologous to PKC fa mily and unique amino terminal leucine zipper-like sequences,was purif ied partially from COS7 cells transfected with the cDNA construct enco ding human PKN for enzymatic characterization of the enzyme. Using ser ine containing synthetic peptides based on PKC pseudosubstrate sites a s the phosphate acceptors, kinase activities estimated from partially purified PKN were not stimulated by Ca2+/phosphatidylserine/diolein bu t were activated several-fold to several tens-fold by 40 mu M unsatura ted fatty acids, such as arachidonic acid, linoleic acid, and oleic ac id. Autophosphorylation of the immunoprecipitates using anti-PKN antis erum was also stimulated by various unsaturated fatty acids. Limited p roteolysis of PKN with trypsin induced an enhancement of the peptide k inase activity that was almost independent of arachidonic acid. (C) 19 94 Academic Press, Inc.