Calmodulin and acidic compounds alter basic protein phosphorylation by the protein kinase from human platelets.
A cyclic nucleotide-independent protein kinase of human platelets, which phosphorylated histones, myelin basic protein and protamine and did not catalyze the phosphorylation of acidic proteins such as casein, phosvitin and myosin light chain, has been purified approx. 1,500-fold from the crude extract by steps of DEAE-cellulose, Sephadex G-200, hydroxylapatite and phosphoryl cellulose column chromatography. The substrate phosphorylation by this kinase was markedly enhanced by calmodulin even in the absence of Ca2+, when mixed histone was used as a substrate. The interaction of the kinase with mixed histone resulted in an irreversible inactivation of the enzyme. Calmodulin prevented this inactivation, and this compound produced an apparent increase in histone phosphorylation by the kinase. It should be noted that acidic polypeptides such as troponin-C, phospholipids and nucleic acids have a similar ability. The addition of Ca2+ reduced the effect of calmodulin more than the effects of other acidic compounds.
D001792:Blood Platelets / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009696:Nucleic Acids / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood* / Q000302:isolation & purification; D011506:Proteins / Q000378:metabolism*; D013379:Substrate Specificity
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D006657:Histones; D009696:Nucleic Acids; D010455:Peptides; D010743:Phospholipids; D011506:Proteins; D011494:Protein Kinases; D002118:Calcium