title: Inhibition of Acanthamoeba myosin I heavy chain kinase by Ca(2+)-calmodulin.
abstract: The actin-activated Mg(2+)-ATPase activity of Acanthamoeba myosins I depends on phosphorylation of their single heavy chains by myosin I heavy chain kinase. Kinase activity is enhanced > 50-fold by autophosphorylation at multiple sites. The rate of kinase autophosphorylation is increased approximately 20-fold by acidic phospholipids independent of the presence of Ca2+ and diglycerides. We show in this paper that Ca(2+)-calmodulin inhibits phospholipid-stimulated autophosphorylation of myosin I heavy chain kinase and hence also inhibits the catalytic activity of unphosphorylated kinase in the presence of phospholipid. Ca(2+)-calmodulin does not inhibit kinase activity in the absence of phospholipid. Micromolar Ca(2+)-calmodulin also inhibits binding of myosin I heavy chain kinase to phospholipid vesicles and purified plasma membranes. Proteolytic removal of a 7-kDa NH2-terminal segment from the 97-kDa kinase prevents binding of both calmodulin and phospholipid; therefore, we propose that they bind to the same or overlapping sites. These data provide a mechanism by which Ca2+ could inhibit the actin-activated Mg(2+)-ATPase activity of the myosin I isozymes in vivo and thus regulate myosin I-dependent motile activities.
authors.affiliation: Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: H
authors.initials: H
authors.lastname: Brzeska
authors.forename: D
authors.initials: D
authors.lastname: Kulesza-Lipka
authors.forename: E D
authors.initials: ED
authors.lastname: Korn
mesh_terms: D000048:Acanthamoeba / Q000201:enzymology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D008081:Liposomes; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation; D010770:Phosphotransferases / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D011485:Protein Binding; D015800:Protozoan Proteins
chemical_list: D002147:Calmodulin; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D015800:Protozoan Proteins; D004533:Egtazic Acid; D010770:Phosphotransferases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C033142:myosin-heavy-chain kinase; D002118:Calcium