title: Dictyostelium myosin II heavy-chain kinase A is activated by heparin, DNA and acidic phospholipids and inhibited by polylysine, polyarginine and histones.
abstract: Dictyostelium myosin II heavy-chain kinase A (MHCK A) is activated by autophosphorylation. Heparin and DNA, as well as vesicles composed of phosphatidylserine or phosphatidylinositol, were found to increase the initial rate of MHCK A autophosphorylation 5-10-fold in a Ca(2+)-independent manner. The negatively charged molecules also increased the activity of the autophosphorylated MHCK A by about 2-fold. In contrast, positively charged polypeptides such as poly(D-lysine), poly(L-lysine), poly(L-arginine) and histones strongly inhibited (IC50 of 0.5 micrograms/ml) the activity of the active, autophosphorylated MHCK A. Similar levels of inhibition, on a weight basis, were observed for poly(L-lysine) fractions with molecular weights from 3800 to 150,000-300,000. The inhibition was competitive with respect to peptide substrate and mixed with respect to ATP. At much higher concentrations poly(L-lysine) also inhibited the ability of MHCK A to autophosphorylate. It is proposed that negatively charged compounds and autophosphorylation increase the activity of MHCK A by weakening the interaction between the catalytic domain and a positively charged autoinhibitory domain.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ontario, Canada.
authors.forename: Q G
authors.initials: QG
authors.lastname: Medley
authors.forename: W L
authors.initials: WL
authors.lastname: Bagshaw
authors.forename: T
authors.initials: T
authors.lastname: Truong
authors.forename: G P
authors.initials: GP
authors.lastname: Côté
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004247:DNA / Q000494:pharmacology*; D004023:Dictyostelium / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D006493:Heparin / Q000494:pharmacology*; D006657:Histones / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011107:Polylysine / Q000494:pharmacology*; D015800:Protozoan Proteins
chemical_list: D006657:Histones; D010455:Peptides; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; D010743:Phospholipids; D015800:Protozoan Proteins; D011107:Polylysine; C015462:polyarginine; D006493:Heparin; D004247:DNA; D010770:Phosphotransferases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C033142:myosin-heavy-chain kinase