Properties of a microtubule-associated cofactor-independent protein kinase from pig brain.
A protein kinase activity was identified in pig brain that co-purified with microtubules through repeated cycles of temperature-dependent assembly and disassembly. The microtubule-associated protein kinase (MTAK) phosphorylated histone H1; this activity was not stimulated by cyclic nucleotides. Ca2+ plus calmodulin, phospholipids or polyamines. MTAK did not phosphorylate synthetic peptides which are substrates for cyclic AMP-dependent protein kinase, cyclic GMP-dependent protein kinase. Ca2+/calmodulin-dependent protein kinase II, protein kinase C or casein kinase II. MTAK activity was inhibited by trifluoperazine [IC50 (median inhibitory concn.) = 600 microM] in a Ca2+-independent fashion. Ca2+ alone was inhibitory [IC50 = 4 mM). MTAK was not inhibited by heparin, a potent inhibitor of casein kinase II, nor a synthetic peptide inhibitor of cyclic AMP-dependent protein kinase. MTAK demonstrated a broad pH maximum (7.5-8.5) and an apparent Km for ATP of 45 microM. Mg2+ was required for enzyme activity and could not be replaced by Mn2+. MTAK phosphorylated serine and threonine residues on histone H1. MTAK is a unique cofactor-independent protein kinase that binds to microtubule structures.
Scott
C W
CW
Department of Pharmacology, ICI Americas, Wilmington, DE 19897.
Caputo
C B
CB
Salama
A I
AI
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002122:Calcium Chloride / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002413:Cations, Divalent; D004591:Electrophoresis, Polyacrylamide Gel; D006657:Histones / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008870:Microtubules / Q000201:enzymology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D013552:Swine; D014268:Trifluoperazine / Q000494:pharmacology
D000596:Amino Acids; D002413:Cations, Divalent; D006657:Histones; D047428:Protein Kinase Inhibitors; D014268:Trifluoperazine; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002122:Calcium Chloride