title: Characterization of a 67-kDa S6 protein kinase from rat liver.
abstract: Fractionation of rat liver cytosol on DEAE-cellulose resolved two S6 kinases eluting at 25 mM KCl (peak I) and 100 mM KCl (peak II). The apparent molecular weights of the peak I and peak II kinases are 26,300 and 67,000, respectively. The peak II kinase was further purified and characterized. Incubation of the kinase with [gamma-32P] ATP and Mg2+ resulted in the incorporation of 32P predominantly into a 67-kDa band. Optimal activity of the kinase was observed in the presence of 5 mM Mg2+ and in the pH range of 8.0-8.5. The Km for ATP and 40S subunit were 7.3 microM and 1.5 microM, respectively. The Mg(2+)-stimulated kinase activity was inhibited by various divalent metals, NaF, and polyamines. The properties of the peak II S6 kinase are very similar or identical to the previously described mitogen-activated S6 protein kinase and may represent the nonactivated form of this enzyme.
authors.affiliation: Department of Biology, University of Waterloo, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Howard
authors.forename: T J
authors.initials: TJ
authors.lastname: Singh
mesh_terms: D000818:Animals; D001665:Binding Sites; D002413:Cations, Divalent / Q000494:pharmacology; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D011494:Protein Kinases / Q000737:chemistry*; D051381:Rats; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D007527:Isoenzymes; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins; D011494:Protein Kinases; D008274:Magnesium