title: Purification of rat liver nuclear protein kinase NI.
abstract: Rat liver nuclear protein kinase NI, which appears in the flowthrough of DEAE-Sephadex columns, has been purified approximately 15,000-fold from soluble nuclear protein with yields of up to 10%. The method of purification involved chromatography of the DEAE-flowthrough protein successively on phosvitin-Sepharose and casein-Sepharose followed by rechromatography on phosvitin-Sepharose. The purified enzyme has an s20,w and molecular weight of 3.7 and 47,000, respectively, as determined by sucrose density gradient centrifugation in 0.4 M NaCl. A similar molecular weight of 42,000 was determined by gel filtration using Sephadex G-100. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed a single polypeptide with a molecular weight of 25,000. Protein kinase NI therefore consists of a dimer of two identical subunits. Protein kinase NI exhibits maximal activity on casein substrate and is not stimulated by 10(-5) to 10(-4) M cAMP or cGMP when either casein or histone H2b is used as a substrate.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D002846:Chromatography, Affinity; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D008722:Methods; D011494:Protein Kinases / Q000302:isolation & purification*; D051381:Rats; D013379:Substrate Specificity
chemical_list: D000242:Cyclic AMP; D011494:Protein Kinases; D006152:Cyclic GMP