In vitro phosphorylation of proteins tightly bound to DNA by protein kinase NII

1. 1. Highly purified DNA from calf thymus was phosphorylated with protein kinase NII. 2. 2. Digestion with proteinase K of this DNA demonstrates proteins as phosphorylated component. 3. 3. Gel filtration chromatography on Bio-Gel A-0.5m gel column shows a major protein peak between 50 and 70 kDa. 4. 4. SDS gel electrophoresis, after hydrolysis, to digest completely DNA, shows three major phosphorylated bands corresponding to polypeptides of Mr between 31 and 21 kDa. 5. 5. After high voltage electrophoresis on TLC plates tryptic digested polypeptides show very similar phosphopeptides patterns.