Protein kinase associated with hnRNP from Hela cell nuclei. Partial purification and properties

The protein kinase previously described as an endogenous activity present in ribonucleoprotein particles containing heterogenous RNA from HeLa cells (Blanchard et al, Eur. J. Biochem (1977), 79, 11-131) has been partially purified by a combination of chromatography on DEAE cellulose, phosphocellulose and Sephacryl S-200. It is able to phosphorylate exogenous substrates, among which casein is the most efficient. Its enzymatic properties were found to be quite similar to those described for the endogenous activity. Its activity is independent of cyclic AMP as well as of the calcium-dependent regulator protein and is inhibited by hemin. Its native molecular weight is around 48,000 as determined by gel filtration.