Open AccessPreferential Phosphorylation of Basic Non‐histone Proteins by Nuclear Protein Kinase NII from Rat Liver
Author(s) -
HASUMA Tadayoshi,
YUKIOKA Munehiko,
NAKAJIMA Satoshi,
MORISAWA Seiji,
INOUE Akira
Publication year - 1980
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1980.tb04801.x
Subject(s) - histone , casein kinase 2 , biochemistry , protein kinase a , microbiology and biotechnology , biology , phosphorylation , nuclear protein , mitogen activated protein kinase kinase , dna , gene , transcription factor
Rat liver nuclear protein kinase NII, Which is independent of cyclic nucleotides, phosphorylated both the acidic protein casein and the basic histone preparation, soluble in 0.25 M HCl, which was extracted from the cell nuclei. When the isolated nuclei were incubated with [ 32 P]ATP in the presence of protein kinase NII, more than 95% of the 32 P‐labelled proteins was recovered in the 0.25 M HCl extract. In order to analyze the substrate proteins of protein kinase NII, a histone preparation free from the endogenous protein kinase activities was used as substrate. The results demonstrated that histones were not phosphorylated, except for a faint 32 P incorporation into the H3 fraction. Instead, multiple non‐histone proteins were highly phosphorylated, which were present in a minor quantity in the histone preparation. The molecular weights of the main phosphorylated proteins were 72000, 68000, 56000, 47000, 46000, 43000, 38000 and 32000. Isoelectric focusing demonstrated the basic nature of the phosphorylated proteins, and as much as 72% of 32 P radioactivity was distributed in the pH region higher than 7.0. Furthermore, many proteins phosphorylated in the isolated nuclei with added protein kinase NII were also found to be basic non‐histone proteins. These results indicate that protein kinase NII preferentially phosphorylates in vitro a set of nuclear basic non‐histone proteins.