JBC, Vol. 252, Issue 19, 6660-6665, Oct, 1977
Purification of rat liver nuclear protein kinase NII
W. Thornburg and T. J. Lindell
Rat liver nuclear protein kinase activity (NII), which is eluted from
DEAE-Sephadex columns, has been purified approximately 1500-fold from
solubilized nuclear protein. The method of purification involved
chromatography of protein eluted from DEAE-Sephadex successively on
phosvitin-Sepharose, mixed histone-Sepharose, and histone H2b-Sepharose
followed by gel filtration on Sephadex G-200. Resulting preparations are
homogeneous by polyacrylamide gel electrophoresis. The enzyme consists of
three polypeptides with molecular weights of 42,000 (alpha), 39,000
(alpha'), and 26,000 (beta) which are present in the ratio 1:1:2 indicating
that the enzyme has a minimum tetrameric subunit composition of
alphaalpha'beta2. The molecular weight and s20,w of the purified enzyme
were 123,000 and 7.0, respectively, as determined by sucrose density
gradient centrifugation in 0.4 M NaCl. The enzyme has maximal activity with
phosvitin as substrate and is not stimulated by 10(-5) to 10(-4) M cAMP or
cGMP using H2b as substrate.