Heterogeneity of protein kinase NII

Abstract

Protein kinase NII has a αα'β2 subunit structure, and consists of a chromatographically heterogeneous population. By two-dimensional polyacrylamide gel electrophoresis, each subunit was resolved into multiple polypeptides with various pI values: α subunit, 4 spots; α' subunit, 10 spots; and β subunit, 4 spots. NII underwent autophosphorylation on β subunits. Fractions of α and α' polypeptides also occurred as phosphoforms as shown by alkaline phosphatase treatment. In addition, α' subunit had another motif for heterogeneity, which separated α' polypeptides into two groups, and was exemplified by NIIa and NIIb that showed different enzyme kinetics and the nuclear localization. We interpret these results to account for the basis of the functional as well as molecular heterogeneities of protein kinase NII.Protein kinase NIIHeterogeneitySubunit polypeptide2D Polyacrylamide gel electrophoresisAlkaline phosphataseAutophosphorylatio