Reconstitution of heterologous and chimeric casein kinase II with recombinant subunits from human and Drosophila: Identification of species-specific differences in the Β subunit

Casein kinase II is composed of two catalytic (a) and two regulatory (Β) subunits, the amino acid sequences of the α and Β subunits are highly conserved between species. To examine whether heterologous casein kinase II could be formed, recombinant α and Β subunits from human and Drosophila were reconstituted from inclusion bodies. Casein kinase II containing either human α and Drosophila Β or Drosophila α and human Β subunits exhibited enzymatic properties similar to those of the homologous holoenzymes with regard to specific activity, salt optima, and autophosphorylation. However, renaturation and reconstitution of casein kinase II was dependent on the type of Β subunits and the redox conditions, with the Drosophila Β subunits requiring more reduced conditions. Chimeric Β subunits prepared from human and Drosophila cDNA revealed that the N-terminal region was responsible for the requirement for the reduced redox state during renaturation. The N-terminal region also affected solubility and electrophoretic mobility of the Β subunit.