Oligomeric Casein Kinase II Isoforms Are Expressed in Bovine Tissues and Adrenocortical Cells in Culture

Abstract

Casein kinase II is a ubiquitous serine-threonine kinase made of two different (α and β) subunits, with an α2β2 stoichiometry, α bearing the catalytic site of the enzyme. Two different genes encode two different (α and α′) catalytic subunits. The present work shows that at least two forms of CKII (CKIIa and CKIIb) can be isolated from bovine tissues and adrenocortical cells in culture. The use of specific antibodies developed against the α and α′ subunits disclosed that while CKIIa contains both α and α′, the α subunit was highly prominent in CKIIb. This suggests that CKIIb may be an α2β2 oligomer whereas CKIIa may be an αα′β2 moiety or an αα′β2 and α2β2 mixture. Transition from quiescence to proliferation was concomitant with an average two fold increase in total cell CKII activity involving both CKIIa and CKIIb isoforms. The two isoforms were found in cytosolic and particulate adrenocortical subcellular preparations and they similarly increased their association to intracellular organelles in response to growth stimulatory conditions.