PROSITE documentation PDOC00845

Casein kinase II regulatory subunit signature

Casein kinase II (CK-2) [1] is an ubiquitous eukaryotic serine/threonine protein kinase which is found both in the cytoplasm and the nucleus and whose substrates are numerous. It generally phosphorylates Ser or Thr at the N-terminal of stretch of acidic residues (see <PDOC00006>). CK-2 exists as an heterotetramer composed of two catalytic subunits (α) and two regulatory subunits (β). In most species there are two closely related isoforms of the catalytic subunit: α and α'. Some species, such as fungi and plants, express two forms of regulatory subunits: β and β'. The β subunit plays a complex role in regulating the basal catalytic activity of the α subunit. The β subunit is a highly conserved protein of about 25 Kd that contains, in its central section, a cysteine-rich motif that could be involved in binding a metal such as zinc [2]. We have used this region as a signature pattern.