Casein kinase II subunit beta is a protein that in humans is encoded by the CSNK2Bgene.[5][6] It is a ubiquitous protein kinase which regulates metabolic pathways, signal transduction, transcription, translation, and replication. The enzyme localizes to the endoplasmic reticulum and the Golgi apparatus.[7]
Casein kinase, a ubiquitous, well-conserved protein kinase involved in cellmetabolism and differentiation, is characterised by its preference for Serine or Threonine in acidic stretches of amino acids. The enzyme is a tetramer of 2 alpha- and 2 beta-subunits.[8][9] However, some species (e.g., mammals) possess 2 related forms of the alpha-subunit (alpha and alpha'), while others (e.g., fungi) possess 2 related beta-subunits (beta and beta').[10] The alpha-subunit is the catalytic unit and contains regions characteristic of serine/threonine protein kinases. The beta-subunit is believed to be regulatory, possessing an N-terminal auto-phosphorylation site, an internal acidic domain, and a potential metal-binding motif.[10] The beta subunit is a highly conserved protein of about 25kDa that contains, in its central section, a cysteine-rich motif, CX(n)C, that could be involved in binding a metal such as zinc.[11] The mammalian beta-subunit genepromoter shares common features with those of other mammalian protein kinases and is closely related to the promoter of the regulatory subunit of cAMP-dependent protein kinase.[10]