| Type: | Domain | Name: | Casein kinase II, regulatory subunit, alpha-helical |
| Description: | Protein phosphorylation, which plays a key role in most cellular activities, is a reversible process mediated by protein kinases and phosphoprotein phosphatases. Protein kinases catalyse the transfer of the gamma phosphate from nucleotide triphosphates (often ATP) to one or more amino acid residues in a protein substrate side chain, resulting in a conformational change affecting protein function. Phosphoprotein phosphatases catalyse the reverse process. Protein kinases fall into three broad classes, characterised with respect to substrate specificity []:Serine/threonine-protein kinasesTyrosine-protein kinasesDual specificity protein kinases (e.g. MEK - phosphorylates both Thr and Tyr on target proteins)Protein kinase function is evolutionarily conserved from Escherichia coli to human []. Protein kinases play a role in a multitude of cellular processes, including division, proliferation, apoptosis, and differentiation []. Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins. The catalytic subunits of protein kinases are highly conserved, and several structures have been solved [], leading to large screens to develop kinase-specific inhibitors for the treatments of a number of diseases [].Casein kinase, a ubiquitous, well-conserved protein kinase involved in cell metabolism and differentiation, is characterised by its preference for Ser or Thr in acidic stretches of amino acids. The enzyme is a tetramer of 2 alpha- and 2 beta-subunits [, ]. 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') []. 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 []. 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 []. The mammalian beta-subunit gene promoter 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 [].This entry represents the N-terminal alpha-helical domain, which has an orthogonal bundle topology. | Short Name: | Casein_kin_II_reg-sub_a-hlx |
