Casein kinase II phosphorylation site

Casein kinase II (CK-2) is a protein serine/threonine kinase whose activity is independent of cyclic nucleotides and calcium. CK-2 phosphorylates many different proteins. The substrate specificity [1] of this enzyme can be summarized as follows:

(1) Under comparable conditions Ser is favored over Thr.
(2) An acidic residue (either Asp or Glu) must be present three residues from
the C-terminal of the phosphate acceptor site.
(3) Additional acidic residues in positions +1, +2, +4, and +5 increase the
phosphorylation rate. Most physiological substrates have at least one
acidic residue in these positions.
(4) Asp is preferred to Glu as the provider of acidic determinants.
(5) A basic residue at the N-terminal of the acceptor site decreases the
phosphorylation rate, while an acidic one will increase it.

-Consensus pattern: [ST]-x(2)-[DE]
                              [S or T is the phosphorylation site]

-Note: this pattern is found in most of the known physiological substrates.

-Last update: May 1991 / Text revised.

[ 1] Pinna L.A. Biochim. Biophys. Acta 1054:267-284(1990).
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