Phosphorylation of cyclin-dependent kinase 2 peptides enhances metal binding

Abstract

The cyclin-dependent kinase CDK2 is inactivated by phosphorylation on either of the two neighbouring residues Thr14 or Tyr15. The effect of phosphorylation on metal ion binding has been investigated with peptides incorporating residues 6-20 of CDK2. The stoichiometry of Ca(2+) binding increased from 1 in the un- and singly-phosphorylated peptides to 2 in the doubly phosphorylated peptide, without large changes in the affinity (75-250 microM). In contrast although binding of ferric ions to the un-phosphorylated peptide was not detected, both singly- and doubly-phosphorylated peptides bound two Fe(3+) ions. Binding of Ca(2+) or Zn(2+) ions to the doubly phosphorylated CDK2 peptide did not caus..