A SURFACE-PLASMON-RESONANCE ANALYSIS OF POLYLYSINE INTERACTIONS WITH A PEPTIDE SUBSTRATE OF PROTEIN-KINASE CK2 AND WITH THE ENZYME

The mechanism of protein kinase CK2 (CK2) activity stimulation by poly lysine has been studied by surface plasmon resonance (SPR). The kineti cs of the polylysine interaction with a peptide substrate of the enzym e, and with the enzyme itself, have been investigated. A peptide conta ining a threonine (T) residue surrounded by a cluster of negatively ch arged acidic [arginine (R) and glutamic acid(E)] residues, RRREEETEEE, and specifically phosphorylated by CK2, was selected. Polylysine inte racts with both the enzyme and the peptide substrate. The rate constan t, the stoichiometry of the polylysine-peptide substrate interaction a nd the kinetic parameters of the stimulated enzyme were used to calcul ate the polylysine-dependent stimulation of CK2. The results are in ag reement with experimentally determined polylysine-dependent stimulatio n. The polylysine-enzyme interaction is too slow to account for enzyme stimulation. The behaviour of polylysine is not reproduced by the pol yamine spermine. The results are consistent with a substrate-mediated mechanism of CK2 stimulation by polylysine, and they suggest that the CK2 stimulation by polyamines occurs by a different mechanism.