Binding of Polyamines to an Autonomous Domain of the Regulatory Subunit of Protein Kinase CK2 Induces a Conformational Change in the Holoenzyme

• Published in: The Journal of biological chemistry Vol. 272; no. 33; pp. 20820 - 20827
• Main Authors: Leroy, Didier, Heriché, Jean-Karim, Filhol, Odile, Chambaz, Edmond M., Cochet, Claude
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.08.1997; American Society for Biochemistry and Molecular Biology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.33.20820

The means by which the cell regulates protein kinase CK2 remain obscure. However, natural polyamines, cellular compounds required for cell proliferation, have been reported to strongly stimulate CK2-mediated phosphorylation of a number of substrates. Using spermine analogs, we have shown that polyamines directly interact with the CK2 β subunit, and the chemical features of the highly acidic binding site (Asp51-Tyr80) have been determined. In the present study, we show that the isolated β subunit region extending from residue Asp51 to Pro110 exhibits a specific and efficient polyamine binding activity similar to that of the entire β subunit. Moreover, the replacement of Glu60, Glu61, and Glu63 of the β subunit by 3 alanine residues leads to a loss of the spermine-induced stimulation of CK2 activity which correlates with a decrease in spermine binding affinity. Thermal stability studies indicate that the binding of spermine induces a 4 °C decrease of the Tm value for the holoenzyme. This was confirmed by circular dichroism analyses, which show that the 6 °C negative shift of the CK2Tm value provoked by spermine binding, reflects a conformational change in the kinase. Together, these observations strongly suggest that this newly defined polyamine-binding domain is involved in the intrasteric regulation of CK2 activity.