The Metal-binding Properties of DREAM

• Published in: The Journal of biological chemistry 2002-03, Vol.277 (13), p.10955-10966
• Main Authors: Craig, Theodore A., Benson, Linda M., Venyaminov, Sergei Yu, Klimtchuk, Elena S., Bajzer, Zeljko, Prendergast, Franklyn G., Naylor, Stephen, Kumar, Rajiv
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109660200

DREAM, an EF-hand protein, associates with and modulates the activity of presenilins and Kv4 potassium channels in neural and cardiac tissues and represses prodynorphin and c-fos gene expression by binding to DNA response elements in these genes. Information concerning the metal-binding properties of DREAM and the consequences of metal binding on protein structure are important in understanding how this protein functions in cells. We now show that DREAM binds 1 mol of calcium/mol of protein with relatively high affinity and another 3 mol of calcium with lower affinity. DREAM binds 1 mol of magnesium/mol of protein. DREAM, pre-loaded with 1 mol of calcium, binds 1 mol of magnesium, thus demonstrating that the magnesium-binding site is distinct from the high affinity calcium-binding site. Analysis of metal binding to mutant DREAM protein constructs localizes the high affinity calcium-binding site and the magnesium-binding site to EF-hands 3 or 4. Binding of calcium but not magnesium changes the conformation, stability, and α-helical content of DREAM. Calcium, but not magnesium, reduces the affinity of apo-DREAM for specific DNA response elements in the prodynorphin and c-fos genes. We conclude that DREAM binds calcium and magnesium and that calcium, but not magnesium, modulates DREAM structure and function.