ZN2+ BINDING TO CARDIAC CALSEQUESTRIN

Zn2+ binding to canine cardiac calsequestrin was investigated using th e Zn2+ specific fluorescence dye salicylcarbohydrazone (SACH), Zn-65(2 +) overlay and Zn2+-IDA chromatography. Cardiac calsequestrin binds si milar to 200 moles of Zn2+/mole of protein with the K-d=300 mu M. Zn2 binding to calsequestrin was further confirmed by Zn-65(2+) overlay a nd Zn2+-dependent aggregation of the protein. However, calsequestrin d id not bind to a Zn2+-IDA-agarose column, indicating that histidine re sidues may not be involved in Zn2+ binding to the protein. Circular di chroism revealed only minor Zn2+-dependent conformational changes in c alsequestrin. We conclude that calsequestrin is a Ca2+- and Zn2+-bindi ng protein and that Zn2+ may modulate the structure and function of th e protein. (C) 1995 Academic Press, Inc.