Identification of a major bovine heart Ca2+ binding protein

The 100,000 x g supernatant of bovine heart has been chromatographed on DEAE-cellulose and the resultant fractions have been analyzed for both calcium binding activity and calmodulin activity. Of the four peaks of calcium binding activity detected by this procedure only a single peak (peak IV) was identified as calmodulin. The calcium binding activity of the largest peak (peak III) has been subjected to further purification and a single calcium binding protein of Mr 63,000 isolated. Biochemical and immunological results documented that the 63 kDa protein is identical to calregulin. The results of this study identify calregulin as a major bovine heart calcium binding protein.