Human liver calreticulin: characterization and Zn(2+)-dependent interaction with phenyl-sepharose

A 60-kDa human calreticulin was isolated from liver homogenates. The protein was identified as calreticulin by its NH2-terminal amino acid sequence, by its mobility in SDS-PAGE, by its immunoreactivity with anti-calreticulin antibodies, by its Ca2+ binding, and by its localization to isolated ER membranes. In this study we show that Ca2+ binding to calreticulin results in Ca(2+)-dependent aggregation and precipitation of the protein. We also show that calreticulin and calsequestrin bind Zn2+ in 65Zn2+ overlay. In addition we have discovered that calreticulin exhibits a Zn(2+)-dependent interaction with hydrophobic matrix of phenyl-Sepharose that can be utilized in the purification of the protein.