COMPARISON OF CALREGULINS FROM VERTEBRATE LIVERS

Calregulins were purified from bovine, rabbit and chicken liver, and their structural properties were compared. Significant differences between the three calregulins include a lower Mr for chicken calregulin (57000) than for rabbit and bovine calregulin (63000), and the glycosylation of only bovine calregulin. Amino acid compositon and peptide maps of the three calregulins were very similar. No major differences were detected in the Ca2+-binding properties of the three proteins. Zn2+-induced changes in calregulin conformation and hydrophobicity monitored by intrinsic protein fluorescence and the hydrophobic fluorescent probe 8-anilino-1-naphthelenesulphonate were very similar, suggesting that the Zn2+-dependent increase in the hydrophobicity of bovine, rabbit and chicken calregulin was conserved. These studies more fully define what is a calregulin, demonstrate that calregulin is a relatively invariant constituent of vertebrate liver, and indicate that calregulin structure has been highly conserved in bovine, chicken and rabbit liver.