The Search for Homologous Proteins Related to the Process of Calcification in Bone and Shell

Abstract

A possibility that homologous proteins in bone and nacre have the common function to form skeletons of vertebrate and mollusc has been suggested in recent years. In this study, acidic proteins, which are characteristically rich in aspartic acid and glycine residues, were efficiently extracted and isolated from shells by decalcification using acetic acid. To search for new proteins in bone, we applied to bovine femoral cortical bone the same methods as those for shells, such as acetic acid decalcification and ion-exchange chromatography under the acidic condition. Amino acid composition of acetate-soluble protein was almost similar to that of collagen, a major component of bone matrix. Amino acid sequencing analysis of fractions adsorbed on an ion-exchange column demonstrated that a trace of acidic proteins rich in glutamic acid residue might emerge from an excess amount of collagen. It is expected that such new proteins with high affinity for collagen are involved in the process of tissue calcification of bone.