THE AMINO-ACID-SEQUENCE OF EMU OSTEOCALCIN - GAS-PHASE SEQUENCING OF GLA-CONTAINING PROTEINS

Abstract

Osteocalcin (OC), the major gamma carboxyglutamic acid (Gla)-containing protein of vertebrate bone, has been isolated from bones of the emu (Dromaius novaehollandae) and the primary structure determined by a combination of gas phase N-terminal sequencing of the intact molecule and a proteolytic fragment, and carboxypeptidase Y C-terminal sequencing. Gla residues were located by counting tritium radioactivity in fractions from the N-terminal sequencing of the tritiated/thermally decarboxylated molecule. Emu OC consists of 48 amino acid residues containing 3 Gla residues, and a single disulphide bond. The C-terminal 29 residues are identical to those of the human and sheep OC sequences. Alignm..