Isolation and partial characterization of crystal matrix protein as a potent inhibitor of calcium oxalate crystal aggregation: evidence of activation peptide of human prothrombin.

In order to clarify the characteristics of crystal matrix protein (CMP), which exhibits a remarkable affinity for calcium oxalate crystals and may be important in stone pathogenesis, we have isolated CMP from macromolecular matrix substances of newly-formed calcium oxalate crystals. Purification of CMP consisted of calcium oxalate crystal formation, dissolution of crystals, electrodialysis, anion exchange chromatography and high-performance liquid chromatography. CMP showed the protein band of 31 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequence of CMP was identical to that of human prothrombin. Both anti-CMP polyclonal antibody and anti-human prothrombin antibody cross-reacted well with human prothrombin and CMP in Western blotting. Its amino acid composition and its molecular weight of 31 kDa strongly suggest that CMP is the activation peptide of human prothrombin.