1995 Fiscal Year Final Research Report Summary
IDENTIFICATION OF HYDROXYAPATITE-BINDING SITES OF HYDROXYAPATITE-BINDING PROTEINS IN MINERALIZED TISSUES
| Project/Area Number |
06671845
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Functional basic dentistry
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
FUJISAWA Ryuichi HOKKAIDO UNIV., FAC.OF DENTISTRY,INSTRUCTER, 歯学部, 助手 (40190029)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Calcification / Hydroxyapatite / Osteonectin / Phosphoprotein / Peptide synthesis |
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| Research Abstract |
1. Identification of hydroxyapatite-binding sites using proteolytic analysis
We examined hydroxyapatite-binding sites by proteolytic digestion of proteins adsorbed on hydroxyapatite crystals. Proteins examined were phosphophoryn, a unique phosphoprotein of dentin, and osteonectin, an acidic glycoprotein of bone. Phosphophoryn in solution was resistant to proteinases because of its high level of phophorylation. Phosphophoryn adsorbed on the crystals was attacked by the proteinases, indicating an extended structure of this protein on surface of the crystal. We digested osteonectin adsorbed on the crystal with a proteinase, and found that a ftagment was left adsorbed on the crystal even after the digestion. The peptide contained domains I and II of osteonectin. The hydroxyapatite-binding sites may be localized within these domains.
2. Synthesis of peptides having affinity to hydroxyapatite
There is a Glu-rich wequence in the domains I and II of osteonectin. Consecutive sequences of Glu or Asp are present in other hydroxyapatite-binding proteins of bone and dentin. We synthesized Glu_6 and Asp_6 peptides as models of these sequences, and examined their affinity to hydroxyapatite. The peptides were bound to the crystals with an association constant of 10^6M^<-1>. We conclude that these consecutive sequences of acidic amino acids constitute the hydroxyapatite-binding sites.
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