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Characterization and identification of a human dentin phosphophoryn
S R Chang1, D Chiego, B H Clarkson
1Department of Cariology, Restorative Science, and Endodontics, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109, U.S.A.
Calcified Tissue International
|September 1, 1996
Summary
Researchers identified a human dentin phosphoprotein from immature tooth apices. This protein shares an N-terminal amino acid sequence with rat phosphoprotein, suggesting conserved functions in dentin formation.
Area of Science:
- Biochemistry
- Biomaterials Science
- Developmental Biology
Background:
- Dentin phosphoproteins are crucial for dentin mineralization.
- Previous studies have identified phosphoproteins in various species, but characterization in human immature teeth requires further investigation.
Purpose of the Study:
- To characterize an intact dentin phosphoprotein from immature human tooth apices.
- To determine its molecular weight, subunit composition, and amino acid sequence.
Main Methods:
- Immature human third molar apices were decalcified using EDTA.
- Proteins were separated using SDS-PAGE under reducing and non-reducing conditions.
- Purification involved precipitation with CaCl2 and MgCl2, followed by ion-exchange chromatography (DEAE-Sepharose CL6B).
- Amino acid composition and N-terminal sequencing were performed.
Main Results:
- Four distinct protein bands were identified on SDS-PAGE with molecular weights of 140, 60, 50, and 34 kDa.
- The lower molecular weight bands (60, 50, 34 kDa) were absent under non-reducing conditions, suggesting they are subunits of the 140 kDa protein.
- The purified phosphoprotein was rich in serine and aspartic acid residues.
- The N-terminal peptide sequence Asp-Asp-Pro was identified.
Conclusions:
- An intact dentin phosphoprotein has been identified and characterized from immature human tooth apices.
- The findings suggest that the lower molecular weight bands represent subunits of the larger phosphoprotein.
- The identified N-terminal sequence is identical to that of rat incisor phosphoprotein, indicating potential evolutionary conservation.