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Human amelogenins: sequences of "TRAP" molecules
A G Fincham1, Y Y Hu, Z Pavlova
1Laboratory for Developmental Biology, University of Southern California, Los Angeles 90089-0191.
Calcified Tissue International
|October 1, 1989
Summary
Researchers identified two forms of tyrosine-rich amelogenin polypeptides (TRAPs) in human enamel, suggesting variations in enamel protein processing and potential gene-level differences contributing to complexity in dental biomineralization.
Area of Science:
- Biochemistry
- Developmental Biology
- Biomineralization
Background:
- Amelogenins are key extracellular proteins regulating enamel biomineralization.
- Amelogenins are proline-rich, hydrophobic proteins processed from a primary gene product.
- Human amelogenin genes on X and Y chromosomes suggest potential genetic polymorphism.
Purpose of the Study:
- Investigate amelogenin polymorphism in developing human dental enamel.
- Characterize tyrosine-rich amelogenin polypeptides (TRAPs) in human enamel.
Main Methods:
- Size-exclusion and reversed-phase high-performance liquid chromatography (HPLC) for protein fractionation.
- Automated gas-phase sequencing for polypeptide characterization.
- Analysis of TRAP molecular size and amino acid sequences.
Main Results:
- Two TRAPs (TRAP-1 and TRAP-2) of approximately 5 kDa were isolated.
- TRAP-1 (44 residues) and TRAP-2 (42 residues) showed differences in carboxy-terminal sequence.
- Residue #25 in human TRAP-2 was refractory to sequencing, differing from TRAP-1.
Conclusions:
- Two TRAP forms, differing by dipeptide cleavage, are common in mammalian enamel proteins.
- Human developing enamel may exhibit four TRAP forms due to gene polymorphism or alternative splicing coupled with processing.