Protein nanoribbons template enamel mineralization

Research output: Contribution to journalArticle

Abstract

As the hardest tissue formed by vertebrates, enamel represents nature's engineering masterpiece with complex organizations of fibrous apatite crystals at the nanometer scale. Supramolecular assemblies of enamel matrix proteins (EMPs) play a key role as the structural scaffolds for regulating mineral morphology during enamel development. However, to achieve maximum tissue hardness, most organic content in enamel is digested and removed at the maturation stage, and thus knowledge of a structural protein template that could guide enamel mineralization is limited at this date. Herein, by examining a gene-modified mouse that lacked enzymatic degradation of EMPs, we demonstrate the presence of protein nanoribbons as the structural scaffolds in developing enamel matrix. Using in vitro mineralization assays we showed that both recombinant and enamel-tissue-based amelogenin nanoribbons are capable of guiding fibrous apatite nanocrystal formation. In accordance with our understanding of the natural process of enamel formation, templated crystal growth was achieved by interaction of amelogenin scaffolds with acidic macromolecules that facilitate the formation of an amorphous calcium phosphate precursor which gradually transforms into oriented apatite fibers along the protein nanoribbons. Furthermore, this study elucidated that matrix metalloproteinase-20 is a critical regulator of the enamel mineralization as only a recombinant analog of a MMP20-cleavage product of amelogenin was capable of guiding apatite mineralization. This study highlights that supramolecular assembly of the scaffold protein, its enzymatic processing, and its ability to interact with acidic carrier proteins are critical steps for proper enamel development.

Details

Authors
  • Yushi Bai
  • Zanlin Yu
  • Larry Ackerman
  • Yan Zhang
  • Johan Bonde
  • Wu Li
  • Yifan Cheng
  • Stefan Habelitz
Organisations
External organisations
  • University of California, San Francisco
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Dentistry
  • Physiology

Keywords

  • biomineralization, enamel, hydroxyapatite, nanoribbon structure, protein assembly
Original languageEnglish
Pages (from-to)19201-19208
Number of pages8
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number32
Publication statusPublished - 2020
Publication categoryResearch
Peer-reviewedYes