Solid-State NMR Identification of Intermolecular Interactions in Amelogenin Bound to Hydroxyapatite

Area of Science:

• Biomineralization
• Materials Science
• Structural Biology

Background:

• Biomineralization processes form hierarchical hard tissues like bone and teeth.
• Mimicking biomineralization can yield novel materials with unique properties.
• Structural characterization of biomineralization proteins is crucial for mimicking their function, but challenging due to their surface-bound nature.

Purpose of the Study:

• To investigate the intermolecular interactions and structure of amelogenin, the primary protein in early enamel formation.
• To understand how amelogenin self-assembles into oligomers on hydroxyapatite surfaces.
• To develop new strategies for studying surface-bound biomineralization proteins.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy was employed to analyze amelogenin oligomers bound to hydroxyapatite.
• Intermolecular dipolar couplings were measured to identify protein-protein interactions.
• Molecular dynamics simulations were used to corroborate the experimental findings.

Main Results:

• Solid-state NMR identified intermolecular interactions supporting amelogenin dimer formation, stabilized by C-terminal residues.
• A previously disordered protein, amelogenin, adopted a β-sheet structure in multiple regions when bound to hydroxyapatite.
• These findings represent the first reported intermolecular protein-protein interactions for a biomineralization protein.

Conclusions:

• The study provides novel insights into amelogenin's structural behavior and interactions during enamel formation.
• Solid-state NMR offers a viable strategy for characterizing surface-bound biomineralization proteins.
• Understanding these interactions advances the field of enamel development and biomaterials design.