Altered self-assembly and apatite binding of amelogenin induced by N-terminal proline mutation

Abstract

Objective: A single Pro-70 to Thr (p.P70T) mutation of amelogenin is known to result in hypomineralised amelogenesis imperfecta (AI). This study aims to test the hypothesis that the given mutation affects the self-assembly of amelogenin molecules and impairs their ability to conduct the growth of apatite crystals.

Design: Recombinant human full-length wild-type (rh174) and p.P70T mutated amelogenins were analysed using dynamic light scattering (DLS), protein quantification assay and atomic force microscopy (AFM) before and after the binding of amelogenins to hydroxyapatite crystals. The crystal growth modulated by both amelogenins in a dynamic titration system was observed using AFM.

Results: As compared to rh174 amelogenin, p.P70T mutant displayed significantly increased sizes of the assemblies, higher binding affinity to apatite, and decreased crystal height.

Conclusion: Pro-70 plays an important structural role in the biologically relevant amelogenin self-assembly. The disturbed regularity of amelogenin nanospheres by this single mutation resulted in an increased binding to apatite and inhibited crystal growth.