title: A solution NMR investigation into the impaired self-assembly properties of two murine amelogenins containing the point mutations T21→I or P41→T.
abstract: Amelogenesis imperfecta describes a group of inherited disorders that results in defective tooth enamel. Two disorders associated with human amelogenesis imperfecta are the point mutations T21→I or P40→T in amelogenin, the dominant protein present during the early stages of enamel biomineralization. The biophysical properties of wildtype murine amelogenin (M180) and two proteins containing the equivalent mutations in murine amelogenin, T21→I (M180-I) and P41→T (M180-T), were probed by NMR spectroscopy. At low protein concentration (0.1mM), M180, M180-I, and M180-T are predominately monomeric at pH 3.0 in 2% acetic acid and neither mutation produces a major structural change. Chemical shift perturbation studies as a function of protein (0.1-1.8mM) or NaCl (0-400mM) concentrations show that the mutations affect the self-association properties by causing self-assembly at lower protein or salt concentrations, relative to wildtype amelogenin, with the largest effect observed for M180-I. Under both conditions, the premature self-assembly is initiated near the N-terminus, providing further evidence for the importance of this region in the self-assembly process. The self-association of M180-I and M180-T at lower protein concentrations and lower ionic strengths than wildtype M180 may account for the clinical phenotypes of these mutations, defective enamel formation.
authors.affiliation: Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA. garry.buchko@pnnl.gov
authors.forename: Garry W
authors.initials: GW
authors.lastname: Buchko
authors.forename: Genyao
authors.initials: G
authors.lastname: Lin
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Tarasevich
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Shaw
mesh_terms: D053523:Amelogenin / Q000737:chemistry* / Q000235:genetics*; D000818:Animals; D001665:Binding Sites; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D051379:Mice; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding; D013329:Structure-Activity Relationship
chemical_list: D053523:Amelogenin
keywords: Amelogenesis imperfecta; Amelogenin; Biomineralization; Enamel; Intrinsic disorder; Nanospheres
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