title: Amelogenin supramolecular assembly in nanospheres defined by a complex helix-coil-PPII helix 3D-structure.
abstract: Tooth enamel, the hardest material in the human body, is formed within a self-assembled matrix consisting mostly of amelogenin proteins. Here we have determined the complete mouse amelogenin structure under physiological conditions and defined interactions between individual domains. NMR spectroscopy revealed four major amelogenin structural motifs, including an N-terminal assembly of four α-helical segments (S9-V19, T21-P33, Y39-W45, V53-Q56), an elongated random coil region interrupted by two 3(10) helices (∼P60-Q117), an extended proline-rich PPII-helical region (P118-L165), and a charged hydrophilic C-terminus (L165-D180). HSQC experiments demonstrated ipsilateral interactions between terminal domains of individual amelogenin molecules, i.e. N-terminal interactions with corresponding N-termini and C-terminal interactions with corresponding C-termini, while the central random coil domain did not engage in interactions. Our HSQC spectra of the full-length amelogenin central domain region completely overlapped with spectra of the monomeric Amel-M fragment, suggesting that the central amelogenin coil region did not involve in assembly, even in assembled nanospheres. This finding was confirmed by analytical ultracentrifugation experiments. We conclude that under conditions resembling those found in the developing enamel protein matrix, amelogenin molecules form complex 3D-structures with N-terminal α-helix-like segments and C-terminal PPII-helices, which self-assemble through ipsilateral interactions at the N-terminus of the molecule.
authors: Brodie Laboratory for Craniofacial Genetics, College of Dentistry, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors: Xu
authors: X
authors: Zhang
authors: Benjamin E
authors: BE
authors: Ramirez
authors: Xiubei
authors: X
authors: Liao
authors: Thomas G H
authors: TG
authors: Diekwisch
mesh_terms: D053523:Amelogenin / Q000737:chemistry*; D020816:Amino Acid Motifs; D000818:Animals; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008958:Models, Molecular; D054118:Nanospheres / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D012995:Solubility; D013696:Temperature
chemical_list: D053523:Amelogenin; D010446:Peptide Fragments; D010455:Peptides; C011083:polyproline