title: Small-angle X-ray scattering and computer-aided molecular modeling studies of 20 kDa fragment of porcine amelogenin: does amelogenin adopt an elongated bundle structure?
abstract: Amelogenins, which are major matrix constituents in the developing tooth, play a regulatory role in the process of enamel crystal formation. Porcine amelogenin with 173 amino acid residues is rich in proline, glutamine, leucine, and histidine. We utilized the small-angle X-ray scattering (SAXS) technique to examine the solution structure of porcine amelogenin. Samples used were two porcine amelogenins with apparent molecular weights of 20 kDa (amino acids 1 to 148) and 13 kDa (amino acids 46 to 148) on SDS-PAGE. Prior to SAXS measurements, the protein samples were dissolved in 2% (v/v) acetic acid to give a concentration range up to 10 mg/ml. Comparison between Rg (the overall radius of gyration) and Rc (the cross-sectional radius of gyration) revealed that the 20 kDa amelogenin exists in this solution as asymmetric particles with a length of about 15 nm, presumably corresponding of dimers. Based on these experimental data and computer-aided molecular modeling studies, we propose that the 20 kDa amelogenin adopts an elongated bundle structure which mainly consists of extended structures similar to polyproline II and/or beta-strand, interspersed with beta-turn or loop.
authors.affiliation: School of Health Sciences, Sapporo Medical University. matusima@shs.sapmed.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Matsushima
authors.forename: Y
authors.initials: Y
authors.lastname: Izumi
authors.forename: T
authors.initials: T
authors.lastname: Aoba
mesh_terms: D053523:Amelogenin; D000595:Amino Acid Sequence; D000818:Animals; D003746:Dental Enamel Proteins / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012542:Scattering, Radiation; D013552:Swine
chemical_list: D053523:Amelogenin; D003746:Dental Enamel Proteins