title: Micelle structure of amelogenin in porcine secretory enamel.
abstract: Even during the secretory stage of amelogenesis, enamel crystals thicken as amelogenins (the major protein component) decrease. To explain this phenomenon, we propose a model for amelogenin structure and function based upon the hypothesis that amelogenin forms micelles. Solubility and hydrophobicity analyses suggest that all but the hydrophilic amelogenin C-terminal regions aggregate via hydrophobic bonds to form a micelle core. Amelogenin micelles may form super-assemblies via their C-termini (KTKREEVD), which contain complementary positive (KTKR) and negative (EEVD) elements. Disassembly of the micelles through controlled proteolysis provides space for crystal growth. Initial cleavage (by enamelysin) removes the surface-accessible amelogenin C-terminus, exposing the middle portion to cleavage (by EMSP1). As a result, the 13-kDa amelogenin, a rod-shaped domain based upon ultrafiltration and transmission electron microscopy studies, is released. This model explains how amelogenin is able to 'space' and support the ribbon-like crystals and continuously yield space as the crystals thicken, until they are sufficiently mature to support themselves.
authors.affiliation: Department of Biochemistry and Anatomy, Tsurumi University, Yokhama, Japan. fukae-m@tsurumi-u.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Fukae
authors.forename: R
authors.initials: R
authors.lastname: Yamamoto
authors.forename: T
authors.initials: T
authors.lastname: Karakida
authors.forename: S
authors.initials: S
authors.lastname: Shimoda
authors.forename: T
authors.initials: T
authors.lastname: Tanabe
mesh_terms: D000566:Amelogenesis; D053523:Amelogenin / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D003460:Crystallization; D003743:Dental Enamel / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D008969:Molecular Sequence Data; D015394:Molecular Structure; D034421:Sus scrofa; D013552:Swine
chemical_list: D053523:Amelogenin; D008823:Micelles