title: Analysis of secondary structure and self-assembly of amelogenin by variable temperature circular dichroism and isothermal titration calorimetry.
abstract: Amelogenin is a proline-rich enamel matrix protein known to play an important role in the oriented growth of enamel crystals. Amelogenin self-assembles to form nanospheres and higher order structures mediated by hydrophobic interactions. This study aims to obtain a better insight into the relationship between primary-secondary structure and self-assembly of amelogenin by applying computational and biophysical methods. Variable temperature circular dichroism studies indicated that under physiological pH recombinant full-length porcine amelogenin contains unordered structures in equilibrium with polyproline type II (PPII) structure, the latter being more populated at lower temperatures. Increasing the concentration of rP172 resulted in the promotion of folding to an ordered beta-structured assembly. Isothermal titration calorimetry dilution studies revealed that at all temperatures, self-assembly is entropically driven due to the hydrophobic effect and the molar heat of assembly (DeltaH(A)) decreases with temperature. Using a computational approach, a profile of domains in the amino acid sequence that have a high propensity to assemble and to have PPII structures has been identified. We conclude that the assembly properties of amelogenin are due to complementarity between the hydrophobic and PPII helix prone regions.
authors.affiliation: Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, 90033, USA.
authors.forename: Rajamani
authors.initials: R
authors.lastname: Lakshminarayanan
authors.forename: Il
authors.initials: I
authors.lastname: Yoon
authors.forename: Balachandra G
authors.initials: BG
authors.lastname: Hegde
authors.forename: Daming
authors.initials: D
authors.lastname: Fan
authors.forename: Chang
authors.initials: C
authors.lastname: Du
authors.forename: Janet
authors.initials: J
authors.lastname: Moradian-Oldak
mesh_terms: D053523:Amelogenin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002151:Calorimetry / Q000379:methods*; D002942:Circular Dichroism / Q000379:methods*; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013552:Swine; D013696:Temperature
chemical_list: D053523:Amelogenin; D011994:Recombinant Proteins