Analysis of secondary structure and self‐assembly of amelogenin by variable temperature circular dichroism and isothermal titration calorimetry |
| |
Authors: | Rajamani Lakshminarayanan Il Yoon Balachandra G. Hegde Daming Fan Chang Du Janet Moradian‐Oldak |
| |
Affiliation: | 1. Center for Craniofacial Molecular Biology, School of Dentistry, University of Southern California, Los Angeles, California 90033;2. Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California 90095;3. Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California 90033;4. Zilka Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 |
| |
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 β‐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 (ΔHA) 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. Proteins 2009. © 2009 Wiley‐Liss, Inc. |
| |
Keywords: | amelogenin nanospheres enamel biomineralization modular structure polyproline type II supramolecular self‐assembly |
|
|