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1 Institut National de la Santé et de la Recherche Médicale (INSERM) U710, Université Montpellier 2, F-34095 Montpellier cédex 5, France2 INSERM U431, Institut Féderatif de Recherche (IFR) 122, F-34095 Montpellier cédex 5, France
(RECEIVED July 26, 2004; FINAL REVISION November 6, 2004; ACCEPTED December 20, 2004)
The native conformation of host-encoded cellular prion protein (PrPC) is metastable. As a result of a post-translational event, PrPC can convert to the scrapie form (PrPSc), which emerges as the essential constituent of infectious prions. Despite thorough research, the mechanism underlying this conformational transition remains unknown. However, several studies have highlighted the importance of the N-terminal region spanning residues 90154 in PrP folding. In order to understand why PrP folds into two different conformational states exhibiting distinct secondary and tertiary structure, and to gain insight into the involvement of this particular region in PrP transconformation, we studied the pressure-induced unfolding/ refolding of recombinant Syrian hamster PrP expanding from residues 90231, and compared it with heat unfolding. By using two intrinsic fluorescent variants of this protein (Y150W and F141W), conformational changes confined to the 132160 segment were monitored. Multiple conformational states of the Trp variants, characterized by their spectroscopic properties (fluorescence and UV absorbance in the fourth derivative mode), were achieved by tuning the experimental conditions of pressure and temperature. Further insight into unexplored conformational states of the prion protein, likely to mimic the in vivo structural change, was obtained from pressure-assisted cold unfolding. Furthermore, salt-induced conformational changes suggested a structural stabilizing role of Tyr150 and Phe141 residues, slowing down the conversion to a
-sheet form.
Keywords: prion protein; high pressure; protein folding; thermodynamic stability; fluorescence variants
Article and publication are at http://www.proteinscience.org/cgi/doi/10.1110/ps.04989405.
Reprint requests to: Reinhard Lange, INSERM U710, CC 105, Université de Montpellier 2, Place Eugène Bataillon, F-34095 Montpellier cédex 5, France; e-mail: lange{at}montp.inserm.fr; fax: +(33) 467-14-33-86.
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