title: Copper(II)-induced secondary structure changes and reduced folding stability of the prion protein.
abstract: The cellular isoform of the prion protein PrP(C) is a Cu(2)(+)-binding cell surface glycoprotein that, when misfolded, is responsible for a range of transmissible spongiform encephalopathies. As changes in PrP(C) conformation are intimately linked with disease pathogenesis, the effect of Cu(2+) ions on the structure and stability of the protein has been investigated. Urea unfolding studies indicate that Cu(2+) ions destabilise the native fold of PrP(C). The midpoint of the unfolding transition is reduced by 0.73 ± 0.07 M urea in the presence of 1 mol equiv of Cu(2+). This equates to an appreciable difference in free energy of unfolding (2.02 ± 0.05 kJ mol(-1) at the midpoint of unfolding). We relate Cu(2)(+)-induced changes in secondary structure for full-length PrP(23-231) to smaller Cu(2)(+) binding fragments. In particular, Cu(2+)-induced structural changes can directly be attributed to Cu(2+) binding to the octarepeat region of PrP(C). Furthermore, a β-sheet-like transition that is observed when Cu ions are bound to the amyloidogenic fragment of PrP (residues 90-126) is due only to local Cu(2+) coordination to the individual binding sites centred at His95 and His110. Cu(2+) binding does not directly generate a β-sheet conformation within PrP(C); however, Cu(2+) ions do destabilise the native fold of PrP(C) and may make the transition to a misfolded state more favourable.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
authors.forename: Nadine D
authors.initials: ND
authors.lastname: Younan
authors.forename: Mark
authors.initials: M
authors.lastname: Klewpatinond
authors.forename: Paul
authors.initials: P
authors.lastname: Davies
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Ruban
authors.forename: David R
authors.initials: DR
authors.lastname: Brown
authors.forename: John H
authors.initials: JH
authors.lastname: Viles
mesh_terms: D000465:Algorithms; D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D011328:Prions / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects*; D017433:Protein Structure, Secondary / Q000187:drug effects*; D017550:Spectroscopy, Fourier Transform Infrared; D014508:Urea / Q000494:pharmacology
chemical_list: D010446:Peptide Fragments; D011328:Prions; C428437:prion protein (23-231); D003300:Copper; D014508:Urea