title: Conformational pH dependence of intermediate states during oligomerization of the human prion protein.
abstract: Intermediate states are key to understanding the molecular mechanisms governing protein misfolding. The human prion protein (PrP) can follow various misfolding pathways, and forms a soluble beta-sheet-rich oligomer under acidic, mildly denaturing, high salt conditions. Here we describe a fast conformational switch from the native alpha-monomer to monomeric intermediate states under oligomer-forming conditions, followed by a slower oligomerization process. We observe a pH dependence of the secondary structure of these intermediate forms, with almost native-like alpha-helical secondary structure at pH 4.1 and predominantly beta-sheet characteristics at pH 3.6. NMR spectroscopy differentiates these intermediate states from the native protein and indicates dynamic rearrangements of secondary structure elements characteristic of a molten globule. The alpha-helical intermediate formed at pH 4.1 can convert to the beta-sheet conformation at pH 3.6 but not vice versa, and neither state can be reconverted to an alpha-monomer. The presence of methionine rather than valine at codon 129 accelerates the rate of oligomer formation from the intermediate state.
authors.affiliation: Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, Oxford OX1 3QZ, United Kingdom. remo.gerber@lincoln.oxon.org
authors.forename: Remo
authors.initials: R
authors.lastname: Gerber
authors.forename: Abdessamad
authors.initials: A
authors.lastname: Tahiri-Alaoui
authors.forename: P J
authors.initials: PJ
authors.lastname: Hore
authors.forename: William
authors.initials: W
authors.lastname: James
mesh_terms: D003062:Codon; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019906:Nuclear Magnetic Resonance, Biomolecular; D011328:Prions / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D003062:Codon; D011328:Prions