title: Oligomerization of the human prion protein proceeds via a molten globule intermediate.
abstract: The conformational transition of the human prion protein from an alpha-helical to a beta-sheet-rich structure is believed to be the critical event in prion pathogenesis. The molecular mechanism of misfolding and the role of intermediate states during this transition remain poorly understood. To overcome the obstacle of insolubility of amyloid fibrils, we have studied a beta-sheet-rich misfolded isoform of the prion protein, the beta-oligomer, which shares some structural properties with amyloid, including partial proteinase resistance. We demonstrate here that the beta-oligomer can be studied by solution-state NMR spectroscopy and obtain insights into the misfolding mechanism via its transient monomeric precursor. It is often assumed that misfolding into beta-sheet-rich isoforms proceeds via a compatible precursor with a beta-sheet subunit structure. We show here, on the contrary, evidence for an almost natively alpha-helix-rich monomeric precursor state with molten globule characteristics, converting in vitro into the beta-oligomer. We propose a possible mechanism for the formation of the beta-oligomer, triggered by intermolecular contacts between constantly rearranging structures. It is concluded that the beta-oligomer is not preceded by precursors with beta-sheet structure but by a partially unfolded clearly distinguishable alpha-helical state.
authors.affiliation: Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom. remo.gerber@chem.ox.ac.uk
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: D000682:Amyloid / Q000737:chemistry; D019281:Dimerization; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011328:Prions / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: D000682:Amyloid; D011328:Prions