title: Nucleation-dependent conformational conversion of the Y145Stop variant of human prion protein: structural clues for prion propagation.
abstract: One of the most intriguing disease-related mutations in human prion protein (PrP) is the Tyr to Stop codon substitution at position 145. This mutation results in a Gerstmann-Straussler-Scheinker-like disease with extensive PrP amyloid deposits in the brain. Here, we provide evidence for a spontaneous conversion of the recombinant polypeptide corresponding to the Y145Stop variant (huPrP23-144) from a monomeric unordered state to a fibrillar form. This conversion is characterized by a protein concentration-dependent lag phase and has characteristics of a nucleation-dependent polymerization. Atomic force microscopy shows that huPrP23-144 fibrils are characterized by an apparent periodicity along the long axis, with an average period of 20 nm. Fourier-transform infrared spectra indicate that the conversion is associated with formation of beta-sheet structure. However, the infrared bands for huPrP23-144 are quite different from those for a synthetic peptide PrP106-126, suggesting conformational non-equivalence of beta-structures in the disease-associated Y145Stop variant and a frequently used short model peptide. To identify the region that is critical for the self-seeded assembly of huPrP23-144 amyloid, experiments were performed by using the recombinant polypeptides corresponding to prion protein fragments 23-114, 23-124, 23-134, 23-137, 23-139, and 23-141. Importantly, none of the fragments ending before residue 139 showed a propensity for conformational conversion to amyloid fibrils, indicating that residues within the 138-141 region are essential for this conversion.
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University, 3109 Adelbert Road, Cleveland, OH 44106, USA.
authors.forename: Bishwajit
authors.initials: B
authors.lastname: Kundu
authors.forename: Nilesh R
authors.initials: NR
authors.lastname: Maiti
authors.forename: Eric M
authors.initials: EM
authors.lastname: Jones
authors.forename: Krystyna A
authors.initials: KA
authors.lastname: Surewicz
authors.forename: David L
authors.initials: DL
authors.lastname: Vanik
authors.forename: Witold K
authors.initials: WK
authors.lastname: Surewicz
mesh_terms: D019943:Amino Acid Substitution; D018388:Codon, Terminator / Q000235:genetics; D019286:Endopeptidase K; D014644:Genetic Variation; D016098:Gerstmann-Straussler-Scheinker Disease / Q000209:etiology / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry; D010449:Peptide Mapping; D011328:Prions / Q000737:chemistry* / Q000235:genetics* / Q000648:ultrastructure; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D018388:Codon, Terminator; D010446:Peptide Fragments; D011328:Prions; D011994:Recombinant Proteins; D019286:Endopeptidase K