title: Conformational plasticity of the Gerstmann-Sträussler-Scheinker disease peptide as indicated by its multiple aggregation pathways.
abstract: The existence of several prion strains and their capacity of overcoming species barriers seem to point to a high conformational adaptability of the prion protein. To investigate this structural plasticity, we studied here the aggregation pathways of the human prion peptide PrP82-146, a major component of the Gerstmann-Sträussler-Scheinker amyloid disease. By Fourier transform infrared (FT-IR) spectroscopy, electron microscopy, and atomic force microscopy (AFM), we monitored the time course of PrP82-146 fibril formation. After incubation at 37 degrees C, the unfolded peptide was found to aggregate into oligomers characterized by intermolecular beta-sheet infrared bands. At a critical oligomer concentration, the emergence of a new FT-IR band allowed to detect fibril formation. A different intermolecular beta-sheet interaction of the peptides in oligomers and in fibrils is, therefore, detected by FT-IR spectroscopy, which, in addition, suggests a parallel orientation of the cross beta-sheet structures of PrP82-146 fibrils. By AFM, a wide distribution of PrP82-146 oligomer volumes--the smallest ones containing from 5 to 30 peptides--was observed. Interestingly, the statistical analysis of AFM data enabled us to detect a quantization in the oligomer height values differing by steps of approximately 0.5 nm that could reflect an orientation of oligomer beta-strands parallel with the sample surface. Different morphologies were also detected for fibrils that displayed high heterogeneity in their twisting periodicity and a complex hierarchical assembly. Thermal aggregation of PrP82-146 was also investigated by FT-IR spectroscopy, which indicated for these aggregates an intermolecular beta-sheet interaction different from that observed for oligomers and fibrils. Unexpectedly, random aggregates, induced by solvent evaporation, were found to display a significant alpha-helical structure as well as several beta-sheet components. All these results clearly point to a high plasticity of the PrP82-146 peptide, which was found to be capable of undergoing several aggregation pathways, with end products displaying different secondary structures and intermolecular interactions.
authors.affiliation: Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Natalello
authors.forename: Valery V
authors.initials: VV
authors.lastname: Prokorov
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Tagliavini
authors.forename: Michela
authors.initials: M
authors.lastname: Morbin
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Forloni
authors.forename: Marten
authors.initials: M
authors.lastname: Beeg
authors.forename: Claudia
authors.initials: C
authors.lastname: Manzoni
authors.forename: Laura
authors.initials: L
authors.lastname: Colombo
authors.forename: Marco
authors.initials: M
authors.lastname: Gobbi
authors.forename: Mario
authors.initials: M
authors.lastname: Salmona
authors.forename: Silvia Maria
authors.initials: SM
authors.lastname: Doglia
mesh_terms: D000682:Amyloid / Q000648:ultrastructure; D016098:Gerstmann-Straussler-Scheinker Disease / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010455:Peptides / Q000737:chemistry*; D011328:Prions / Q000737:chemistry* / Q000648:ultrastructure; D020836:Protein Structure, Quaternary; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000682:Amyloid; D010455:Peptides; D011328:Prions