title: Perturbation of the secondary structure of the scrapie prion protein under conditions that alter infectivity.
abstract: Limited proteolysis of the scrapie prion protein (PrPSc) generates PrP 27-30, which polymerizes into amyloid. By attenuated total reflection-Fourier transform infrared spectroscopy, PrP 27-30 polymers contained 54% beta-sheet, 25% alpha-helix, 10% turns, and 11% random coil; dispersion into detergent-lipid-protein-complexes preserved infectivity and secondary structure. Almost 60% of the beta-sheet was low-frequency infrared-absorbing, reflecting intermolecular aggregation. Decreased low-frequency beta-sheet and increased turn content were found after SDS/PAGE, which disassembled the amyloid polymers, denatured PrP 27-30, and diminished scrapie infectivity. Acid-induced transitions were reversible, whereas alkali produced an irreversible transition centered at pH 10 under conditions that diminished infectivity. Whether PrPSc synthesis involves a transition in the secondary structure of one or more domains of the cellular prion protein from alpha-helical, random coil, or turn into beta-sheet remains to be established.
authors.affiliation: Department of Neurology, University of California, San Francisco 94143.
authors.forename: M
authors.initials: M
authors.lastname: Gasset
authors.forename: M A
authors.initials: MA
authors.lastname: Baldwin
authors.forename: R J
authors.initials: RJ
authors.lastname: Fletterick
authors.forename: S B
authors.initials: SB
authors.lastname: Prusiner
mesh_terms: D000818:Animals; D001921:Brain / Q000382:microbiology*; D002499:Centrifugation, Density Gradient; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K; D006863:Hydrogen-Ion Concentration; D011328:Prions / Q000737:chemistry* / Q000302:isolation & purification / Q000472:pathogenicity; D011487:Protein Conformation; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012697:Serine Endopeptidases; D012995:Solubility; D013055:Spectrophotometry, Infrared
chemical_list: D011328:Prions; D012697:Serine Endopeptidases; D019286:Endopeptidase K