title: Parallel in-register intermolecular β-sheet architectures for prion-seeded prion protein (PrP) amyloids.
abstract: Structures of the infectious form of prion protein (e.g. PrP(Sc) or PrP-Scrapie) remain poorly defined. The prevalent structural models of PrP(Sc) retain most of the native α-helices of the normal, noninfectious prion protein, cellular prion protein (PrP(C)), but evidence is accumulating that these helices are absent in PrP(Sc) amyloid. Moreover, recombinant PrP(C) can form amyloid fibrils in vitro that have parallel in-register intermolecular β-sheet architectures in the domains originally occupied by helices 2 and 3. Here, we provide solid-state NMR evidence that the latter is also true of initially prion-seeded recombinant PrP amyloids formed in the absence of denaturants. These results, in the context of a primarily β-sheet structure, led us to build detailed models of PrP amyloid based on parallel in-register architectures, fibrillar shapes and dimensions, and other available experimentally derived conformational constraints. Molecular dynamics simulations of PrP(90-231) octameric segments suggested that such linear fibrils, which are consistent with many features of PrP(Sc) fibrils, can have stable parallel in-register β-sheet cores. These simulations revealed that the C-terminal residues ∼124-227 more readily adopt stable tightly packed structures than the N-terminal residues ∼90-123 in the absence of cofactors. Variations in the placement of turns and loops that link the β-sheets could give rise to distinct prion strains capable of faithful template-driven propagation. Moreover, our modeling suggests that single PrP monomers can comprise the entire cross-section of fibrils that have previously been assumed to be pairs of laterally associated protofilaments. Together, these insights provide a new basis for deciphering mammalian prion structures.
authors.affiliation: From the Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, NIAID, National Institutes of Health, Hamilton, Montana 59840 and.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Groveman
authors.affiliation: the Computational Biology Section, Bioinformatics and Computational Biosciences Branch, NIAID, and.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Dolan
authors.affiliation: From the Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, NIAID, National Institutes of Health, Hamilton, Montana 59840 and.
authors.forename: Lara M
authors.initials: LM
authors.lastname: Taubner
authors.affiliation: From the Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, NIAID, National Institutes of Health, Hamilton, Montana 59840 and.
authors.forename: Allison
authors.initials: A
authors.lastname: Kraus
authors.affiliation: Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Reed B
authors.initials: RB
authors.lastname: Wickner
authors.affiliation: From the Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, NIAID, National Institutes of Health, Hamilton, Montana 59840 and bcaughey@nih.gov.
authors.forename: Byron
authors.initials: B
authors.lastname: Caughey
mesh_terms: D000682:Amyloid / Q000378:metabolism*; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D004220:Disulfides / Q000737:chemistry; D017348:Microscopy, Electron, Scanning Transmission; D008958:Models, Molecular; D011134:Polysaccharides / Q000737:chemistry; D011328:Prions / Q000737:chemistry / Q000378:metabolism*; D059748:Proteolysis
chemical_list: D000682:Amyloid; D004220:Disulfides; D011134:Polysaccharides; D011328:Prions
keywords: Amyloid; Molecular Dynamics; Nuclear Magnetic Resonance (NMR); Prion; Protein Structure