title: A structural model for Alzheimer's beta -amyloid fibrils based on experimental constraints from solid state NMR.
abstract: We present a structural model for amyloid fibrils formed by the 40-residue beta-amyloid peptide associated with Alzheimer's disease (Abeta(1-40)), based on a set of experimental constraints from solid state NMR spectroscopy. The model additionally incorporates the cross-beta structural motif established by x-ray fiber diffraction and satisfies constraints on Abeta(1-40) fibril dimensions and mass-per-length determined from electron microscopy. Approximately the first 10 residues of Abeta(1-40) are structurally disordered in the fibrils. Residues 12-24 and 30-40 adopt beta-strand conformations and form parallel beta-sheets through intermolecular hydrogen bonding. Residues 25-29 contain a bend of the peptide backbone that brings the two beta-sheets in contact through sidechain-sidechain interactions. A single cross-beta unit is then a double-layered beta-sheet structure with a hydrophobic core and one hydrophobic face. The only charged sidechains in the core are those of D23 and K28, which form salt bridges. Fibrils with minimum mass-per-length and diameter consist of two cross-beta units with their hydrophobic faces juxtaposed.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
authors.forename: Aneta T
authors.initials: AT
authors.lastname: Petkova
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ishii
authors.forename: John J
authors.initials: JJ
authors.lastname: Balbach
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Antzutkin
authors.forename: Richard D
authors.initials: RD
authors.lastname: Leapman
authors.forename: Frank
authors.initials: F
authors.lastname: Delaglio
authors.forename: Robert
authors.initials: R
authors.lastname: Tycko
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40)