title: Solid state NMR reveals a pH-dependent antiparallel beta-sheet registry in fibrils formed by a beta-amyloid peptide.
abstract: We report solid state nuclear magnetic resonance (NMR) measurements that probe the supramolecular organization of beta-sheets in the cross-beta motif of amyloid fibrils formed by residues 11-25 of the beta-amyloid peptide associated with Alzheimer's disease (Abeta(11-25)). Fibrils were prepared at pH 7.4 and pH 2.4. The solid state NMR data indicate that the central hydrophobic segment of Abeta(11-25) (sequence LVFFA) adopts a beta-strand conformation and participates in antiparallel beta-sheets at both pH values, but that the registry of intermolecular hydrogen bonds is pH-dependent. Moreover, both registries determined for Abeta(11-25) fibrils are different from the hydrogen bond registry in the antiparallel beta-sheets of Abeta(16-22) fibrils at pH 7.4 determined in earlier solid state NMR studies. In all three cases, the hydrogen bond registry is highly ordered, with no detectable "registry-shift" defects. These results suggest that the supramolecular organization of beta-sheets in amyloid fibrils is determined by a sensitive balance of multiple side-chain-side-chain interactions. Recent structural models for Abeta(11-25) fibrils based on X-ray fiber diffraction data are inconsistent with the solid state NMR data at both pH values.
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: A T
authors.initials: AT
authors.lastname: Petkova
authors.forename: G
authors.initials: G
authors.lastname: Buntkowsky
authors.forename: F
authors.initials: F
authors.lastname: Dyda
authors.forename: R D
authors.initials: RD
authors.lastname: Leapman
authors.forename: W-M
authors.initials: WM
authors.lastname: Yau
authors.forename: R
authors.initials: R
authors.lastname: Tycko
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000648:ultrastructure*; D006801:Humans; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008854:Microscopy, Electron; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010446:Peptide Fragments / Q000737:chemistry / Q000648:ultrastructure; D017433:Protein Structure, Secondary
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments