title: Molecular-level examination of Cu2+ binding structure for amyloid fibrils of 40-residue Alzheimer's β by solid-state NMR spectroscopy.
abstract: Cu(2+) binding to Alzheimer's β (Aβ) peptides in amyloid fibrils has attracted broad attention, as it was shown that Cu ion concentration elevates in Alzheimer's senile plaque and such association of Aβ with Cu(2+) triggers the production of neurotoxic reactive oxygen species (ROS) such as H(2)O(2). However, detailed binding sites and binding structures of Cu(2+) to Aβ are still largely unknown for Aβ fibrils or other aggregates of Aβ. In this work, we examined molecular details of Cu(2+) binding to amyloid fibrils by detecting paramagnetic signal quenching in 1D and 2D high-resolution (13)C solid-state NMR (SSNMR) for full-length 40-residue Aβ(1-40). Selective quenching observed in (13)C SSNMR of Cu(2+)-bound Aβ(1-40) suggested that primary Cu(2+) binding sites in Aβ(1-40) fibrils include N(ε) in His-13 and His-14 and carboxyl groups in Val-40 as well as in Glu sidechains (Glu-3, Glu-11, and/or Glu-22). (13)C chemical shift analysis demonstrated no major structural changes upon Cu(2+) binding in the hydrophobic core regions (residues 18-25 and 30-36). Although the ROS production via oxidization of Met-35 in the presence of Cu(2+) has been long suspected, our SSNMR analysis of (13)C(ε)H(3)-S- in M35 showed little changes after Cu(2+) binding, excluding the possibility of Met-35 oxidization by Cu(2+) alone. Preliminary molecular dynamics (MD) simulations on Cu(2+)-Aβ complex in amyloid fibrils confirmed binding sites suggested by the SSNMR results and the stabilities of such bindings. The MD simulations also indicate the coexistence of a variety of Cu(2+)-binding modes unique in Aβ fibril, which are realized by both intra- and intermolecular contacts and highly concentrated coordination sites due to the in-register parallel β-sheet arrangements.
authors.affiliation: Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
authors.forename: Sudhakar
authors.initials: S
authors.lastname: Parthasarathy
authors.forename: Fei
authors.initials: F
authors.lastname: Long
authors.forename: Yifat
authors.initials: Y
authors.lastname: Miller
authors.forename: Yiling
authors.initials: Y
authors.lastname: Xiao
authors.forename: Dan
authors.initials: D
authors.lastname: McElheny
authors.forename: Kent
authors.initials: K
authors.lastname: Thurber
authors.forename: Buyong
authors.initials: B
authors.lastname: Ma
authors.forename: Ruth
authors.initials: R
authors.lastname: Nussinov
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ishii
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); D003300:Copper