Solution NMR studies of the A beta(1-40) and A beta(1-42) peptides establish that the Met35 oxidation state affects the mechanism of amyloid formation.

Published

Journal Article

The pathogenesis of Alzheimer's disease is characterized by the aggregation and fibrillation of the 40-residue A beta(1-40) and 42-residue A beta(1-42) peptides into amyloid plaques. The structural changes associated with the conversion of monomeric A beta peptide building blocks into multimeric fibrillar beta-strand aggregates remain unknown. Recently, we established that oxidation of the methionine-35 side chain to the sulfoxide (Met35(red) --> Met35(ox)) significantly impedes the rate of aggregation and fibrillation of the A beta peptide. To explore this effect at greater resolution, we carefully compared the (1)H, (15)N, and (13)C NMR chemical shifts of four A beta peptides that had the Met35 reduced or oxidized (A beta(1-40)Met35(red), A beta(1-40)Met35(ox), A beta(1-42)Met35(red), and A beta(1-42)Met35(ox)). With the use of a special disaggregation protocol, the highly aggregation prone A beta peptides could be studied at higher, millimolar concentrations (as required by NMR) in aqueous solution at neutral pH, remaining largely monomeric at 5 degrees C as determined by sedimentation equilibrium studies. The NOE, amide-NH temperature coefficients, and chemical shift indices of the (1)H alpha, (13)C alpha, and (13)C beta established that the four peptides are largely random, extended chain structures, with the Met35(ox) reducing the propensity for beta-strand structure at two hydrophobic regions (Leu17-Ala21 and Ile31-Val36), and turn- or bendlike structures at Asp7-Glu11 and Phe20-Ser26. Additional NMR studies monitoring changes that occur during aging at 37 degrees C established that, along with a gradual loss of signal/noise, the Met35(ox) significantly hindered upfield chemical shift movements of the 2H NMR signals for the His6, His13, and His14 side chains. Taken together, the present NMR studies demonstrate that the Met35(red) --> Met35(ox) conversion prevents aggregation by reducing both hydrophobic and electrostatic association and that the A beta(1-40)Met35(red), A beta(1-40)Met35(ox), A beta(1-42)Met35(red), and A beta(1-42)Met35(ox) peptides may associate differently, through specific, sharp changes in structure during the initial stages of aggregation.

Full Text

Duke Authors

Cited Authors

  • Hou, L; Shao, H; Zhang, Y; Li, H; Menon, NK; Neuhaus, EB; Brewer, JM; Byeon, I-JL; Ray, DG; Vitek, MP; Iwashita, T; Makula, RA; Przybyla, AB; Zagorski, MG

Published Date

  • February 2004

Published In

Volume / Issue

  • 126 / 7

Start / End Page

  • 1992 - 2005

PubMed ID

  • 14971932

Pubmed Central ID

  • 14971932

Electronic International Standard Serial Number (EISSN)

  • 1520-5126

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/ja036813f

Language

  • eng