Methionine Oxidation Changes the Mechanism of Aβ Peptide Binding to the DMPC Bilayer
Date
2019
Authors
Lockhart, Christopher
Smith, Amy K.
Klimov, Dmitri K.
Journal Title
Journal ISSN
Volume Title
Publisher
Scientific Reports
Abstract
Using all-atom explicit solvent replica exchange molecular dynamics simulations with solute tempering, we study the efect of methionine oxidation on Aβ10–40 peptide binding to the zwitterionic DMPC bilayer. By comparing oxidized and reduced peptides, we identifed changes in the binding mechanism caused by this modifcation. First, Met35 oxidation unravels C-terminal helix in the bound peptides. Second, oxidation destabilizes intrapeptide interactions and expands bound peptides. We explain these outcomes by the loss of amphiphilic character of the C-terminal helix due to oxidation. Third, oxidation “polarizes” Aβ binding to the DMPC bilayer by strengthening the interactions of the C-terminus with lipids while largely releasing the rest of the peptide from bilayer. Fourth, in contrast to the wild-type peptide, oxidized Aβ induces signifcantly smaller bilayer thinning and drop in lipid density within the binding footprint. These observations are the consequence of mixing oxidized peptide amino acids with lipids promoted by enhanced Aβ conformational fuctuations. Fifth, methionine oxidation reduces the afnity of Aβ binding to the DMPC bilayer by disrupting favorable intrapeptide interactions upon binding, which ofset the gains from better hydration. Reduced binding afnity of the oxidized Aβ may represent the molecular basis for its reduced cytotoxicity.