Binding to the lipid monolayer induces conformational transition in Aβ monomer

Using implicit solvent atomistic model and replica exchange molecular dynamics, we study binding of A beta monomer to zwitterionic dimyristoylphosphatidylcholine (DMPC) lipid monolayer. Our results suggest that A beta binding to the monolayer is governed primarily by positively charged and aromatic amino acids. Lysine residues tend to interact with surface choline and phosphorous lipid groups, whereas aromatic amino acids penetrate deeper into the monolayer, reaching its hydrophobic core. We show that binding to the DMPC monolayer causes a dramatic conformational transition in A beta monomer, resulting in chain extension, loss of intrapeptide interactions, and formation of beta-structure. This conformational transition is far more significant than that occurring during the initial stages of aggregation in water. We also found that A beta binding perturbs surface ordering of lipids interacting with A beta.