Binding of amyloid β-peptide to ganglioside micelles is dependent on histidine-13

Amyloid β-peptide (Aβ) is a major component of plaques in Alzheimer's disease, and formation of senile plaques has been suggested to originate from regions of neuronal membrane rich in gangliosides. Here we demonstrate using NMR on ¹⁵N-labelled Aβ-(1–40) and Aβ-(1–42) that the interaction with ganglioside G_M1 micelles is localized to the N-terminal region of the peptide, particularly residues His¹³ to Leu¹⁷, which become more helical when bound. The key interaction is with His¹³, which undergoes a G_M1-specific conformational change. The sialic acid residue of the ganglioside headgroup is important for determining the nature of the conformational change. The isolated pentasaccharide headgroup of G_M1 is not bound, suggesting the need for a polyanionic surface. Binding to heparin confirms this suggestion, since binding is of similar affinity but does not produce the same conformational changes in the peptide. A comparison of Aβ-(1–40) and Aβ-(1–42) indicates that binding to G_M1 micelles is not related to oligomerization, which occurs at the C-terminal end. These results imply that binding to ganglioside micelles causes a transition from random coil to α-helix in the N-terminal region, leaving the C-terminal region unstructured.