Molecular Determinants of the Interaction Between the C‐Terminal Domain of Alzheimer's β‐Amyloid Peptide and Apolipoprotein E α‐Helices

: In a previous work, we predicted and demonstrated that the 29‐42‐residue fragment of β‐amyloid peptide (Aβ peptide) has in vitro capacities close to those of the titled fragment of viral fusion proteins. We further demonstrated that apolipoprotein E2 and E3 but not apolipoprotein E4 can decrease the fusogenic activity of Aβ(29‐42) via a direct interaction. Therefore, we suggested that this fragment is implicated in the neurotoxicity of Aβ and in the protective effects of apolipoprotein E in Alzheimer's disease. Because structurally related apolipoproteins do not interact with the Aβ C‐terminal domain but inhibit viral fusion, we suggested that interactions existing between fusogenic peptides and apolipoproteins are selective and responsible for the inhibition of fusion. In this study, we simulated interactions of all amphipathic helices of apolipoproteins E and A‐I with Aβ and simian immunodeficiency virus (SIV) fusogenic fragments by molecular modeling. We further calculated cross‐interactions that do not inhibit fusion in vitro. The results suggest that interactions of hydrophobic residues are the major event to inhibit the fusogenic capacities of Aβ(29‐42) and SIV peptides. Selectivity of those interactions is due to the steric complementarity between bulky hydrophobic residues in the fusogenic fragments and hydrophobic residues in the apolipoprotein C‐terminal amphipathic helices.