Interaction of the apolipoprotein A-I model peptides with liposomes

Two amphiphilic peptides, Amp1 and Amp2, were synthesized according to the sequence of the lipid binding domain in apolipoprotein. Amp2 has a Val residue substituted for the Lys at the 4th position of Amp1. Intrinsic fluorescence spectra, peptide-induced leakage of calcein-loaded liposomes, quenching of tryptophan fluorescence by iodide and acrylamide, circular dichroism spectra, and measurement of the membrane penetration depth of tryptophan residue with spin-labeled phospholipids indicate unexceptionally that Amp1 interacted more strongly with the lipid bilayer than Amp2. It is proposed that class A amphiphilic alpha-helix is buried in the membrane in such a way that its long axis is oriented parallel to the membrane plane, and the electrostatic interaction between the positively charged residues located at the polar-nonpolar interface of the amphiphilic helix with the negatively charged head groups of phospholipids is important to the lipid affinity of the amphiphilic peptide.