Interactions of an antimicrobial peptide, magainin 2, with lipopolysaccharide-containing liposomes as a model for outer membranes of gram-negative bacteria.

F12W-magainin 2 preferentially interacted with lipopolysaccharide-containing bilayers, permeabilizing the membranes, compared with lipopolysaccharide-free phosphatidylcholine vesicles. Using this system, we demonstrated for the first time that the magainin peptide forms a helix upon binding to lipopolysaccharide. Incorporation of lipid A into phosphatidylcholine liposomes also enhanced interactions with the peptide. The presence of Mg2+, which nullifies the peptide's antibacterial activity against gram-negative bacteria, again weakened the interactions between the peptide and lipopolysaccharide-doped bilayers. This system seems to be useful for investigating the molecular details of peptide-lipopolysaccharide interactions.