Why and how are peptide-lipid interactions utilized for self-defense? Magainins and tachyplesins as archetypes

Animals as well as plants defend themselves against invading pathogenic microorganisms utilizing cationic antimicrobial peptides, which rapidly kill various microbes without exerting toxicity against the host. Physicochemical peptide-lipid interactions provide attractive mechanisms for innate immunity. Many of these peptides form cationic amphipathic secondary structures, typically alpha-helices and beta-sheets, which can selectively interact with anionic bacterial membranes by the aid of electrostatic interactions. Rapid, peptide-induced membrane permeabilization is an effective mechanism of antimicrobial action. This review article summarizes interactions with lipid bilayers of magainins (alpha-helix) and tachyplesins (beta-sheet) discovered in frog skin and horseshoe crab hemolymph, respectively, as archetypes, emphasizing that the mode of interaction is strongly dependent on the physicochemical properties not only of the peptide, but also of the target membrane.