Structure and interactions of magainin antibiotic peptides in lipid bilayers: a solid-state nuclear magnetic resonance investigation

Many organisms use antibiotic peptides as a defensemechanism, thereby supplementing or replacing theimmune system (1). Magainins are a family of 21 to 26residue peptides found in the skin and other organs offrogs (2, 3) with a broad spectrum of antibacterial,antifungal, and tumorcidal activity (2-4).They disruptthe electrochemical ionic gradient across cell mem­branes, probably by forming oligomeric peptide ionchannels (4-6). Whereas these peptides show stronginteractionswith bacterial and acidic model membranes(2, 7, 8), they do not lyse formed circulating vertebrateblood cells (3, 4). Multidimensional solution nuclearmagnetic resonance (NMR) experiments show thatmagainin is unstructured in aqueous solution and exhib­its a high a-helixcontent in trifluoroethanollwater (9)and in micelles (Shon, K., M. Zasloff, and S. J. Opella,unpublished data). Helical wheel analysis indicates thatsuch a helix is amphipathic. Solid-stateNMR spectros­copy was used to study the structure, dynamics andinteractions ofmagainins associated with lipid bilayers.