title: Mechanism of synergism between antimicrobial peptides magainin 2 and PGLa.
abstract: The antimicrobial peptides magainin 2 and PGLa, discovered in the skin of the African clawed frog, Xenopus laevis, exhibit marked synergism [Westerhoff, H. V., Zasloff, M., Rosner, J. L., Hendler, R. W., de Waal, A., Vaz Gomes, A., Jongsma, A. P. M., Riethorst, A., and Juretic, D., Eur. J. Biochem. 228, 257-264 (1995)], although the mechanism is not yet clear. They are believed to kill bacteria by permeabilizing membranes. In this study, we examined the interactions of these peptides in lipid bilayers. PGLa, like magainin 2, preferentially interacts with acidic lipids, forming an amphipathic helix. The peptide induces the release of a water-soluble dye, calcein, entrapped within liposomes. The coexistence of magainin 2 enhances membrane permeabilization, which is maximal at a 1:1 molar ratio. Fluorescence experiments using L18W-PGLa revealed that both peptides form a stoichiometric 1:1 complex in the membrane phase with an association free energy of -15 kJ/mol. Single amino acid mutations in magainin 2 significantly altered the synergistic activity, suggesting that precise molecular recognition is involved in complex formation. The complex as well as each component peptide form peptide-lipid supramolecular complex pores, which mediate the mutually coupled transbilayer transport of dye, lipid, and the peptide per se. The rate of pore formation rate is in the order complex >/= PGLa > magainin 2, whereas the pore lifetime is in the order magainin 2 > complex > PGLa. Therefore, the synergism is a consequence of the formation of a potent heterosupramolecular complex, which is characterized by fast pore formation and moderate pore stability.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Japan. katsumim@pharm.kyoto-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Y
authors.initials: Y
authors.lastname: Mitani
authors.forename: K Y
authors.initials: KY
authors.lastname: Akada
authors.forename: O
authors.initials: O
authors.lastname: Murase
authors.forename: S
authors.initials: S
authors.lastname: Yoneyama
authors.forename: M
authors.initials: M
authors.lastname: Zasloff
authors.forename: K
authors.initials: K
authors.lastname: Miyajima
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism*; D023181:Antimicrobial Cationic Peptides; D001692:Biological Transport; D002942:Circular Dichroism; D004357:Drug Synergism; D004530:Egg Yolk; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D046911:Macromolecular Substances; D054806:Magainins; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010539:Permeability; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D011498:Protein Precursors; D013050:Spectrometry, Fluorescence; D029867:Xenopus Proteins; D014982:Xenopus laevis
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D054806:Magainins; C088254:PGLa prepropeptide; D010455:Peptides; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D011498:Protein Precursors; D029867:Xenopus Proteins; C053301:magainin 2 peptide, Xenopus