title: Enhanced membrane permeabilization and antibacterial activity of a disulfide-dimerized magainin analogue.
abstract: A cysteine substitution analogue of magainin-2 amide (magainin-F12W, N22C; denoted here as mag-N22C), and a disulfide-linked dimer prepared by air oxidation [(mag-N22C)(2)], were compared in their ability to release carboxyfluorescein (CF) from 100-nm large unilamellar vesicles (LUV) and to kill the Gram negative bacteria Stenotrophomonas maltophilia and Escherichia coli. The disulfide-dimerized peptide showed enhanced permeabilization and antimicrobial activity, when compared with the monomeric peptide, that was particularly marked at very low peptide concentrations. The enhanced CF-releasing activity of the dimer at low concentrations in vesicles results from (i) enhanced binding to negatively charged membrane surfaces and (ii) a low concentration dependence for permeabilization in the dimer compared to the monomer. The unique properties of the dimeric peptide suggest a role for structural diversity of antimicrobial peptides in frog skin, including the recent identification of a heterodimer composed of disulfide-linked amphipathic helical peptides [Batista et al. (2001) FEBS Lett. 494, 85-89]. Disulfide-dimerization of pore-forming, positively charged, amphipathic helical peptides may be a useful general approach to the generation of peptide antimicrobials having activity at very low concentrations.
authors.affiliation: Biochemistry Department and Molecular Recognition Centre, Bristol University, School of Medical Sciences, University Walk, Bristol BS8 1TD, U.K. c.dempsey@bris.ac.uk
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Dempsey
authors.forename: Shohta
authors.initials: S
authors.lastname: Ueno
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Avison
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002942:Circular Dichroism; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry*; D004912:Erythrocytes / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005452:Fluoresceins / Q000032:analysis; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D054806:Magainins; D008969:Molecular Sequence Data; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D020615:Stenotrophomonas maltophilia / Q000187:drug effects / Q000254:growth & development; D013329:Structure-Activity Relationship; D029867:Xenopus Proteins; D014982:Xenopus laevis
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D004220:Disulfides; D005452:Fluoresceins; D008051:Lipid Bilayers; D054806:Magainins; D029867:Xenopus Proteins; C053301:magainin 2 peptide, Xenopus; C024098:6-carboxyfluorescein