title: The interactions of histidine-containing amphipathic helical peptide antibiotics with lipid bilayers. The effects of charges and pH.
abstract: The alpha-helix of the designed amphipathic peptide antibiotic LAH(4 )(KKALLALALHHLAHLALHLALALKKA-NH(2)) strongly interacts with phospholipid membranes. The peptide is oriented parallel to the membrane surface under acidic conditions, but transmembrane at physiological pH (Bechinger, B. (1996) J. Mol. Biol. 263, 768-775). LAH(4) exhibits antibiotic activities against Escherichia coli and Bacillus subtilis; the peptide does not, however, lyse human red blood cells at bacteriocidal concentrations. The antibiotic activities of LAH(4) are 2 orders of magnitude more pronounced at pH 5 when compared with pH 7.5. Although peptide association at low pH is reduced when compared with pH 7.5, the release of the fluorophore calcein from large unilamellar 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol vesicles is more pronounced at pH values where LAH(4) adopts an orientation along the membrane surface. The calcein release experiments thereby parallel the results obtained in antibiotic assays. Despite a much higher degree of association, calcein release activity of LAH(4) is significantly decreased for negatively charged membranes. Pronounced differences in the interactions of LAH(4) with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol or 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine membranes also become apparent when the mechanisms of dye release are investigated. The results presented in this paper support models in which antibiotic activity is caused by detergent-like membrane destabilization, rather than pore formation by helical peptides in transmembrane alignments.
authors.affiliation: Max-Planck-Institute for Biochemistry, Am Klopferspitz 18A, 82152 Martinsried, Germany.
authors.forename: T C
authors.initials: TC
authors.lastname: Vogt
authors.forename: B
authors.initials: B
authors.lastname: Bechinger
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D023181:Antimicrobial Cationic Peptides; D001412:Bacillus subtilis; D002942:Circular Dichroism; D003911:Dextrans; D004926:Escherichia coli; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006639:Histidine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D008969:Molecular Sequence Data; D010455:Peptides; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D003911:Dextrans; D005452:Fluoresceins; D005456:Fluorescent Dyes; C122154:LAH(4) protein, synthetic; D008051:Lipid Bilayers; D008081:Liposomes; D010455:Peptides; C015219:fluorescein isothiocyanate dextran; D006639:Histidine; D016650:Fluorescein-5-isothiocyanate; C007740:fluorexon