title: Tryptophan-containing lipopeptide antibiotics derived from polymyxin B with activity against Gram positive and Gram negative bacteria.
abstract: Resistance to all known antibiotics is a growing concern worldwide, and has renewed the interest in antimicrobial peptides, a structurally diverse class of amphipathic molecules that essentially act on the bacterial membrane. Propelled by the antimicrobial potential of this compound class, we have designed three new lipopeptides derived from polymyxin B, sp-34, sp-96 and sp-100, with potent antimicrobial activity against both Gram positive and Gram negative bacteria. The three peptides bind with high affinity to lipopolysaccharide as demonstrated by monolayer penetration and dansyl-displacement. The interaction with the cytoplasmic membrane has been elucidated by biophysical experiments with model membranes of POPG or POPE/POPG (6:4), mimicking the Gram positive and Gram negative bacterial membrane. Trp-based fluorescence experiments including steady-state, quenching, anisotropy and FRET, reveal selectivity for anionic phospholipids and deep insertion into the membrane. All three lipopeptides induce membrane fusion and leakage from anionic vesicles, a process that is favored by the presence of POPE. The molecules bind to zwitterionic POPC vesicles, a model of the eukaryotic membrane, but in a different way, with lower affinity, less penetration into the bilayer and no fusion or permeabilization of the membrane. Results in model membranes are consistent with flow cytometry experiments in Escherichia coli and Staphylococcus aureus using a membrane potential sensitive dye (bis-oxonol) and a nucleic acid dye (propidium iodide), suggesting that the mechanism of action is based on membrane binding and collapse of membrane integrity by depolarization and permeabilization.
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Barcelona, Joan XXIII s/n, 08028 Barcelona, Spain; Department of Organic Chemistry, Faculty of Chemistry, University of Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
authors.forename: Ariadna
authors.initials: A
authors.lastname: Grau-Campistany
authors.affiliation: Laboratory of Microbiology, Faculty of Pharmacy, University of Barcelona, Joan XXIII s/n, 08028 Barcelona, Spain.
authors.forename: Ángeles
authors.initials: Á
authors.lastname: Manresa
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Barcelona, Joan XXIII s/n, 08028 Barcelona, Spain; Nanocience and Nanotechnology Institute IN2UB, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Pujol
authors.affiliation: Department of Organic Chemistry, Faculty of Chemistry, University of Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
authors.forename: Francesc
authors.initials: F
authors.lastname: Rabanal
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, University of Barcelona, Joan XXIII s/n, 08028 Barcelona, Spain; Nanocience and Nanotechnology Institute IN2UB, Spain. Electronic address: ycajal@ub.edu.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Cajal
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D004926:Escherichia coli / Q000254:growth & development*; D011112:Polymyxin B / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000254:growth & development*
chemical_list: D000900:Anti-Bacterial Agents; D011112:Polymyxin B