title: Clavanin permeabilizes target membranes via two distinctly different pH-dependent mechanisms.
abstract: The pH dependence of the antimicrobial and membrane activity of clavanin A, a peptide antibiotic that is rich in histidines and glycines, was analyzed in growth and membrane leakage experiments. Clavanin A more effectively inhibited the growth of the test organism Lactobacillus sake when the pH of the medium was lowered. Whereas the wild-type peptide efficiently released fluorophores from unilamellar vesicles at neutral pH according to a nonspecific permeabilization mechanism, it did not permeabilize model bilayers at low pH. It was therefore suggested that this peptide uses a distinct mode of action under acidic conditions different than that used around neutral pH. However, at low pH, the membrane is still the target for clavanin A, as the peptide collapsed both vital transmembrane proton gradients and ion gradients under these conditions. Clavanin A did not act as a ionophore across phospholipid bilayers, indicating that membrane constituents other than membrane phospholipids are involved in the dissipation of transmembrane ion gradients. Membrane proteins that generate transmembrane ion gradients are suggested to be the targets for clavanin A at low pH. In addition to the histidines, the three glycine residues of clavanin A are shown to play an important role in the specific mode of interaction with these membrane targets. These residues may induce a flexible hydrophobic conformation that allows the peptide to exert different membrane activities. This study demonstrates that clavanin A is a special membrane-active peptide that has access to two markedly distinct pH-dependent modes of actions.
authors.affiliation: Department Coating Systems and Active Ingredients, Renewable Resources, Agrotechnological Research Institute, Wageningen University and Research Centre, Bornsesteeg 59, 6708 PD Wageningen, The Netherlands. e.j.m.vankan@ato.wag-ur.nl
authors.forename: Ellen J M
authors.initials: EJ
authors.lastname: van Kan
authors.forename: Rudy A
authors.initials: RA
authors.lastname: Demel
authors.forename: Eefjan
authors.initials: E
authors.lastname: Breukink
authors.forename: Arie
authors.initials: A
authors.lastname: van der Bent
authors.forename: Ben
authors.initials: B
authors.lastname: de Kruijff
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D001798:Blood Proteins / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002942:Circular Dichroism; D005452:Fluoresceins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000187:drug effects / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D011522:Protons
chemical_list: D000900:Anti-Bacterial Agents; D001798:Blood Proteins; D005452:Fluoresceins; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D011522:Protons; C106713:clavanin A; C017251:1,2-oleoylphosphatidylcholine; D011188:Potassium; C007740:fluorexon