title: Ovotransferrin antimicrobial peptide (OTAP-92) kills bacteria through a membrane damage mechanism.
abstract: Ovotransferrin antimicrobial peptide (OTAP-92) is a cationic fragment of hen ovotransferrin (OTf). OTAP-92 consists of 92 amino acid residues located within the 109-200 sequence of the N-lobe of OTf. This study was aimed to delineate the antimicrobial mechanism of OTAP-92 and to identify its interaction with bacterial membranes. OTAP-92 caused permeation of Escherichia coli outer membrane (OM) to 1-N-phenylnaphthylamine fluorescent probe in a dose-dependent manner. These results suggested that OTAP-92 crossed the bacterial OM by a self-promoted uptake. Cytoplasmic membrane of E. coli was found to be the target for OTAP-92 bactericidal activity, as assayed by the unmasking of cytoplasmic beta-galactosidase due to membrane permeabilization in a kinetic manner. Pretreatment of bacteria with uncoupler, carbonyl cyanide m-chlorophenylhydrazone, markedly enhanced permeation of cytoplasmic membrane, suggesting that the membrane permeation due to OTAP-92 is independent of the transmembrane potential. In an E. coli phospholipid liposome model, it was demonstrated that OTAP-92 has the ability to dissipate the transmembrane electrochemical potential. Intrinsic fluorescence spectra of the two tryptophan residues in OTAP-92, using liposomal membrane, have identified the lipid-binding region as a helix-sheet motif, and suggested an adjacent Ca(2+)-sensitive site within OTAP-92. These data indicated that OTAP-92 possesses a unique structural motif similar to the insect defensins. Further, this cationic antimicrobial peptide is capable of killing Gram-negative bacteria by crossing the OM by a self-promoted uptake and cause damage to the biological function of cytoplasmic membrane.
authors.affiliation: Department of Biochemistry and Biotechnology, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, 890-0065, Kagoshima, Japan. hishamri@chem.agri.kagoshima-u.ac.jp
authors.forename: H R
authors.initials: HR
authors.lastname: Ibrahim
authors.forename: Y
authors.initials: Y
authors.lastname: Sugimoto
authors.forename: T
authors.initials: T
authors.lastname: Aoki
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects*; D002645:Chickens; D003207:Conalbumin / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects*; D005260:Female; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D013211:Staphylococcus aureus / Q000187:drug effects*; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; C417037:OTAP 92; D010446:Peptide Fragments; D003207:Conalbumin; D014634:Valinomycin