title: Synergism of Leu-Lys rich antimicrobial peptides and chloramphenicol against bacterial cells.
abstract: To investigate the antibiotic activity and synergistic effect, analogues were designed to increase not only net positive charge by Lys-substitution but also hydrophobic helix region by Leu-substitution from CA (1-8)-MA (1-12) hybrid peptide (CA-MA). In particular, CA-MA analogue P5 (P5), designed by flexible region (GIG-->P)-substitution, Lys- (positions 4, 8, 14, 15) and Leu- (positions 5, 6, 12, 13, 16, 17, 20) substitutions, showed potent antibacterial activity in minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC) without having hemolytic activity. In addition, P5 and chloramphenicol has potent synergistic effect against tested cell lines. As determined by propidium iodide (PI) staining, flow cytometry showed that P5 plus chloramphenicol-treated cells had higher fluorescence intensity than untreated, P5- and chloramphenicol-treated cells. The effect on plasma membrane was examined by investigating the transmembrane potential depolarizing experiments of S. aureus with P5 and chloramphenicol. The result showed that the peptide exerts its antibacterial activity by acting on the plasma membrane. Furthermore, P5 caused significant morphological alterations of S. aureus, as shown by scanning electron microscopy. Our results suggest that peptide P5 is an excellent candidate as a lead compound for the development of novel anti-infective agents and synergistic effects with conventional antibiotic agents but lack hemolytic activity.
authors.affiliation: Research Center for Proteineous Materials, Chosun University, 375 Seosuk-Dong, Dong-Ku, Kwangju 501-759, Korea.
authors.forename: Yoonkyung
authors.initials: Y
authors.lastname: Park
authors.forename: Soon Nang
authors.initials: SN
authors.lastname: Park
authors.forename: Seong-Cheol
authors.initials: SC
authors.lastname: Park
authors.forename: Sun Oh
authors.initials: SO
authors.lastname: Shin
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Sung-Jin
authors.initials: SJ
authors.lastname: Kang
authors.forename: Mi-Hyun
authors.initials: MH
authors.lastname: Kim
authors.forename: Chan-Young
authors.initials: CY
authors.lastname: Jeong
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Hahm
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000138:chemical synthesis / Q000737:chemistry; D023181:Antimicrobial Cationic Peptides / Q000008:administration & dosage* / Q000138:chemical synthesis / Q000737:chemistry; D001419:Bacteria / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002701:Chloramphenicol / Q000008:administration & dosage*; D015195:Drug Design; D004357:Drug Synergism; D004912:Erythrocytes / Q000187:drug effects / Q000648:ultrastructure; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D002701:Chloramphenicol