title: Bactericidal effect of Naja nigricollis toxin γ is related to its membrane-damaging activity.
abstract: The aim of the present study is to investigate the causal relationship between membrane-damaging activity and bactericidal activity of Naja nigricollis toxin γ. Toxin γ showed a similar inhibitory activity on the growth of Staphylococcus aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria). Antibacterial activity of toxin γ correlated positively with increase in membrane permeability of bacterial cells. Morphological examination showed that toxin γ disrupted the integrity of bacterial membrane. Toxin γ showed similar binding capability with lipopolysaccharide (LPS) and lipoteichoic acid (LTA), and destabilization of LPS layer and inhibition of LTA biosynthesis on cell wall increased bactericidal effect of toxin γ on E. coli and S. aureus, respectively. Although the potency of toxin γ on permeabilizing model membrane of E. coli and S. aureus was similar, the mode of interaction between toxin γ and model membrane of E. coli and S. aureus differed. Membrane-damaging activity of toxin γ was inhibited by either LPS or LTA. Nevertheless, LPS and LTA altered differently membrane-bound conformation of toxin γ. Taken together, our data suggest that bactericidal activity of toxin γ depends on its ability to induce membrane permeability, and that LPS and LTA structurally suppresses bactericidal effect of toxin γ.
authors.affiliation: Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan.
authors.forename: Li-Wen
authors.initials: LW
authors.lastname: Chen
authors.forename: Pei-Hsiu
authors.initials: PH
authors.lastname: Kao
authors.forename: Yaw-Syan
authors.initials: YS
authors.lastname: Fu
authors.forename: Wan-Ping
authors.initials: WP
authors.lastname: Hu
authors.forename: Long-Sen
authors.initials: LS
authors.lastname: Chang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism; D002463:Cell Membrane Permeability; D002473:Cell Wall / Q000378:metabolism; D004179:Cobra Cardiotoxin Proteins / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D008070:Lipopolysaccharides / Q000378:metabolism / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D013211:Staphylococcus aureus / Q000187:drug effects; D013682:Teichoic Acids / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004179:Cobra Cardiotoxin Proteins; D008070:Lipopolysaccharides; D013682:Teichoic Acids; C550831:toxin-gamma protein, Naja nigricollis; C009900:lipoteichoic acid