The aim of the study is to investigate the causal relationship between membrane-damaging activity and antibacterial action of cardiotoxins from Naja naja atra (Taiwan cobra) cardiotoxin 3 (CTX3) and Naja nigricollis (Egyptian cobra) toxin gamma. Compared with that on Escherichia coli (E. coli, Gram-negative bacteria), CTX3 showed a greater growth inhibition on Staphylococcus aureus (S. aureus, Gram-positive bacteria). Antibacterial avtivity of toxin gamma toward E. coli and S. aureus was similar. Bactericidal action of cardiotoxins positively correlated with increase in membrane permeability of bacterial cells. Morphological examination showed that cardiotoxins disrupted the integrity of bacterial membrane. Cardiotoxins showed similar binding capability with lipopolysaccharide (LPS) and lipoteichoic acid (LTA), and destabilization of LPS layer and inhibition of LTA biosynthesis on cell wall promoted bactericidal effect of cardiotoxins on E. coli and S. aureus, respectively. CTX3 notably permeabilized model membrane of S. aureus and toxin gamma had similar activity on the permeabilization of bacterial model membrane used. Membrane-damaging activity of cardiotoxins was inhibited by either LPS or LTA, while increasing concentrations of cardiotoxins counteracted the inhibitory action of LPS and LTA. Oxidation of Met residues on loop II of cardiotoxins simultaneously attenuated membrane-permeabilizing activity and bactericidal effect of cardiotoxins. Taken together, our data indicate that antibacterial action of cardiotoxins depend on their ability to induce membrane permeability.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0608111-170241 |
| Date | 08 June 2011 |
| Creators | Chen, Li-wen |
| Contributors | Shinne-Ren Lin, Long-Sen Chang, Chun-Chang Chang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0608111-170241 |
| Rights | off_campus_withheld, Copyright information available at source archive |
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