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Intermedilysin, a novel cytotoxin specific for human cells secreted by Streptococcus intermedius UNS46 isolated from
H Nagamune1, C Ohnishi, A Katsuura
1Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, Japan.
Abstract:
A novel cytotoxin (intermedilysin) specific for human cells was identified as a cytolytic factor of Streptococcus intermedius UNS46 isolated from a human liver abscess. Intermedilysin caused human cell death with membrane blebs. Intermedilysin was purified from UNS46 culture medium by means of gel filtration and hydrophobic chromatography. The purified toxin was resolved into major and minor bands of 54 and 53 kDa, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These proteins reacted with an antibody against intermedilysin. Five internal peptide fragments of intermedilysin were sequenced and found to have 42 to 71% homology with the thiol-activated cytotoxin pneumolysin. However, the action of intermedilysin differed from that of thiol-activated cytotoxins, especially in terms of a lack of activation by dithiothreitol and resistance to treatments with N-ethylmaleimide and 5,5'-dithio-bis-(2-nitrobenzoic acid), although cholesterol inhibited the toxin activity. Intermedilysin was potently hemolytic on human erythrocytes but was 100-fold less effective on chimpanzee and cynomolgus monkey erythrocytes. Intermedilysin was not hemolytic in nine other animal species tested. Since human erythrocytes treated with trypsin were far less sensitive to intermedilysin than were the intact cells, a cell membrane protein(s) may participate in the intermedilysin action. These data demonstrated that intermedilysin is distinguishable from all known bacterial cytolysins.
Insights
A novel Streptococcus intermedius cytotoxin, intermedilysin, specifically targets human cells, causing cell death. This bacterial toxin exhibits unique properties distinct from known cytolysins.
Area of Science:
- Microbiology
- Toxicology
- Cell Biology
Background:
- Streptococcus intermedius is associated with human infections, including liver abscesses.
- Bacterial toxins play a significant role in pathogenesis.
- Understanding novel toxins is crucial for developing targeted therapies.
Purpose of the Study:
- To identify and characterize a novel cytotoxin from Streptococcus intermedius UNS46.
- To investigate the specificity and mechanism of action of this new toxin, named intermedilysin.
- To differentiate intermedilysin from known bacterial cytolysins.
Main Methods:
- Isolation and purification of intermedilysin from bacterial culture.
- Biochemical characterization including SDS-PAGE and peptide sequencing.
- Functional assays to determine hemolytic activity and cell-specific toxicity.
- Comparative analysis with known thiol-activated cytotoxins.
Main Results:
- Intermedilysin, a cytolytic factor specific for human cells, was purified.
- The toxin showed potent hemolytic activity on human erythrocytes but limited activity on other species.
- Intermedilysin's mechanism differed from thiol-activated toxins, lacking dithiothreitol activation and N-ethylmaleimide sensitivity.
- Cholesterol inhibited intermedilysin activity, and cell membrane proteins likely mediate its action.
Conclusions:
- Intermedilysin is a novel bacterial cytotoxin produced by Streptococcus intermedius.
- It exhibits unique human cell specificity and a distinct mechanism of action.
- Intermedilysin represents a new class of bacterial cytolysins.