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Involvement of [beta]-glucans in the wide-spectrum antimicrobial activity of Williopsis saturnus var. mrakii MUCL 41968 killer toxin.
- Source :
-
Molecular medicine (Cambridge, Mass.) [Mol Med] 2002 Nov; Vol. 8 (11), pp. 686-94. - Publication Year :
- 2002
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Abstract
- Background: Williopsis saturnus var. mrakii MUCL 41968 secretes a 85-kDa glycoprotein killer toxin (WmKT) that displays a cytocidal activity against a wide range of microorganisms, making WmKT a promising candidate for the development of new antimicrobial molecules. Although the killing mechanism of WmKT is still unknown, the toxin was recently proposed to bind to the surface of sensitive microorganisms through the recognition of beta-glucans. Indeed, Saccharomyces cerevisiae strains sensitive to the toxin become resistant when mutated in their beta-glucan synthesis pathway.<br />Materials and Methods: To investigate the interaction of WmKT with beta-glucans, we examined in agar diffusion assays the WmKT activity in the presence of enzymes displaying beta-glucanase activity. The toxin activity was also investigated using spheroplasts derived from sensitive yeast cells. The hydrolytic activity of WmKT was studied using specific glucosidase inhibitors as well as various sugar molecules covalently linked to p-nitrophenyl as potential substrates. Finally, the ultrastructural modifications induced by WmKT activity on sensitive yeasts were assessed by scanning electron microscopy.<br />Results: The data reported here support the hypothesis that WmKT binds to sensitive cells using surface-exposed beta-glucans. Indeed beta-glucanase exerts an antagonistic effect on WmKT activity and spheroplasts derived from WmKT-sensitive yeast cells are shown to be resistant to WmKT, suggesting that cell wall beta-glucans are required for WmKT lethal effect. Because WmKT exhibits amino acid sequence similarities with proteins suspected to be glucanase, we also investigated the effect of castanospermine, a potent glucosidase inhibitor, on WmKT activity. Castanospermine completely abolished WmKT killer activity as well as its hydrolytic enzymatic activity against p-nitrophenyl beta-D-glucopyranoside. The scanning electron microscopy analysis of sensitive yeast cells treated with the toxin reveals that WmKT causes cell wall modifications similar to those observed with zymolyase.<br />Conclusion: The results reported in this study show that WmKT activity requires an interaction between the mycocin and the cell wall beta-glucans. Moreover, they indicate that WmKT acts on sensitive yeast cells through a hydrolytic activity directed against cell wall beta-glucans that disrupts the yeast cell wall integrity leading to death.
- Subjects :
- Amphotericin B pharmacology
Anti-Bacterial Agents
Antifungal Agents pharmacology
Cell Death
Colony Count, Microbial
Drug Resistance, Microbial
Enzyme Inhibitors pharmacology
Flow Cytometry
Hydrolases pharmacology
Indolizines pharmacology
Killer Factors, Yeast
Nitrophenols metabolism
Saccharomyces cerevisiae ultrastructure
Saccharomyces cerevisiae Proteins
beta-Glucosidase antagonists & inhibitors
beta-Glucosidase metabolism
Anti-Infective Agents pharmacology
Fungal Proteins pharmacology
Glucans metabolism
Mycotoxins pharmacology
Saccharomyces cerevisiae drug effects
Spheroplasts drug effects
Subjects
Details
- Language :
- English
- ISSN :
- 1076-1551
- Volume :
- 8
- Issue :
- 11
- Database :
- MEDLINE
- Journal :
- Molecular medicine (Cambridge, Mass.)
- Publication Type :
- Academic Journal
- Accession number :
- 12520085