Characterization of a Williopsis saturnus var. mrakii high molecular weight secreted killer toxin with broad-spectrum antimicrobial activity

• Published in: Journal of antimicrobial chemotherapy Vol. 49; no. 6; pp. 961 - 971
• Main Authors: Guyard, Cyril, Séguy, Nathalie, Cailliez, Jean-Charles, Drobecq, Hervé, Polonelli, Luciano, Dei-Cas, Eduardo, Mercenier, Annick, Menozzi, Franco D.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.06.2002; Oxford Publishing Limited (England)
• Subjects: Amino Acid Sequence - genetics; Anti-Infective Agents - chemistry; Anti-Infective Agents - isolation & purification; Anti-Infective Agents - pharmacology; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antifungal agents; Biological and medical sciences; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungal Proteins - pharmacology; Killer Factors, Yeast; Medical sciences; Molecular Sequence Data; Molecular Weight; Mycotoxins - chemistry; Mycotoxins - genetics; Mycotoxins - metabolism; Mycotoxins - pharmacology; Pharmacology. Drug treatments; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae Proteins; Yeast; Pneumocystis carinii; Glycosylation; Biological activity; Cell wall; Protein; Pichia; Fungi; Toxin; Antifungal agent; Ascomycetes; Fungi Imperfecti; Saccharomyces cerevisiae; Aminoacid sequence; Thallophyta
• ISSN: 0305-7453; 1460-2091; 1460-2091
• DOI: 10.1093/jac/dkf040

Williopsis saturnus var. mrakii MUCL 41968 secretes a killer toxin (WmKT), which is active against a wide range of pathogens. From the W. saturnus var. mrakii MUCL 41968 culture supernatant a protein of 85 kDa with killer activity was purified to homogeneity. The purified protein was demonstrated to be a killer toxin since it displays the toxin activity and cross-reacts with mAbKT4, a monoclonal antibody that blocks WmKT activity. Its partial amino acid sequencing revealed that WmKT might be related to yeast SUN proteins, but not to other killer toxins described. Immunofluorescence studies using polyclonal antibodies raised against purified WmKT revealed that it acts by binding to the cell surface of sensitive strains. We showed that WmKT is inactive against mutant strains of Saccharomyces cerevisiae deficient in the synthesis of β-glucans, indicating that these polysaccharides constitute the target of the toxin. WmKT was demonstrated to induce rapid lethal cell permeation, since strong propidium iodide labelling was shown for sensitive strains treated with the killer toxin. These findings indicate that WmKT is a novel killer toxin whose molecular characterization may lead to the development of new wide-spectrum antimicrobial compounds.