Journal of Antimicrobial Chemotherapy (2002) 49, 961-971
© 2002 The British Society for Antimicrobial Chemotherapy
Characterization of a Williopsis saturnus var. mrakii high molecular weight secreted killer toxin with broad-spectrum antimicrobial activity
1Département de Microbiologie des Ecosystèmes and 2IFR17, Institut Pasteur de Lille, 1 rue Calmette, BP 245, 59019 Lille; 3Laboratoire de Mycologie, Université de Bourgogne, Faculté de Pharmacie et de Médecine, 7 boulevard Jeanne d’Arc, BP 87900, 21079 Dijon Cedex; 4Faculté Libre des Sciences, Université Catholique, Lille; 5UMR 8525, Université de Lille II, Institut de Biologie de Lille, 1 rue Calmette, 59019 Lille, France; 6Dipartimento di Patologia e Medicina di Laboratorio, Sezione di Microbiologia, Università degli Studi di Parma, Parma, Italy; 7Centre Hospitalier et Faculté de Médecine, Lille; 8INSERM U447, Mécanismes Moléculaires de la Pathogénie Microbienne, Institut Pasteur de Lille, Institut de Biologie de Lille, 1 rue Calmette, 59019 Lille, France
Received 3 August 2001; returned 14 December 2001; revised 25 January 2002; accepted 19 February 2002.
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 ß-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.
* Corresponding author. Tel: +33-3-20-87-71-57; Fax: +33-3-20-87-79-08; E-mail: Cyril.Guyard{at}pasteur-lille.fr
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