摘要：Killer factor is known to be a proteinaceous toxin in many strains of industrial yeasts. The genomes of the toxins have been mapped on double-stranded RNA molecules, a linear double-stranded DNA plasmid and a chromosome. These particles may prove to be of far-reaching importance in eucaryotic microorganisms when their nature is better understood, but for some time they were considered a major nuisance. Many killer systems were studied so far in various genera of yeast: Saccharomyces , Ustilago , Kluyveromyces , Pichia , Williopsis , Candida , Debaryomyces and others. The best understood is the killer system K1 in Saccharomyces cerevisiae . Two types of dsRNA in the cytoplasmic virus-like paticles control this system. The killing mechanism of this toxin consists of two phases. The first step involves a rapid binding of heterodimeric killer protein to cell wall receptors containing 1 ,6 -β-D- glucan as an essential component. The permeabilization of the membrane proton gradient, efflux of potassium ions, subsequent release of ATP and of low molecular metabolites, and finally death of the cell. In industrial processes, contamination with killer toxin-producing yeasts species is a potential problem in fermentations; in baking, brewing and wine making processes.
关键词：Killer yeast; mechanism of toxin; problems in industry
