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Substitution of cysteines in the yeast viral killer toxin K1 precursor reveals novel insights in heterodimer formation and immunity.

ABSTRACT: The killer toxin K1 is a virally encoded fungal A/B toxin acting by disrupting plasma membrane integrity. The connection of ? and ? constitutes a critical feature for toxin biology and for decades the formation of three disulphide bonds linking the major toxin subunits was accepted as status quo. Due to the absence of experimental evidence, the involvement of each cysteine in heterodimer formation, K1 lethality and immunity was systematically analysed. Substitution of any cysteine in ? led to a complete loss of toxin dimer secretion and toxicity, whereas K1 toxin derivatives carrying mutations of C248, C312 or the double mutation C248-312 were active against spheroplasted cells. Importantly, substitution of the C95 and C107 in the toxin precursor completely abolished the mediation of functional immunity. In contrast, K1 toxicity, i.e. its ionophoric effect, does not depend on the cysteine residues at all. In contrast to the literature, our data imply the formation of a single disulphide bond involving C92 in ? and C239 in ?. This finding not only refines the current model stated for decades but also provides new opportunities to elucidate the mechanisms underlying K1 toxicity and immunity at the molecular level.

SUBMITTER: Gier S

PROVIDER: S-EPMC6739482 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Substitution of cysteines in the yeast viral killer toxin K1 precursor reveals novel insights in heterodimer formation and immunity.

Gier Stefanie S Lermen Matthias M Schmitt Manfred J MJ Breinig Frank F

Scientific reports 20190911 1

The killer toxin K1 is a virally encoded fungal A/B toxin acting by disrupting plasma membrane integrity. The connection of α and β constitutes a critical feature for toxin biology and for decades the formation of three disulphide bonds linking the major toxin subunits was accepted as status quo. Due to the absence of experimental evidence, the involvement of each cysteine in heterodimer formation, K1 lethality and immunity was systematically analysed. Substitution of any cysteine in α led to a ...[more]

PMID: 31511600

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Project description:The killer phenomenon in yeast (Saccharomyces cerevisiae) not only provides the opportunity to study host-virus interactions in a eukaryotic model but also represents a powerful tool to analyze potential coadaptional events and the role of killer yeast in biological diversity. Although undoubtedly having a crucial impact on the abundance and expression of the killer phenotype in killer-yeast harboring communities, the influence of a particular toxin on its producing host cell has not been addressed sufficiently. In this study, we describe a model system of two K1 killer yeast strains with distinct phenotypical differences pointing to substantial selection pressure in response to the toxin secretion level. Transcriptome and lipidome analyses revealed specific and intrinsic host cell adaptions dependent on the amount of K1 toxin produced. High basal expression of genes coding for osmoprotectants and stress-responsive proteins in a killer yeast strain secreting larger amounts of active K1 toxin implies a generally increased stress tolerance. Moreover, the data suggest that immunity of the host cell against its own toxin is essential for the balanced virus-host interplay providing valuable hints to elucidate the molecular mechanisms underlying K1 immunity and implicating an evolutionarily conserved role for toxin immunity in natural yeast populations.IMPORTANCE The killer phenotype in Saccharomyces cerevisiae relies on the cytoplasmic persistence of two RNA viruses. In contrast to bacterial toxin producers, killer yeasts necessitate a specific immunity mechanism against their own toxin because they bear the same receptor populations as sensitive cells. Although the killer phenomenon is highly abundant and has a crucial impact on the structure of yeast communities, the influence of a particular toxin on its host cell has been barely addressed. In our study, we used two derivatives secreting different amount of the killer toxin K1 to analyze potential coadaptional events in this particular host/virus system. Our data underline the dependency of the host cell's ability to cope with extracellular toxin molecules and intracellular K1 molecules provided by the virus. Therefore, this research significantly advances the current understanding of the evolutionarily conserved role of this molecular machinery as an intrinsic selection pressure in yeast populations.

Dataset Information

Substitution of cysteines in the yeast viral killer toxin K1 precursor reveals novel insights in heterodimer formation and immunity.

Publications

Substitution of cysteines in the yeast viral killer toxin K1 precursor reveals novel insights in heterodimer formation and immunity.

Similar Datasets

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