K1 represents a heterodimeric A/B toxin secreted by virus-infected Saccharomyces cerevisiae strains. In a two-staged receptor-mediated process, the ionophoric activity of K1 leads to an uncontrolled influx of protons, culminating in the breakdown of the cellular transmembrane potential of sensitive cells. K1 killer yeast necessitate not only an immunity mechanism saving the toxin-producing cell from its own toxin but, additionally, a molecular system inactivating the toxic α subunit within the secretory pathway. In this study, different derivatives of the K1 precursor were constructed to analyze the biological function of particular structural components and their influence on toxin activity as well as the formation of protective immunity. Our data implicate an inactivation of the α subunit during toxin maturation and provide the basis for an updated model of K1 maturation within the host cell's secretory pathway.IMPORTANCE The killer phenotype in the baker's yeast Saccharomyces cerevisiae relies on two double-stranded RNA viruses that are persistently present in the cytoplasm. As they carry the same receptor populations as sensitive cells, killer yeast cells need-in contrast to various bacterial toxin producers-a specialized immunity mechanism. The ionophoric killer toxin K1 leads to the formation of cation-specific pores in the plasma membrane of sensitive yeast cells. Based on the data generated in this study, we were able to update the current model of toxin processing, validating the temporary inactivation of the toxic α subunit during maturation in the secretory pathway of the killer yeast.

中文翻译：

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通过定点诱变分析酵母杀手毒素K1前体的过程：对毒性和免疫力的影响。

K1代表被病毒感染的酿酒酵母菌株分泌的异二聚体A / B毒素。在两阶段的受体介导的过程中，K1的离子活性导致质子不受控制地涌入，最终导致敏感细胞的细胞跨膜电位破坏。K1杀手酵母不仅需要一种免疫机制，使毒素产生细胞免于自身毒素的侵害，而且还需要使分泌途径中的有毒α亚基失活的分子系统。在这项研究中，构造了K1前体的不同衍生物，以分析特定结构成分的生物学功能及其对毒素活性的影响以及保护性免疫的形成。我们的数据暗示了毒素成熟过程中α亚基的失活，并为宿主细胞分泌途径内K1成熟的更新模型提供了基础。重要面包酵母酵母中的杀手表型依赖于两种双链RNA病毒，即持续存在于细胞质中。与各种敏感的细菌产生者相比，杀伤性酵母细胞与敏感细胞具有相同的受体群体，因此需要一种专门的免疫机制。离子杀伤毒素K1导致敏感酵母细胞的质膜中形成阳离子特异性孔。根据这项研究产生的数据，我们能够更新当前的毒素加工模型，