STKE

Insider Versus Outsider

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Science  29 Jun 2001:
Vol. 292, Issue 5526, pp. 2401
DOI: 10.1126/science.292.5526.2401c

Strains of Saccharomyces cerevisiae infected with a small RNA virus secrete a toxin that kills uninfected yeast. The toxin activates TOK1, a potassium channel in the plasma membrane, and promotes unchecked K+ efflux, which causes cell death. How infected yeast remain immune has remained a mystery, although some evidence has pointed to an intracellular mechanism that protects infected yeast cells. Sesti et al. show that even in the presence of extracellular toxin, TOK1 channels of infected cells remain inactive due to an interaction of intracellular toxin with the channel. Experiments with a mutant toxin that did not kill yeast but could still confer resistance to externally applied wild-type toxin suggests a role for the mutant protein in large-scale pharmaceutical productions, where killer strains of yeast are a concern. — JN

Cell105, 637 (2001).

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