title: After chitin docking, toxicity of Kluyveromyces lactis zymocin requires Saccharomyces cerevisiae plasma membrane H+-ATPase.
abstract: Zymocin, a three-subunit (alpha beta gamma) toxin complex from Kluyveromyces lactis, imposes a cell cycle block on Saccharomyces cerevisiae. Phenotypic analysis of the resistant kti10 mutant implies a membrane defect, suggesting that KTI10 represents a gene involved early in the zymocin response. Consistently, KTI10 is shown here to be allelic to PMA1 encoding H(+)-ATPase, a plasma membrane H(+) pump vital for membrane energization (Delta Psi). Like pma1 mutants, kti10 cells lose viability at low pH, indicating a pH homeostasis defect, and resist the antibiotic hygromycin B, uptake of which is known to be Pma1 and Delta Psi sensitive. Similar to kti10 cells, pma1 mutants with reported H(+) pump defects survive in the presence of exozymocin but do not resist endogenous expression of its lethal gamma-toxin subunit. Based on DNA sequence data, kti10 cells are predicted to produce a malfunctional Pma1 variant with expression levels that are normal. Intriguingly, zymocin protection of kti10 cells is suppressed by excess H(+), a scenario ineffective in bypassing resistance of chitin or toxin target mutants. Together with unaltered zymocin docking and gamma-toxin import events in kti10 cells, our data suggest that Pma1's role in zymocin action is likely to involve activation of gamma-toxin in a step following its cellular uptake.
authors.affiliation: Biologicum, Institut für Genetik, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, D-06120 Halle (Saale), Germany.
authors.forename: Constance
authors.initials: C
authors.lastname: Mehlgarten
authors.forename: Raffael
authors.initials: R
authors.lastname: Schaffrath
mesh_terms: D000483:Alleles; D000935:Antifungal Agents / Q000494:pharmacology; D002686:Chitin / Q000378:metabolism*; D004271:DNA, Fungal / Q000737:chemistry / Q000302:isolation & purification; D025141:Drug Resistance, Fungal; D000431:Ethanol / Q000633:toxicity; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D006921:Hygromycin B / Q000494:pharmacology; D055646:Killer Factors, Yeast; D007716:Kluyveromyces; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009183:Mycotoxins / Q000378:metabolism / Q000633:toxicity*; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D004271:DNA, Fungal; D055646:Killer Factors, Yeast; D008565:Membrane Proteins; D009183:Mycotoxins; D029701:Saccharomyces cerevisiae Proteins; C058975:zymocin; D002686:Chitin; D000431:Ethanol; D006921:Hygromycin B; D006180:Proton-Translocating ATPases