RESUMO
A triple mutant strain of Saccharomyces cerevisiae lacking its own Na+-ATPases and Na+/H+ antiporters (enal-4delta nha1delta nhx1delta) was used for the expression of the Oryza sativa NHX1 gene encoding a putative vacuolar Na+/H+ exchanger. Upon expression in yeast cells, the OsNhx 1p is not a transport system specific only for sodium cations but it has a broad substrate specificity for at least four alkali metal cations (Na+, Li+, K+ and Rb+) and is able to substitute for the endogenous yeast ScNhx1 antiporter. Its activity contributes to sequestration of alkali metal cations in intracellular vesicles.
Assuntos
Oryza/metabolismo , Saccharomyces cerevisiae/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Sequência de Bases , DNA de Plantas/genética , Genes Fúngicos , Genes de Plantas , Teste de Complementação Genética , Metais/metabolismo , Metais/farmacologia , Mutação , Oryza/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Trocadores de Sódio-Hidrogênio/genética , Vacúolos/metabolismoRESUMO
The possible correlation between plasma membrane fluidity changes induced by modified cultivation conditions and cell sensitivity to the killer toxin K1 of Saccharomyces cerevisiae were investigated. Cells grown under standard conditions exhibited high toxin sensitivity. Both a membrane fluidity drop and fluidity rise brought about markedly reduced sensitivity to the toxin. These results do not fit the hypothesis of physiological relevance of direct toxin-lipid interaction, suggesting that the essential event in killer toxin action is interaction with membrane protein(s) that can be negatively influenced by any changes of membrane fluidity.
