Ros R, Montesinos C, Rimon A, Padan E, Serrano R
Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Spain.
J Bacteriol. 1998 Jun;180(12):3131-6. doi: 10.1128/JB.180.12.3131-3136.1998.
The bacterial Na+ (Li+)/H+ antiporter NhaA has been expressed in the yeast Saccharomyces cerevisiae. NhaA was present in both the plasma membrane and internal membranes, and it conferred lithium but not sodium tolerance. In cells containing the yeast Ena1-4 (Na+, Li+) extrusion ATPase, the extra lithium tolerance conferred by NhaA was dependent on a functional vacuolar H+ ATPase and correlated with an increase of lithium in an intracellular pool which exhibited slow efflux of cations. In yeast mutants without (Na+, Li+) ATPase, lithium tolerance conferred by NhaA was not dependent on a functional vacuolar H+ ATPase and correlated with a decrease of intracellular lithium. NhaA was able to confer sodium tolerance and to decrease intracellular sodium accumulation in a double mutant devoid of both plasma membrane (Na+, Li+) ATPase and vacuolar H+ ATPase. These results indicate that the bacterial antiporter NhaA expressed in yeast is functional at both the plasma membrane and the vacuolar membrane. The phenotypes conferred by its expression depend on the functionally of plasma membrane (Na+, Li+) ATPase and vacuolar H+ ATPase.
细菌的Na+(Li+)/H+逆向转运蛋白NhaA已在酿酒酵母中表达。NhaA存在于质膜和内膜中，它赋予酵母锂耐受性而非钠耐受性。在含有酵母Ena1 - 4(Na+, Li+)外向ATP酶的细胞中，NhaA赋予的额外锂耐受性依赖于功能性液泡H+ ATP酶，并且与细胞内池中锂的增加相关，该细胞内池表现出阳离子的缓慢外流。在没有(Na+, Li+)ATP酶的酵母突变体中，NhaA赋予的锂耐受性不依赖于功能性液泡H+ ATP酶，并且与细胞内锂的减少相关。NhaA能够在缺乏质膜(Na+, Li+)ATP酶和液泡H+ ATP酶的双突变体中赋予钠耐受性并减少细胞内钠的积累。这些结果表明，在酵母中表达的细菌逆向转运蛋白NhaA在质膜和液泡膜上均有功能。其表达所赋予的表型取决于质膜(Na+, Li+)ATP酶和液泡H+ ATP酶的功能。
