Kinclova-Zimmermannova Olga, Sychrová Hana
Department of Membrane Transport, Institute of Physiology AS CR, v.v.i., Videnska 1083, 142 20 Prague 4-Krc, Czech Republic.
Microbiology (Reading). 2007 Aug;153(Pt 8):2603-2612. doi: 10.1099/mic.0.2007/008011-0.
The physiological role of Candida albicans Cnh1, a member of the Na+/H+ antiporter family, was characterized. Though CaCnh1p had broad substrate specificity and mediated efflux of at least four alkali metal cations upon heterologous expression in Saccharomyces cerevisiae, its presence in C. albicans cells was important especially for potassium homeostasis. In C. albicans, CaCnh1p tagged with GFP was localized in the plasma membrane of cells growing as both yeasts and hyphae. Deletion of CNH1 alleles did not affect tolerance to NaCl, LiCl or CsCl, but resulted in increased sensitivity to high external concentrations of KCl and RbCl. The potassium and rubidium tolerance of a cnh1 homozygous mutant was fully restored by reintegration of CNH1 into the genome. The higher sensitivity of the cnh1/cnh1 mutant to external KCl was caused by a lower K+ efflux from these cells. Together, the functional characterization of the CaCnh1 antiporter in C. albicans revealed that this antiporter plays a significant role in C. albicans physiology. It ensures potassium and rubidium tolerance and participates in the regulation of intracellular potassium content of C. albicans cells.
白色念珠菌Cnh1（一种Na+/H+反向转运蛋白家族成员）的生理作用得到了表征。尽管CaCnh1p具有广泛的底物特异性，并且在酿酒酵母中异源表达时介导至少四种碱金属阳离子的外流，但其在白色念珠菌细胞中的存在对于钾离子稳态尤为重要。在白色念珠菌中，标记有绿色荧光蛋白（GFP）的CaCnh1p定位于以酵母和菌丝形式生长的细胞的质膜中。CNH1等位基因的缺失不影响对NaCl、LiCl或CsCl的耐受性，但导致对高浓度外部KCl和RbCl的敏感性增加。通过将CNH1重新整合到基因组中，cnh1纯合突变体对钾和铷的耐受性得以完全恢复。cnh1/cnh1突变体对外部KCl的较高敏感性是由这些细胞中较低的K+外流引起的。总之，白色念珠菌中CaCnh1反向转运蛋白的功能表征表明，这种反向转运蛋白在白色念珠菌生理学中起着重要作用。它确保了对钾和铷的耐受性，并参与了白色念珠菌细胞内钾含量的调节。
