Fluoride export (FEX) proteins from fungi, plants and animals are 'single barreled' channels containing one functional and one vestigial ion pore.
Fluoride export (FEX) proteins from fungi, plants and animals are 'single barreled' channels containing one functional and one vestigial ion pore.
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DOI：
10.1371/journal.pone.0177096
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Strobel SA
中科院分区：
文献类型：
--
作者：
Berbasova T;Nallur S;Sells T;Smith KD;Gordon PB;Tausta SL;Strobel SA
酵母和其他真菌中的氟化物输出蛋白（FEX）提供了对氟化物（F-）的耐受性，氟化物是一种环境中普遍存在的阴离子。FEX有效地消除细胞内的氟化物，否则会积累在有毒浓度。细菌中的FEX同源物Fluc是由两个相同或相似的亚基二聚化形成的“双管”通道。酵母和其他真核生物中的FEX是由两个亚基共价融合产生的单体。因此，两个潜在的氟化物孔都是由同一蛋白质的不同部分产生的。在这里，我们确定FEX蛋白质从两个多细胞真核生物，植物拟南芥和动物双齿藻queenslandica，通过展示显着的耐氟性时，这些蛋白质在酵母酿酒酵母中异源表达。真核FEX功能的重要残基通过系统发育序列比对和使用酵母生长测定的功能分析来确定。氟化物通道的关键残基仅保存在两个潜在的氟化物运输孔中的一个中。FEX活性在该保守孔中的残基突变后被消除，这表明只有一个孔是功能性的。相同的拓扑结构对于新鉴定的来自植物和动物的FEX蛋白是保守的。这些数据表明，FEX家族的氟化物通道在真核生物中是“单管”的转运蛋白，含有一个功能孔和第二个非功能的同源基因融合事件的残留物。
The fluoride export protein (FEX) in yeast and other fungi provides tolerance to fluoride (F-), an environmentally ubiquitous anion. FEX efficiently eliminates intracellular fluoride that otherwise would accumulate at toxic concentrations. The FEX homolog in bacteria, Fluc, is a ‘double-barreled’ channel formed by dimerization of two identical or similar subunits. FEX in yeast and other eukaryotes is a monomer resulting from covalent fusion of the two subunits. As a result, both potential fluoride pores are created from different parts of the same protein. Here we identify FEX proteins from two multicellular eukaryotes, a plant Arabidopsis thaliana and an animal Amphimedon queenslandica, by demonstrating significant fluoride tolerance when these proteins are heterologously expressed in the yeast Saccharomyces cerevisiae. Residues important for eukaryotic FEX function were determined by phylogenetic sequence alignment and functional analysis using a yeast growth assay. Key residues of the fluoride channel are conserved in only one of the two potential fluoride-transporting pores. FEX activity is abolished upon mutation of residues in this conserved pore, suggesting that only one of the pores is functional. The same topology is conserved for the newly identified FEX proteins from plant and animal. These data suggest that FEX family of fluoride channels in eukaryotes are ‘single-barreled’ transporters containing one functional pore and a second non-functional vestigial remnant of a homologous gene fusion event.