Grass Gregor, Otto Markus, Fricke Beate, Haney Christopher J, Rensing Christopher, Nies Dietrich H, Munkelt Doreen
Institut für Mikrobiologie, Martin-Luther-Universität Halle, Kurt-Mothes-Str. 3, Halle 06120, Germany.
Arch Microbiol. 2005 Jan;183(1):9-18. doi: 10.1007/s00203-004-0739-4. Epub 2004 Nov 11.
The Escherichia coli yiiP gene encodes an iron transporter, ferrous iron efflux (FieF), which belongs to the cation diffusion facilitator family (CDF). Transcription of fieF correlated with iron concentration; however, expression appeared to be independent of the ferrous iron uptake regulator Fur. Absence of FieF led to decreased growth of E. coli cells in complex growth medium but only if fur was additionally deleted. The presence of EDTA was partially able to relieve this growth deficiency. Expression of fieF in trans rendered the double deletion strain more tolerant to iron. Furthermore, E. coli cells exhibited reduced accumulation of (55)Fe when FieF was expressed in trans. FieF catalyzed active efflux of Zn(II) in antiport with protons energized by NADH via the transmembrane pH gradient in everted membrane vesicles. Using the iron-sensitive fluorescent indicator PhenGreen-SK encapsulated in proteoliposomes, transmembrane fluxes of iron cations were measured with purified and reconstituted FieF by fluorescence quenching. This suggests that FieF is an iron and zinc efflux system, which would be the first example of iron detoxification by efflux in any organism.
大肠杆菌的yiiP基因编码一种铁转运蛋白——亚铁离子外排蛋白（FieF），它属于阳离子扩散促进蛋白家族（CDF）。fieF的转录与铁浓度相关；然而，其表达似乎独立于亚铁离子摄取调节蛋白Fur。FieF的缺失导致大肠杆菌细胞在复合生长培养基中的生长速度下降，但前提是fur基因也被额外删除。乙二胺四乙酸（EDTA）的存在能够部分缓解这种生长缺陷。fieF的反式表达使双缺失菌株对铁更具耐受性。此外，当fieF进行反式表达时，大肠杆菌细胞对（55）Fe的积累减少。FieF通过由NADH经翻转膜囊泡中的跨膜pH梯度提供能量的质子反向转运催化Zn（II）的主动外排。使用包裹在蛋白脂质体中的铁敏感荧光指示剂PhenGreen-SK，通过荧光猝灭法用纯化并重组的FieF测量铁阳离子的跨膜通量。这表明FieF是一种铁和锌外排系统，这将是任何生物体中通过外排进行铁解毒的首个例子。
