Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware, USA.
Appl Environ Microbiol. 2013 Dec;79(23):7210-9. doi: 10.1128/AEM.02322-13. Epub 2013 Sep 13.
Reactive oxygen species are generated by redox reactions and the Fenton reaction of H2O2 and iron that generates the hydroxyl radical that causes severe DNA, protein, and lipid damage. We screened Escherichia coli genomic libraries to identify a fragment, containing cueR, ybbJ, qmcA, ybbL, and ybbM, which enhanced resistance to H2O2 stress. We report that the ΔybbL and ΔybbM strains are more susceptible to H2O2 stress than the parent strain and that ybbL and ybbM overexpression overcomes H2O2 sensitivity. The ybbL and ybbM genes are predicted to code for an ATP-binding cassette metal transporter, and we demonstrate that YbbM is a membrane protein. We investigated various metals to identify iron as the likely substrate of this transporter. We propose the gene names fetA and fetB (for Fe transport) and the gene product names FetA and FetB. FetAB allows for increased resistance to oxidative stress in the presence of iron, revealing a role in iron homeostasis. We show that iron overload coupled with H2O2 stress is abrogated by fetA and fetB overexpression in the parent strain and in the Δfur strain, where iron uptake is deregulated. Furthermore, we utilized whole-cell electron paramagnetic resonance to show that intracellular iron levels in the Δfur strain are decreased by 37% by fetA and fetB overexpression. Combined, these findings show that fetA and fetB encode an iron exporter that has a role in enhancing resistance to H2O2-mediated oxidative stress and can minimize oxidative stress under conditions of iron overload and suggest that FetAB facilitates iron homeostasis to decrease oxidative stress.
活性氧由氧化还原反应和 H2O2 与铁的芬顿反应生成，生成羟基自由基，导致严重的 DNA、蛋白质和脂质损伤。我们筛选了大肠杆菌基因组文库，以鉴定一个包含 cueR、ybbJ、qmcA、ybbL 和 ybbM 的片段，该片段增强了对 H2O2 应激的抗性。我们报告说，与亲本菌株相比，ΔybbL 和 ΔybbM 菌株对 H2O2 应激更敏感，并且 ybbL 和 ybbM 的过表达克服了 H2O2 敏感性。ybbL 和 ybbM 基因预测编码一种 ATP 结合盒金属转运体，我们证明 YbbM 是一种膜蛋白。我们研究了各种金属，以确定铁是该转运体的可能底物。我们提出了基因名称 fetA 和 fetB（用于铁运输）和基因产物名称 FetA 和 FetB。FetAB 允许在存在铁的情况下增加对氧化应激的抗性，揭示了其在铁稳态中的作用。我们表明，铁过载与 H2O2 应激的联合作用被 fetA 和 fetB 在亲本菌株和 fur 缺失菌株中的过表达所消除，在 fur 缺失菌株中，铁摄取被失调。此外，我们利用全细胞电子顺磁共振波谱法表明，fetA 和 fetB 过表达使 fur 缺失菌株中的细胞内铁水平降低了 37%。综上所述，这些发现表明 fetA 和 fetB 编码一种铁外排泵，它在增强对 H2O2 介导的氧化应激的抗性方面发挥作用，并在铁过载和氧化应激的条件下降低氧化应激，提示 FetAB 有助于铁稳态以降低氧化应激。
