Overexpression of Reactive Cysteine-Containing 2-Nitrobenzoate Nitroreductase (NbaA) and Its Mutants Alters the Sensitivity of Escherichia coli to Reactive Oxygen Species by Reprogramming a Reg
详细信息 查看全文
- 作者：Yong-Hak Kim ; Myeong-Hee Yu
- 刊名：Journal of Proteome Research
- 出版年：2012
- 出版时间：June 1, 2012
- 年：2012
- 卷：11
- 期：6
- 页码：3219-3230
- 全文大小：468K
- 年卷期：v.11,no.6(June 1, 2012)
- ISSN：1535-3907
文摘
The effects of redox-sensitive proteins on Escherichia coli were investigated by overexpressing Pseudomonas 2-nitrobenzoate nitroreductase (NbaA) and its mutants. Overexpression of wild-type and mutant NbaA proteins significantly altered the sensitivity of E. coli to antibiotics and reactive oxygen species regardless of the enzyme activity for reduction of 2-nitrobenzoic acid. The overexpressed proteins rendered cells 100鈥?0000-fold more sensitive to superoxide anion (O2鈥⑩€?/sup>)-generating paraquat and 10鈥?00-fold more resistant to H2O2. A significant increase in intracellular levels of O2鈥⑩€?/sup>, but not H2O2, was observed during expression of wild-type and truncated (螖65鈥?4, 螖193鈥?16, and 螖65鈥?4螖193鈥?16) NbaA. From two-dimensional nonreducing/reducing sodium dodecyl sulfate鈥損olyacrylamide gel electrophoresis and mass spectrometry analyses, 29 abundant proteins in the cytoplasm were identified to form interchain disulfide bonds, when cells were exposed to polymyxin B. Of them, down-regulation and modifications of SodB, KatE, and KatG were strongly associated with elevated cellular O2鈥⑩€?/sup> levels. Western blotting showed up-regulation of cell death signal sensor, CpxA, and down-regulation of cytoplasmic superoxide dismutase, SodB, with 2-fold up-regulation of heterodimeric integration host factor, Ihf. Activity gel assays revealed significant reduction of glyceraldehyde-3-phosphate dehydrogenase with constant levels of 6-phosphogluconate dehydrogenase. These changes would support a high level of NADPH to reduce H2O2-induced disulfide bonds by forced expression of thioredoxin A via thioredoxin reductase. Thus, overexpression of wild-type and truncated NbaA partially compensates for the lack of KatE and KatG to degrade H2O2, thereby enhancing disulfide bond formation in the cytoplasm, and modifies a regulatory network of disulfide-bonded proteins to increase intracellular O2鈥⑩€?/sup> levels.