<i>Escherichia coli</i> pyruvate:flavodoxin oxidoreductase, YdbK - regulation of expression and biological roles in protection against oxidative stress

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  • Nakayama Takayuki
    Laboratory of Stress Response Biology, Department of Biological Sciences, Graduate School of Science, Kyoto University
  • Yonekura Shin-Ichiro
    Laboratory of Stress Response Biology, Department of Biological Sciences, Graduate School of Science, Kyoto University
  • Yonei Shuji
    Laboratory of Stress Response Biology, Department of Biological Sciences, Graduate School of Science, Kyoto University
  • Zhang-Akiyama Qiu-Mei
    Laboratory of Stress Response Biology, Department of Biological Sciences, Graduate School of Science, Kyoto University

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  • Escherichia coli pyruvate:flavodoxin oxidoreductase, YdbK-regulation of expression and biological roles in protection against oxidative stress

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Abstract

E. coli YdbK is predicted to be a pyruvate:flavodoxin oxidoreductase (PFOR). However, enzymatic activity and the regulation of gene expression of it are not well understood. In this study, we found that E. coli cells overexpressing the ydbK gene had enhanced PFOR activity, indicating the product of ydbK to be a PFOR. The PFOR was labile to oxygen. The expression of ydbK was induced by superoxide generators such as methyl viologen (MV) in a SoxS-dependent manner after a lag period. We identified a critical element upstream of ydbK gene required for the induction by MV and proved direct binding of SoxS to the element. E. coli ydbK mutant was highly sensitive to MV, which was enhanced by additional inactivation of fpr gene encoding ferredoxin (flavodoxin):NADP(H) reductase (FPR). Aconitase activity, a superoxide sensor, was more extensively decreased by MV in the E. coli ydbK mutant than in wild-type strain. The induction level of soxS gene was higher in E. coli ydbK fpr double mutant than in wild-type strain. These results indicate that YdbK helps to protect cells from oxidative stress. It is possible that YdbK maintains the cellular redox state together with FPR and is involved in the reduction of oxidized proteins including SoxR in the late stages of the oxidative stress response in E. coli.

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