Tao K, Makino K, Yonei S, Nakata A, Shinagawa H
Laboratory of Radiation Biology, Faculty of Science, Kyoto University.
J Biochem. 1991 Feb;109(2):262-6.
The Escherichia coli oxyR gene is required for the induction of a regulon that is inducible by hydrogen peroxide and confers resistance to oxidative stresses. We constructed a plasmid system that greatly overproduced OxyR protein and purified the protein. OxyR protein specifically bound to the upstream regulatory regions of the oxyR and katG genes as demonstrated by the gel-retardation assay and the DNase I footprinting experiment, and activated the transcription initiation of the katG gene in vitro. Using a plasmid carrying an oxyR'-'lacZ fusion gene, we studied the regulation of oxyR expression in vivo. The expression of oxyR was not induced by the treatment with a low concentration of hydrogen peroxide which induces the genes in the oxyR regulon. The expression of the oxyR'-'lacZ gene was higher in an oxyR-deletion strain than in the oxyR+ strain, and was repressed by overexpressing the OxyR protein. These results suggest that OxyR protein functions as a repressor for oxyR, in addition to its known function as a transcriptional activator for the genes in the oxyR regulon.
大肠杆菌的oxyR基因对于一个可被过氧化氢诱导并赋予对氧化应激抗性的调节子的诱导是必需的。我们构建了一个能大量过量表达OxyR蛋白的质粒系统并纯化了该蛋白。凝胶阻滞试验和DNase I足迹实验表明，OxyR蛋白特异性地结合到oxyR和katG基因的上游调控区域，并在体外激活了katG基因的转录起始。利用携带oxyR'-'lacZ融合基因的质粒，我们在体内研究了oxyR表达的调控。低浓度过氧化氢处理可诱导oxyR调节子中的基因，但不会诱导oxyR的表达。oxyR'-'lacZ基因在oxyR缺失菌株中的表达高于oxyR+菌株，并且通过过量表达OxyR蛋白而受到抑制。这些结果表明，OxyR蛋白除了作为oxyR调节子中基因的转录激活因子这一已知功能外，还作为oxyR的阻遏物发挥作用。
