MOLECULAR CHARACTERIZATION OF THE SOXRS GENES OF ESCHERICHIA-COLI - 2 GENES CONTROL A SUPEROXIDE STRESS REGULON
MOLECULAR CHARACTERIZATION OF THE SOXRS GENES OF ESCHERICHIA-COLI - 2 GENES CONTROL A SUPEROXIDE STRESS REGULON
复制标题
DOI：
10.1093/nar/19.16.4479
复制
发表时间：
1991-08-25
影响因子：
14.9
通讯作者：
DEMPLE, B
中科院分区：
文献类型：
--
作者：
AMABILECUEVAS, CF;DEMPLE, B
大肠杆菌K12的soxR位点介导了一个复杂的氧化应激调控的转录激活，以响应超氧化物生成（氧化还原循环）剂。我们通过监测DELTA-soxR突变的互补，克隆了soxR位点，该位点位于遗传图谱上靠近uvrA基因的92.2 min处。在δ -soxR菌株中，来自soxR区的亚克隆同时恢复了细胞对氧化还原循环剂phenazine methosulfate的抗性，以及对另一种氧化还原循环剂百草枯至少两种调节蛋白（葡萄糖-6-磷酸脱氢酶和核酸内切酶IV）的诱导能力。DNA序列分析显示存在两个参与激活soxR调控的基因。这两个基因分别被命名为soxR和soxS，它们的5'端相距仅85 bp。预测的12.9 kda SoxS蛋白与单组分基因调控因子AraC家族相关，但仅对应于这些蛋白的假定dna结合区域。17.1 kda的SoxR蛋白仅与MerR蛋白家族具有显著的同源性，包括预测的dna结合螺旋-旋转-螺旋和一簇半胱氨酸残基，这些残基与调节MerR对Hg2+反应的活性相似。这表明SoxR可能是一种金属结合基因调节剂，作为细胞内超氧化物的传感器。SoxS显然是调控子基因的近端激活因子：无论细胞是否暴露于百草枯，SoxS的个体表达都会影响体内至少三种调控子蛋白的抗生素抗性和高水平表达，而SoxS的个体表达则不会。这些数据，加上最近报道的soxS基因的百草枯诱导性（Wu， I., and Weiss， B. (1990) J. Bacteriol. 173, 2864 - 2871），表明soxS和soxS可能构成了一种新型的双组分调控系统，在该系统中，两种蛋白顺序激活各种调控基因的转录，以响应超氧胁迫。
The soxR locus of Escherichia coli K12 mediates transcriptional activation of a complex oxidative stress regulon in response to superoxide-generating (redox-cycling) agents. We have cloned the soxR locus, which is positioned near the uvrA gene at 92.2 min on the genetic map, by monitoring complementation of a DELTA-soxR mutation. Subclones from the soxR region in the DELTA-soxR strain simultaneously restored cellular resistance to the redox-cycling agent phenazine methosulfate and inducibility of at least two of the regulon proteins, glucose-6-phosphate dehydrogenase and endonuclease IV, by paraquat, another redox-cycling agent. DNA sequence analysis revealed the presence of two genes involved in activating the soxR regulon. These genes, named soxR and soxS, are arranged divergently with their 5' ends separated by only 85 bp. The predicted 12.9-kDa SoxS protein is related to the AraC family of one-component gene regulators, but corresponds only to the putative DNA-binding regions of these proteins. The 17.1-kDa SoxR protein bears significant homology only to the MerR family of proteins including a predicted DNA-binding helix-turn-helix and a cluster of cysteine residues positioned similarly to those that regulate the activity of MerR in response to Hg2+. This suggests that SoxR could be a metal-binding gene regulator that acts as the intracellular sensor for superoxide. SoxS is evidently the proximal activator of the regulon genes: antibiotic resistance and high-level expression of at least three of the regulon proteins was effected in vivo by the individual expression of SoxS, but not of SoxR, whether or not the cells were exposed to paraquat. These data, together with the recently reported paraquat-inducibility of the soxS gene (Wu, I., and Weiss, B. (1 990) J. Bacteriol. 173, 2864 - 2871), indicate that SoxR and SoxS may constitute a novel type of two-component regulatory system in which the two proteins act sequentially to activate transcription of the various regulon genes in response to superoxide stress.