Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M139PT, UK.
Mol Microbiol. 2011 Jul;81(2):457-72. doi: 10.1111/j.1365-2958.2011.07705.x. Epub 2011 May 26.
We have characterized the csoR-copA-copZ copper resistance operon of the important human intracellular pathogen Listeria monocytogenes. Transcription of the operon is specifically induced by copper, and mutants lacking the P₁-type ATPase CopA have reduced copper tolerance and over-accumulate copper relative to wild type. The copper-responsive repressor CsoR autoregulates transcription by binding to a single 32 bp site spanning the -10 and -35 elements of the promoter. Copper co-ordination by CsoR derepresses transcription of the operon and alters CsoR:DNA complex assembly as determined by DNase I footprinting and electrophoretic mobility shift assays, with some DNA-binding capacity being retained in the presence of 2 mole equivalents of copper. Analysis of the CsoR copper sensory site demonstrated that substitution of Cys⁴² with Ala generated a CsoR variant that was unresponsive to copper. Importantly, in the absence of CopZ, copper responsiveness of csoR-copA-copZ expression is substantially increased, implying that CopZ reduces the access of CsoR to copper. Furthermore, CopZ is shown to confer copper resistance in mutants lacking copper-inducible csoR-copA-copZ expression, thus providing protection from the deleterious effects of copper within the cytoplasm.
我们对人类重要的细胞内病原体李斯特菌的 csoR-copA-copZ 铜抗性操纵子进行了特征描述。该操纵子的转录特异性地被铜诱导，并且缺乏 P₁型 ATP 酶 CopA 的突变体相对于野生型而言铜耐受性降低且铜过度积累。铜反应性阻遏物 CsoR 通过结合跨越启动子-10 和-35 元件的单个 32 bp 位点来自我调节转录。CsoR 通过与铜配位来解除对操纵子的转录抑制，并改变 CsoR:DNA 复合物组装，如 DNase I 足迹法和电泳迁移率变动分析所确定的，在存在 2 摩尔当量铜的情况下保留一些 DNA 结合能力。对 CsoR 铜感应位点的分析表明，用丙氨酸取代 Cys⁴² 生成了对铜无反应的 CsoR 变体。重要的是，在没有 CopZ 的情况下，csoR-copA-copZ 表达的铜反应性显著增加，这意味着 CopZ 降低了 CsoR 对铜的获取。此外，CopZ 赋予了缺乏铜诱导的 csoR-copA-copZ 表达的突变体铜抗性，从而防止铜在细胞质内产生有害影响。
