Sawers R G
Lehrstuhl für Mikrobiologie, Universität München, Germany.
Mol Microbiol. 1991 Jun;5(6):1469-81. doi: 10.1111/j.1365-2958.1991.tb00793.x.
A gene library of chromosomal DNA from Pseudomonas aeruginosa contained a DNA fragment which was able to restore anaerobic growth to an Escherichia coli fnr deletion mutant on glycerol/nitrate medium. The cloned gene (termed anr) was sequenced and shown to encode a protein of 244 amino acids with a calculated molecular weight of 27,129. The deduced amino acid sequence of the anr gene product showed considerable similarity to the FNR protein from E. coli. Expression of the anr gene in a T7 promoter/polymerase system identified ANR as a 31 kDa protein. Transcriptional analysis of the anr gene showed that it is monocistronic but apparently lacks the equivalent sites for negative autoregulation which have been shown to be present in the promoter region of the E. coli fnr gene. The ANR protein was shown to activate transcription of the pfl gene in E. coli in response to anaerobiosis, as well as being able to restore the activity of three anaerobically inducible enzymes. A P. aeruginosa mutant incapable of growing anaerobically with nitrate or on arginine was fully complemented by the anr gene, indicating that it probably has a function in controlling anaerobic gene expression in Pseudomonas. Further corroboration for this assumption was provided by S1 nuclease analysis of transcription of the multiple promoters of the E. coli pfl operon in P. aeruginosa. Transcription was induced by oxygen limitation and was completely ANR-dependent in both aerobic and anaerobic cells. Removal of the upstream regulatory sequence of the pfl operon, which includes the sequences required for FNR-dependent regulation in E. coli, removed ANR-dependent transcriptional control of the remaining pfl promoters, irrespective of the cellular oxygen status. These results imply that the mechanisms by which ANR and FNR regulate transcription are fundamentally similar.
铜绿假单胞菌染色体DNA基因文库包含一个DNA片段，该片段能够使大肠杆菌fnr缺失突变体在甘油/硝酸盐培养基上恢复厌氧生长。对克隆的基因（称为anr）进行测序，结果显示其编码一个由244个氨基酸组成的蛋白质，计算分子量为27,129。anr基因产物推导的氨基酸序列与大肠杆菌的FNR蛋白有相当大的相似性。在T7启动子/聚合酶系统中anr基因的表达鉴定出ANR为一种31 kDa的蛋白质。对anr基因的转录分析表明它是单顺反子，但显然缺乏大肠杆菌fnr基因启动子区域中已显示存在的负自调控等效位点。结果表明，ANR蛋白可响应厌氧状态激活大肠杆菌中pfl基因的转录，并且还能够恢复三种厌氧诱导酶的活性。一个不能利用硝酸盐或精氨酸进行厌氧生长的铜绿假单胞菌突变体被anr基因完全互补，这表明它可能在控制铜绿假单胞菌厌氧基因表达中发挥作用。对铜绿假单胞菌中大肠杆菌pfl操纵子多个启动子转录的S1核酸酶分析为这一假设提供了进一步的证据。转录受氧限制诱导，并且在需氧和厌氧细胞中均完全依赖ANR。去除pfl操纵子的上游调控序列，其中包括大肠杆菌中FNR依赖性调控所需的序列，无论细胞的氧状态如何，均去除了剩余pfl启动子的ANR依赖性转录控制。这些结果表明，ANR和FNR调节转录的机制在根本上是相似的。
