Pantel I, Lindgren P E, Neubauer H, Götz F
Mikrobielle Genetik, Universität Tübingen, Germany.
Mol Gen Genet. 1998 Jul;259(1):105-14. doi: 10.1007/s004380050794.
Physiological and genetic characterization of Staphylococcus carnosus nitrate reductase-negative mutants led to the identification of the nitrate reductase operon, narGHJI. Transcription from the nar promoter was stimulated by anaerobiosis, nitrate, and nitrite. This is in accordance with the nitrate reductase activities determined with benzyl viologen as electron donor. However, in the presence of oxygen and nitrate, high transcriptional initiation but low nitrate reductase activity was observed. Since the alphabeta complex of the nitrate reductase formed during anaerobic growth was insensitive to oxygen, other oxygen-sensitive steps (e.g., post-transcriptional mechanisms, molybdenum cofactor biosynthesis) must be involved. The nitrate-reducing system in S. carnosus displays similarities to the dissimilatory nitrate reductases of Escherichia coli. However, in the S. carnosus nar promoter, no obvious Fnr and integration host factor recognition sites are present; only one site that is related to the E. coli NarL consensus sequence was found. Studies to determine whether the E. coli proteins NarL and Fnr are functional at the S. carnosus narGHJI promoter indicated that the promoter is not functional in E. coli.
肉葡萄球菌硝酸盐还原酶阴性突变体的生理和遗传特性研究，促成了硝酸盐还原酶操纵子narGHJI的鉴定。nar启动子的转录受厌氧、硝酸盐和亚硝酸盐的刺激。这与以苄基紫精作为电子供体测定的硝酸盐还原酶活性一致。然而，在有氧和硝酸盐存在的情况下，观察到高转录起始但低硝酸盐还原酶活性。由于厌氧生长期间形成的硝酸盐还原酶的αβ复合物对氧不敏感，因此必然涉及其他氧敏感步骤（例如转录后机制、钼辅因子生物合成）。肉葡萄球菌中的硝酸盐还原系统与大肠杆菌的异化硝酸盐还原酶有相似之处。然而，在肉葡萄球菌nar启动子中，没有明显的Fnr和整合宿主因子识别位点；仅发现一个与大肠杆菌NarL共有序列相关的位点。关于大肠杆菌蛋白NarL和Fnr在肉葡萄球菌narGHJI启动子上是否起作用的研究表明，该启动子在大肠杆菌中无功能。
