School of Biosciences, University of Birmingham, Birmingham, UK.
FEMS Microbiol Lett. 2011 Dec;325(2):108-14. doi: 10.1111/j.1574-6968.2011.02385.x. Epub 2011 Sep 8.
A β-galactosidase assay for detecting the accumulation of NO in the Escherichia coli cytoplasm has been developed based on the sensitive response of the transcription repressor, NsrR, to NO. The hcp promoter is repressed by NsrR in the absence of nitric oxide, but repression is relieved when NO accumulates in the cytoplasm. Most, but not all, of this NO is formed by the interaction of the membrane-associated nitrate reductase, NarG, with nitrite. External NO at physiologically relevant concentrations does not equilibrate across the E. coli membrane with NsrR in the cytoplasm. The periplasmic nitrite reductase, NrfAB, is not required to prevent equilibration of NO across the membrane. External NO supplied at the highest concentration reported to occur in vivo does not damage FNR sufficiently to affect transcription from the hcp or hmp promoters or from a synthetic promoter. We suggest that the capacity of E. coli to reduce NO is sufficient to prevent its accumulation from external sources in the cytoplasm.
我们基于转录阻遏物 NsrR 对 NO 敏感的反应，开发了一种用于检测大肠杆菌细胞质中 NO 积累的β-半乳糖苷酶测定法。在不存在一氧化氮的情况下，hcp 启动子受到 NsrR 的抑制，但当细胞质中积累 NO 时，抑制作用被解除。大部分（但不是全部）NO 是由膜结合型硝酸盐还原酶 NarG 与亚硝酸盐相互作用形成的。在生理相关浓度下，外部 NO 不会与细胞质中的 NsrR 在大肠杆菌膜上达到平衡。周质亚硝酸盐还原酶 NrfAB 对于防止 NO 在膜上达到平衡不是必需的。报道的在体内存在的最高浓度的外部 NO 不会对 FNR 造成足够的损伤，从而不会影响 hcp 或 hmp 启动子或合成启动子的转录。我们认为，大肠杆菌还原 NO 的能力足以防止其从细胞质中的外部来源积累。
