Nitric oxide homeostasis in Salmonella typhimurium -: Roles of respiratory nitrate reductase and flavohemoglobin
Nitric oxide homeostasis in Salmonella typhimurium -: Roles of respiratory nitrate reductase and flavohemoglobin
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DOI：
10.1074/jbc.m708019200
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发表时间：
2008-04-25
影响因子：
4.8
通讯作者：
Poole, Robert K.
中科院分区：
文献类型：
--
作者：
Gilberthorpe, Nicola J.;Poole, Robert K.
一氧化氮（NO）在生物系统中主要通过NO还原酶以及硝酸盐还原酶和亚硝酸盐还原酶的活性产生。在这里，我们表明，沙门氏菌肠道血清型鼠伤寒（S。鼠伤寒沙门氏菌）能够在加入亚硝酸盐（NO2-）后产生极谱可检测的NO。NO积累对NO清除剂2-（4-羧基苯基）-4，4，5，5-四甲基咪唑啉-1-氧基-3-氧化物敏感。fnr突变体和fnr hmp双突变体均不产生NO，表明FNR正调控的蛋白质参与NO从NO2-的进化。与以往在大肠杆菌中的研究结果相反，我们证明，无论是周质亚硝酸盐还原酶（NrfA）或胞质亚硝酸盐还原酶（NirB）都不参与S。鼠伤寒。然而，缺乏膜结合硝酸还原酶NarGHI的突变细胞和来自这些细胞的膜不能产生NO，这表明，在野生型S.在鼠伤寒沙门氏菌中，这种酶负责NO的产生。膜末端氧化酶不能解释测量的NO水平。硝酸还原酶抑制剂，叠氮化物，废除NO进化沙门氏菌，和NO的生产只发生在没有从硝酸盐的测定;这两个功能揭示了显着的相似性之间的NO生成活性的这种细菌和植物。与E. coli、S.鼠伤寒hmp突变体在需氧和厌氧条件下均产生NO。在有氧条件下，当存在功能性黄素血红蛋白时，检测不到NO。我们提出了一个稳态机制在S。在鼠伤寒沙门氏菌中，通过硝酸还原酶由NO2-产生的NO解抑制Hmp表达（通过FNR和NsrR）和NorV表达（通过NorR），从而限制NO毒性。
Nitric oxide (NO) is generated in biological systems primarily via the activity of NO synthases and nitrate and nitrite reductases. Here we show that Salmonella enterica serovar Typhimurium (S. typhimurium) grown anaerobically with nitrate is capable of generating polarographically detectable NO after nitrite (NO2-) addition. NO accumulation is sensitive to the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. Neither an fnr mutant nor an fnr hmp double mutant produces NO, indicating the involvement in NO evolution from NO2- of protein(s) positively regulated by FNR. Contrary to previous findings in Escherichia coli, we demonstrate that neither the periplasmic nitrite reductase (NrfA) nor the cytoplasmic nitrite reductase (NirB) is involved in NO production in S. typhimurium. However, mutant cells lacking the membrane-bound nitrate reductase, NarGHI, and membranes derived from these cells are unable to produce NO, demonstrating that, in wild-type S. typhimurium, this enzyme is responsible for NO production. Membrane terminal oxidases cannot account for the NO levels measured. The nitrate reductase inhibitor, azide, abrogates NO evolution by Salmonella, and production of NO occurs only in the absence from the assays of nitrate; both features reveal a marked similarity between the NO-generating activities of this bacterium and plants. Unlike the situation in E. coli, an S. typhimurium hmp mutant produces NO both aerobically and anaerobically. Under aerobic conditions, when a functional flavohemoglobin is present, no NO is detectable. We propose a homeostatic mechanism in S. typhimurium, in which NO produced from NO2- by nitrate reductase derepresses Hmp expression (via FNR and NsrR) and NorV expression (via NorR) and thus limits NO toxicity.