Respiratory detoxification of nitric oxide by the cytochrome c nitrite reductase of Escherichia coli
Respiratory detoxification of nitric oxide by the cytochrome c nitrite reductase of Escherichia coli
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DOI：
10.1074/jbc.m200731200
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发表时间：
2002-06-28
影响因子：
4.8
通讯作者：
Richardson, DJ
中科院分区：
文献类型：
--
作者：
Poock, SR;Leach, ER;Richardson, DJ
一氧化氮是宿主抵御侵袭性病原体的关键成分。大肠埃希菌细胞色素c亚硝酸盐还原酶(NRFA)催化亚硝酸盐的呼吸还原，但体外研究表明它也能还原一氧化氮。活体内后一种反应的生理意义从未被评估过。在这项研究中，我们测量了在周质亚硝酸盐还原活跃或缺乏的菌株中，大肠杆菌对一氧化氮的还原。从厌氧培养中获得的NRF(+)细胞具有一氧化氮合酶活性，生理电子供给量为60nmolmin(-1)mg干重(-1)，体内NRFA周转数为390no。S(-1)进行了计算。在NRF(-)菌株中未检测到一氧化氮合酶活性。比较NRF(+)和NRF(-)菌株的厌氧生长情况，发现NRFA(-)菌株对一氧化氮的敏感性更高。琼脂平板扩散法对亚硝化试剂S-亚硝基-N-乙酰青霉胺也有较高的敏感性。NRF(-)菌株的氧气呼吸对一氧化氮的敏感性也高于NRF(+)亲本菌株。结果表明，细胞色素c亚硝酸盐还原酶具有较强的细胞色素C还原能力和对大肠杆菌的解毒能力。许多致病肠道细菌的基因组分析显示存在NRF基因。这项研究提出了这样一种可能性，即这反映了细胞色素c亚硝酸盐还原酶在缺氧环境中一氧化氮管理中的重要作用。
Nitric oxide is a key element in host defense against invasive pathogens. The periplasmic cytochrome c nitrite reductase (NrfA) of Escherichia coli catalyzes the respiratory reduction of nitrite, but in vitro studies have shown that it can also reduce nitric oxide. The physiological significance of the latter reaction in vivo has never been assessed. In this study the reduction of nitric oxide by Escherichia coli was measured in strains active or deficient in periplasmic nitrite reduction. Nrf(+) cells, harvested from cultures grown anaerobically, possessed a nitric-oxide reductase activity with physiological electron donation of 60 nmol min(-1) mg dry wt(-1), and an in vivo turnover number of NrfA of 390 NO. s(-1) was calculated. Nitric-oxide reductase activity could not be detected in Nrf(-) strains. Comparison of the anaerobic growth of Nrf(+) and Nrf(-) strains revealed a higher sensitivity to nitric oxide in the NrfA(-) strains. A higher sensitivity to the nitrosating agent S-nitroso-N-acetyl penicillamine (SNAP) was also observed in agar plate disk-diffusion assays. Oxygen respiration by E. coli was also more sensitive to nitric oxide in the Nrf(-) strains compared with the Nrf(+) parent strain. The results demonstrate that active periplasmic cytochrome c nitrite reductase can confer the capacity for nitric oxide reduction and detoxification on E. coli. Genomic analysis of many pathogenic enteric bacteria reveals the presence of nrf genes. The present study raises the possibility that this reflects an important role for the cytochrome c nitrite reductase in nitric oxide management in oxygen-limited environments.