School of Biosciences and Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK.
Mol Microbiol. 2021 Jul;116(1):29-40. doi: 10.1111/mmi.14713. Epub 2021 Apr 3.
How anaerobic bacteria protect themselves against nitric oxide-induced stress is controversial, not least because far higher levels of stress were used in the experiments on which most of the literature is based than bacteria experience in their natural environments. This results in chemical damage to enzymes that inactivates their physiological function. This review illustrates how transcription control mechanisms reveal physiological roles of the encoded gene products. Evidence that the hybrid cluster protein, Hcp, is a major high affinity NO reductase in anaerobic bacteria is reviewed: if so, its trans-nitrosation activity is a nonspecific secondary consequence of chemical inactivation. Whether the flavorubredoxin, NorV, is equally effective at such low [NO] is unknown. YtfE is proposed to be an enzyme rather than a source of iron for the repair of iron-sulfur proteins damaged by nitrosative stress. Any reaction catalyzed by YtfE needs to be revealed. The concentration of NO that accumulates in the cytoplasm of anaerobic bacteria is unknown, but indirect evidence indicates that it is in the pM to low nM range. Also unknown are the functions of the NO-inducible cytoplasmic proteins YgbA, YeaR, or YoaG. Experiments to resolve some of these questions are proposed.
厌氧菌如何保护自己免受一氧化氮诱导的应激一直存在争议，这主要是因为大多数文献所依据的实验中使用的应激水平远远高于细菌在其自然环境中所经历的水平。这会导致酶的化学损伤，从而使其生理功能失活。本综述说明了转录控制机制如何揭示编码基因产物的生理作用。综述了杂种簇蛋白 Hcp 是厌氧菌中主要的高亲和力一氧化氮还原酶的证据：如果是这样，其反硝化活性是化学失活的非特异性次要后果。风味红血素 NorV 是否同样有效地在如此低的 [NO] 水平下发挥作用尚不清楚。YtfE 被提议为修复受硝化应激损伤的铁硫蛋白的酶，而不是铁源。需要揭示 YtfE 催化的任何反应。在厌氧细菌的细胞质中积累的 NO 浓度未知，但间接证据表明其在 pM 到低 nM 范围内。NO 诱导的细胞质蛋白 YgbA、YeaR 或 YoaG 的功能也未知。提出了一些实验来解决其中的一些问题。
