氧化还原介导的VHb（玻璃体血红蛋白）与OxyR的相互作用：在氧化应激下VHb生物合成的新调节。,Biochemical Journal - X-MOL

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氧化还原介导的VHb（玻璃体血红蛋白）与OxyR的相互作用：在氧化应激下VHb生物合成的新调节。
Biochemical Journal ( IF 4.4 ) Pub Date : 2009-12-23 , DOI: 10.1042/bj20091417
Arvind Anand ₁ , Brian T Duk , Sandeep Singh , Meltem Y Akbas , Dale A Webster , Benjamin C Stark , Kanak L Dikshit

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来自玻璃体球菌VHb的细菌血红蛋白显示出几种异常的特性，这些特性在珠蛋白家族中是独特的。当在玻璃体或大肠杆菌中从其天然启动子表达编码VHb的基因vgb时，在缺氧条件下VHb的水平增加50倍以上，在氧化胁迫下显着下降，这表明vgb启动子在两种情况下的功能相似生物。在本研究中，我们表明VHb在大肠杆菌中的表达诱导了抗氧化剂基因katG（过氧化氢酶-过氧化物酶G）和sodA（超氧化物歧化酶A）并赋予了抗氧化应激的显着保护作用。相反，当vgb在大肠杆菌的oxyR突变体中表达时，VHb水平升高，并且该菌株显示出对氧化应激的高度敏感性，而没有诱导抗氧化剂基因。这表明氧化应激调节剂OxyR参与介导VHb在氧化应激下的保护作用。在vgb启动子中鉴定出一个可能的OxyR结合位点，凝胶位移分析证实了它与氧化的OxyR的相互作用，这种相互作用被转录激活因子Fnr（富马酸盐和硝酸盐还原酶）的还原形式所破坏。这表明OxyR和Fnr的氧化还原状态调节了它们与vgb启动子的相互作用。在二次杂交筛选实验中和体外，VHb与还原型OxyR相关，在存在NADH的情况下将其转化为氧化态，已知该条件下VHb会生成H2O2。这些发现揭示了一种新颖的机制，通过这种机制VHb可以将信号传输至OxyR以自动调节其自身的生物合成，同时激活氧化应激功能。本文首次报道了通过VHb激活OxyR，也表明VHb也参与了许多其他基因的转录控制。

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Redox-mediated interactions of VHb (Vitreoscilla haemoglobin) with OxyR: novel regulation of VHb biosynthesis under oxidative stress.

The bacterial haemoglobin from Vitreoscilla, VHb, displays several unusual properties that are unique among the globin family. When the gene encoding VHb, vgb, is expressed from its natural promoter in either Vitreoscilla or Escherichia coli, the level of VHb increases more than 50-fold under hypoxic conditions and decreases significantly during oxidative stress, suggesting similar functioning of the vgb promoter in both organisms. In the present study we show that expression of VHb in E. coli induced the antioxidant genes katG (catalase-peroxidase G) and sodA (superoxide dismutase A) and conferred significant protection from oxidative stress. In contrast, when vgb was expressed in an oxyR mutant of E. coli, VHb levels increased and the strain showed high sensitivity to oxidative stress without induction of antioxidant genes; this indicates the involvement of the oxidative stress regulator OxyR in mediating the protective effect of VHb under oxidative stress. A putative OxyR-binding site was identified within the vgb promoter and a gel-shift assay confirmed its interaction with oxidized OxyR, an interaction which was disrupted by the reduced form of the transcriptional activator Fnr (fumurate and nitrate reductase). This suggested that the redox state of OxyR and Fnr modulates their interaction with the vgb promoter. VHb associated with reduced OxyR in two-hybrid screen experiments and in vitro, converting it into an oxidized state in the presence of NADH, a condition where VHb is known to generate H2O2. These observations unveil a novel mechanism by which VHb may transmit signals to OxyR to autoregulate its own biosynthesis, simultaneously activating oxidative stress functions. The activation of OxyR via VHb, reported in the present paper for the first time, suggests the involvement of VHb in transcriptional control of many other genes as well.

更新日期：2019-11-01

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