O2 and Reactive Oxygen Species Detoxification Complex, Composed of O2-Responsive NADH:Rubredoxin Oxidoreductase-Flavoprotein A2-Desulfoferrodoxin Operon Enzymes, Rubperoxin, and Rubredoxin, in Clostridium acetobutylicum
O2 and Reactive Oxygen Species Detoxification Complex, Composed of O2-Responsive NADH:Rubredoxin Oxidoreductase-Flavoprotein A2-Desulfoferrodoxin Operon Enzymes, Rubperoxin, and Rubredoxin, in Clostridium acetobutylicum
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DOI：
10.1128/aem.01425-08
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发表时间：
2009-02-15
影响因子：
4.4
通讯作者：
Niimura, Youichi
中科院分区：
文献类型：
--
作者：
Kawasaki, Shinji;Sakai, Yu;Niimura, Youichi
丙酮丁醇梭菌是一种专性厌氧生物，在连续氧流培养条件下正常生长，细胞充分消耗氧。O-2响应性NADH：红氧还蛋白氧化还原酶操纵子由三个基因（nror、fprA 2和dsr）组成，编码NROR、功能上未表征的黄素蛋白A2（FprA 2）和预测的超氧化物还原酶铁氧还蛋白（Dsr），已被提出参与对O-2胁迫的防御。为了功能上表征这些蛋白质，来自C.纯化在大肠杆菌中表达的重组NROR（rNROR）、FprA 2、Dsr和红氧还蛋白（Rd）。纯化的天然NROR和rNROR都表现出弱的H2 O2形成NADH氧化酶活性，被Rd轻微激活。NROR、Rd和FprA 2的混合物作为对O-2具有高亲和力的有效的H2O形成NADH氧化酶发挥功能（对O-2的Km为2.9 +/-0.4 μ M）。NROR、Rd和Dsr的混合物作为NADH依赖性O-2（-）还原酶发挥作用。NROR、Rd和Rubperoxin的混合物（Rpr，一种赤藓红蛋白同系物）作为一种低效的形成H ↓ [2] O的NADH氧化酶，但作为一种高效的NADH过氧化物酶，对O ↓ [2]的亲和力低，对H ↓ [2] O ↓ [2]的亲和力高（对O ↓ [2]和H ↓ [2] O ↓ [2]的K（m）为303 +/-39 μ M，
Clostridium acetobutylicum, an obligate anaerobe, grows normally under continuous-O-2-flow culture conditions, where the cells consume O-2 proficiently. An O-2-responsive NADH: rubredoxin oxidoreductase operon composed of three genes (nror, fprA2, and dsr), encoding NROR, functionally uncharacterized flavoprotein A2 (FprA2), and the predicted superoxide reductase desulfoferrodoxin (Dsr), has been proposed to participate in defense against O-2 stress. To functionally characterize these proteins, native NROR from C. acetobutylicum, recombinant NROR (rNROR), FprA2, Dsr, and rubredoxin (Rd) expressed in Escherichia coli were purified. Purified native NROR and rNROR both exhibited weak H2O2-forming NADH oxidase activity that was slightly activated by Rd. A mixture of NROR, Rd, and FprA2 functions as an efficient H2O-forming NADH oxidase with a high affinity for O-2 (the K-m for O-2 is 2.9 +/- 0.4 mu M). A mixture of NROR, Rd, and Dsr functions as an NADH-dependent O-2(-) reductase. A mixture of NROR, Rd, and rubperoxin (Rpr, a rubrerythrin homologue) functions as an inefficient H2O-forming NADH oxidase but an efficient NADH peroxidase with a low affinity for O-2 and a high affinity for H2O2 (the K(m)s for O-2 and H2O2 are 303 +/- 39 mu M and