Were there any "misassignments" among iron-sulfur clusters N4, N5 and N6b in NADH-quinone oxidoreductase (complex I)?
Were there any "misassignments" among iron-sulfur clusters N4, N5 and N6b in NADH-quinone oxidoreductase (complex I)?
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DOI：
10.1016/j.bbabio.2008.04.032
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发表时间：
2008-07-01
影响因子：
4.3
通讯作者：
Nakamaru-Ogiso, Eiko
中科院分区：
文献类型：
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作者：
Ohnishi, Tomoko;Nakamaru-Ogiso, Eiko
牛心脏线粒体中的NADH-醌氧化还原酶（复合物1）具有约1百万Da的分子量，由45个不同的亚基组成。这是迄今为止已知的最大的能量转换复合体。细菌复合物I更简单，更小，但基本的氧化还原组分和电子和质子转移的基本机制是相同的。在过去的三十年里，Ohnishi等人在液氦温度附近进行了广泛的EPR研究，并表征了复合物I中的大多数铁硫簇合物。最近，Yakovlev et al. [G. Yakovlev，T. Reda，J. Hirst，重新评估NADH中铁硫簇的EPR谱和酶结构之间的关系：醌氧化还原酶，Proc. Natl. Acad. Sci.联合S. A. 104（2007）12720-12725]通过声称在簇N4、N5和N6 b之间存在EPR“错配”来挑战Ohnishi的小组（为了防止混淆，我们使用当前的共识命名法作为昵称）。他们声称，我们错误地将来自N5簇的EPR信号分配给了N4簇，并将来自N6 b簇的信号分配给了N4簇。他们还提出簇N5具有（4Cys）-配体。基于我们的定点突变实验的积累的历史数据和最近的结果，我们证实了簇N5具有我们所预测的（1His + 3Cys）-配体。我们发现E.当样品温度在3 K左右，微波功率大于5 mW时，可以清晰地检测到大肠杆菌N5簇的信号。因此，赫斯特的研究小组在任何EPR条件下都无法检测到N5信号，这在他们的PNAS论文中报道。他们似乎把N4群的信号错配到了N5群。至于N4和N6 b簇之间“错配”的说法，这是不可能的，因为我们的诱变系统不含N6 b簇。因此，我们认为，我们在工作中没有做任何“错配”。(c)2008 Elsevier B. V.保留所有权利。
NADH-quinone oxidoreductase (complex 1) in bovine heart mitochondria has a molecular weight of approximately 1 million Da composed of 45 distinct subunits. It is the largest energy transducing complex so far known. Bacterial complex I is simpler and smaller, but the essential redox components and the basic mechanisms of electron and proton translocation are the same. Over the past three decades, Ohnishi et al. have pursued extensive EPR studies near liquid helium temperatures and characterized most of the iron-sulfur clusters in complex I. Recently, Yakovlev et al. [G. Yakovlev, T. Reda, J. Hirst, Reevaluating the relationship between EPR spectra and enzyme structure for the iron-sulfur clusters in NADH:quinone oxidoreductase, Proc. Natl. Acad. Sci. U. S. A. 104 (2007) 12720-12725] challenged Ohnishi's group by claiming that there were EPR "misassignments" among clusters N4, N5 and N6b (in order to prevent confusion, we used current consensus nomenclature, as the nickname). They claimed that we misassigned EPR signals arising from cluster N5 to cluster N4, and signals from cluster N6b to cluster N4. They also proposed that cluster N5 has (4Cys)-ligands. Based on the accumulated historical data and recent results of our site-specific mutagenesis experiments, we confirmed that cluster N5 has (1His + 3Cys)-ligands as we had predicted. We revealed that E. coli cluster N5 signals could be clearly detected at the sample temperature around 3 K with microwave power higher than 5 mW. Thus Hirst's group could not detect N5 signals under any of their EPR conditions, reported in their PNAS paper. It seems that they misassigned the signals from cluster N4 to N5. As to the claim of "misassignment" between clusters N4 and N6b, that was not a possibility because our mutagenesis systems did not contain cluster N6b. Therefore, we believe that we have not made any "misassignment" in our work. (c) 2008 Elsevier B.V. All rights reserved.