FT-IR spectroscopic characterization of NADH:ubiquinone oxidoreductase (complex I) from Escherichia coli:: Oxidation of FeS cluster N2 is coupled with the protonation of an aspartate or glutamate side chains
FT-IR spectroscopic characterization of NADH:ubiquinone oxidoreductase (complex I) from Escherichia coli:: Oxidation of FeS cluster N2 is coupled with the protonation of an aspartate or glutamate side chains
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DOI：
10.1021/bi000842a
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发表时间：
2000-09-05
期刊：
影响因子：
2.9
通讯作者：
Friedrich, T
中科院分区：
文献类型：
--
作者：
Hellwig, P;Scheide, D;Friedrich, T
质子泵 NADH：泛醌氧化还原酶，也称为复合物 I，是许多呼吸链的第一个能量转换复合物。它将电子从 NADH 到泛醌的转移与质子跨膜易位结合起来。一个 FMN 和最多九个铁硫 (FeS) 簇参与氧化还原反应。到目前为止，配合物 I 主要通过 EPR 和紫外可见光谱进行描述。在这里，我们首次报告了复合物 I 的红外光谱表征。获得了来自大肠杆菌的复合物 I 和该复合物的 NADH 脱氢酶片段的电化学诱导 FT-IR 差异光谱，用于关键的潜在步骤。两种制剂中 FMN 的光谱贡献是通过使用模型化合物进行比较得出的，结果出乎意料地小。此外，FT-IR 差异光谱表明 FMN 和 FeS 簇的氧化还原跃迁引起多肽主链的强烈重组。复合物 I 光谱中的其他信号反映了由高电位 FeS 簇 N2 的氧化还原转变引起的贡献，该簇不存在于 NADH 脱氢酶片段中。这些信号的一部分归因于质子化/去质子化的 Asp 或 Glu 侧链的重组。在这些数据的基础上，我们讨论了 N2 在复合物 I 质子易位中的作用。
The proton-pumping NADH:ubiquinone oxidoreductase, also called complex I, is the first energy-transducing complex of many respiratory chains. It couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. One FMN and up to nine iron-sulfur (FeS) clusters participate in the redox reaction. So far, complex I has been described mainly by means of EPR- and UV-vis spectroscopy. Here, we report for the first time an infrared spectroscopic characterization of complex I. Electrochemically induced FT-IR difference spectra of complex I from Escherichia coli and of the NADH dehydrogenase fragment of this complex were obtained for critical potential steps. The spectral contributions of the FMN in both preparations were derived from a comparison using model compounds and turned out to be unexpectedly small. Furthermore, the FT-IR difference spectra reveal that the redox transitions of the FMN and of the FeS clusters induce strong reorganizations of the polypeptide backbone. Additional signals in the spectra of complex I reflect contributions induced by the redox transition of the high-potential FeS cluster N2 which is not present in the NADH dehydrogenase fragment. Part of these signals are attributed to the reorganization of protonated/deprotonated Asp or Glu side chains. On the basis of these data we discuss the role of N2 for proton translocation of complex I.