Direct assignment of EPR spectra to structurally defined iron-sulfur clusters in complex I by double electron-electron resonance
Direct assignment of EPR spectra to structurally defined iron-sulfur clusters in complex I by double electron-electron resonance
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DOI：
10.1073/pnas.0908050107
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发表时间：
2010-02-02
影响因子：
11.1
通讯作者：
Hirst, Judy
中科院分区：
文献类型：
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作者：
Roessler, Maxie M.;King, Martin S.;Hirst, Judy
在氧化磷酸化过程中，络合物I(NADH：苯醌氧化还原酶)将电子传递耦合到跨能量转换膜的质子转移。络合物I包含一个黄素单核苷酸来氧化NADH，以及一系列异常长的铁-硫(FeS)簇，在几个亚单位中，用于将电子转移到苯二酚。要理解络合物I中的耦合电子转移，需要详细了解单个团簇和团簇的性质，因此需要光谱数据和结构数据的关联：事实证明，这是一项具有挑战性的任务。对来自牛的配合物I的EPR研究证实，EPR信号N1b、N2和N3分别来自75 kDa亚基中的2Fe簇，以及Psst和51 kDa亚基中的4Fe簇(位置2、7和1，沿着从黄素延伸的七簇链)。其他星团要么躲过了检测，要么没有确定的信号分配。在这里，我们将双电子-电子共振(DER)光谱与嗜热嗜热杆菌复合体I的亲水结构域结构相结合。通过明确考虑簇的磁矩和鹿实验的取向选择性，信号N4被指定为TYKY亚基中的第一个4Fe簇(位置5)，信号N5被指定为75 kDa亚基中的全半胱氨酸连接的4Fe簇(位置3)。讨论了我们的工作对络合物I的电子转移和能量传递机制的影响。
In oxidative phosphorylation, complex I (NADH: quinone oxidoreductase) couples electron transfer to proton translocation across an energy-transducing membrane. Complex I contains a flavin mononucleotide to oxidize NADH, and an unusually long series of iron-sulfur (FeS) clusters, in several subunits, to transfer the electrons to quinone. Understanding coupled electron transfer in complex I requires a detailed knowledge of the properties of individual clusters and of the cluster ensemble, and so it requires the correlation of spectroscopic and structural data: This has proved a challenging task. EPR studies on complex I from Bos taurus have established that EPR signals N1b, N2 and N3 arise, respectively, from the 2Fe cluster in the 75 kDa subunit, and from 4Fe clusters in the PSST and 51 kDa subunits (positions 2, 7, and 1 along the seven-cluster chain extending from the flavin). The other clusters have either evaded detection or definitive signal assignments have not been established. Here, we combine double electron-electron resonance (DEER) spectroscopy on B. taurus complex I with the structure of the hydrophilic domain of Thermus thermophilus complex I. By considering the magnetic moments of the clusters and the orientation selectivity of the DEER experiment explicitly, signal N4 is assigned to the first 4Fe cluster in the TYKY subunit (position 5), and N5 to the all-cysteine ligated 4Fe cluster in the 75 kDa subunit (position 3). The implications of our assignment for the mechanisms of electron transfer and energy transduction by complex I are discussed.