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首页> 外文期刊>Journal of biological inorganic chemistry: JBIC: a publication of the Society of Biological Inorganic Chemistry >Combined M?ssbauer spectroscopic, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of the radical SAM enzyme spore photoproduct lyase
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Combined M?ssbauer spectroscopic, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of the radical SAM enzyme spore photoproduct lyase

机译：结合的Msssbauer光谱，多边缘X射线吸收光谱和自由基SAM酶孢子光产物裂解酶的密度泛函理论研究

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摘要

Spore photoproduct lyase (SPL), a member of the radical S-adenosyl-l-methionine (SAM) superfamily, catalyzes the direct reversal of the spore photoproduct, a thymine dimer specific to bacterial spores, to two thymines. SPL requires SAM and a redox-active [4Fe–4S] cluster for catalysis. M?ssbauer analysis of anaerobically purified SPL indicates the presence of a mixture of cluster states with the majority (40 %) as [2Fe–2S]~(2+) clusters and a smaller amount (15 %) as [4Fe–4S]~(2+) clusters. On reduction, the cluster content changes to primarily (60 %) [4Fe–4S]~+. The speciation information from M?ssbauer data allowed us to deconvolute iron and sulfur K-edge X-ray absorption spectra to uncover electronic (X-ray absorption near-edge structure, XANES) and geometric (extended X-ray absorption fine structure, EXAFS) structural features of the Fe–S clusters, and their interactions with SAM. The iron K-edge EXAFS data provide evidence for elongation of a [2Fe–2S] rhomb of the [4Fe–4S] cluster on binding SAM on the basis of an Fe…Fe scatterer at 3.0 ?. The XANES spectra of reduced SPL in the absence and presence of SAM overlay one another, indicating that SAM is not undergoing reductive cleavage. The X-ray absorption spectroscopy data for SPL samples and data for model complexes from the literature allowed the deconvolution of contributions from [2Fe–2S] and [4Fe–4S] clusters to the sulfur K-edge XANES spectra. The analysis of pre-edge features revealed electronic changes in the Fe–S clusters as a function of the presence of SAM. The spectroscopic findings were further corroborated by density functional theory calculations that provided insights into structural and electronic perturbations that can be correlated by considering the role of SAM as a catalyst or substrate.
机译：孢子光产物裂解酶（SPL）是自由基S-腺苷-1-蛋氨酸（SAM）超家族的成员，它催化孢子光产物（一种特定于细菌孢子的胸腺嘧啶二聚体）直接逆转为两个胸腺嘧啶。 SPL需要SAM和具有氧化还原活性的[4Fe–4S]簇进行催化。 M？ssbauer分析厌氧纯化的SPL表明存在簇状态的混合物，其中大多数（40％）为[2Fe–2S]〜（2+）簇，而少量（15％）为[4Fe–4S] 〜（2+）个集群。还原后，团簇含量主要变为[4Fe–4S]〜+（60％）。来自Msssbauer数据的形态信息使我们能够对铁和硫的K边缘X射线吸收光谱进行反卷积，以发现电子（X射线吸收近边缘结构XANES）和几何（扩展的X射线吸收精细结构EXAFS） ）Fe–S团簇的结构特征，以及它们与SAM的相互作用。铁K边缘EXAFS数据提供了在结合铁（3.0？）的基础上，在结合SAM时[4Fe-4S]团簇的[2Fe-2S]菱形伸长的证据。在不存在和存在SAM的情况下，还原的SPL的XANES光谱彼此重叠，表明SAM没有进行还原裂解。来自文献的SPL样品的X射线吸收光谱数据和模型配合物的数据允许将[2Fe–2S]和[4Fe–4S]簇的贡献解卷积到硫K边缘XANES光谱。对边缘特征的分析表明，Fe-S团簇中的电子变化是SAM的作用。密度泛函理论计算进一步证实了光谱学的发现，这些计算提供了对结构和电子扰动的见解，可以通过考虑SAM作为催化剂或底物的作用进行关联。

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