硫 K 边 X 射线吸收谱研究 DNA 结合对内切酶 III 和 MutY 中 [FeS] 位点的影响。
Sulfur K-Edge XAS Studies of the Effect of DNA Binding on the [FeS] Site in EndoIII and MutY.
机构信息
Department of Chemistry, Stanford University , Stanford, California 94035, United States.
Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University , Menlo Park, California 94025, United States.
出版信息
J Am Chem Soc. 2017 Aug 23;139(33):11434-11442. doi: 10.1021/jacs.7b03966. Epub 2017 Aug 10.
S K-edge X-ray absorption spectroscopy (XAS) was used to study the [FeS] clusters in the DNA repair glycosylases EndoIII and MutY to evaluate the effects of DNA binding and solvation on Fe-S bond covalencies (i.e., the amount of S 3p character mixed into the Fe 3d valence orbitals). Increased covalencies in both iron-thiolate and iron-sulfide bonds would stabilize the oxidized state of the [FeS] clusters. The results are compared to those on previously studied [FeS] model complexes, ferredoxin (Fd), and to new data on high-potential iron-sulfur protein (HiPIP). A limited decrease in covalency is observed upon removal of solvent water from EndoIII and MutY, opposite to the significant increase observed for Fd, where the [FeS] cluster is solvent exposed. Importantly, in EndoIII and MutY, a large increase in covalency is observed upon DNA binding, which is due to the effect of its negative charge on the iron-sulfur bonds. In EndoIII, this change in covalency can be quantified and makes a significant contribution to the observed decrease in reduction potential found experimentally in DNA repair proteins, enabling their HiPIP-like redox behavior.
S 边 X 射线吸收光谱（XAS）被用于研究 DNA 修复糖苷酶 EndoIII 和 MutY 中的 [FeS] 簇，以评估 DNA 结合和溶剂化对 Fe-S 键共价性（即 S 3p 轨道杂化进入 Fe 3d 价轨道的程度）的影响。铁-硫醇和铁-硫化物键的共价性增加会稳定 [FeS] 簇的氧化态。结果与先前研究的 [FeS] 模型配合物铁氧还蛋白（Fd）以及高电位铁硫蛋白（HiPIP）的新数据进行了比较。与 Fd 显著增加的情况相反，EndoIII 和 MutY 中溶剂水去除后共价性略有降低，而 Fd 中的 [FeS] 簇暴露于溶剂中。重要的是，在 EndoIII 和 MutY 中，DNA 结合会导致共价性显著增加，这是由于其负电荷对铁-硫键的影响。在 EndoIII 中，这种共价性的变化可以定量，并对实验中观察到的 DNA 修复蛋白还原电位的降低做出重要贡献，使其具有类似于 HiPIP 的氧化还原行为。
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