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首页> 外文学位 >Spectroscopic and electronic structure studies of iron- and manganese-dependent superoxide dismutases: Geometric and electronic factors contributing to catalytic activity.
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Spectroscopic and electronic structure studies of iron- and manganese-dependent superoxide dismutases: Geometric and electronic factors contributing to catalytic activity.

机译：依赖铁和锰的超氧化物歧化酶的光谱和电子结构研究：有助于催化活性的几何和电子因素。

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摘要

The highly homologous Fe- and Mn-containing superoxide dismutases (FeSOD and MnSOD) from Escherichia coli nonetheless display striking metal specificities, therefore providing ideal systems through which to explore the role of the second sphere in tuning metalloenzyme active site properties. A combination of spectroscopic and computational methods have been utilized to study the geometric and electronic properties of the wildtype FeSOD and MnSOD, the catalytically inactive Fe-substituted MnSOD (Fe:MnSOD) and Mn-substituted FeSOD (Mn:FeSOD), and several variants of FeSOD with varying degrees of catalytic activity, including the Q69H, Q69A, and Q69E mutants.; Despite their dramatically different catalytic activities, species in the Fe-bound (FeSOD, Fe:MnSOD and the Q69X variants of FeSOD) and the Mn-bound proteins (MnSOD, Mn:FeSOD) respectively exhibit virtually identical absorption, circular dichroism (CD), magnetic CD (MCD) and VTVH MCD data. Therefore spectroscopy alone cannot provide direct insight into the mechanism by which catalytic activity is tuned by SODS. Through the use of computational methods, including density functional theory and semi-empirical INDO/S-CI calculations, different interactions between the second sphere and the active site metal in FeSOD and MnSOD have been identified and their significance with respect to catalytic activity has been explored.; Although subtle differences in the second sphere do not directly influence the active-site structures and the spectroscopic signatures of the resting enzymes, binding of azide (a substrate analogue) to the oxidized enzymes induces striking differences in both crystallographic and spectroscopic data. Most intriguingly, a remarkable correlation has been established between the energies of the dominant N3 → Fe3+ ligand-to-metal charge transfer transition and the reduction midpoint potentials of the resting enzymes as well as the strengths of the H-bond interaction between the second sphere and the coordinated solvent. Combined quantum mechanics/molecular mechanics methodologies in conjunction with INDO/S-CI calculations have been used to generate experimentally-validated active-site models for the azide complexes of FeSOD, Fe:MnSOD, and the Q69A, Q69E FeSOD mutants, and the geometric and electronic factors contributing to the distinct second-sphere tuning of active site/substrate analogue interactions have been explored.
机译：然而，来自大肠杆菌的高度同源的含Fe和Mn的超氧化物歧化酶（FeSOD和MnSOD）显示出惊人的金属特异性，因此提供了理想的系统，通过该系统可探索第二个球在调节金属酶活性位点性质中的作用。光谱和计算方法的组合已被用于研究野生型FeSOD和MnSOD，催化失活的Fe取代MnSOD（Fe：MnSOD）和Mn取代FeSOD（Mn：FeSOD）的几何和电子性质，以及几种变体具有不同程度的催化活性的FeSOD，包括Q69H，Q69A和Q69E突变体。尽管它们的催化活性截然不同，但铁结合的（FeSOD，Fe：MnSOD和Q69X的FeSOD变体）和锰结合的蛋白（MnSOD，Mn：FeSOD）中的物质分别表现出几乎相同的吸收，圆二色性（CD） ，磁性CD（MCD）和VTVH MCD数据。因此，仅靠光谱学无法直接了解SODS调节催化活性的机理。通过使用包括密度泛函理论和半经验INDO / S-CI计算在内的计算方法，已经确定了FeSOD和MnSOD中第二个球体与活性位点金属之间的不同相互作用，并且它们对于催化活性的重要性已经得到确认。探索。尽管第二个球体中的细微差异不会直接影响静止酶的活性位点结构和光谱特征，但叠氮化物（一种底物类似物）与氧化酶的结合会在晶体学和光谱学数据上引起惊人的差异。最有趣的是，在主要的N3→Fe3 +配体到金属的电荷转移跃迁的能量与静止酶的还原中点电位以及第二个球之间的H键相互作用的强度之间建立了显着的相关性。和配位溶剂。结合量子力学/分子力学方法和INDO / S-CI计算，已生成FeSOD，Fe：MnSOD和Q69A，Q69E FeSOD突变体的叠氮化物配合物的实验验证活性位点模型并探索了有助于主动位点/底物模拟相互作用的独特第二球调节的电子因素。

著录项

  • 作者

    Xie, Juan.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Chemistry Inorganic.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 227 p.
  • 总页数 227
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无机化学;
  • 关键词

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