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Biophysical characterization of electron transfer proteins containing multiple metallocofactors: Investigation of the adomet radical and cytochrome c peroxidase enzyme superfamilies

机译：包含多种金属因子的电子转移蛋白的生物物理特征：扁豆自由基和细胞色素c过氧化物酶超家族的研究

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摘要

Metallocofactors are ubiquitous in nature, serving multiple purposes in proteins. These metallocofactors typically act as the site of catalysis or as an electron relay to move electrons within the protein, or within the cell, and are very energetically costly to manufacture. Yet, in nature it can appear that supernumerary, or 'auxiliary' cofactors are apparent, with no clear function. In this thesis, I address the question of what roles additional cofactors play, and why they are retained.;The radical S-adenosylmethionine (AdoMet) enzyme superfamily has displayed great diversity in the cofactor requirements for its members. Some members of this family contain only the canonical [4Fe-4S] cluster, which reductively cleaves AdoMet to initiate chemistry, while others have additional [2Fe-2S] or [4Fe-4S] clusters. Even greater cofactor complexity is seen with the B 12-dependent subclass, featuring a cobalamin-binding domain in addition to the canonical FeS cluster. The majority of this thesis has focused on using the technique of protein film electrochemistry (PFE) to study members of various subclasses of this superfamily: a dehydrogenase: BtrN, two methylthiotransferases: MiaB and RimO, as well as OxsB and TsrM, two B12-dependent enzymes. By evaluating the redox properties of members of different subclasses, we have been able to shed light on the redox properties of this superfamily, in general, and observed that the redox properties of auxiliary clusters can differ widely between subclasses (e.g. BtrN versus MiaB). PFE has also been used to evaluate five ferredoxins that are possible electron donors for MiaB from Thermotoga maritima..;Additionally, bacterial cytochrome c peroxidases (bCCPs) are diheme enzymes catalyzing the detoxification of hydrogen peroxide; however, a novel subclass of bCCPs containing a third heme-binding motif has been identified in enteric pathogens. Protein film electrochemistry has been used to study the redox properties of Escherichia coli YhjA, a member of this subgroup. Further characterization of this novel bCCP was achieved with electron paramagnetic resonance, optical spectroscopy, and steady-state kinetics. Through characterizing YhjA and members of the AdoMet radical enzyme superfamily, we have shed light on the role these additional cofactors play in the mechanism and how these enzymes are tuned for their specific chemistries.
机译：金属因子在自然界中普遍存在，在蛋白质中具有多种用途。这些金属因子通常充当催化部位或电子中继器，以移动蛋白质内或细胞内的电子，并且在制造上非常耗能。但是，在自然界中，似乎似乎是多余的或“辅助”辅助因子，没有明确的功能。在这篇论文中，我解决了附加辅因子起什么作用以及为什么保留这些辅酶的问题。自由基S-腺苷甲硫氨酸（AdoMet）酶超家族对其成员的辅因子要求显示出极大的多样性。该家族的某些成员仅包含典范的[4Fe-4S]团簇，该簇可还原性裂解AdoMet以引发化学反应，而其他成员则具有其他[2Fe-2S]或[4Fe-4S]团簇。依赖于B 12的子类具有更大的辅因子复杂性，除了经典的FeS簇外，还具有钴胺素结合域。本论文的大部分重点是使用蛋白质膜电化学（PFE）技术研究该超家族的各个亚类的成员：脱氢酶：BtrN，两个甲硫基转移酶：MiaB和RimO，以及OxsB和TsrM，两个B12-依赖性酶。通过评估不同子类成员的氧化还原特性，我们能够大致了解该超家族的氧化还原特性，并观察到辅助簇的氧化还原特性在子类之间可能存在很大差异（例如BtrN与MiaB）。 PFE还被用于评估五种铁氧还蛋白，它们可能是来自海洋栖热菌的MiaB的电子供体。此外，细菌细胞色素C过氧化物酶（bCCP）是催化过氧化氢解毒的双血红素酶；然而，在肠道病原体中已经鉴定出了含有第三种血红素结合基序的新型bCCP亚类。蛋白膜电化学已用于研究该亚类成员大肠杆菌YhjA的氧化还原特性。该新型bCCP的进一步表征是通过电子顺磁共振，光谱学和稳态动力学实现的。通过表征YhjA和AdoMet自由基酶超家族的成员，我们阐明了这些额外的辅因子在机理中的作用以及如何针对其特定化学性质调节这些酶。

著录项

  • 作者

    Maiocco, Stephanie J.;

  • 作者单位

    Boston University.;

  • 授予单位 Boston University.;
  • 学科 Biochemistry.;Biophysics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 203 p.
  • 总页数 203
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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