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首页> 外文期刊>Biochemistry >Design of a Redox-Linked Active Metal Site: Manganese Bound to Bacterial Reaction Centers at a Site Resembling That of Photosystem II
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Design of a Redox-Linked Active Metal Site: Manganese Bound to Bacterial Reaction Centers at a Site Resembling That of Photosystem II

机译：氧化还原有效金属位点的设计：在类似于照片II的网站上与细菌反应中心结合的锰

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摘要

Metals bound to proteins perform a number of crucial biological reactions,including the oxidation of water by a manganese cluster in photosystem II.Although evolutionary related to photosystem II,bacterial reaction centers lack both a strong oxidant and a manganese cluster for mediating the multielectron and proton transfer needed for water oxidation.In this study,carboxylate residues were introduced by mutagenesis into highly oxidizing reaction centers at a site homologous to the manganese-binding site of photosystem II.In the presence of manganese,light-minus-dark difference optical spectra of reaction centers from the mutants showed a lack of the oxidized bacteriochlorophyll dimer,while the reduced primary quinone was still present,demonstrating that manganese was serving as a secondary electron donor.On the basis of these steady-state optical measurements,the mutant with the highest-affinity site had a dissociation constant of approximately 1 MUM.For the highest-affinity mutant,a first-order rate with a lifetime of 12 ms was observed for the reduction of the oxidized bacteriochlorophyll dimer by the bound manganese upon exposure to light.The dependence of the amplitude of this component on manganese concentration yielded a dissociation constant of approximately 1 MUM,similar to that observed in the steady-state measurements.The three-dimensional structure determined by X-ray diffraction of the mutant with the high-affinity site showed that the binding site contains a single bound manganese ion,three carboxylate groups(including two groups introduced by mutagenesis),a histidine residue,and a bound water molecule.These reaction centers illustrate the successful design of a redox active metal center in a protein complex.
机译：与蛋白质结合的金属表现了许多关键的生物反应，包括在照相系统II中的锰簇氧化水。虽然与照相系统II相关的进化，细菌反应中心缺乏强烈的氧化剂和用于介导多电体和质子的锰簇水氧化所需的转移。本研究中，羧酸盐残基被诱变成高度氧化反应中心，该位点在与照相系统的锰结合位点同源的位点。在锰的存在，轻的 - 暗暗差异光谱的存在下来自突变体的反应中心表现出缺乏氧化的菌氯基丙二聚体，而仍然存在降低的原发性醌，证明锰用作二次电子供体。这些稳态光学测量的基础，突变体具有最高的突变体 - 除了最高亲和突变体，AF的解离常数在暴露于光时，观察到含有12ms的终毫升12 ms的IRST订购率。该组分振幅对锰浓度的依赖性产生了约1米，类似的解离常数在稳态测量中观察到的。由突变体与高亲和力点确定的X射线衍射确定的三维结构表明，结合位点含有三个羧酸锰基团（包括引入的两组通过诱变），组氨酸残基和结合的水分子。这些反应中心说明了在蛋白质复合物中的氧化还原活性金属中心的成功设计。

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  • 来源
    《Biochemistry》 |2005年第20期|共6页
  • 作者

    M.Thielges; G.Uyeda; A.Camara-Artigas; L.Kalman; J.C.Williams; J.P.Allen;

  • 作者单位

    Department of Chemistry and Biochemistry Arizona State University Tempe Arizona 85287;

    Department of Chemistry and Biochemistry Arizona State University Tempe Arizona 85287;

    Department of Chemistry and Biochemistry Arizona State University Tempe Arizona 85287;

    Department of Chemistry and Biochemistry Arizona State University Tempe Arizona 85287;

    Department of Chemistry and Biochemistry Arizona State University Tempe Arizona 85287;

    Department of Chemistry and Biochemistry Arizona State University Tempe Arizona 85287;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生物化学;
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