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首页> 外文期刊>Biochemistry >The Diheme Cytochrome c4 from Vibrio cholerae Is a Natural Electron Donor to the Respiratory cbb3 Oxygen Reductase
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The Diheme Cytochrome c4 from Vibrio cholerae Is a Natural Electron Donor to the Respiratory cbb3 Oxygen Reductase

机译：霍乱弧菌的二氢细胞色素c4是呼吸性cbb3氧还原酶的天然电子供体

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The respiratory chain of Vibrio cholerae contains three bd-type quinol oxygen reductases as well asnone cbb3 oxygen reductase. The cbb3 oxygen reductase has been previously isolated and characterized;nhowever, the natural mobile electron donor(s) that shuttles electrons between the bc1 complex and the cbb3noxygen reductase is not known. The most likely candidates are the diheme cytochrome c4 and monohemencytochrome c5, which have been previously shown to be present in the periplasmof aerobically grown culturesnof V. cholerae. Both cytochromes c4 and c5 fromV. cholerae have been cloned and expressed heterologously innEscherichia coli. It is shown that reduced cytochrome c4 is a substrate for the purified cbb3 oxygen reductasenand can support steady state oxygen reductase activity of at least 300 en-1n/s. In contrast, reduced cytochrome c5nis not a good substrate for the cbb3 oxygen reductase. Surprisingly, the dependence of the oxygen reductasenactivity on the concentration of cytochrome c4 does not exhibit saturation. Global spectroscopic analysis ofnthe time course of the oxidation of cytochrome c4 indicates that the apparent lack of saturation is due to thenstrong dependence of KMand Vmax on the concentration of oxidized cytochrome c4.Whether this is an artifactnof the in vitro assay or has physiological significance remains unknown. Cyclic voltammetry was used tondetermine that the midpoint potentials of the two hemes in cytochrome c4 are 240 and 340 mV (vs standardnhydrogen electrode), similar to the electrochemical properties of other c4-type cytochromes.Genomic analysisnshows a strong correlation between the presence of a c4-type cytochrome and a cbb3 oxygen reductase withinnthe β- and γ-proteobacterial clades, suggesting that cytochrome c4 is the likely natural electron donor tonthe cbb3 oxygen reductases within these organisms. These would include the β-proteobacteria Neisserianmeningitidis and Neisseria gonnorhoeae, in which the cbb3 oxygen reductases are the only terminal oxidases inntheir respiratory chains, and the γ-proteobacterium Pseudomonas stutzeri.
机译：霍乱弧菌的呼吸链包含三种bd型喹诺氧还原酶以及无cbb3氧还原酶。 cbb3氧还原酶已经过分离和表征；但是，尚不知道在bc1配合物和cbb3n氧还原酶之间穿梭电子的天然移动电子供体。最可能的候选药物是二血红素细胞色素c4和单血色素c5，先前已证明它们存在于霍乱弧菌需氧生长培养物的周质中。来自V的细胞色素c4和c5。霍乱已经被克隆并在大肠杆菌中异源表达。结果表明，还原的细胞色素c4是纯化的cbb3氧还原酶的底物，可以支持至少300 en-1n / s的稳态氧还原酶活性。相反，还原的细胞色素c5nis不是cbb3氧还原酶的良好底物。令人惊讶地，氧还原酶活性对细胞色素c4浓度的依赖性没有表现出饱和。对细胞色素c4氧化时间过程的全球光谱分析表明，明显的饱和度缺乏是由于KM和Vmax强烈依赖于氧化的细胞色素c4的浓度所致。 。循环伏安法用于确定细胞色素c4中两个血红素的中点电势分别为240和340 mV（相对于标准氢电极），与其他c4型细胞色素的电化学性质相似。基因组分析显示c4存在之间的强相关性β-和γ-蛋白菌进化枝中的p-型细胞色素和cbb3氧还原酶，表明细胞色素c4是这些生物体内cbb3氧还原酶的可能的天然电子供体。其中包括β-变形杆菌Neisserianmeningitidis和Neisseria gonnorhoeae，其中cbb3氧还原酶是呼吸链中唯一的末端氧化酶，以及γ-变形杆菌Pseudomonas stutzeri。

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  • 来源
    《Biochemistry》 |2010年第35期|p.7494-7503|共10页
  • 作者

    Hsin-Yang Chang Young Ahn Laura A. Pace Myat T. Lin Yun-Hui Lin and Robert B. Gennis;

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    ‡Department of Biochemistry, University of Illinois, Urbana, Illinois 61801,§Center for Biophysics and Computational Biology,University of Illinois, Urbana, Illinois 61801, and ) Department of Chemistry, University of Illinois, Urbana, Illinois 61801.^These authors contributed equally to this work.;

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