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首页> 外文期刊>Journal of biological inorganic chemistry: JBIC: a publication of the Society of Biological Inorganic Chemistry >Metalloproteins: structure and function-A covalent mechanism at an unusual reactive thiolateligated heme
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Metalloproteins: structure and function-A covalent mechanism at an unusual reactive thiolateligated heme

机译：金属蛋白：结构和功能-在不寻常的反应性硫代甲酸酯化血红素上的共价机制

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University, South Parks Road, OX1 3QR Oxford, UK TsdA is a diheme cytochrome c which reversibly catalyzes the oxidation of thiosulfate to tetrathionate. This enzyme is important in gut microbiology and the biogeochemical sulfur cycle. Catalysis is expected to involve an unusual cysteine/histidine ligated heme. By solving the first structure of this enzyme by X-ray crystallography to 1.3 ?resolution we have been able to dissect the catalytic mechanism at this heme. We have shown that the heme-ligating thiolate is indeed reactive and can dissociate from the heme to be covalently modified with alkylating reagents. Additionally, a covalent reaction intermediate can be detected by acid-quenching the enzyme mid-reaction, or by performing stalled half-reactions. We have characterised these cysteine adducts, their formation and their stability by a combination of X-ray crystallography, mass spectrometry, various spectroscopic techniques and protein film electrochemistry. We propose a tentative catalytic mechanism based on our data.
机译：英国，牛津大学，South Parks Road，OX1 3QR，TsdA是一种双血红素细胞色素c，可逆地催化硫代硫酸盐氧化为四硫代酸盐。该酶在肠道微生物学和生物地球化学硫循环中很重要。预期催化涉及不寻常的半胱氨酸/组氨酸连接的血红素。通过X射线晶体学解析该酶的第一个结构至1.3？分辨率，我们已经能够剖析该血红素的催化机理。我们已经表明，血红素连接的硫醇盐确实是反应性的，并且可以从血红素上解离以与烷基化试剂共价修饰。另外，可以通过酸淬灭酶中间反应或通过进行停滞的半反应来检测共价反应中间体。我们通过X射线晶体学，质谱，各种光谱技术和蛋白质膜电化学的组合，对这些半胱氨酸加合物，其形成及其稳定性进行了表征。我们根据我们的数据提出了一种暂定的催化机制。

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