EXAFS STUDIES OF MIXED METAL HYBRID HEMOGLOBINS

大肠埃希氏菌初级酶中单一锌位点的结构 用X射线吸收光谱(XAS)对其进行了研究。《锌》 在天然引物酶中发现有三个四面体连接的位点 平均距离为2.37±0.02E的硫化物和一个组氨酸 氮气位于2.11±0.02 E的距离处。 镁？或锰？-醋酸盐的浓度会增加 通过一个或两个N/O配体与锌配位，使平均 N/O配基距离为2.19×10~(-3)E。 锌的位置结构也增加了一到两个配位。 HN/O配体，但平均距离为2.05±0.03E，差异显著 与添加ATP不同，ATP的添加在 错误是镁？还是锰？-醋酸盐。更高的贝壳显示出相当大的 改变用手支撑着构象的改变。因此，锌的位置是 三硫三氧改性成八面体配位 (或氮)配体，其中一个可能是组氨酸氮。 这些结果与其他结果相比表明，初级酶锌位置是 与大肠杆菌RNA中的HEssential锌位点相似 也能被其起始核苷酸协调的聚合酶 首页--期刊主要分类--期刊题录与文摘--期刊详细文摘内容 生物化学267：25560-25567,1992年。有鉴于此， 高镁构象结果表明，高镁 底物酶变得不活跃，因为锌被阻止 协调三磷酸腺苷。

The structure of the single zinc site in primase from Escherichia coli was studied using X-ray absorption spectroscopy (XAS). The zinc site in native primase was found to be tetrahedrally ligated by three sulfurs at an average distance of 2.37 ?0.02E and one histidine nitrogen located at a distance of 2.11? 0.02 E. Addition of high concentrations of Mg ?or Mn?- acetate causes an increase in the coordination of the zinc by one or two N/O ligands so that the average N/O ligand distance is 2.19 1 0.03 E. When ssDNA was added to primase, Hthe zinc site structure also increases the coordination by one or two HN/O ligands, but the average distance is 2.05 ? 0.03 E, significantly Hdifferent from the addition of ATP which gave results within the error Hof Mg ?or Mn?-acetate. The higher shells show considerable changes Hand support a conformation change. Thus, the zinc site is altered to Hoctahedral coordination by three sulfur and three oxygen (or nitrogen) Hligands, one of which could be a histidine nitrogen. These results Hand others indicate that the primase zinc site is similar to the Hessential zinc site from Escherichia coli RNA polymerase which can Halso be coordinated by its initiating nucleotide ATP (Wu, F.Y.H., HHuang, W.J., Sinclair, R.B., Powers, L. Journal of Biological HChemistry 267: 25560-25567, 1992. In light of this, the high-magnesium conformation result suggests that high magnesium primase becomes inactive because the zinc is prevented from coordinating ATP.