Nickel coordination is regulated by the DNA-bound state of NikR
Nickel coordination is regulated by the DNA-bound state of NikR
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DOI：
10.1038/nsb890
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发表时间：
2003-02-01
期刊：
影响因子：
--
通讯作者：
Maroney, MJ
中科院分区：
文献类型：
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作者：
Carrington, PE;Chivers, PT;Maroney, MJ
镍在大肠杆菌和其他微生物中的摄取是由NikR阻遏物或其同源物转录调控的。在这里，我们报告的高亲和力镍结合位点的结构在NikR和显示，它显着响应DNA结合。X-射线吸收光谱表明，镍的holo-NikR蛋白结合在一个新的四坐标平面网站组成的两个组氨酸，一个额外的O-或N-供体配体和一个S-供体配体。将NikR中的His 87、His 89、Cys 95或Glu 97定点突变为丙氨酸消除了高亲和力的镍结合并消除了DNA结合，但保持了稳定的蛋白质折叠。NikR结构的一个意想不到的特征是镍配位响应DNA结合。当NikR与操作DNA结合时，由O-或N-供体配体组成但缺乏半胱氨酸的六配位镍位点形成。由于镍结合和DNA结合是由NikR内的不同结构域介导的，因此涉及两个结构域之间的通信链接，这与以下发现一致：对应于NikR的C-末端结构域的片段中的镍结合位点在结构上不同于holo-NikR中发现的镍结合位点。
The uptake of nickel in Escherichia coli and other microorganisms is transcriptionally regulated by the NikR repressor or its homologs. Here we report the structure of the high-affinity nickel-binding site in NikR and show that it responds dramatically to DNA binding. X-ray absorption spectroscopy reveals that nickel in the holo-NikR protein is bound in a novel four-coordinate planar site consisting of two histidines, one additional O- or N-donor ligand and one S-donor ligand. Site-directed mutation of His87, His89, Cys95 or Glu97 in NikR to alanine eliminates high-affinity nickel binding and abolishes DNA binding but maintains stable protein folding. An unanticipated feature of the NikR structure is that the nickel coordination responds to DNA binding. A six-coordinate nickel site composed of O- or N-donor ligands, but lacking cysteine, forms when NikR binds to operator DNA. Because nickel binding and DNA binding are mediated by different domains within NikR, a communication link between the two domains is implicated, consistent with the finding that the nickel-binding site in a fragment corresponding to the C-terminal domain of NikR is structurally distinct from that found in holo-NikR.