Solution structure of a paradigm ArsR family zinc sensor in the DNA-bound state
Solution structure of a paradigm ArsR family zinc sensor in the DNA-bound state
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DOI：
10.1073/pnas.0905558106
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发表时间：
2009-10-27
影响因子：
11.1
通讯作者：
Giedroc, David P.
中科院分区：
文献类型：
--
作者：
Arunkumar, Alphonse I.;Campanello, Gregory C.;Giedroc, David P.
金黄色葡萄球菌CzrA是来自普遍存在的金属传感器蛋白的ArsR家族的锌依赖性转录阻遏物。锌（II）结合到一对亚基间C-末端α 5-感应位点，距离DNA结合界面约15埃，并变构抑制DNA结合。这种调节的特征在于约为+6 kcal mol（-1）的大的变构偶联自由能（Δ Gc），其分子起源知之甚少。在这里，我们报告的解决方案四级结构的同二聚体CzrA绑定到一个回文28 bp的czr运营商，一个结构，提供了一个机会，比较两个变构的“结束”状态的ArsR家族传感器。Zn（II）结合驱动从“封闭”DNA结合状态到低亲和力“开放”构象的四级结构开关，这是由于二聚体内有翼螺旋DNA结合结构域的相对取向发生急剧变化。Zn（II）结合也有效地淬灭apo-CzrA的快速和中间时间尺度的内部运动，同时稳定天然状态系综。相比之下，DNA结合显着增强蛋白质的运动在变构网站和降低的α 5螺旋的稳定性，通过H-D溶剂交换测量。这项研究揭示了全球结构和动力学的变化如何在细菌金属传感器蛋白的一个大的亚家族中驱动远程变构反应，并提供了关于ArsR传感器蛋白的其他结构类别如何通过金属结合进行调节的见解。
Staphylococcus aureus CzrA is a zinc-dependent transcriptional repressor from the ubiquitous ArsR family of metal sensor proteins. Zn(II) binds to a pair of intersubunit C-terminal alpha 5-sensing sites, some 15 angstrom distant from the DNA-binding interface, and allosterically inhibits DNA binding. This regulation is characterized by a large allosteric coupling free energy (Delta Gc) of approximately +6 kcal mol(-1), the molecular origin of which is poorly understood. Here, we report the solution quaternary structure of homodimeric CzrA bound to a palindromic 28-bp czr operator, a structure that provides an opportunity to compare the two allosteric "end" states of an ArsR family sensor. Zn(II) binding drives a quaternary structural switch from a "closed" DNA-binding state to a low affinity "open" conformation as a result of a dramatic change in the relative orientations of the winged helical DNA binding domains within the dimer. Zn(II) binding also effectively quenches both rapid and intermediate timescale internal motions of apo-CzrA while stabilizing the native state ensemble. In contrast, DNA binding significantly enhances protein motions in the allosteric sites and reduces the stability of the alpha 5 helices as measured by H-D solvent exchange. This study reveals how changes in the global structure and dynamics drive a long-range allosteric response in a large subfamily of bacterial metal sensor proteins, and provides insights on how other structural classes of ArsR sensor proteins may be regulated by metal binding.