DNA distortion mechanism for transcriptional activation by ZntR, a Zn(II)-responsive MerR homologue in Escherichia coli
DNA distortion mechanism for transcriptional activation by ZntR, a Zn(II)-responsive MerR homologue in Escherichia coli
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DOI：
10.1074/jbc.274.53.37517
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发表时间：
1999-12-31
影响因子：
4.8
通讯作者：
O'Halloran, TV
中科院分区：
文献类型：
--
作者：
Outten, CE;Outten, FW;O'Halloran, TV
针对多种逆境反应转录因子，已经提出了类似于Merr的DNA扭曲机制。最近研究发现，与MerR同源的大肠杆菌ZNTR蛋白参与了锌(II)解毒相关基因zntA对锌(II)的应答调节。为了确定MerR DNA扭曲机制在MerR家族成员中是否保守，我们将ZntR纯化为均一，并证明它是一种锌受体，是刺激zntA启动子上的锌反应转录所必需的且充分的。生化、DNA足迹和体外转录实验表明，apo-ZntR结合在启动子的非典型20碱基对间隔区，并以类似于apo-merR的方式扭曲DNA。将锌(II)加入到锌受体中，将其转化为转录激活蛋白，从而引起DNA构象的变化。这些变化显然使启动子成为RNA聚合酶的更好底物。我们认为，这个锌敏感的MERR同源基因以类似于其他胁迫反应转录因子的方式重组目标启动子。锌受体金属调节蛋白是一种直接的锌(II)感受器，催化锌外流基因的转录激活，从而防止细胞内锌(II)超过一个最佳但未知的浓度。
MerR-like DNA distortion mechanisms have been proposed for a variety of stress-responsive transcription factors. The Escherichia coli ZntR protein, a homologue of MerR, has recently been shown to mediate Zn(II)responsive regulation of zntA, a gene involved in Zn(II) detoxification. To determine whether the MerR DNA distortion mechanism is conserved among MerR family members, we have purified ZntR to homogeneity and shown that it is a zinc receptor that is necessary and sufficient to stimulate Zn-responsive transcription at the zntA promoter. Biochemical, DNA footprinting, and in vitro transcription assays indicate that apo-ZntR binds in the atypical 20-base pair spacer region of the promoter and distorts the DNA in a manner that is similar to apo-MerR. The addition of Zn(II) to ZntR converts it to a transcriptional activator protein that introduces changes in the DNA conformation. These changes apparently make the promoter a better substrate for RNA polymerase. We propose that this zinc-sensing homologue of MerR restructures the target promoter in a manner similar to that of other stress-responsive transcription factors. The ZntR metalloregulatory protein is a direct Zn(II) sensor that catalyzes transcriptional activation of a zinc efflux gene, thus preventing intracellular Zn(II) from exceeding an optimal but as yet unknown concentration.