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首页> 外文期刊>Journal of Molecular Biology >Structural mechanism of transcriptional autorepression of the Escherichia coli RelB/RelE antitoxin/toxin module.
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Structural mechanism of transcriptional autorepression of the Escherichia coli RelB/RelE antitoxin/toxin module.

机译：大肠杆菌RelB / RelE抗毒素/毒素模块转录自动阻遏的结构机制。

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摘要

The Escherichia coli chromosomal relBE operon encodes a toxin-antitoxin system, which is autoregulated by its protein products, RelB and RelE. RelB acts as a transcriptional repressor and RelE functions as a cofactor to enhance the repressor activity of RelB. Here, we present the NMR-derived structure of a RelB dimer and show that a RelB dimer recognizes a hexad repeat in the palindromic operator region through a ribbon-helix-helix motif. Our biochemical data show that two weakly associated RelB dimers bind to the adjacent repeats in the 3'-site of the operator (O(R)) at a moderate affinity (K(d), approximately 10(-5) M). However, in the presence of RelE, a RelB tetramer binds two distinct binding sites within the operator region, each with an enhanced affinity (K(d), approximately 10(-6) M for the low-affinity site, O(L), and 10(-8) M for the high-affinity site, O(R)). We propose that the enhanced affinity for the operator element is mediated by a cooperative DNA binding by a pair of RelB dimers and that the interaction between RelB dimers is strongly augmented by the presence of the cognate toxin RelE.
机译：大肠杆菌染色体relBE操纵子编码一种毒素-抗毒素系统，该系统由其蛋白质产物RelB和RelE自动调节。 RelB充当转录阻遏物，RelE充当辅助因子以增强RelB的阻遏物活性。在这里，我们介绍RelB二聚体的NMR衍生结构，并显示RelB二聚体通过带状-螺旋-螺旋基序识别回文操纵子区域中的hexad重复序列。我们的生化数据显示，两个弱关联的RelB二聚体以中等亲和力（K（d），大约10（-5）M）结合到操纵子（O（R））3'-位的相邻重复序列。但是，在存在RelE的情况下，RelB四聚体结合了操纵子区域内的两个不同的结合位点，每个结合位点均具有增强的亲和力（K（d），对于低亲和力位点O（L）约为10（-6）M ，高亲和力位点O（R）为10（-8）M。我们提出，通过一对RelB二聚体的合作DNA结合来介导对操纵元件的增强亲和力，并且通过关联毒素RelE的存在，RelB二聚体之间的相互作用会大大增强。

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