Conformational change of DNA bound to transcription factor response to environmental change

[2Fe-2S] 转录因子 SoxR 在大肠杆菌中充当氧化应激传感器。在氧化状态下，通过扭曲靶 DNA 启动子区域以启动 RNA 聚合酶的转录来激活转录，而蛋白质的非活性还原状态仍然未表征。通过分别用荧光探针2-氨基嘌呤(2Ap)和吡咯-dC位点特异性取代启动子寡核苷酸的腺嘌呤和胞嘧啶碱基，直接观察启动子DNA的氧化还原依赖性构象变化。 SoxR-DNA 复合物中 [2Fe-2S] 簇的还原显着削弱了掺入 DNA 中心部分的 2Ap 部分的荧光强度。这些结果强烈表明，氧化还原变化在DNA启动子区中央A-T碱基对范围内引起了巨大的构象变化。

The [2Fe-2S] transcriptional factor SoxR functions as a sensor of oxidative stress in Escherichia coli. In the oxidized state, transcription is activated by distorting the target DNA promoter region to initiate transcription by RNA polymerase, while the inactive reduced state of the protein remains uncharacterized. The redox-dependent conformational change of the promoter DNA was directly observed by site-specifically replacing the adenine and cytosine bases of the promoter oligonucleotide with the fluorescent probes 2-aminopurine (2Ap) and pyrrolo-dC, respectively. Reduction of the [2Fe-2S] cluster in SoxR-DNA complex dramatically weakened the fluorescence intensity of the 2Ap moieties incorporated into the central part of the DNA. These results strongly suggested that the redox change caused a large conformational change within the region confined to the central A-T base pairs in the promoter region of the DNA.