A protein that activates expression of a multidrug efflux transporter upon binding the transporter substrates.
A protein that activates expression of a multidrug efflux transporter upon binding the transporter substrates.
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DOI：
10.1016/s0021-9258(18)46956-6
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发表时间：
1994-11
期刊：
影响因子：
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通讯作者：
M. Ahmed;C. Borsch;S. Taylor;N. Vázquez-Laslop;A. Neyfakh
中科院分区：
文献类型：
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作者：
M. Ahmed;C. Borsch;S. Taylor;N. Vázquez-Laslop;A. Neyfakh
多药转运蛋白是膜蛋白，通过未知的机制识别多种有毒化合物并将其从细胞中排出。我们发现枯草芽孢杆菌多药转运蛋白 Bmr 的两种底物罗丹明 6G 和四苯基膦 (TPP) 在转录水平上增强 Bmr 表达。基因敲除实验表明，这种增强需要位于 bmr 基因下游的开放阅读框。该开放阅读框的蛋白质产物 BmrR 与几种已知的细菌转录激活蛋白（例如 MerR 和 TipAL）显示出明显的序列同源性。凝胶迁移率变化和 DNase 保护测定表明 BmrR 作为二聚体与 bmr 基因启动子特异性结合。此外，罗丹明和 TPP 增强了这种结合的亲和力，因此表明这些结构不同的分子直接与 BmrR 相互作用。事实上，我们发现 BmrR 以化学计量结合罗丹明 6G（一个罗丹明分子/BmrR 二聚体），并且 TPP 与罗丹明竞争这种结合。我们的结果表明，Bmr 表达的某些底物的增强是由于调节蛋白 BmrR 能够结合结构不同的化合物，从而导致转运蛋白基因的转录增强。
Multidrug transporters are membrane proteins which, by an unknown mechanism, recognize diverse toxic compounds and efflux them from cells. We found that two substrates of the Bacillus subtilis multidrug transporter Bmr, rhodamine 6G and tetraphenylphosphonium (TPP), enhance Bmr expression at the level of transcription. Gene knock-out experiments demonstrated that an open reading frame located immediately downstream of the bmr gene is required for this enhancement. The protein product of this open reading frame, BmrR, shows distinct sequence homology to several known bacterial transcription activator proteins, such as MerR and TipAL. Gel-mobility shift and DNase protection assays indicated that BmrR binds specifically, as a dimer, to the bmr gene promoter. Furthermore, the affinity of this binding was enhanced by rhodamine and TPP, thus suggesting that these structurally dissimilar molecules interact directly with BmrR. Indeed, we found that BmrR bound rhodamine 6G stoichiometrically, one rhodamine molecule/BmrR dimer, and that TPP competed with rhodamine for this binding. Our results indicate that the enhancement of Bmr expression by some of its substrates is due to the ability of the regulatory protein, BmrR, to bind structurally dissimilar compounds resulting in enhanced transcription of the transporter gene.