Substrate induction of siderophore transport in Bacillus subtilis mediated by a novel one-component regulator
Substrate induction of siderophore transport in Bacillus subtilis mediated by a novel one-component regulator
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DOI：
10.1111/j.1365-2958.2007.05905.x
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发表时间：
2007-10-01
影响因子：
3.6
通讯作者：
Helmann, John D.
中科院分区：
文献类型：
--
作者：
Gaballa, Ahmed;Helmann, John D.
当铁缺乏时，枯草芽孢杆菌表达参与铁载体杆菌素(BB)合成和吸收的基因，并通过吸收系统盗取其他微生物的铁载体。在这里，我们证明了编码Fe-BB摄取系统的feuAB-CybA操纵子的转录诱导是由直接上游基因编码的BTR(以前的YbbB)介导的。BTR含有一个AraC型DNA结合域，融合到与FeuA相关的底物结合蛋白(SBP)结构域，FeuA是摄取Fe-BB的底物结合蛋白。当细胞受到铁限制时，Fur介导的对BTR的抑制被解除，BTR与邻近FeuA的保守的直接重复序列结合来激活。文字记录离子。如果存在BB，BTR会进一步激活feuA的表达。BTR与apo-BB和Fe-BB都有很高的亲和力，与单独的BTR相比，作为转录激活剂的效果显著增强。尽管遗传分析表明这两个铁载体与BTR底物结合域有不同的相互作用，但BTR也可以激活转录，以响应结构上相似的铁载体Enterobactin。因此，FeuABC转运蛋白在铁饥饿的条件下，当Fur介导的抑制被解除时，以及在其同源底物存在的情况下，都是最佳表达的。
When iron is scarce, Bacillus subtilis expresses genes involved in the synthesis and uptake of the siderophore bacillibactin (BB) and uptake systems to pirate other microbial siderophores. Here, we demonstrate that transcriptional induction of the feuAB-CybbA operon, encoding the Fe-BB uptake system, is mediated by Btr (formerly YbbB), which is encoded by the immediately upstream gene. Btr contains an AraC-type DNA binding domain fused to a substrate binding protein (SBP) domain related to FeuA, the SBP for Fe-BB uptake. When cells are iron-limited, the Fur-mediated repression of btr is relieved and Btr binds to a conserved direct repeat sequence adjacent to feuA to activate. transcript ion. If BB is present, Btr further activates feuA expression. Btr binds with high affinity to both apo-BB and Fe-BB, and the resulting complex displays a significantly increased efficacy as a transcriptional activator relative to Btr alone. Btr can also activate transcription in response to the structurally similar siderophore enterobactin, although genetic analyses indicate that the two siderophores make distinct interactions with the Btr substrate binding domain. Thus, the FeuABC transporter is optimally expressed under conditions of iron starvation, when Fur-mediated repression is relieved, and in the presence of its cognate substrate.