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首页> 外文期刊>Journal of bacteriology >Regulation of the Rhodobacter sphaeroides 2.4.1 hemA Gene by PrrA and FnrL
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Regulation of the Rhodobacter sphaeroides 2.4.1 hemA Gene by PrrA and FnrL

机译：PrrA和FnrL对球形红球菌2.4.1 hemA基因的调控

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Part of the oxygen responsiveness of Rhodobacter sphaeroides 2.4.1 tetrapyrrole production involves changes in transcription of the hemA gene, which codes for one of two isoenzymes catalyzing 5-aminolevulinic acid synthesis. Regulation of hemA transcription from its two promoters is mediated by the DNA binding proteins FnrL and PrrA. The two PrrA binding sites, binding sites I and II, which are located upstream of the more-5′ hemA promoter (P1), are equally important to transcription under aerobic conditions, while binding site II is more important under anaerobic conditions. By using phosphoprotein affinity chromatography and immunoblot analyses, we showed that the phosphorylated PrrA levels in the cell increase with decreasing oxygen tensions. Then, using both in vivo and in vitro methods, we demonstrated that the relative affinities of phosphorylated and unphosphorylated PrrA for the two binding sites differ and that phosphorylated PrrA has greater affinity for site II. We also showed that PrrA regulation is directed toward the P1 promoter. We propose that the PrrA component of anaerobic induction of P1 transcription is attributable to higher affinity of phosphorylated PrrA than of unphosphorylated PrrA for binding site II. Anaerobic activation of the more-3′ hemA promoter (P2) is thought to involve FnrL binding to an FNR consensuslike sequence located upstream of the P2 promoter, but the contribution of FnrL to P1 induction may be indirect since the P1 transcription start is within the putative FnrL binding site. We present evidence suggesting that the indirect action of FnrL works through PrrA and discuss possible mechanisms.
机译：球形芽孢杆菌2.4.1的部分氧响应性产生四吡咯涉及 hemA 基因的转录变化，该基因编码两种催化5-氨基乙酰丙酸合成的同工酶之一。 DNA结合蛋白FnrL和PrrA介导 hemA 从其两个启动子的转录。位于更多5' hemA 启动子（P1）上游的两个PrrA结合位点，即结合位点I和II，对于有氧条件下的转录同样重要，而结合位点II更重要。在厌氧条件下很重要。通过使用磷蛋白亲和色谱和免疫印迹分析，我们发现细胞中的磷酸化PrrA水平随着氧张力的降低而增加。然后，使用体内和体外方法，我们证明了磷酸化和未磷酸化的PrrA对两个结合位点的相对亲和力不同，并且磷酸化的PrrA对位点II具有更大的亲和力。我们还表明，PrrA调控是针对P1启动子的。我们建议厌氧诱导P1转录的PrrA组件归因于磷酸化PrrA的亲和力高于未磷酸化PrrA对结合位点II的亲和力。更多的3' hemA 启动子（P2）的厌氧活化被认为涉及FnrL与位于P2启动子上游的FNR共有序列相似的结合，但是FnrL对P1诱导的贡献可能是间接的，因为P1转录起点位于推定的FnrL结合位点内。我们提供的证据表明FnrL的间接作用通过PrrA起作用，并讨论了可能的机制。

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