Switching control of expression of ptsG from the Mlc regulon to the NagC regulon
Switching control of expression of ptsG from the Mlc regulon to the NagC regulon
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DOI：
10.1128/jb.00315-08
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Plumbridge, Jacqueline
中科院分区：
文献类型：
--
作者：
El Qaidi, Samir;Plumbridge, Jacqueline
Mic和NagC转录抑制子与类似的23-bp操纵子结合。序列是弱回文的，只有四个位置完全保守。在体内没有观察到阻遏物之间的交叉调节，但没有明显的碱基可以负责操纵位点的歧视。为了研究操作识别的基础，并试图了解是什么区分NagC网站从Mic网站，我们进行了诱变实验，以转换ptsG从Mlc调控的基因到NagC调控的基因。在ptsG的上游有两个Mic操纵子，为了将ptsG转换为NagC调节子，需要改变两个操纵子的两个不同特征。首先，我们用GC碱基对替换了从算子对称中心起+/-11位的AT碱基对。其次，我们改变了操作符中心区域（对称中心周围的位置-4到+4）中CG碱基对的顺序。我们的研究结果表明，在这些位置的任何一个变化都足以失去Mic的监管，但这两种类型的变化在两个运营商是必要的转换ptsG的基因由NagC调节。此外，这些实验证实了两个操纵子对于NagC的调节是必要的。我们还表明，调节ptsG的麦克风涉及一些合作绑定的麦克风的两个运营商。
The Mic and NagC transcriptional repressors bind to similar 23-bp operators. The sequences are weakly palindromic, with just four positions totally conserved. There is no cross regulation observed between the repressors in vivo, but there are no obvious bases which could be responsible for operator site discrimination. To investigate the basis for operator recognition and to try to understand what differentiates NagC sites from Mic sites, we have undertaken mutagenesis experiments to convert ptsG from a gene regulated by Mlc into a gene regulated by NagC. There are two Mic operators upstream of ptsG, and to switch ptsG to the NagC regulon, it was necessary to change two different characteristics of both operators. Firstly, we replaced the AT base pair at position +/-11 from the center of symmetry of the operators with a GC base pair. Secondly, we changed the sequence of the CG base pairs in the central region of the operator (positions -4 to +4 around the center of symmetry). Our results show that changes at either of these locations are sufficient to lose regulation by Mic but that both types of changes in both operators are necessary to convert ptsG to a gene regulated by NagC. In addition, these experiments confirmed that two operators are necessary for regulation by NagC. We also show that regulation of ptsG by Mic involves some cooperative binding of Mic to the two operators.