The Crl-RpoS regulon of Escherichia coli
The Crl-RpoS regulon of Escherichia coli
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DOI：
10.1074/mcp.m600191-mcp200
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发表时间：
2007-04-01
影响因子：
7
通讯作者：
Geiselmann, Johannes
中科院分区：
文献类型：
--
作者：
Lelong, Cecile;Aguiluz, Kryssia;Geiselmann, Johannes
RNA聚合酶的RpoS亚基控制着许多参与固定期和不同胁迫条件的基因的表达。调控蛋白Cri通过与RpoS全酶的直接相互作用增加RpoS的活性。为了确定Cri调控的程度，我们使用二维SDS-PAGE测量了Cri在30℃固定期调节大肠杆菌蛋白质组表达的作用。通过比较四种菌株(野生型，crl(-), rpoS（-）和crl（-)rpoS(-)）的蛋白质组，我们观察到74个点的强度在至少一个突变环境中被修饰。通过质谱分析鉴定出62个点，对应40种不同的蛋白质。它们被分为四大类：DNA代谢、中枢代谢、对环境变化的反应和杂项。有三种蛋白质专门参与群体感应：TnaA（将色氨酸转化为吲哚的色氨酸酶）、WrbA（色氨酸抑制物结合蛋白）和YgaG（与自动诱导-2合成酶LuxS同源）。由于对Cri表达的调控知之甚少，我们研究了可扩散分子对CH表达的影响。通过Western blotting实验，我们发现，在30℃下，在指数相和固定相之间的过渡阶段产生的可扩散分子诱导CH过早表达。吲哚被测试为潜在的候选之一：在37℃时，它以恒定的浓度存在于细胞外培养基中，但在30℃时，其浓度在过渡阶段达到峰值。当吲哚加入到培养基中时，它也在转录和翻译水平上以依赖于Cri的方式诱导Cri过早表达。因此，甲烷可以通过吲哚浓度被认为是一种新的环境传感器。
The RpoS subunit of RNA polymerase controls the expression of numerous genes involved in stationary phase and in response to different stress conditions. The regulatory protein Cri increases the activity of RpoS by direct interaction with the RpoS holoenzyme. To define the extent of the Cri regulon, we used two-dimensional SDS-PAGE to measure the role of Cri in regulating the expression of the Escherichia coli proteome in stationary phase at 30 degrees C. By comparing the proteome of four strains (wild type, crl(-), rpoS(-), and crl(-)rpoS(-)), we observed that the intensity of 74 spots was modified in at least one mutant context. 62 spots were identified by mass spectrometry and correspond to 40 distinct proteins. They were classified in four main categories: DNA metabolism, central metabolism, response to environmental modifications, and miscellaneous. Three proteins were specifically involved in quorum sensing: TnaA (the tryptophanase that converts tryptophan to indole), WrbA (Trp repressor-binding protein), and YgaG (homologous to LuxS, autoinducer-2 synthase). Because little is known about the regulation of Cri expression, we investigated the influence of diffusible molecules on the expression of CH. Using Western blotting experiments, we showed that, at 30 degrees C, a diffusible molecule(s) produced during the transition phase between the exponential and stationary phases induces a premature expression of CH. Indole was tested as one of the potential candidates: at 37 degrees C, it is present in the extracellular medium at a constant concentration, but at 30 degrees C, its concentration peaks during the transition phase. When indole was added to the culture medium, it also induced prematurely the expression of Cri at both the transcriptional and translational levels in a Cri-dependent manner. CH may thus be considered a new environmental sensor via the indole concentration.