External-pH-Dependent expression of the maltose regulon and ompF gene in Escherichia coli is affected by the level of glycerol kinase, encoded by glpK
External-pH-Dependent expression of the maltose regulon and ompF gene in Escherichia coli is affected by the level of glycerol kinase, encoded by glpK
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DOI：
10.1128/jb.183.19.5675-5683.2001
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发表时间：
2001-10-01
影响因子：
3.2
通讯作者：
Laloi, P
中科院分区：
文献类型：
--
作者：
Chagneau, C;Heyde, M;Laloi, P
麦芽糖系统在大肠杆菌中的表达受生长介质(Pho)的pH在转录和翻译水平上的调节。以甘油为碳源，编码麦芽糖调节子转录激活子的麦芽在酸性介质中的转录比在碱性介质中弱。当以3-磷酸甘油或琥珀酸为碳源时，无论pho如何，麦芽转录都很高。相反，当以麦芽糖为碳源时，无论pho如何，麦芽的表达都很低。与pho相关的麦芽转录增加需要生长介质中甘油的存在和甘油激酶(GlpK)的表达。GlpK转录水平的变化对MALT转录有很大影响。事实上，已经分离到glpFKX启动子向下突变，在该突变存在的情况下，MALT的表达增加。当从高拷贝数的质粒中表达glpK时，依赖于glpK的麦芽糖系统的减少表达变得有效，而与pho无关。对这种抑制的分析表明，glpFKX扩增不再抑制不依赖于环状AMP(CAMP)-cAMP受体蛋白(CRP)复合体的MalTp1和MalTp10启动子。因此，依赖GlpK的麦芽糖系统的抑制需要cAMP-CRP复合体。我们认为，pho可能影响GlpK、磷酸转移酶介导的葡萄糖摄取和腺苷环化酶之间的复杂相互作用。
The expression of the maltose system in Escherichia coli is regulated at both transcriptional and translational levels by the pH of the growth medium (pHo). With glycerol as the carbon source, transcription of malT, encoding the transcriptional activator of the maltose regulon, is weaker in acidic medium than in alkaline medium. malT transcription became high, regardless of the pHo, when glycerol-3-phosphate or succinate was used as the carbon source. Conversely, malT expression was low, regardless of the pHo, when maltose was used as the carbon source. The increase in malT transcription, associated with the pHo, requires the presence of glycerol in the growth medium and the expression of the glycerol kinase (GlpK). Changes in the level of glpK transcription had a great effect on malT transcription. Indeed, a glpFKX promoter-down mutation has been isolated, and in the presence of this mutation, malT expression was increased. When glpK was expressed from a high-copy-number plasmid, the glpK-dependent reduced expression of the maltose system became effective regardless of the pHo. Analysis of this repression showed that a malTp1 malTp10 promoter, which is independent of the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex, was no longer repressed by glpFKX amplification. Thus, GlpK-dependent repression of the maltose system requires the cAMP-CRP complex. We propose that the pHo may affect a complex interplay between GlpK, the phosphotransferase-mediated uptake of glucose, and the adenylate cyclase.