Gutierrez C, Gordia S, Bonnassie S
Laboratoire de Microbiologie et Génétique Moléculaire, UPR 9007 du CNRS, Toulouse, France.
Mol Microbiol. 1995 May;16(3):553-63. doi: 10.1111/j.1365-2958.1995.tb02418.x.
osmE, an osmotically inducible gene of Escherichia coli, was physically mapped on the bacterial chromosome, cloned and sequenced. osmE appeared to encode a 12,021 Da protein of unknown function, with a lipoprotein-type signal sequence at the amino-terminus. The osmE reading frame was confirmed by sequencing the junction of an osmE-phoA gene fusion. osmE was demonstrated to be transcribed as a single cistron. A phi [osmEp-lac] operon fusion was constructed, and analysis of its expression demonstrated that osmE osmotic regulation probably occurs at the transcriptional level. The osmE promoter was identified by both S1 nuclease and primer extension mapping of the 5' end of the osmE mRNA, by deletion analysis and by identification of a point mutation reducing its activity. Sequence information sufficient for expression and osmotic regulation is present on a DNA fragment extending from positions -37 to +52 with respect to the osmE transcription start. Uninduced expression of the osmE-lac fusion was increased in the presence of mutations in the hns and himA genes. The osmE promoter overlaps a promoter for a gene transcribed in the opposite direction, efg. Transcription from the efg promoter is only weakly affected by osmotic pressure and is independent of the presence of an intact OsmE protein.
osmE是大肠杆菌的一个渗透压诱导基因，已在细菌染色体上进行了物理定位、克隆和测序。osmE似乎编码一种功能未知的12,021 Da蛋白质，其氨基末端有一个脂蛋白型信号序列。通过对osmE-phoA基因融合体的连接点进行测序，证实了osmE的阅读框。已证明osmE作为一个单一顺反子进行转录。构建了一个φ[osmEp-lac]操纵子融合体，对其表达的分析表明，osmE的渗透压调节可能发生在转录水平。通过S1核酸酶和对osmE mRNA 5'端的引物延伸图谱分析、缺失分析以及鉴定一个降低其活性的点突变，确定了osmE启动子。在相对于osmE转录起始位点从-37到+52的DNA片段上，存在足以进行表达和渗透压调节的序列信息。在hns和himA基因发生突变的情况下，osmE-lac融合体的未诱导表达增加。osmE启动子与一个向相反方向转录的基因efg的启动子重叠。来自efg启动子的转录仅受到渗透压的微弱影响，并且与完整的OsmE蛋白的存在无关。
