Zengel J M, Lindahl L
Department of Biology, University of Rochester, NY 14627.
Biochim Biophys Acta. 1990 Aug 27;1050(1-3):317-22. doi: 10.1016/0167-4781(90)90188-8.
The str operon of Escherichia coli contains the genes for ribosomal proteins S7 and S12 as well as elongation factors G and Tu (EF-G, EF-Tu). We have previously reported that there is a secondary promoter for expression of EF-Tu mapping within the upstream fus gene encoding EF-G (Zengel, J.M. and Lindahl, L. (1982) Mol. Gen. Genet. 185, 487-492) and have identified several potential promoter sequences within fus (Zengel, J.M., Archer, R.H. and Lindahl, L. (1984) Nucleic Acids Res. 12, 2181-2192). We have now further characterized this promoter activity. Measurements of transcription rates from various regions of the str operon in cells carrying the fus gene and the beginning of the tufA gene on a high copy number plasmid confirmed that transcription was initiated within a 600 bp EcoRI fragment in the distal portion of the fus gene. Furthermore, T1 nuclease mapping studies identified two 5' ends within this region, one about 400 bases upstream of tufA, the other about 270 bases upstream, suggesting that there are two tufA promoters within the fus gene. Both of these promoters are active in the intact chromosomal str operon.
大肠杆菌的str操纵子包含核糖体蛋白S7和S12以及延伸因子G和Tu（EF-G、EF-Tu）的基因。我们之前报道过，在编码EF-G的上游fus基因内存在一个用于EF-Tu表达的二级启动子（曾格尔，J.M.和林达尔，L.（1982年）《分子与普通遗传学》185卷，487 - 492页），并且已经在fus基因内鉴定出了几个潜在的启动子序列（曾格尔，J.M.、阿彻，R.H.和林达尔，L.（1984年）《核酸研究》12卷，2181 - 2192页）。我们现在进一步对该启动子活性进行了表征。对携带fus基因和高拷贝数质粒上tufA基因起始部分的细胞中str操纵子各个区域的转录速率进行测量，证实转录起始于fus基因远端的一个600 bp的EcoRI片段内。此外，T1核酸酶图谱分析研究在该区域内鉴定出了两个5'端，一个在tufA上游约400个碱基处，另一个在其上游约270个碱基处，这表明在fus基因内存在两个tufA启动子。这两个启动子在完整的染色体str操纵子中均有活性。
