Keen J, Williams J, Busby S
School of Biochemistry, University of Birmingham, U.K.
Biochem J. 1996 Sep 1;318 ( Pt 2)(Pt 2):443-9. doi: 10.1042/bj3180443.
The Escherichia coli melAB promoter has been cloned on a short DNA fragment and subjected to deletion mutagenesis, random mutagenesis and site-directed mutagenesis. In previous work we had shown that expression from the melAB promoter is triggered by melibiose and that this requires the MelR transcription activator. Melibiose-dependent expression is suppressed by deletions that remove both DNA-binding sites for MelR and by point mutations in the -10 hexamer, the -35 hexamer and the region just upstream of the -35 hexamer. The point mutations identify promoter elements that are essential for triggering the melAB promoter. The importance of these elements was confirmed by site-directed mutagenesis. The results show that the organization of the melAB promoter is fundamentally different from the organization of other bacterial promoters controlled by homologues of MelR.
大肠杆菌melAB启动子已被克隆到一个短DNA片段上，并进行了缺失诱变、随机诱变和定点诱变。在之前的工作中，我们已经表明，melAB启动子的表达由蜜二糖触发，这需要MelR转录激活因子。去除MelR的两个DNA结合位点的缺失以及-10六聚体、-35六聚体和-35六聚体上游区域的点突变会抑制蜜二糖依赖性表达。这些点突变确定了触发melAB启动子所必需的启动子元件。通过定点诱变证实了这些元件的重要性。结果表明，melAB启动子的结构与由MelR同源物控制的其他细菌启动子的结构有根本不同。
