Martínez-Argudo I, Ruiz-Vázquez R M, Murillo F J
Departamento de Genética y Microbiología, Facultad de Biologia, Universidad de Murcia, Spain.
Mol Microbiol. 1998 Nov;30(4):883-93. doi: 10.1046/j.1365-2958.1998.01129.x.
Expression of the Myxococcus xanthus gene crtl is controlled by a light-inducible promoter. The activity of this promoter depends on CarQ, a sigma factor of the extracytoplasmic function (ECF) subfamily. Here, we show thatthe minimum DNA stretch reproducing normal expression of crtl extends from a few bases upstream of the -35 position to a site well downstream of the transcriptional start. The downstream DNA contains an enhancer-like element that remains active when displaced upstream of the promoter. Experimental evidence is provided for the activity of the crtl promoter being critically dependent on a pentanucleotide sequence centred at the -31 position. The similarity of this sequence with the consensus for ECF-sigma-dependent promoters from other bacteria is discussed. The activity of the crtl promoter also depends on certain basepairs at the -10 region. Hence, the operation of ECF-sigma-factors seems to require binding to two different DNA sites, although the -10 sequences of different ECF-sigma-dependent promoters are unrelated to one another, and the ECF-sigma-factors themselves lack the conserved domain known to mediate binding of other sigma-factors to the -10 DNA site.
黄色粘球菌基因crtl的表达受光诱导启动子的控制。该启动子的活性取决于CarQ，一种胞外功能（ECF）亚家族的σ因子。在此，我们表明，能够重现crtl正常表达的最小DNA片段从-35位置上游的几个碱基延伸到转录起始位点下游的一个位点。下游DNA包含一个增强子样元件，当它被转移到启动子上游时仍然具有活性。实验证据表明，crtl启动子的活性关键取决于以-31位置为中心的一个五核苷酸序列。讨论了该序列与其他细菌的ECF-σ依赖性启动子共有序列的相似性。crtl启动子的活性还取决于-10区域的某些碱基对。因此，ECF-σ因子的作用似乎需要与两个不同的DNA位点结合，尽管不同的ECF-σ依赖性启动子的-10序列彼此无关，并且ECF-σ因子本身缺乏已知介导其他σ因子与-10 DNA位点结合的保守结构域。
