Eguchi Yoko, Oshima Taku, Mori Hirotada, Aono Rikizo, Yamamoto Kaneyoshi, Ishihama Akira, Utsumi Ryutaro
Department of Bioscience and Biotechnology, Graduate School of Agriculture of Kinki University, 3327-204, Nakamachi, Nara 631-8505, Japan.
Research and Education Center for Genetic Information, Nara Institute of Science and Technology, Ikoma 630-0101, Japan.
Microbiology (Reading). 2003 Oct;149(Pt 10):2819-2828. doi: 10.1099/mic.0.26460-0.
A constitutively active mutant of histidine kinase sensor EvgS was found to confer multi-drug resistance (MDR) to an acrA-deficient Escherichia coli, indicating the relationship between the two-component system EvgAS and the expression of the MDR system. The observed MDR also depended on an outer-membrane channel, TolC. Microarray and S1 mapping assays indicated that, in the presence of this constitutive mutant EvgS, the level of transcription increased for some MDR genes, including the drug efflux genes emrKY, yhiUV, acrAB, mdfA and tolC. Transcription in vitro of emrK increased by the addition of phosphorylated EvgA. Transcription activation of tolC by the activated EvgS was, however, dependent on both EvgAS and PhoPQ (Mg(2+)-responsive two-component system), in agreement with the presence of the binding site (PhoP box) for the regulator PhoP in the tolC promoter region. Transcription in vitro of yhiUV also appears to require an as-yet-unidentified additional transcriptional factor besides EvgA. Taken together we propose that the expression of the MDR system is under a complex regulatory network, including the phosphorylated EvgA serving as the master regulator.
研究发现，组氨酸激酶传感器EvgS的组成型活性突变体可使acrA缺陷型大肠杆菌具有多药耐药性（MDR），这表明双组分系统EvgAS与MDR系统的表达之间存在关联。观察到的MDR还依赖于外膜通道TolC。微阵列和S1作图分析表明，在存在这种组成型突变体EvgS的情况下，包括药物外排基因emrKY、yhiUV、acrAB、mdfA和tolC在内的一些MDR基因的转录水平升高。添加磷酸化的EvgA可增加emrK的体外转录。然而，活化的EvgS对tolC的转录激活依赖于EvgAS和PhoPQ（Mg(2+)响应双组分系统），这与tolC启动子区域中调节因子PhoP的结合位点（PhoP框）的存在一致。yhiUV的体外转录似乎除了EvgA之外还需要一种尚未鉴定的额外转录因子。综上所述，我们提出MDR系统的表达受一个复杂的调控网络控制，其中磷酸化的EvgA作为主要调节因子。
