A new Bacillus cereus DNA-binding protein, HlyIIR, negatively regulates expression of B-cereus haemolysin II
A new Bacillus cereus DNA-binding protein, HlyIIR, negatively regulates expression of B-cereus haemolysin II
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DOI：
10.1099/mic.0.27142-0
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发表时间：
2004-11-01
期刊：
影响因子：
2.8
通讯作者：
Severinov, K
中科院分区：
文献类型：
--
作者：
Budarina, ZI;Nikitin, DV;Severinov, K
溶血素II，Hlyll，是由蜡状芽孢杆菌产生的几种细胞毒性蛋白质之一，蜡状芽孢杆菌是一种引起食物中毒的机会性人类病原体。hlyll基因赋予大肠杆菌细胞溶血活性。这里有一个新的B。cereus基因hlyllR位于hlyll的下游，调节hlyll的表达。推导的HIyllR的氨基酸序列与TetR/AcrA家族的原核DNA结合转录调节因子相似。使用基因融合和引物延伸测定法测量溶血活性水平和hlyll启动子活性水平表明，在大肠杆菌中，hlyll/R存在时hlyll转录降低。重组HlyIIR结合到hlyII启动子转录起始点上游48 bp中心的22 bp反向DNA重复序列。体外转录研究表明，HlyllR通过结合22 bp重复序列和RNA聚合酶，并通过减少催化活性开放启动子复合物的形成，抑制从hlyll启动子的转录。
Haemolysin ll, Hlyll, is one of several cytotoxic proteins produced by Bacillus cereus, an opportunistic human pathogen that causes food poisoning. The hlyll gene confers haemolytic activity to Escherichia coli cells. Here a new B. cereus gene, hlyllR, which is located immediately downstream of hlyll and regulates hlyll expression, is reported. The deduced amino acid sequence of HIyllR is similar to prokaryotic DNA-binding transcriptional regulators of the TetR/AcrA family. Measurements of haemolytic activity levels and of hlyll promoter activity levels using gene fusions and primer-extension assays demonstrated that, in E coli, hlyll transcription decreased in the presence of hlyll/R. Recombinant HlyllR binds to a 22 bp inverted DNA repeat centred 48 bp upstream of the hlyll promoter transcription initiation point. In vitro transcription studies showed that HlyllR inhibits transcription from the hlyll promoter by binding to the 22 bp repeat and RNA polymerase, and by decreasing the formation of the catalytically competent open promoter complex.