Budarina Zhanna I, Nikitin Dmitri V, Zenkin Nikolay, Zakharova Marina, Semenova Ekaterina, Shlyapnikov Michael G, Rodikova Ekaterina A, Masyukova Svetlana, Ogarkov Oleg, Baida Gleb E, Solonin Alexander S, Severinov Konstantin
The Institute of Biochemistry and Physiology of Micro-organisms, Nauki Avenue, 5, Pushchino, 142292 Russia.
Waksman Institute for Microbiology, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Microbiology (Reading). 2004 Nov;150(Pt 11):3691-3701. doi: 10.1099/mic.0.27142-0.
Haemolysin II, HlyII, is one of several cytotoxic proteins produced by Bacillus cereus, an opportunistic human pathogen that causes food poisoning. The hlyII gene confers haemolytic activity to Escherichia coli cells. Here a new B. cereus gene, hlyIIR, which is located immediately downstream of hlyII and regulates hlyII expression, is reported. The deduced amino acid sequence of HlyIIR is similar to prokaryotic DNA-binding transcriptional regulators of the TetR/AcrA family. Measurements of haemolytic activity levels and of hlyII promoter activity levels using gene fusions and primer-extension assays demonstrated that, in E. coli, hlyII transcription decreased in the presence of hlyIIR. Recombinant HlyIIR binds to a 22 bp inverted DNA repeat centred 48 bp upstream of the hlyII promoter transcription initiation point. In vitro transcription studies showed that HlyIIR inhibits transcription from the hlyII promoter by binding to the 22 bp repeat and RNA polymerase, and by decreasing the formation of the catalytically competent open promoter complex.
溶血素II（HlyII）是蜡样芽孢杆菌产生的几种细胞毒性蛋白之一，蜡样芽孢杆菌是一种可导致食物中毒的机会性人类病原体。hlyII基因赋予大肠杆菌细胞溶血活性。本文报道了一个新的蜡样芽孢杆菌基因hlyIIR，它位于hlyII的紧邻下游并调节hlyII的表达。HlyIIR推导的氨基酸序列与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分析对溶血活性水平和hlyII启动子活性水平进行测量，结果表明，在大肠杆菌中，hlyIIR存在时hlyII转录减少。重组HlyIIR与位于hlyII启动子转录起始点上游48 bp处的一个22 bp反向DNA重复序列结合。体外转录研究表明，HlyIIR通过与22 bp重复序列和RNA聚合酶结合，并减少具有催化活性的开放启动子复合物的形成，从而抑制hlyII启动子的转录。
