Yang Ji, Dogovski Con, Hocking Dianna, Tauschek Marija, Perugini Matt, Robins-Browne Roy M
Department of Microbiology and Immunology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
J Mol Biol. 2009 Dec 11;394(4):591-9. doi: 10.1016/j.jmb.2009.10.033. Epub 2009 Oct 21.
The global virulence regulatory protein RegA, an AraC-like regulator, controls the expression of more than 60 genes in the mouse enteric pathogen Citrobacter rodentium. In the presence of bicarbonate, RegA activates the transcription of a number of virulence determinants and inhibits the expression of a series of housekeeping genes. To elucidate the molecular mechanism by which bicarbonate stimulates RegA activity, we carried out biophysical and mutational analyses. Our data indicate that RegA exists as a dimer in solution regardless of bicarbonate concentration. A leucine zipper, located in the region downstream of the N-terminal domain, is responsible for dimerisation. The N-terminal arm itself is involved in modulating the response to bicarbonate, which appears to bind to a region comprising a series of beta-sheets within the N-terminal domain. The presence of bicarbonate relieves the autoinhibition of RegA activity by its N-terminal arm. RegA is the first example of a bacterial virulence regulator that utilises the light switch mechanism, previously described for the Escherichia coli AraC protein, to respond to a gut-associated effector that controls its activity.
全局毒力调节蛋白RegA是一种类AraC调节蛋白，可控制小鼠肠道病原体鼠柠檬酸杆菌中60多个基因的表达。在碳酸氢盐存在的情况下，RegA激活许多毒力决定因素的转录，并抑制一系列管家基因的表达。为了阐明碳酸氢盐刺激RegA活性的分子机制，我们进行了生物物理和突变分析。我们的数据表明，无论碳酸氢盐浓度如何，RegA在溶液中均以二聚体形式存在。位于N端结构域下游区域的亮氨酸拉链负责二聚化。N端臂本身参与调节对碳酸氢盐的反应，碳酸氢盐似乎与N端结构域内包含一系列β折叠的区域结合。碳酸氢盐的存在通过其N端臂解除了RegA活性的自抑制。RegA是细菌毒力调节蛋白的第一个例子，它利用先前针对大肠杆菌AraC蛋白描述的光开关机制，对控制其活性的肠道相关效应物作出反应。
