Molecular dissection of VirB, a key regulator of the virulence cascade of Shigella flexneri
Molecular dissection of VirB, a key regulator of the virulence cascade of Shigella flexneri
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DOI：
10.1074/jbc.m111429200
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发表时间：
2002-05-03
影响因子：
4.8
通讯作者：
Dorman, CJ
中科院分区：
文献类型：
--
作者：
Beloin, C;McKenna, S;Dorman, CJ
VirB蛋白是兼性肠侵袭性病原体福氏志贺菌毒力基因表达的关键调节因子。虽然遗传学证据表明，它是位于该细菌中的230-kb质粒上的毒力基因转录激活所必需的，但迄今为止，缺乏VirB是DNA结合蛋白的证据。尽管VirB与参与质粒分配的蛋白质具有广泛的同源性，但它不类似于任何已知的常规转录因子。在这里，我们第一次表明，VirB结合到体内的毒力基因的启动子区。我们还表明，VirB形成二聚体和更高的寡聚体结构在体内和体外，这种属性是独立的DNA结合。VirB的寡聚化活性分布在两个结构域上：亮氨酸拉链样基序和可能形成三重卷曲结构的羧基末端结构域。VirB具有螺旋-转角-螺旋基序，这是DNA结合所必需的。该蛋白的氨基末端结构域也是DNA结合和毒力基因激活所必需的。VirB的可能性，需要一个辅助因子在体内与靶启动子的特异性相互作用进行了讨论。
The VirB protein is a key regulator of virulence gene expression in the facultative enteroinvasive pathogen Shigella flexneri. While genetic evidence has shown that it is required for activation of transcription of virulence genes located on a 230-kb plasmid in this bacterium, hitherto, evidence that VirB is a DNA-binding protein has been lacking. Although VirB shows extensive homology to proteins involved in plasmid partitioning, it does not resemble any known conventional transcription factor. Here we show for the first time that VirB binds to the promoter regions of the virulence genes in vivo. We also show that VirB forms dimeric and higher oligomeric structures both in vivo and in vitro and that this property is independent of DNA binding. The oligomerization activity of VirB is distributed over two, domains: a leucine zipper-like motif and a carboxyl-terminal domain likely to form triple coiled structures. VirB possesses a helix-turn-helix motif, which is required for DNA binding. The amino-terminal domain of the protein is also required for DNA binding and virulence gene activation. The possibility that VirB requires a co-factor for specific interaction with target promoters in vivo is discussed.