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首页> 外文期刊>Journal of bacteriology >The Integrity of the Periplasmic Domain of the VirA Sensor Kinase Is Critical for Optimal Coordination of the Virulence Signal Response in Agrobacterium tumefaciens
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The Integrity of the Periplasmic Domain of the VirA Sensor Kinase Is Critical for Optimal Coordination of the Virulence Signal Response in Agrobacterium tumefaciens

机译：VirA传感器激酶周质域的完整性对于根癌农杆菌中毒力信号响应的最佳协调至关重要。

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摘要

The plant pathogen Agrobacterium tumefaciens responds to three main signals at the plant-bacterium interface: phenolics, such as acetosyringone (AS), monosaccharides, and acidic pH (～5.5). These signals are transduced via the chromosomally encoded sugar binding protein ChvE and the Ti plasmid-encoded VirA/VirG two-component regulatory system, resulting in the transcriptional activation of the Ti plasmid virulence genes. Here, we present genetic and physical evidence that the periplasmic domain of VirA dimerizes independently of other parts of the protein, and we examine the effects of several engineered mutations in the periplasmic and transmembrane regions of VirA on vir-inducing capacity as indicated by AS sensitivity and maximal level of vir-inducing activity at saturating AS levels. The data indicate that helix-breaking mutations throughout the periplasmic domain of VirA or mutations that reposition the second transmembrane domain (TM2) of VirA relieve the periplasmic domain's repressive effects on the maximal activity of this kinase in response to phenolics, effects normally relieved only when ChvE, sugars, and low pH are also present. Such relief, however, does not sensitize VirA to low concentrations of phenolics, the other major effect of the ChvE-sugar and low pH signals. We further demonstrate that amino acid residues in a small Trg-like motif in the periplasmic domain of VirA are crucial for transmission of the ChvE-sugar signal to the cytoplasmic domain. These experiments provide evidence that small perturbations in the periplasmic domain of VirA can uncouple sugar-mediated changes in AS sensitivity from the sugar-mediated effects on maximal activity.
机译：植物病原菌 Agrobacterium tumefaciens 响应植物-细菌界面上的三个主要信号：酚类，例如乙酰丁香酮（AS），单糖和酸性pH（〜5.5）。这些信号通过染色体编码的糖结合蛋白ChvE和Ti质粒编码的VirA / VirG两组分调节系统进行转导，从而导致Ti质粒毒力基因的转录激活。在这里，我们提供了遗传和物理证据，表明VirA的周质结构域独立于蛋白质的其他部分而二聚化，并且我们研究了VirA的周质和跨膜区域中的几个工程突变对 vir -的影响AS敏感性和饱和AS水平下最大水平的 vir 诱导活性表明了其诱导能力。数据表明，在整个VirA的周质结构域中破坏螺旋的突变或重新定位VirA的第二个跨膜结构域（TM2）的突变均缓解了周质结构域对该酚类化合物最大活性的抑制作用，这种反应通常在酚也存在ChvE，糖和低pH值。但是，这种缓解不会使VirA对低浓度的酚类药物，ChvE糖的另一主要作用和低pH信号敏感。我们进一步证明，在VirA的周质结构域中小的Trg样基序中的氨基酸残基对于ChvE糖信号向细胞质结构域的传递至关重要。这些实验提供了证据，表明在VirA的周质结构域中发生小的扰动可以使糖介导的AS敏感性变化与糖介导的最大活性效应脱钩。

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