Pleiotropic phenotypes caused by genetic ablation of the receiver module of the Agrobacterium tumefaciens VirA protein
Pleiotropic phenotypes caused by genetic ablation of the receiver module of the Agrobacterium tumefaciens VirA protein
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DOI：
10.1128/jb.178.15.4710-4716.1996
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发表时间：
1996-08-01
影响因子：
3.2
通讯作者：
Winans, SC
中科院分区：
文献类型：
--
作者：
Chang, CH;Zhu, J;Winans, SC
根癌农杆菌的VirA蛋白是一种跨膜感觉激酶，其响应于从植物伤口部位释放的化学信号而磷酸化VirG反应调节剂。VirA含有两个组件激酶模块，并在其羧基末端，接收器模块。我们以前提供的证据表明，这个接收器模块抑制激酶模块的活性，抑制可能被磷酸化中和。在这份报告中，我们提供了额外的证据表明，过度表达的接收器模块的反式可以恢复低水平的基础活性缺乏接收器模块的VirA突变蛋白。我们还表明，消融的接收器模块恢复活性的非活性病毒A（三角洲324-413）突变体，其中有一个指定的连接器模块的区域内的删除。这表明接头模块的缺失不会使激酶模块变性，而是将激酶锁定为表型无活性构象，并且这种无活性需要接收器模块。这些数据提供了遗传学证据，激酶和受体模块的VirA获得其天然构象自主。接收器模块还限制了具有刺激活性的酚类化合物的种类，因为去除该模块会导致其他非刺激性酚类化合物如4-羟基苯乙酮刺激vir基因表达。
The VirA protein of Agrobacterium tumefaciens is a transmembrane sensory kinase that phosphorylates the VirG response regulator in response to chemical signals released from plant wound sites. VirA contains both a two-component kinase module and, at its carboxyl terminus, a receiver module. We previously provided evidence that this receiver module inhibited the activity of the kinase module and that inhibition might be neutralized by phosphorylation. In this report, we provide additional evidence for this model by showing that overexpressing the receiver module in trans can restore low-level basal activity to a VirA mutant protein lacking the receiver module. We also show that ablation of the receiver module restores activity to the inactive VirA (Delta 324-413) mutant, which has a deletion within a region designated the linker module. This indicates that deletion of the linker module does not denature the kinase module, but rather locks the kinase into a phenotypically inactive conformation, and that this inactivity requires the receiver module. These data provide genetic evidence that the kinase and receiver modules of VirA attain their native conformations autonomously. The receiver module also restricts the variety of phenolic compounds that have stimulatory activity, since removal of this module causes otherwise nonstimulatory phenolic compounds such as 4-hydroxyacetophenone to stimulate vir gene expression.