The HopX (AvrPphE) family of Pseudomonas syringae type III effectors require a catalytic triad and a novel N-terminal domain for function.
The HopX (AvrPphE) family of Pseudomonas syringae type III effectors require a catalytic triad and a novel N-terminal domain for function.
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DOI：
10.1094/mpmi-20-4-0346
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发表时间：
2007-03
期刊：
影响因子：
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通讯作者：
Zachary L. Nimchuk;E. Fisher;D. Desveaux;Jeff H. Chang;J. Dangl
中科院分区：
文献类型：
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作者：
Zachary L. Nimchuk;E. Fisher;D. Desveaux;Jeff H. Chang;J. Dangl
许多革兰氏阴性植物病原菌在感染过程中采用 III 型分泌系统将效应蛋白直接递送到宿主细胞中。在易感宿主上，III 型效应子通过操纵宿主防御途径来帮助病原体生长。在抗性宿主上，一些效应器可以激活特定宿主抗病（R）基因，从而产生快速有效的免疫反应。人们对这些过程的生化基础知之甚少。 HopX (AvrPphE) 家族是植物病原细菌中广泛分布的 III 型效应子。我们确定 HopX 家族成员是由保守的假定的基于半胱氨酸的催化三联体和保守的潜在靶标/辅因子相互作用结构域组成的模块化蛋白。 HopX 可溶于宿主细胞。假定的催化三联体残基对于抗性豆宿主的无毒活性和特定拟南芥基因型中细胞死亡反应的产生是必需的。这些活动还需要假定的目标/辅助因子相互作用域。我们的数据表明，与胞质宿主靶标的特异性相互作用和修饰可驱动耐药宿主中的 HopX 识别，并可能有助于易感宿主的毒力。令人惊讶的是，嗜肺军团菌基因组被发现含有一种在序列和结构域排列上与HopX相似的蛋白质，这表明这些蛋白质也可能有助于动物发病机制，并且可以通过不同的分泌系统递送至植物和动物宿主。
Many gram-negative plant pathogenic bacteria employ type III secretion systems to deliver effector proteins directly into the host cell during infection. On susceptible hosts, type III effectors aid pathogen growth by manipulating host defense pathways. On resistant hosts, some effectors can activate specific host disease resistance (R) genes, leading to generation of rapid and effective immune responses. The biochemical basis of these processes is poorly understood. The HopX (AvrPphE) family is a widespread type III effector among phytopathogenic bacteria. We determined that HopX family members are modular proteins composed of a conserved putative cysteine-based catalytic triad and a conserved potential target/cofactor interaction domain. HopX is soluble in host cells. Putative catalytic triad residues are required for avirulence activity on resistant bean hosts and for the generation of a cell-death response in specific Arabidopsis genotypes. The putative target/cofactor interaction domain is also required for these activities. Our data suggest that specific interaction with and modification of a cytosolic host target drives HopX recognition in resistant hosts and may contribute to virulence in susceptible hosts. Surprisingly, the Legionella pneumophila genome was found to contain a protein with similarity to HopX in sequence and domain arrangement, suggesting that these proteins might also contribute to animal pathogenesis and could be delivered to plant and animal hosts by diverse secretion systems.