Type III effector activation via nucleotide binding, phosphorylation, and host target interaction.
Type III effector activation via nucleotide binding, phosphorylation, and host target interaction.
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DOI：
10.1371/journal.ppat.0030048
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发表时间：
2007-03
期刊：
影响因子：
6.7
通讯作者：
Dangl, Jeffery L
中科院分区：
文献类型：
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作者：
Desveaux, Darrell;Singer, Alex U;Wu, Ai-Jiuan;McNulty, Brian C;Musselwhite, Laura;Nimchuk, Zachary;Sondek, John;Dangl, Jeffery L
将假单胞菌III型效应蛋白无毒蛋白B（Avr B）递送到植物细胞中，在那里它靶向拟南芥RIN 4蛋白（对斑点假单胞菌蛋白1 [RPM 1]相互作用蛋白的抗性）。RIN 4是宿主基础防御反应的调节因子。通过AvrB靶向RIN 4被宿主RPM1核苷酸结合富含亮氨酸的重复抗病蛋白识别，导致加速的防御反应、病原体生长的停止和感染部位的过敏性宿主细胞死亡。我们在2.3 nm分辨率下确定了与RIN 4的AvrB结合片段复合的AvrB的结构。我们还确定了AvrB与结合在RIN 4结合域附近的结合口袋中的腺苷二磷酸复合物的结构。对于RIN 4相互作用重要的AvrB残基是RPM 1完全激活所必需的。与腺苷二磷酸接触的AvrB残基也是启动RPM 1功能所必需的。AvrB的核苷酸结合残基也是未知拟南芥蛋白磷酸化所必需的。我们得出结论，AvrB在宿主细胞内通过核苷酸结合和随后的磷酸化被激活，并且独立地与RIN 4相互作用。我们的数据表明，激活的AvrB，结合RIN 4，间接识别的RPM 1启动植物免疫系统功能。许多细菌病原体使用一种称为III型分泌系统的专门蛋白质“注射针”来帮助定植高等生物的细胞。III型分泌针附着在宿主细胞上，是在宿主细胞内作用的各种细菌蛋白质的输送管道。这些蛋白质被称为III型效应子。它们操纵宿主细胞生物学，以帮助细菌病原体在宿主中定植。我们研究了一种来自植物病原细菌假单胞菌的III型效应子。这种效应物称为无毒蛋白B（Avr B），靶向植物细胞质膜的内表面，在那里它与称为RIN 4（对斑点假单胞菌蛋白相互作用蛋白的抗性）的膜结合宿主蛋白相互作用。RIN 4在AvrB和一种迄今为止未知的额外宿主因子的存在下被磷酸化。我们为AvrB与RIN 4的结合提供了结构基础，并为AvrB在宿主内的作用提供了可能的机制。AvrB激活及其结合RIN 4的能力已经进化为帮助病原体，然而在拟南芥中，RIN 4的AvrB依赖性磷酸化被植物免疫系统感知，导致病原体生长迅速停止。
The Pseudomonas syringae type III effector protein avirulence protein B (AvrB) is delivered into plant cells, where it targets the Arabidopsis RIN4 protein (resistance to Pseudomonas maculicula protein 1 [RPM1]–interacting protein). RIN4 is a regulator of basal host defense responses. Targeting of RIN4 by AvrB is recognized by the host RPM1 nucleotide-binding leucine-rich repeat disease resistance protein, leading to accelerated defense responses, cessation of pathogen growth, and hypersensitive host cell death at the infection site. We determined the structure of AvrB complexed with an AvrB-binding fragment of RIN4 at 2.3 Å resolution. We also determined the structure of AvrB in complex with adenosine diphosphate bound in a binding pocket adjacent to the RIN4 binding domain. AvrB residues important for RIN4 interaction are required for full RPM1 activation. AvrB residues that contact adenosine diphosphate are also required for initiation of RPM1 function. Nucleotide-binding residues of AvrB are also required for its phosphorylation by an unknown Arabidopsis protein(s). We conclude that AvrB is activated inside the host cell by nucleotide binding and subsequent phosphorylation and, independently, interacts with RIN4. Our data suggest that activated AvrB, bound to RIN4, is indirectly recognized by RPM1 to initiate plant immune system function. Many bacterial pathogens use a specialized protein “injection needle” called a type III secretion system to help colonize cells of higher organisms. The type III secretion needle attaches to a host cell and is the delivery conduit for a variety of bacterial proteins that act inside of the host cell. These proteins are called type III effectors. They manipulate host cell biology in order to help the bacterial pathogen colonize the host. We studied one type III effector from plant pathogenic bacteria called Pseudomonas syringae. This effector, termed avirulence protein B (AvrB), is targeted to the inner face of the plant cell plasma membrane, where it interacts with a membrane-bound host protein called RIN4 (resistance to Pseudomonas maculicula protein–interacting protein). RIN4 is phosphorylated in the presence of AvrB and an as-yet-unknown additional host factor. We provide a structural basis for the binding of AvrB to RIN4 and a possible mechanism of action for AvrB inside the host. AvrB activation and its ability to bind RIN4 have evolved to help the pathogen, yet in Arabidopsis, the AvrB-dependent phosphorylation of RIN4 is sensed by the plant immune system, leading to a rapid halt in pathogen growth.