Structural Insights into a Unique Legionella pneumophila Effector LidA Recognizing Both GDP and GTP Bound Rab1 in Their Active State
Structural Insights into a Unique Legionella pneumophila Effector LidA Recognizing Both GDP and GTP Bound Rab1 in Their Active State
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DOI：
10.1371/journal.ppat.1002528
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发表时间：
2012-03-01
期刊：
影响因子：
6.7
通讯作者：
Gu, Lichuan
中科院分区：
文献类型：
--
作者：
Cheng, Wei;Yin, Kun;Gu, Lichuan
细胞内病原体嗜肺军团菌劫持内质网（ER）衍生的囊泡，以产生细菌复制所需的细胞器，称为含军团菌的空泡（LCV）。成熟的LCV涉及收购Rab1，这是介导的细菌效应蛋白SidM/DrrA。SidM/DrrA是一种双功能酶，具有Rab1特异性GDP解离抑制剂（GDI）置换因子（GDF）和鸟嘌呤核苷酸交换因子（GEF）的活性。据报道，另一种Rab1相互作用的细菌效应蛋白LidA也促进SidM/DrrA介导的Rab1向LCV的募集。在这里，我们报告的晶体结构的LidA复合物与GDP和GTP结合Rab1分别。结构比较显示，GDP-Rab1结合LidA表现出与GTP-Rab1的活性和几乎相同的构象，表明LidA可以破坏Rab1的开关功能，使其持续活性。与GTP一样，LidA通过与其两个保守的开关区域相互作用维持GDP-Rab1处于活性构象。与结构观察结果一致，生物化学测定表明LidA与GDP-和GTP-Rab1的结合同样良好，亲和力约为7.5 nM。我们认为，与Rab1的紧密相互作用允许LidA促进SidM/DrrA催化的Rab1从GDI释放。综上所述，我们的研究结果支持了一种独特的机制，通过这种机制，细菌效应蛋白调节Rab1再循环。
The intracellular pathogen Legionella pneumophila hijacks the endoplasmic reticulum (ER)-derived vesicles to create an organelle designated Legionella-containing vacuole (LCV) required for bacterial replication. Maturation of the LCV involved acquisition of Rab1, which is mediated by the bacterial effector protein SidM/DrrA. SidM/DrrA is a bifunctional enzyme having the activity of both Rab1-specific GDP dissociation inhibitor (GDI) displacement factor (GDF) and guanine nucleotide exchange factor (GEF). LidA, another Rab1-interacting bacterial effector protein, was reported to promote SidM/DrrA-mediated recruitment of Rab1 to the LCV as well. Here we report the crystal structures of LidA complexes with GDP- and GTP-bound Rab1 respectively. Structural comparison revealed that GDP-Rab1 bound by LidA exhibits an active and nearly identical conformation with that of GTP-Rab1, suggesting that LidA can disrupt the switch function of Rab1 and render it persistently active. As with GTP, LidA maintains GDP-Rab1 in the active conformation through interaction with its two conserved switch regions. Consistent with the structural observations, biochemical assays showed that LidA binds to GDP- and GTP-Rab1 equally well with an affinity approximately 7.5 nM. We propose that the tight interaction with Rab1 allows LidA to facilitate SidM/DrrA-catalyzed release of Rab1 from GDIs. Taken together, our results support a unique mechanism by which a bacterial effector protein regulates Rab1 recycling.