VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System.
VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System.
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DOI：
10.1371/journal.ppat.1005735
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发表时间：
2016-06
期刊：
影响因子：
6.7
通讯作者：
Coulthurst SJ
中科院分区：
文献类型：
--
作者：
Cianfanelli FR;Alcoforado Diniz J;Guo M;De Cesare V;Trost M;Coulthurst SJ
VI型分泌系统（T6SS）在细菌病原体中普遍存在，通过将有毒效应蛋白直接传递到靶细胞中，作为对竞争者细菌和真核宿主的有效武器。在HCP的管子上，上面是VGRG尖峰，可以通过含PAAR结构域的蛋白质的最终尖端扩展认为可以通过特定的HCP，VGRG或PAAR蛋白（共价（“专业””）或非共价（“货物”效应）提供。 ，蛋白质组学和生化方法，以阐明特定的VGRG和PAAR同源物在T6SS功能和效应子特异性中的作用，揭示了新方面和意外T6S的效应子的微妙之处。发现PAAR蛋白对于T6SS功能至关重要，与设计作为“核心” T6S组件一致。需要组装功能性T6S，并且在Marcescens中的三个不同的VGRG-PAAR组件暴露了不同的效应子的特异性和效率，我们发现两个不同的含PAAR的RHS蛋白可以与同一VGRG蛋白质配对EAGR蛋白参与了这些相互作用，天然VGRG-RHS-EAGR复合物被分离出来，EAGR之间的特定相互作用鉴定出Cognate RHS蛋白定义了PAAR蛋白在T6S中的重要而灵活的作用，并突出了具有差异效应子特异性和靶细胞递送效率的机械的不同版本。
致病细菌使用称为“ VI型分泌系统”（T6SS）的生物学纳米机，将有毒蛋白发射到其他细胞中。人类，动物或植物有助于细菌引起感染。了解有关机械如何募集效应并将其从细菌细胞发射到目标细胞中的更多信息。是其他T6SS的好模型。这些版本可以发射不同的效果子，并以不同的效率将效果传递到目标细胞中。细胞如此有效。
The Type VI secretion system (T6SS) is widespread among bacterial pathogens and acts as an effective weapon against competitor bacteria and eukaryotic hosts by delivering toxic effector proteins directly into target cells. The T6SS utilises a bacteriophage-like contractile machinery to expel a puncturing device based on a tube of Hcp topped with a VgrG spike, which can be extended by a final tip from a PAAR domain-containing protein. Effector proteins are believed to be delivered by specifically associating with particular Hcp, VgrG or PAAR proteins, either covalently (‘specialised’) or non-covalently (‘cargo’ effectors). Here we used the T6SS of the opportunistic pathogen Serratia marcescens, together with integratecd genetic, proteomic and biochemical approaches, to elucidate the role of specific VgrG and PAAR homologues in T6SS function and effector specificity, revealing new aspects and unexpected subtleties in effector delivery by the T6SS. We identified effectors, both cargo and specialised, absolutely dependent on a particular VgrG for delivery to target cells, and discovered that other cargo effectors can show a preference for a particular VgrG. The presence of at least one PAAR protein was found to be essential for T6SS function, consistent with designation as a ‘core’ T6SS component. We showed that specific VgrG-PAAR combinations are required to assemble a functional T6SS and that the three distinct VgrG-PAAR assemblies in S. marcescens exhibit distinct effector specificity and efficiency. Unexpectedly, we discovered that two different PAAR-containing Rhs proteins can functionally pair with the same VgrG protein. Showing that accessory EagR proteins are involved in these interactions, native VgrG-Rhs-EagR complexes were isolated and specific interactions between EagR and cognate Rhs proteins identified. This study defines an essential yet flexible role for PAAR proteins in the T6SS and highlights the existence of distinct versions of the machinery with differential effector specificity and efficiency of target cell delivery. Pathogenic bacteria use a biological nanomachine called the ‘Type VI secretion system’ (T6SS) to fire toxic proteins into other cells. These target cells can be rival bacterial cells, allowing the T6SS-wielding bacteria to outcompete other pathogens or harmless bacteria, or cells of a human, animal or plant, to help the bacteria cause an infection. The T6SS can deliver multiple different toxins, known as ‘effectors’, into target cells. This work aimed to learn more about how the machinery is able to recruit effectors and fire them from the bacterial cell into the target cell. To do this, we used a T6SS in Serratia marcescens, a pathogen causing hospital-acquired infections, which kills competitor bacteria very efficiently and is a good model for other T6SSs. We found that recently-identified components of the T6SS, called PAAR proteins, are an essential part of the machinery and also that several different versions of the machinery can form. These versions are able to fire different subsets of effectors and to deliver effectors into target cells with different efficiency. Our results help us to better understand how the T6SS machinery is able to deploy so many different toxins and kill competitor bacterial cells so effectively.