The VgrG proteins are "à la carte" delivery systems for bacterial type VI effectors.
The VgrG proteins are "à la carte" delivery systems for bacterial type VI effectors.
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DOI：
10.1074/jbc.m114.563429
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发表时间：
2014-06-20
期刊：
影响因子：
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通讯作者：
Filloux A
中科院分区：
文献类型：
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作者：
Hachani A;Allsopp LP;Oduko Y;Filloux A
背景：VI型分泌系统（T6SS）参与细菌战。结果：利用体外细菌杀灭试验鉴定了铜绿假单胞菌中新的h1 - t6ss依赖性毒素。结论：新发现的毒素对特异性VgrG蛋白有一定的需求。意义：VgrG蛋白可能代表t6ss依赖性分泌的一种独立形式，类似于接触依赖性生长抑制（CDI）系统。细菌VI型分泌系统（T6SS）是一种类似于噬菌体尾部的超分子复合物，VgrG蛋白起着穿刺装置的作用。铜绿假单胞菌H1-T6SS已被广泛表征。它参与杀死细菌和传递三种毒素Tse1-3。在这里，我们证明了三个H1-T6SS共同调节的vgrG基因vgrG1abc对细菌杀伤的独立贡献。一个假定的毒素在每个vgrG基因附近编码，支持特定vgrG /毒素偶对的概念。在这方面，VgrG1c参与了Rhs蛋白RhsP1的传递。RhsP1 C末端携带毒性活性，产生这种活性的细菌受到同源免疫的保护。类似地，vgrg1a依赖性毒性与PA0093基因编码的双结构域蛋白有关，该蛋白在C端具有假定的毒素结构域（Toxin_61）。最后，在三个vgrG1abc突变体的互补上可以检测到vgrg1b依赖性杀伤。vgrg1b依赖性杀伤由PA0099介导，具有超家族核酸酶2毒素成员的特点。总的来说，这些数据发展了一个概念，即vgrg是特定效应器递送不可或缺的组成部分。另外几个vgrG基因编码在铜绿假单胞菌基因组上，与其他T6SS基因没有遗传联系。仔细观察这些簇就会发现它们也编码了假定的毒素。总的来说，这些关联进一步支持了VgrG作为载体的原始分泌系统的概念。
Background: The type VI secretion system (T6SS) is involved in bacterial warfare. Results: Novel H1-T6SS-dependent toxins from Pseudomonas aeruginosa are identified using an in vitro bacterial killing assay. Conclusion: The newly identified toxins showed a requirement for specific VgrG proteins. Significance: VgrG proteins may represent an independent form of T6SS-dependent secretion, resembling the contact-dependent growth inhibition (CDI) system. The bacterial type VI secretion system (T6SS) is a supra-molecular complex akin to bacteriophage tails, with VgrG proteins acting as a puncturing device. The Pseudomonas aeruginosa H1-T6SS has been extensively characterized. It is involved in bacterial killing and in the delivery of three toxins, Tse1–3. Here, we demonstrate the independent contribution of the three H1-T6SS co-regulated vgrG genes, vgrG1abc, to bacterial killing. A putative toxin is encoded in the vicinity of each vgrG gene, supporting the concept of specific VgrG/toxin couples. In this respect, VgrG1c is involved in the delivery of an Rhs protein, RhsP1. The RhsP1 C terminus carries a toxic activity, from which the producing bacterium is protected by a cognate immunity. Similarly, VgrG1a-dependent toxicity is associated with the PA0093 gene encoding a two-domain protein with a putative toxin domain (Toxin_61) at the C terminus. Finally, VgrG1b-dependent killing is detectable upon complementation of a triple vgrG1abc mutant. The VgrG1b-dependent killing is mediated by PA0099, which presents the characteristics of the superfamily nuclease 2 toxin members. Overall, these data develop the concept that VgrGs are indispensable components for the specific delivery of effectors. Several additional vgrG genes are encoded on the P. aeruginosa genome and are not linked genetically to other T6SS genes. A closer inspection of these clusters reveals that they also encode putative toxins. Overall, these associations further support the notion of an original form of secretion system, in which VgrG acts as the carrier.