Antibacterial T6SS effectors with a VRR-Nuc domain are structure-specific nucleases.
Antibacterial T6SS effectors with a VRR-Nuc domain are structure-specific nucleases.
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DOI：
10.7554/elife.82437
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发表时间：
2022-10-13
期刊：
影响因子：
7.7
通讯作者：
Bayer-Santos E
中科院分区：
文献类型：
--
作者：
Hespanhol JT;Sanchez-Limache DE;Nicastro GG;Mead L;Llontop EE;Chagas-Santos G;Farah CS;de Souza RF;Galhardo RDS;Lovering AL;Bayer-Santos E
VI型分泌系统（T6SS）向目标竞争者分泌抗菌效应物。沙门氏菌编码5个系统发育上不同的t6ss。在此，我们对邦格里沙门氏菌的SPI-22 T6SS的功能进行了表征，表明其具有抗菌活性，并鉴定了一组抗菌T6SS效应物（TseV1-4），该效应物包含一个n端paar样结构域和一个c端VRR-Nuc结构域，编码在具有DUF3396结构域的同源免疫蛋白（TsiV1-4）旁边。在大肠杆菌中表达TseV2和TseV3是有毒性的，细菌竞争实验证实了TseV2和TseV3是由SPI-22 T6SS分泌的。系统发育分析表明，TseV1-4与参与DNA修复的酶有进化关系。TseV3识别特定的DNA结构，并优先切割张开的臂，产生DNA双链断裂，并在靶细胞中诱导SOS反应。TseV3:TsiV3复合物的晶体结构表明，免疫蛋白可能阻断效应物与DNA底物的相互作用。这些结果扩大了我们对沙门氏菌致病性岛的功能，生物冲突中使用的毒素的进化以及调节这些毒素活性的内源性机制的认识。
The type VI secretion system (T6SS) secretes antibacterial effectors into target competitors. Salmonella spp. encode five phylogenetically distinct T6SSs. Here, we characterize the function of the SPI-22 T6SS of Salmonella bongori showing that it has antibacterial activity and identify a group of antibacterial T6SS effectors (TseV1–4) containing an N-terminal PAAR-like domain and a C-terminal VRR-Nuc domain encoded next to cognate immunity proteins with a DUF3396 domain (TsiV1–4). TseV2 and TseV3 are toxic when expressed in Escherichia coli and bacterial competition assays confirm that TseV2 and TseV3 are secreted by the SPI-22 T6SS. Phylogenetic analysis reveals that TseV1–4 are evolutionarily related to enzymes involved in DNA repair. TseV3 recognizes specific DNA structures and preferentially cleave splayed arms, generating DNA double-strand breaks and inducing the SOS response in target cells. The crystal structure of the TseV3:TsiV3 complex reveals that the immunity protein likely blocks the effector interaction with the DNA substrate. These results expand our knowledge on the function of Salmonella pathogenicity islands, the evolution of toxins used in biological conflicts, and the endogenous mechanisms regulating the activity of these toxins.