Biogenesis and structure of a type VI secretion baseplate
Biogenesis and structure of a type VI secretion baseplate
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DOI：
10.1038/s41564-018-0260-1
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发表时间：
2018-12-01
影响因子：
28.3
通讯作者：
Durand, Eric
中科院分区：
文献类型：
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作者：
Cherrak, Yassine;Rapisarda, Chiara;Durand, Eric
为了支持它们在竞争环境中的生长并引起发病机制，细菌已经进化出广泛的大分子机制来传递特定的效应器和毒素。在这些多蛋白复合物中，VI型分泌系统（T6SS）是一种可收缩的纳米机器，既针对原核细胞，也针对真核细胞。T6SS包括两个功能性亚复合物：一个与噬菌体相关的尾部结构，通过膜复合物固定在细胞包膜上。与其他收缩式喷射系统一样，尾部由一个由护套包裹的内管组成，并安装在底板上。在T6SS中，底板不仅是尾部组装平台，而且还将尾部停靠到膜复合体上，因此充当进化适配器。在这里，我们定义了生物发生途径，并报道了肠聚集性大肠杆菌（EAEC） T6SS的楔形蛋白复合物的低温电镜（cryo-EM）结构。采用综合方法，我们揭示了整个T6SS基板的分子结构及其与尾鞘的相互作用，为其生物发生和功能提供了详细的见解。我们讨论了结构和机制上的相似性，但也揭示了与T4噬菌体和Mu噬菌体基板的关键区别。
To support their growth in a competitive environment and cause pathogenesis, bacteria have evolved a broad repertoire of macromolecular machineries to deliver specific effectors and toxins. Among these multiprotein complexes, the type VI secretion system (T6SS) is a contractile nanomachine that targets both prokaryotic and eukaryotic cells. The T6SS comprises two functional subcomplexes: a bacteriophage-related tail structure anchored to the cell envelope by a membrane complex. As in other contractile injection systems, the tail is composed of an inner tube wrapped by a sheath and built on the baseplate. In the T6SS, the baseplate is not only the tail assembly platform, but also docks the tail to the membrane complex and hence serves as an evolutionary adaptor. Here we define the biogenesis pathway and report the cryo-electron microscopy (cryo-EM) structure of the wedge protein complex of the T6SS from enteroaggregative Escherichia coli (EAEC). Using an integrative approach, we unveil the molecular architecture of the whole T6SS baseplate and its interaction with the tail sheath, offering detailed insights into its biogenesis and function. We discuss architectural and mechanistic similarities but also reveal key differences with the T4 phage and Mu phage baseplates.