Biological and Structural Diversity of Type IV Secretion Systems
Biological and Structural Diversity of Type IV Secretion Systems
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DOI：
10.1128/microbiolspec.psib-0012-2018
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发表时间：
2019-03-01
影响因子：
3.7
通讯作者：
Christie, Peter J.
中科院分区：
文献类型：
--
作者：
Li, Yang Grace;Hu, Bo;Christie, Peter J.
细菌IV型分泌系统(T4SS)是一个功能多样的分泌系统超家族，存在于许多细菌物种中。总体而言，T4SS将DNA、单体和多聚体蛋白底物转移到细菌和真核细胞类型。T4SS由两个大的亚家族组成，接合机和效应器转运器通过建立直接的供体-靶细胞联系来传输它们的货物，第三个小的亚家族能够从环境中输入或向环境中输出底物。这篇综述总结了最近的机制和结构上的发现，这些发现为T4SS如何进化出这样的功能多样性提供了新的线索。目前已知易位信号位于结构折叠的C末端或内部嵌入；这些信号与底物相关的接头蛋白一起介导特定底物与同源的VirD4样受体的对接。对于嗜肺军团菌Dot/ICM系统，最近的工作阐明了适配器依赖的底物加载到VirD4样DotL受体上的结构基础。T4SS机器结构定义的进步现在允许详细比较与农杆菌VIRB/VirD4 T4SS密切相关的纳米机器与那些更远的亲缘关系，例如Dot/ICM和幽门螺杆菌CAG T4SS。最后，越来越明显的是，T4SS已经进化出各种机制，依赖于结合菌毛、膜管或表面粘附素的精加工来与靶细胞建立有效的联系。因此，T4SS通过大量影响底物选择、机器体系结构和靶细胞结合的适应，进化出极端的功能多样性。
The bacterial type IV secretion systems (T4SSs) are a functionally diverse superfamily of secretion systems found in many species of bacteria. Collectively, the T4SSs translocate DNA and monomeric and multimeric protein substrates to bacterial and eukaryotic cell types. T4SSs are composed of two large subfamilies, the conjugation machines and the effector translocators that transmit their cargoes through establishment of direct donor-target cell contacts, and a third small subfamily capable of importing or exporting substrates from or to the milieu. This review summarizes recent mechanistic and structural findings that are shedding new light on how T4SSs have evolved such functional diversity. Translocation signals are now known to be located C terminally or embedded internally in structural folds; these signals in combination with substrate-associated adaptor proteins mediate the docking of specific substrate repertoires to cognate VirD4-like receptors. For the Legionella pneumophila Dot/Icm system, recent work has elucidated the structural basis for adaptor-dependent substrate loading onto the VirD4-like DotL receptor. Advances in definition of T4SS machine structures now allow for detailed comparisons of nanomachines closely related to the Agrobacterium tumefaciens VirB/VirD4 T4SS with those more distantly related, e.g., the Dot/Icm and Helicobacter pylori Cag T4SSs. Finally, it is increasingly evident that T4SSs have evolved a variety of mechanisms dependent on elaboration of conjugative pili, membrane tubes, or surface adhesins to establish productive contacts with target cells. T4SSs thus have evolved extreme functional diversity through a plethora of adaptations impacting substrate selection, machine architecture, and target cell binding.