Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Japan.
G-CHAIN, Gifu University, Gifu, Japan.
Microbiol Immunol. 2022 Feb;66(2):67-74. doi: 10.1111/1348-0421.12951. Epub 2022 Jan 17.
The intracellular bacterial pathogen Legionella pneumophila utilizes the Dot/Icm type IV secretion system to translocate approximately 300 effector proteins to establish a replicative niche known as the Legionella-containing vacuole. The Dot/Icm system is classified as a type IVB secretion system, which is evolutionarily closely related to the I-type conjugation systems and is distinct from type IVA secretion systems, such as the Agrobacterium VirB/D4 system. Although both type IVA and IVB systems directly transport nucleic acids or proteins into the cytosol of recipient cells, the components and architecture of type IVB systems are much more complex than those of type IVA systems. Taking full advantage of rapidly developing cryo-electron microscopy techniques, the structural details of the transport apparatus and coupling complexes in the Dot/Icm system have been clarified in the past few years. In this review, we summarize recent progress in the structural studies of the L. pneumophila type IVB secretion system and the insights gained into the mechanisms of substrate recognition and transport.
胞内细菌病原体嗜肺军团菌利用 Dot/Icm 型 IV 分泌系统将大约 300 种效应蛋白转运至一个被称为军团菌包含的空泡的复制龛位。Dot/Icm 系统被归类为 IVB 型分泌系统，它在进化上与 I 型接合系统密切相关，与 IVA 型分泌系统（如农杆菌 VirB/D4 系统）不同。尽管 IVA 型和 IVB 型系统都能直接将核酸或蛋白质输送到受体细胞的细胞质中，但 IVB 型系统的组成和结构比 IVA 型系统复杂得多。利用快速发展的冷冻电子显微镜技术，过去几年中已经阐明了 Dot/Icm 系统中输送装置和偶联复合物的结构细节。在这篇综述中，我们总结了嗜肺军团菌 IVB 型分泌系统的结构研究的最新进展，以及对底物识别和运输机制的深入了解。
