Zheng Jing, Xiao Hao, Pang Hao, Wang Li, Song Jingdong, Chen Wenyuan, Cheng Lingpeng, Liu Hongrong
Institute of Interdisciplinary Studies, Key Laboratory for Matter Microstructure and Function of Hunan Province, Key Laboratory of Low-dimensional Quantum Structures and Quantum Control, School of Physics and Electronics, Hunan Normal University, Changsha, China.
National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
J Virol. 2025 Jan 31;99(1):e0124924. doi: 10.1128/jvi.01249-24. Epub 2024 Dec 20.
Podophage tails are too short to span the cell envelope during infection. Consequently, podophages initially eject the core proteins within the head for the formation of an elongated trans-envelope channel for DNA ejection. Although the core proteins of bacteriophage T7 have been resolved at near-atomic resolution, the mechanisms of core proteins and DNA ejection remain to be fully elucidated. In this study, we provided improved structures of core proteins in mature T7 and the portal-tail complex in lipopolysaccharide-induced DNA-ejected T7 to resolutions of approximately 3 Å. Using these structures, we identified three small proteins, namely gp14, gp6.7, and gp7.3, and illustrated the conformational changes in and translocation of these proteins from the mature to DNA-ejected states. Our structures indicate that gp6.7, which participates in the assembly of the core and trans-envelope channel, is a core protein, and that gp7.3 serves as a structural scaffold to assist the assembly of the nozzle into the adaptor.
Podophage T7 core proteins form an elongated trans-envelope channel for genomic DNA delivery into the host cell. The structures of the core proteins within the mature T7 and assembled in the periplasmic tunnel form in the DNA-ejected T7 have been resolved previously. Here, we resolved the structures of two new structural proteins (gp6.7 and gp7.3) within mature T7 and receptor-induced DNA-ejected T7. The gp6.7 protein participates in the assembly of the core complex within mature T7 and the trans-envelope channel during T7 infection; therefore, gp6.7 is a core protein. Before T7 infection, gp7.3 plays a role in promoting the assembly of the nozzle into the adaptor.
噬菌粒的尾部太短，无法在感染过程中跨越细胞膜。因此，噬菌粒最初会将头部内的核心蛋白排出，以形成一个用于DNA排出的细长跨膜通道。尽管噬菌体T7的核心蛋白已在近原子分辨率下解析，但核心蛋白和DNA排出的机制仍有待充分阐明。在本研究中，我们将成熟T7中核心蛋白以及脂多糖诱导的DNA排出型T7中的门尾复合物的结构分辨率提高到了约3 Å。利用这些结构，我们鉴定出了三种小蛋白，即gp14、gp6.7和gp7.3，并展示了这些蛋白从成熟状态到DNA排出状态的构象变化和转运过程。我们的结构表明，参与核心和跨膜通道组装的gp6.7是一种核心蛋白，而gp7.3作为一种结构支架，协助喷嘴组装到适配器中。
噬菌粒T7的核心蛋白形成一个细长的跨膜通道，用于将基因组DNA递送到宿主细胞中。成熟T7内的核心蛋白以及DNA排出型T7中组装在周质隧道形式中的结构此前已得到解析。在这里，我们解析了成熟T7和受体诱导的DNA排出型T7中两种新的结构蛋白（gp6.7和gp7.3）的结构。gp6.7蛋白在成熟T7内的核心复合物组装以及T7感染期间的跨膜通道组装中发挥作用；因此，gp6.7是一种核心蛋白。在T7感染之前，gp7.3在促进喷嘴组装到适配器中发挥作用。
