中文摘要：许多尾噬菌体在衣壳的独特顶点装配喷射蛋白和门尾复合物。细胞感染时，喷射蛋白形成一个延伸门尾通道的跨膜通道，用于传递基因组DNA。本文报告了成熟噬菌体T7的结构，包括喷射蛋白，以及完整和空T7颗粒与其细胞受体脂多糖复合物的结构。近原子分辨率重建显示，成熟T7中的喷射蛋白组装成一个核心，由四重基因产物16（gp16）环、八重gp15环和八重gp14环组成。gp15和gp16主要由螺旋束组成，gp16含有降解细菌肽聚糖层的裂解转糖苷酶结构域。当与脂多糖相互作用时，T7尾部喷嘴打开。六重gp14锚定在尾部喷嘴上，将喷嘴延伸至脂多糖脂质双分子层。成熟T7中gp15和gp16的结构表明，它们经历显著的构象变化形成跨膜通道。在gp16中观察到疏水性α螺旋，但在gp15中则无，表明gp15在亲水性周质中形成通道，而gp16在细胞质膜中形成通道。
外文摘要：Many tailed bacteriophages assemble ejection proteins and a portal-tail complex at a unique vertex of the capsid. The ejection proteins form a transenvelope channel extending the portal-tail channel for the delivery of genomic DNA in cell infection. Here, we report the structure of the mature bacteriophage T7, including the ejection proteins, as well as the structures of the full and empty T7 particles in complex with their cell receptor lipopolysaccharide. Our near-atomic-resolution reconstruction shows that the ejection proteins in the mature T7 assemble into a core, which comprises a fourfold gene product 16 (gp16) ring, an eightfold gp15 ring, and a putative eightfold gp14 ring. The gp15 and gp16 are mainly composed of helix bundles, and gp16 harbors a lytic transglycosylase domain for degrading the bacterial peptidoglycan layer. When interacting with the lipopolysaccharide, the T7 tail nozzle opens. Six copies of gp14 anchor to the tail nozzle, extending the nozzle across the lipopolysaccharide lipid bilayer. The structures of gp15 and gp16 in the mature T7 suggest that they should undergo remarkable conformational changes to form the transenvelope channel. Hydrophobic alpha-helices were observed in gp16 but not in gp15, suggesting that gp15 forms the channel in the hydrophilic periplasm and gp16 forms the channel in the cytoplasmic membrane.
外文关键词：bacteriophages；ejection proteins；lipopolysaccharide；genome delivery
作者：Chen, WY；Xiao, H；Wang, L；Wang, XR；Tan, ZX；Han, Z；Li, XW；Yang, F；Liu, ZH；Song, JD；Liu, HR；Cheng, LP
作者单位：Hunan Normal Univ；Chinese Ctr Dis Control & Prevent；Chinese Acad Sci；Hunan Univ Sci & Engn；Tsinghua Univ
期刊名称：PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
期刊影响因子：9.412
出版年份：2021
出版刊次：37
