Xiao Hao, Chen Wenyuan, Pang Hao, Zheng Jing, Wang Li, Feng Hao, Song Jingdong, 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.
College of Life Sciences, Hunan Normal University, Changsha, China.
PLoS Biol. 2025 Apr 17;23(4):e3003104. doi: 10.1371/journal.pbio.3003104. eCollection 2025 Apr.
In the assembly pathway of tailed double-stranded DNA (dsDNA) bacteriophages and herpesviruses, a procapsid with a dodecameric portal for DNA delivery at a unique vertex is initially formed. Appropriate procapsid assembly requires the transient presence of multiple copies of a scaffolding protein (SP), which is absent in the mature virion. However, how the SP contributes to dodecameric portal formation, facilitates portal and coat protein incorporation, and is subsequently released remains unclear because of a lack of structural information. Here, we present the structure of the SP-portal complex within the procapsid of bacteriophage P22 at 3-9 Å resolutions. The AlphaFold2-predicted SP model fits well with the density map of the complex. The SP forms trimers and tetramers that interact to yield a dome-like complex on the portal. Two SP domains mediate multimerization. Each trimer interacts with two neighboring portal subunits. The SP has a loop-hook-like structure that aids in coat protein recruitment during viral assembly. The loops of those SP subunits on the portal are positioned in clefts between adjacent portal subunits. Conformational changes in the portal during phage maturation may trigger the disassembly and release of the SP complex. Our findings provide insights into SP-assisted procapsid assembly in bacteriophage P22 and suggest that this strategy is also implemented by other dsDNA viruses, including herpesviruses.
在有尾双链DNA（dsDNA）噬菌体和疱疹病毒的组装途径中，最初会形成一个原衣壳，其在一个独特的顶点处有一个用于DNA递送的十二聚体门户。合适的原衣壳组装需要一种支架蛋白（SP）的多个拷贝短暂存在，而成熟病毒粒子中不存在这种蛋白。然而，由于缺乏结构信息，SP如何促进十二聚体门户的形成、便于门户蛋白和衣壳蛋白的掺入以及随后如何释放仍不清楚。在这里，我们展示了噬菌体P22原衣壳内SP-门户复合物在3-9埃分辨率下的结构。AlphaFold2预测的SP模型与复合物的密度图非常吻合。SP形成三聚体和四聚体，它们相互作用在门户上产生一个穹顶状复合物。两个SP结构域介导多聚化。每个三聚体与两个相邻的门户亚基相互作用。SP具有类似环钩的结构，有助于在病毒组装过程中募集衣壳蛋白。门户上那些SP亚基的环位于相邻门户亚基之间的裂隙中。噬菌体成熟过程中门户的构象变化可能会触发SP复合物的解体和释放。我们的发现为噬菌体P22中SP辅助的原衣壳组装提供了见解，并表明这种策略也被包括疱疹病毒在内的其他dsDNA病毒所采用。
