Beijing Frontier Research Center for Biological Structure, Center for Infectious Disease Research, SXMU-Tsinghua Collaborative Innovation Center for Frontier Medicine, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, 100084, P.R. China.
Nat Commun. 2023 Sep 5;14(1):5421. doi: 10.1038/s41467-023-41151-7.
Filamentous bacteriophages package their circular, single stranded DNA genome with the major coat protein pVIII and the minor coat proteins pIII, pVII, pVI, and pIX. Here, we report the cryo-EM structure of a ~500 Å long bacteriophage M13 mini variant. The distal ends of the mini phage are sealed by two cap-like complexes composed of the minor coat proteins. The top cap complex consists of pVII and pIX, both exhibiting a single helix structure. Arg33 of pVII and Glu29 of pIX, located on the inner surface of the cap, play a key role in recognizing the genome packaging signal. The bottom cap complex is formed by the hook-like structures of pIII and pVI, arranged in helix barrels. Most of the inner ssDNA genome adopts a double helix structure with a similar pitch to that of the A-form double-stranded DNA. These findings provide insights into the assembly of filamentous bacteriophages.
丝状噬菌体将其圆形、单链 DNA 基因组与主要衣壳蛋白 pVIII 和次要衣壳蛋白 pIII、pVII、pVI 和 pIX 一起包装。在这里，我们报告了一个约 500Å 长的噬菌体 M13 迷你变体的冷冻电镜结构。迷你噬菌体的远端由两个由次要衣壳蛋白组成的帽状复合物封闭。顶部帽复合物由 pVII 和 pIX 组成，两者都呈现出单链结构。pVII 的 Arg33 和 pIX 的 Glu29 位于帽的内表面，在识别基因组包装信号方面发挥关键作用。底部帽复合物由 pIII 和 pVI 的钩状结构组成，排列在螺旋桶中。大多数内部 ssDNA 基因组采用与 A 型双链 DNA 相似的螺旋结构。这些发现为丝状噬菌体的组装提供了深入的了解。
