Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.
Nat Struct Mol Biol. 2011 May;18(5):597-603. doi: 10.1038/nsmb.2023. Epub 2011 Apr 17.
DNA viruses such as bacteriophages and herpesviruses deliver their genome into and out of the capsid through large proteinaceous assemblies, known as portal proteins. Here, we report two snapshots of the dodecameric portal protein of bacteriophage P22. The 3.25-Å-resolution structure of the portal-protein core bound to 12 copies of gene product 4 (gp4) reveals a ~1.1-MDa assembly formed by 24 proteins. Unexpectedly, a lower-resolution structure of the full-length portal protein unveils the unique topology of the C-terminal domain, which forms a ~200-Å-long α-helical barrel. This domain inserts deeply into the virion and is highly conserved in the Podoviridae family. We propose that the barrel domain facilitates genome spooling onto the interior surface of the capsid during genome packaging and, in analogy to a rifle barrel, increases the accuracy of genome ejection into the host cell.
DNA 病毒，如噬菌体和疱疹病毒，通过大型蛋白组装体（称为门户蛋白）将其基因组输送到衣壳内外。在这里，我们报告了噬菌体 P22 的十二聚体门户蛋白的两个快照。分辨率为 3.25Å 的门户蛋白核心与 12 个基因产物 4（gp4）结合，揭示了一个由 24 个蛋白质组成的约 1.1MDa 组装体。出乎意料的是，全长门户蛋白的较低分辨率结构揭示了 C 末端结构域的独特拓扑结构，该结构域形成一个约 200Å 长的α-螺旋桶。该结构域深入插入病毒粒子中，并且在 Podoviridae 家族中高度保守。我们提出，桶状结构域在基因组包装过程中有助于将基因组缠绕到衣壳的内表面上，并且类似于步枪枪管，提高了基因组准确注入宿主细胞的能力。
