Department of Molecular Biology and Biochemistry, University of California, Irvine, California, USA.
J Virol. 2013 Oct;87(20):11200-13. doi: 10.1128/JVI.01372-13. Epub 2013 Aug 7.
Amoebas infected with mimivirus were disrupted at sequential stages of virus production and were visualized by atomic force microscopy. The development of virus factories proceeded over 3 to 4 h postinfection and resulted from the coalescence of 0.5- to 2-μm vesicles, possibly bearing nucleic acid, derived from either the nuclear membrane or the closely associated rough endoplasmic reticulum. Virus factories actively producing virus capsids on their surfaces were imaged, and this allowed the morphogenesis of the capsids to be delineated. The first feature to appear on a virus factory surface when a new capsid is born is the center of a stargate, which is a pentameric protein oligomer. As the arms of the stargate grow from the pentamer, a rough disk the diameter of a capsid thickens around it. This marks the initial emergence of a protein-coated membrane vesicle. The capsid self-assembles on the vesicle. Hillocks capped by different pentameric proteins spontaneously appear on the emerging vesicle at positions that are ultimately occupied by 5-fold icosahedral vertices. A lattice of coat protein nucleates at each of the 5-fold vertices, but not at the stargate, and then spreads outward from the vertices over the surface, merging seamlessly to complete the icosahedral capsid. Filling with DNA and associated proteins occurs by the transfer of nucleic acid from the interior of the virus factory into the nearly completed capsids. The portal, through which the DNA enters, is sealed by a plug of protein having a diameter of about 40 nm. A layer of integument protein that anchors the surface fibers is acquired by the passage of capsids through a membrane enriched in the protein. The coating of surface fibers is similarly acquired when the integument protein-coated capsids pass through a second membrane that has a forest of surface fibers embedded on one side.
被 mimivirus 感染的变形虫在病毒产生的连续阶段被中断，并通过原子力显微镜进行可视化观察。病毒工厂的发展在感染后 3 到 4 小时内进行，是由来自核膜或紧密相关的粗糙内质网的 0.5 到 2 微米的囊泡融合而成的，这些囊泡可能携带核酸。在其表面上正在积极产生病毒衣壳的病毒工厂被成像，这使得衣壳的形态发生可以被描绘出来。当一个新的衣壳诞生时，在病毒工厂表面上出现的第一个特征是星门的中心，星门是五聚体蛋白寡聚物。随着星门的臂从五聚体中生长出来，一个直径与衣壳一样厚的粗糙圆盘在其周围增厚。这标志着一个蛋白质覆盖的膜囊泡的初始出现。衣壳在囊泡上自行组装。不同五聚体蛋白覆盖的峰丘自发地出现在新出现的囊泡上，这些位置最终被五重二十面体顶点占据。在每个五重顶点处，衣壳蛋白核发生晶格，但不在星门处，然后从顶点向表面向外扩展，无缝融合完成二十面体衣壳。DNA 和相关蛋白的填充是通过将核酸从病毒工厂内部转移到几乎完成的衣壳中来实现的。DNA 进入的门户由一个直径约为 40nm 的蛋白塞密封。当衣壳通过富含该蛋白的膜时，会获得一层锚定表面纤维的被膜蛋白。当被被膜蛋白包裹的衣壳通过一侧嵌入有表面纤维的森林的第二膜时，表面纤维的涂层也会以类似的方式获得。
