Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
Structure. 2013 Jul 2;21(7):1225-34. doi: 10.1016/j.str.2013.05.012.
Simple, spherical RNA viruses have well-understood, symmetric protein capsids, but little structural information is available for their asymmetric components, such as minor proteins and their genomes, which are vital for infection. Here, we report an asymmetric structure of bacteriophage MS2, attached to its receptor, the F-pilus. Cryo-electron tomography and subtomographic averaging of such complexes result in a structure containing clear density for the packaged genome, implying that the conformation of the genome is the same in each virus particle. The data also suggest that the single-copy viral maturation protein breaks the symmetry of the capsid, occupying a position that would be filled by a coat protein dimer in an icosahedral shell. This capsomere can thus fulfill its known biological roles in receptor and genome binding and suggests an exit route for the genome during infection.
简单的球形 RNA 病毒具有结构清晰、对称的蛋白质衣壳，但对于其非对称组件（如次要蛋白及其基因组）的结构信息却知之甚少，而这些组件对于感染至关重要。在这里，我们报告了噬菌体 MS2 与其受体 F 菌毛的附着的非对称结构。对这些复合物进行低温电子断层扫描和亚断层平均化处理后得到了一个包含包装基因组的清晰密度的结构，这表明在每个病毒颗粒中基因组的构象是相同的。这些数据还表明，单拷贝的病毒成熟蛋白打破了衣壳的对称性，占据了在二十面体壳中由衣壳蛋白二聚体填充的位置。因此，这个衣壳小体可以在受体和基因组结合中发挥其已知的生物学作用，并为感染过程中基因组的出口途径提供了线索。
