Members of the family Reoviridae package several copies of the viral polymerase complex into their capsid to carry out replication and transcription within viral particles. Classical single-particle reconstruction encounters difficulties resolving structures such as the intraparticle polymerase complex because refinement can converge to an incorrect map and because the map could depict a nonrepresentative subset of particles or an average of heterogeneous particles. Using the nine-segmented Fako virus, we tested hypotheses for the arrangement and number of polymerase complexes within the virion by measuring how well each hypothesis describes the set of cryoelectron microscopy images of individual viral particles. We find that the polymerase complex in Fako virus binds at ten possible sites despite having only nine genome segments. A single asymmetric configuration describes the arrangement of these complexes in both virions and genome-free capsids. Similarities between the arrangements of Reoviridae with 9, 10, and 11 segments indicate the generalizability of this architecture.

呼肠孤病毒科的成员将病毒聚合酶复合物的多个副本包装到其衣壳中，以在病毒颗粒内进行复制和转录。经典的单粒子重建在解析粒子内聚合酶复合物等结构时遇到困难，因为细化可能会收敛到不正确的图，并且因为该图可能描绘粒子的非代表性子集或异质粒子的平均值。使用九段 Fako 病毒，我们通过测量每个假设描述单个病毒颗粒的冷冻电镜图像集的程度，测试了病毒颗粒内聚合酶复合物的排列和数量的假设。我们发现 Fako 病毒中的聚合酶复合物尽管只有 9 个基因组片段，却在 10 个可能的位点结合。单个不对称构型描述了这些复合物在病毒体和无基因组衣壳中的排列。具有 9、10 和 11 节段的呼肠孤病毒科排列之间的相似性表明了该体系结构的普遍性。