Infectious protein crystals are an essential part of the viral lifecycle for double-stranded DNA Baculoviridae and double-stranded RNA cypoviruses. These viral protein crystals, termed occlusion bodies or polyhedra, are dense protein assemblies that form a crystalline array, encasing newly formed virions. Here, using X-ray crystallography we determine the structure of a polyhedrin from Nudiviridae. This double-stranded DNA virus family is a sister-group to the baculoviruses, whose members were thought to lack occlusion bodies. The 70-year-old sample contains a well-ordered lattice formed by a predominantly α-helical building block that assembles into a dense, highly interconnected protein crystal. The lattice is maintained by extensive hydrophobic and electrostatic interactions, disulfide bonds, and domain switching. The resulting lattice is resistant to most environmental stresses. Comparison of this structure to baculovirus or cypovirus polyhedra shows a distinct protein structure, crystal space group, and unit cell dimensions, however, all polyhedra utilise common principles of occlusion body assembly.

感染性蛋白晶体是双链 DNA杆状病毒科和双链 RNA 病毒生命周期的重要组成部分。这些病毒蛋白晶体被称为包涵体或多面体，是形成晶体阵列的致密蛋白组装体，包裹着新形成的病毒体。在这里，我们利用 X 射线晶体学确定了裸病毒科多角体蛋白的结构。这种双链 DNA 病毒家族是杆状病毒的姐妹群，杆状病毒的成员被认为缺乏包涵体。这个有 70 年历史的样本包含一个有序的晶格，该晶格由主要的 α 螺旋结构单元组成，组装成致密、高度互连的蛋白质晶体。晶格通过广泛的疏水和静电相互作用、二硫键和域切换来维持。由此产生的晶格可以抵抗大多数环境压力。该结构与杆状病毒或病毒多面体的比较显示出独特的蛋白质结构、晶体空间群和晶胞尺寸，然而，所有多面体都利用包涵体组装的共同原理。