A New Mutant Class, Made by Targeted Mutagenesis, of Phage PRD1 Reveals That Protein P5 Connects the Receptor Binding Protein to the Vertex

Phage PRD1 and adenovirus share a number of structural and functional similarities, one of which is the vertex organization at the fivefold-symmetry positions. We developed an in vitro mutagenesis system for the linear PRD1 genome in order to make targeted mutations. The role of protein P5 in the vertex structure was examined by this method. Mutation in gene V revealed that protein P5 is essential. The absence of P5 did not compromise the particle assembly or DNA packaging but led to a deficient vertex structure where the receptor binding protein P2, in addition to protein P5, was missing. P5(−) particles also lost their DNA upon purification. Based on this and previously published information we propose a spatial model for the spike structure at the vertices. This resembles to the corresponding structure in adenovirus.

噬菌体PRD1与腺病毒存在多项结构与功能层面的相似性，其中之一为五重对称位点处的顶点组织结构。我们针对线性PRD1基因组开发了体外诱变系统，以实现靶向突变。通过该系统考察了蛋白P5在顶点结构中的功能。对V基因的突变实验证实，蛋白P5是必需的。P5的缺失不会损害颗粒组装或DNA包装过程，但会引发顶点结构缺陷：此时受体结合蛋白P2与蛋白P5均缺失。P5缺失型颗粒在纯化过程中同样会丢失其基因组DNA。基于上述实验结果与已发表的相关资料，我们提出了顶点处刺突结构的空间模型，该模型与腺病毒中的对应结构具有相似性。