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 simil arities, one of which is the vertex organization at the fivefold-symmetry p ositions. We developed an in vitro mutagenesis system for the linear PRD1 g enome in order to make targeted mutations. The role of protein P5 in the ve rtex structure was examined by this method. Mutation in gene V revealed tha t protein P5 is essential. The absence of P5 did not compromise the particl e assembly or DNA packaging but led to a deficient vertex structure where t he receptor binding protein P2, in addition to protein P5, was missing. P5( -) particles also lost their DNA upon purification. Based on this and previ ously published information we propose a spatial model for the spike struct ure at the vertices. This resembles to the corresponding structure in adeno virus.