Structural comparisons between bacteriophage PRD1 and adenovirus have revealed an evolutionary relationship that has contributed significantly to current ideas on virus phylogeny. However, the structural organization of the receptor-binding spike complex and how the different symmetry mismatches are mediated between the spike-complex proteins are not clear. We determined the architecture of the PRD1 spike complex by using electron microscopy and three-dimensional image reconstruction of a series of PRD1 mutants. We constructed an atomic model for the full-length P5 spike protein by using comparative modeling. P5 was shown to be bound directly to the penton base protein P31. P5 and the receptor-binding protein P2 form two separate spikes, interacting with each other near the capsid shell. P5, with a tumor necrosis factor-like head domain, may have been responsible for host recognition before capture of the current receptor-binding protein P2. (+info)
Archaeal proviruses TKV4 and MVV extend the PRD1-adenovirus lineage to the phylum Euryarchaeota.
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