Comparative analysis of the three-dimensional structure of Periplaneta fuliginosa densovirus

The three-dimensional structure of Periplaneta fuliginosa densovirus (pfDNV) is determined at 2.3 nm resolution using the techniques of cryo-electron microscopy and image reconstruction. The pfDNV contains five structural proteins and 60 protein subunits arranged on a T = 1 icosahedral shell with a relatively smooth surface. Its reconstruction reveals its distinct capsid structure from those observed in CPV and GrnDNV. As in GmDNV, spike-like protrusions are not present in pfDNV at the threefold axes; while two small thorn-like protrusions are identified there. However, different from CPV and GmDNV, cylindrical channels along the fivefold axes are closed in pfDNV; while a small thorn-like protrusions, which have not been reported in other parvovirus, are observed there in pfDNV although their function is yet to be investigated. The pfDNV has dimple-like depressions at the icosahedral twofold axes; but has no canyon-like regions encircling the fivefold axes. The icosahedrally well-ordered nucleic acid has also been observed in pfDNV, suggesting that the protein and nucleic acid probably form closed interaction.