STRUCTURE OF AN INSECT PARVOVIRUS (GALLERIA-MELLONELLA DENSOVIRUS) AT3.7 ANGSTROM RESOLUTION

Background: Parvoviruses infect vertebrates, insects and crustaceans. Many arthropod parvoviruses (densoviruses) are highly pathogenic and k ill approximately 90% of the host larvae within days, making them pote ntially effective as selective pesticides. Improved understanding of d ensoviral structure and function is therefore desirable, There are fou r different initiation sites for translation of the densovirus capsid protein mRNA, giving rise to the viral proteins VP1 to VP4. Sixty copi es of the common, C-terminal domain make up the ordered part of the ic osahedral capsid. Results: The Galleria mellonella densovirus (GmDNV) capsid protein consists of a core beta-barrel motif, similar to that f ound in many other viral capsid proteins. The structure most closely r esembles that of the vertebrate parvoviruses, but it has diverged beyo nd recognition in many of the long loop regions that constitute the su rface features and intersubunit contacts. The N termini of twofold-rel ated subunits have swapped their positions relative to those of the ve rtebrate parvoviruses, Unlike in the vertebrate parvoviruses, in GmDNV there is no continuous electron density in the channels running along the fivefold axes of the virus. Electron density corresponding to som e of the single-stranded DNA genome is visible in the crystal structur e, but it is not as well defined as in the vertebrate parvoviruses. Co nclusions: The sequence of the glycine-rich motif, which occupies each of the channels along the fivefold axes in vertebrate viruses, is con served between mammalian and insect parvoviruses, This motif may serve to externalize the N-terminal region of the single VP1 subunit per pa rticle. The domain swapping of the N termini between insect and verteb rate parvoviruses may have the effect of increasing capsid stability i n GmDNV.