Structure of Bombyx mori densovirus 1, a silkworm pathogen.

Bombyx mori densovirus 1 (BmDNV-1), a major pathogen of silkworms, causes significant losses to the silk industry. The structure of the recombinant BmDNV-1 virus-like particle has been determined at 3.1-angstrom resolution using X-ray crystallography. It is the first near-atomic-resolution structure of a virus-like particle within the genus Iteravirus. The particles consist of 60 copies of the 55-kDa VP3 coat protein. The capsid protein has a beta-barrel "jelly roll" fold similar to that found in many diverse icosahedral viruses, including archaeal, bacterial, plant, and animal viruses, as well as other parvoviruses. Most of the surface loops have little structural resemblance to other known parvovirus capsid proteins. In contrast to vertebrate parvoviruses, the N-terminal beta-strand of BmDNV-1 VP3 is positioned relative to the neighboring 2-fold related subunit in a "domain-swapped" conformation, similar to findings for other invertebrate parvoviruses, suggesting domain swapping is an evolutionarily conserved structural feature of the Densovirinae.