The capsid protein self-assembles to form an icosahedral capsid with a T=2 symmetry made of 120 subunits. Homodimer. The 7 kDa polypeptide is acetylated. Autocatalytic proteolysis releases a post-translationally modified peptide that remains associated with nucleic acid within the virion. This peptide is observed only when nucleic acid is packaged in the capsid. Picobirnavirus particles are capable of disrupting biological membranes in vitro.