This is a family of minor capsid proteins, known as VP4, from the dicistroviridae. The dicistroviridae is a group of small, RNA-containing viruses that are closely structurally related to the picornaviridae. VP4 is a short, extended polypeptide chain found within the viral capsid, at the interface between the external protein shell and packaged RNA genome[1].

1: The crystal structure of cricket paralysis virus: the first view of a new virus family. Tate J, Liljas L, Scotti P, Christian P, Lin T, Johnson JE; Nat Struct Biol. 1999;6:765-774. PMID:10426956