Plays an essential role in the assembly of the icosahedral capsid of the virus (PubMed:17035321, PubMed:31530894). Allows the assembly of 3 molecules of hexon protein p72 and formation of a thermostable trimer (PubMed:31530894). Expressed in the late phase of the viral replicative cycle. Belongs to the asfivirus B602L family.