Capsid protein that self-associates to form pentons, building the capsid in association with hexamers of the major capsid protein and one dodecamer of the portal protein. Homopentamer. Interacts with the portal protein. Interacts with the major capsid protein that forms hexamers. Part of the capsid icosahedric shell of the immature virion. Belongs to the Tevenvirinae capsid vertex family.