Scaffolding protein involved in the icosahedric procapsid assembly. Coassembles with the capsid proteins to form the procapsid, in which the scaffolding protein is found within the external shell of icosahedrally arranged capsid protein subunits. In a subsequent step the scaffolding protein molecules are released from the procapsid. Homodimer. Belongs to the SPP1-like scaffolding protein family.