Assembles the procapsid by joining twelve 12S pre-assembly complex into a T=1 icosahedral particle, called 108S procapsid. Ten proteins D bind each 12S complex, which are formed by three pentamers of F, G, B protein and a H protein. The scaffolding protein is released from the provirion after genome packaging to form the mature virion. Component of the procapsid particle composed of 60 copies of the internally located B, 240 copies of the external scaffolding protein D, 60 copies of each of the viral structural proteins F and G, and 12 copies of protein H. Belongs to the microvirus D protein family.