FIG 8.

ΦM9's T=16 asymmetric unit. All 16 unique HK97-like subunits fit together to make the tightly packed capsid. The structural elements of the T=16 capsid include a monomer from the pentameric cap (purple), two full hexamers (green and yellow), and half a hexamer (orange) (colors are as in reference 16). ΦM9's reduced E-loop insertion domain reaches over to an adjacent monomer to make the hexameric repeat. Tight interactions at the 2- and 3-fold symmetry axes complete the asymmetric unit. (Left inset) Additional density appearing α-helical in nature forms the turret at the pentamer. (Right inset) Additional density at the center of the hexamer appears to break the 6-fold symmetry.