FIG. 3.

Diagram showing the salient features of the T = 16 surface lattice of herpesvirus capsids. Pentons (capsomers with five nearest neighbors) are at each of the 12 vertices. There are three classes of hexons (capsomers with six nearest neighbors) distinguished according to their lattice sites. A peripentonal hexon (P hexon) is adjacent to a penton; E hexons are at the middle of each edge and sit on icosahedral twofold axes; and three C hexons are found at the center of each facet (adapted from reference 40). At each trigonal site (a site of local or global threefold symmetry, surrounded by three capsomers) is a triplex (15, 41). These heterotrimeric complexes are indicated by small triangles. Triplexes may be subclassified according to their positions on the surface lattice (52).