Structural Differences Observed in Arboviruses of the Alphavirus and Flavivirus Genera

Figure 5

A family of icosahedra. Shown at the bottom of the large triangle, in blue, are the members of the icosahedra. The triangulation number represents the number of non- or quasiequivalent structural morphological units per asymmetric unit of the icosahedral face. is the only structure with a single equivalent morphological unit per icosahedral face, shown in blue. Neighboring 5-fold vertices of the 3-fold triangular face are connected to one another by three 2-fold axes giving the structure an overall 5-fold, 3-fold, and 2-fold symmetry. The number, also determined by the formula , indicates the relative position of each 5 fold vertex as a function of the number of quasiequivalent morphological units per icosahedral face. Sindbis, with four quasiequivalent conformations of the E1E2 heterodimer, is a structure. In the capsid mutant Y180S/E183G, the flexibility of the capsid protein is altered allowing the mutant protein to adopt a wider range of quasiequivalent conformations that increases the triangular number of the structure. Superimposed on the lattice is a class 3 triangular face outlined in red. Flaviviruses are arranged in this symmetry and belong to the class icosahedra shown in black on the axis.