FIGURE 7.

The Asp-302–His-305 salt bridge in the context of the capsid structure. A, location of Asp-302–His-305 salt bridge on the capsid surface. The view on the left is from the outside looking at the surface of the capsid. The view on the right is along the width of the capsid shell. Subunits of the icosahedral T = 7 (T = triangulation number) capsid are shown in different colors, with Asp-302 in red and His-305 in blue space-filling spheres. B, view along the 2-fold of the asymmetric unit (corresponding to the blue and brown subunits in A). The Asp-302–His-305 salt bridge is poised to swap partners between subunits related by the dyad axis. The D-loops, which link monomers in the capsid through Asp-244–Arg-299, Asp-246–Arg-269, and Lys-249–Glu-81 salt bridges (32), are shown with thicker ribbons colored orange and turquoise.