Structure of Tomato Bushy Stunt Virus: Three-dimensional X-Ray Diffraction Analysis at 30 A Resolution

The design of small, spherical viruses (Caspar and Klug, 1962) raises two sorts of questions. The first concerns the polymorphism of protein in the viral coat: how different are the configurations of quasi-equivalent structure units? Which intersubunit contacts are conserved in the distinct but quasi-equivalent environments, and which are not conserved? The second concerns the packing of the nucleic acid and its role in assembly: how is a linear molecule accommodated in an icosahedrally symmetric shell? To what degree does the nucleic acid stabilize or determine a particular configuration for the protein?