Figure 9.

General breakdown of strict icosahedral symmetry. The general breakdown of the icosahedral symmetry at 1.4 Å resolution is illustrated by subunit M, which exhibits the greatest r.m.s. deviation between the C^α positions of corresponding subunits of the expanded constrained model and the restrained model (see Supplementary Table S4). In (a), the non-­averaged σ_A-weighted difference map using the low-temperature constrained model phases is displayed. In (b), the map in (a) was averaged and demonstrates that much of the error in the model has been averaged away. In (c), the σ_A-weighted difference map, phased by the low-temperature restrained model, exhibits the least amount of density and hence suggests that the model is a better model. Density in all panels is contoured at 2.5σ.