FIG. 3.

Combined electron cryomicroscopy and X-ray crystallography studies of VP2 and VP2* subviral particles. (a) Image of VP2 (left) and VP2* (right) embedded in ice. No major structural difference can be observed. (b) 3D reconstruction of VP2 (blue) and VP2* (green). In red, the atomic model of the VP2 subviral particle is shown at a resolution limited to 15 Å. The upper row shows the reconstructions seen from the top down the threefold axis. The lower row represents a central section through the reconstructions. (c) Result of the fit of the atomic model of IBDV VP2 into the VP2 and VP2* subviral particle reconstructions. The reconstruction electron densities of VP2 (blue) fit well with the VP2 atomic model, which is represented as a red ribbon. At the fivefold axis, the internal cavity is filled in the case of VP2*. Because the C terminus of VP2 points towards this cavity, we can conclude that the cavity is occupied by the C terminus of VP2*.