Figure 2: Features of the 135S-like CAV16 particle.

(a) Electron density map for residues 62–72 of VP1 that penetrate through the capsid. These residues in the mature EV71 are shown as a Cα trace (cyan) for comparison. (b) Relative position of the VP1 N terminus (blue) and VP3 GH loop (red) of CAV16 to the two-fold axis channel (right bottom corner) and the pocket-factor-binding site as viewed from outside the particle. The surrounding capsid is shown as a surface representation with VP1, VP2 and VP3 coloured in blue, green and red, respectively. The VP3 GH loop and the pocket factor of the mature EV71 particle are depicted as ribbons (grey) and space filling (magenta), respectively. (c) Superposition of the pocket-factor-binding site of mature EV71 (grey), empty 80S-like EV71 particle (red) and 135S-like CAV16 (blue). The pocket factor in the mature EV71 is shown as magenta sticks. (d–f) Structural differences in VP1 (blue) and VP3 (red) due to capsid expansion and VP1 egress (d, mature EV71; e, empty 80S-like EV71; f, 135S-like CAV16). Note especially the changes in the VP3 GH loop, which is labelled. As appropriate, the rough inner and outer boundaries of the shell are marked as grey arcs (panels (a,d–f)).