FIG 6.

Difference maps between wt and PVI-L40Q mutant adenoviruses identify structural differences in the vertex region. Shown are difference maps (red) between the wt and the PVI-L40Q mutant superimposed onto the wt average (light gray). The isosurface threshold was set 1.9σ above the mean density. The two most recent, and contradictory, atomic models of wt capsid proteins (PDB 3IYN and 4CWU) were fitted into the wt subtomogram average map (A to D and E to H, respectively). Only penton proteins (red) and peripentonal cement proteins located inside the virion are displayed as ribbons: IIIa (green), V (yellow), and VI (blue). The positions of the peripentonal hexons are indicated by the numbers 1 to 5 in panel A. The superimposed maps are viewed from the outside, with a transparent surface rendering (A and E) or sliced through (B and F) or inside (C and G) the capsid vertex region, as indicated by the pictogram scheme in the middle of each column. (C and G) The difference map shown at a lower threshold of 1.6σ (lighter red) indicates that the structural differences between the wt and PVI-L40Q affects the whole peripentonal area (starfish-like density), with a maximum difference in the peripentonal hexons inner cavity (arrow). (D and H) Direct comparison between the locations of the atomic models and the difference map shows that the difference map includes part of V and is tightly associated with VI (H).