Fig. 3.

Central sections through three-dimensional reconstructions of fJAM-A-labeled FCV classified according to the extent of conformational change show well-resolved sharp features in the class 1 density map (A: preconformational change); interestingly, the CC dimer shows sharp density in this reconstruction, whereas it was previously poorly resolved (white arrow). Classes 2 to 5 (B to E, respectively) show sharp features in the S domains, but the P domains and fJAM-A remain less well resolved. Spherical sections through reconstructions at 20-nm radius provide a clear view of the density at the outer face of the P2 domain in both the AB dimer (white arrowhead) and the CC dimer (white arrow) (F to H). (F) The undecorated FCV reconstruction has sharp density in both AB and CC dimers. (G and H) The class 1 reconstruction likewise shows well-defined features albeit at lower resolution (G), while the class 5 reconstruction (H) shows smearing of density in both AB and CC dimers and elongation of the CC P2 density perpendicular to the long axis of the capsomere (direction of elongation indicated by a double-headed arrow). This strongly suggests that this region tilts away from the icosahedral 2-fold symmetry axis, leading to incoherent averaging of P2–fJAM-A density across that axis in the reconstruction.