Fig. 6: Differences in the E2 intertrimer interactions between PDC and OGDC.

a Two orthogonal views (perpendicular and parallel to the twofold axis) of interacting E2 trimers from the cryo-EM density maps of PDC (green) and OGDC (blue). b Comparison of the intertrimer interface in PDC (green) and OGDC (blue). Interactions involve only two subunits, one from each trimer, as apparent from the left panel where the atomic models (ribbons) of the interacting subunits are superposed in their respective densities. The two interacting subunits shown in a are aligned through their left subunit (monomer 1) and shown together to identify differences at the interacting interfaces with boxed regions shown as insets to highlight differences of their corresponding H2 helix. The inset in red box shows the knob-and-socket interaction of H2 and H7 (colored; rest of ribbon transparent for clarity) at twofold interface in E2p and E2o. c Superimposition and sequence alignment of H2 in E2p and E2o. The helix–kink–helix (kink highlighted in blue) is present in E2o but absent in E2p. Inset in the orange box: enlarged orthogonal view of the diverging H2 trajectories.