Fig. 4.

Comparison of two structures of the active Apaf-1 apoptosome with a symmetry mismatch between the CARD disk and the platform. a A top view is presented of an active apoptosome with the platform in gray ribbons (PDB 5JUY) within the relevant density map. An acentric 8 CARD disk and density for the four CARD-NBD linkers (gold) are shown. A region of density (blue) identified as a p20/p10 catalytic domain of pc-9 is located on the central hub [5]. b A model for an active platform with an 8 CARD disk and a three CARD module on the central hub (PDB 5WVE) [7]. c A close-up view of a, with density for the p20/p10 catalytic domain omitted and a second possible position for this feature indicated (dashed oval; see text and ref. [5] for details). Linker densities in gold are positioned to connect Apaf-1 CARDs in positions 1a, 3a, 5a, and 7a with helix α8 in the NBDs of subunits 1, 3, 5, and 7. d A close-up view of b is shown with relevant CARD-NBD linkers as black lines to their respective Apaf-1 subunits. Apaf-1 CARDs in the three CARD module are shown in gold