Fig. 5. Molecular architecture of the iC3b–CR3 complex.

Multi-scale model of the interaction of iC3b with full CR3 in the upright iC3b^U conformation (a) or the upside-down iC3b^D conformation (b). Model building is explained in the main text and the Supplementary Information. Domains of CR3 α_M and β₂ chains with known atomic structures used for model building are shown as molecular surfaces, while the remaining domains are shown in schematic form. The angle between the hybrid and the βI domains characteristic of the extended open conformation have been modeled approximately from existing structural evidence.