Fig. 1.

Structure of the FH19–20:C3d complex. (A) The asymmetric unit contains one FH19–20 (gray) and two C3d molecules (green and blue). The residues mutated in aHUS patients and located at the interfaces are annotated and shown as green/blue spheres (C3d) or gray spheres (FH19–20). The thioester site residues are in yellow. (B) Close-up view of the FH20–C3d interface and (C) the FH19–C3d interface: FH19–20 is in gray, C3d is in green or blue, the main interface residues are sticks, disulphide bridges are in yellow, and hydrogen bonds are dashed lines. Structure figures were prepared using PyMol (version 1.3; Schrödinger, LLC).