Interactions modulating flap dynamics. (A) Overview of TAFI indicating the interactions shown in panels B and C. (B) Interactions between the dynamic flap and the activation peptide. (C) GEMSA (cyan) bound in the active site of TAFI. (D) Ribbon diagram of the dynamic flap indicating the positions of stabilizing TAFI-IIYQ mutations (cyan), relative to the catalytic site indicated by the bound arginine molecule in the S1′ pocket (green). TAFI colors as in Figure 1A with oxygen (red), nitrogen (blue), and sulfur (yellow). H-bonds are indicated by black dashes.