The detailed interactions of CD97–CD55.A–C, the detailed interactions of EGF1–SCR2/SCR3 (A), EGF2–SCR1/SCR2 (B), EGF5–SCR1 (C) interfaces. CD97 and CD55 domains are colored pink and green, respectively. Interacting residues are shown as sticks and labeled. Dashed lines indicate hydrogen bonds. Yellow spheres represent coordinated calcium. EGF, epidermal growth factor; SCR, short consensus repeat.