Crystal structure of the mouse GP1bαN. (A) A cartoon diagram is shown for the crystal structure of the mouse GPIbαN with the C-terminal LRR capping α-helix colored orange and R-loop colored yellow. GPIbα residues H218 and E222 involved in the interaction with Mac-1 are shown as sticks. The elongated pocket formed in the GPIbα LRR capping region is indicated by a dashed line and represented as a transparent charged surface with key residues lining the pocket shown as sticks. (B) Electron density (2Fo-Fc) from the crystal structure of the mouse GPIbαN C-terminal capping α-helix residues H218 and E222 (gray mesh). (C) Amino acid sequence alignment of GPIbα residues 215 through 223 (human sequence numbering without the signal sequence) from the GPIbα LRR capping α-helix for human, mouse, dog, and cow. Key charged residues 218 and 222 are colored blue and red, respectively.