Crystal structure of the mouse Mac-1 I-domain. (A) A cartoon diagram is shown for the crystal structure of the mouse Mac-1 I-domain (purple) with the crystal contact stabilizing the active conformation derived from the C-terminal helix α7 in orange. The MIDAS bound Mg²⁺ ion is shown as a sphere (green) and key residues are shown as sticks and electrostatic interactions as dashed magenta lines. (B) A close-up view of the MIDAS site with residues from helix α7 labeled. (C) A second view of the Mac-1 I-domain MIDAS site with the crystal contact residue E314 shown coordinating the Mg²⁺ ion and the sidechain hydroxyl of T209. (D) Superposition of the human (gray) and mouse (purple) crystal structures in the region of the MIDAS face. The stabilization glutamic acid is shown as sticks in cyan (human) and orange (mouse).