Alignment of ADAMTS13 Ca²⁺-binding site with other ADAMTS family members. ADAMTS13 metalloprotease domain (residues 171-234) were aligned with corresponding regions of other ADAMTS family members. Regions of amino acid conservation are highlighted in gray. The active site amino acids are boxed/labeled. High-affinity Ca²⁺-binding residues in ADAMTS13 are labeled with arrows. The Cys residues in all ADAMTS family members except ADAMTS2, 3, 13, and 14 that pair to form a disulphide bond are highlighted in black boxes.