Open-book representation of mAb 2021 epitope and paratope. (Left) KPI-2 and (right) Fab 2021 are shown as surface representations. Residues colored on KPI-2 represent epitope residues. Dark green and red represent epitope residues overlapping with the predicted FXa-binding site. The overlap between the epitope and FXa-binding site include amino acid residue R15 (red), the key residue for inhibition of FXa. Heavy and light chain paratope residues are on Fab 2021 represented by dark and light blue, respectively.