<p>Homodimer of human PAD4 (PDB code: 1WDA, <b>Panel A</b>). The active site and calcium-binding site are indicated. Five calcium ions (Ca1–Ca5) are indicated as yellow balls. The substrate analog, benzoyl-L-arginine amide (BAG), is shown as a stick model. Panels B and C display the amino acid residues in the dimer interface of PAD4, which are represented by ball-and-stick models. <b>Panel B</b>: Arg8(A) is ion-paired with Asp547(B), and Asp273(A) is ion-paired with Arg544(B). <b>Panel C</b>: The hydrogen-bonding network formed by Tyr435(B), Tyr237(A) and Glu281(A). The figures were generated with PYMOL (DeLano Scientific LLC, San Carlos, CA, USA).</p
