Localization, molecular structure, and interactions of the AP-FXIII within the FXIII A-subunit dimer. (A) Overview of the FXIII A-subunit dimer. The 2 monomers are shown in yellow and pink with their respective AP-FXIII highlighted in orange and dark pink. (B) Detailed picture of the AP-FXIII of monomer 1. The peptide backbone is shown as an orange ribbon with carbon, nitrogen, and oxygen atoms colored in white, blue, and red, respectively. The position of Val34 of the common Val34Leu polymorphism is indicated in light blue. At the N-terminus of the AP-FXIII, amino acids 1-4 are missing, and the gap at the C-terminus represents the missing amino acids 37 and 38. (C) Immediate molecular environment of the AP-FXIII. All amino acid residues on monomer 1 (green space-filled atoms) and on monomer 2 (pink space-filled atoms) that lie within 5 Å from the amino acid residues of the AP-FXIII (ball-and-stick atoms) are shown. (D) H-bonds between amino acid residues of the AP-FXIII and surrounding amino acid residues are shown as dashed lines. H-bonds are drawn if the distance between H-donor and H-acceptor atoms is less than 3.2 Å. Only amino acid residues forming H-bonds are displayed. Amino acid residues of the AP-FXIII are labeled in orange, the residues of monomers 1 and 2 are labeled in green and pink, respectively.