Figure 1.

(A). Interface structure with selected residues at the A3-C1 domain interface. Top left panel: The molecular surface of the FVIII X-ray crystal structure⁸ was drawn by Swiss PDB viewer showing A1 domain (residues 1-336) in yellow, A2 domain (residues 373-711) in blue, A3 domain (residues 1690-2020) in red, C1 domain (residues 2021-2169) in green, and C2 domain (residues 2170-2332) in grey. Each molecular surface of the interface is viewed in the direction of the arrow and is shown in bottom left panel. Bottom left panel: Electrostatic potential was calculated by Swiss PDB viewer with a simple coulomb interaction mode using a uniform dielectric constant (= 80) and shown as red (negative) and blue (positive). Residues facing A3 and C1 surfaces are drawn in stick representations. Top right panel: Higher magnification of the A3-C1 contact region drawn in ribbon structures. The covalent bond at Lys2020-Cys2021 is indicated by a yellow circle. Several indicated key residues are drawn in stick representations. Bottom right panel: Higher magnification of the A3 surface with electrostatic potential. Arg2116 from C1 is drawn in stick representation. (B) Interface structure with selected residues at the C1-C2 domain interface. Top panel: Higher magnification of the C1-C2 contact region in ribbon structures. The covalent bond at Cys2169-Asp2170 is indicated by yellow circle. Ser2029 and Pro2292 are drawn in stick representations. Each molecular surface of the interface is viewed in the direction of the arrow and is shown in bottom panel. Bottom panel: Molecular surface with electrostatic interaction of C1 (right) and C2 (left) are shown. Residues facing C1 and C2 surfaces are drawn in stick representations. In the stick models hydrogen, carbon, oxygen, nitrogen, and sulfur are colored as cyan, white, red, blue, and yellow, respectively. Ribbon structures represent α-helix (red) and β-strand (green).