Figure 5

Three-dimensional structures of IRF3 and 7. (a) The 3D-structure of the human IRF3 (hIRF3) DBD (PDB 2O6G, from M1 to S112). Residues in the DPHK signature are shown in white with side chains in stick models. Possible hydrogen bonds are represented by dotted magenta lines. Conserved W residues involved in DNA binding are shown in sticks. The boxed area is enlarged in (b). Residues indicated in parentheses are located at the back side of the drawing. (b) The 3D-structure of the DPHK motif area. The part of the hIRF3 protein structure (boxed in a) including the DPHK motif area (G89-F109) and interacting amino acids (T32-H40) are shown. (c) The modeled 3D-structure of the NPHK motif area in the black carp IRF3. The structure was modeled based on the hIRF3 structure (PDB 2PI0). (d) The 3D-structure of the hIRF3 C-terminal region (PDB 2O6G, from D190 to Q422). The IAD and SRD regions are shown in wheat and pink, respectively. The residues in the GASSL motif is shown in white with side chains in stick models. Ten conserved positively charged residues (R, K, and H) involved in the attachment to adaptors are shown in blue. The boxed area is enlarged in (e). Residues indicated in parentheses are located at the back side of the drawing. (e) The 3D-structure of the GASSL motif area. The part of the hIRF3 protein structure (boxed in d) including the GASSL motif area (P369-L403) are shown. (f) The modeled 3D-structure of the GVSSL motif area in the hIRF7. The structure was modeled using the hIRF7 sequence (Q92985, P455-L488) with the hIRF3 structure (PDB 1QWT) as the template. While N389, T390, and S402 in hIRF3 are on β-strands (e), corresponding positions in hIRF7 (S475, S476, and S487) were predicted to be in the loop structure. Structural mining and preparation of graphics were performed using the PyMOL Molecular Graphics System, version 2.3.2 (Schrödinger, LLC, New York, NY, USA; https://pymol.org/).