Fig. 4.

Structural basis of IDO1. a The overall structure of human IDO1 (PDB code: 5WMU). The N-terminal and C-terminal domains are represented by aurantium and purple ribbons, respectively. The helices A–S are named in the order of appearance in the primary sequence. The substrate Trp is colored in cyan and the heme site is colored in green. b Three binding pockets within the active site. The three pockets are colored in magentas (“Pocket A”), orange (“Pocket B”), and jasper (“Pocket C”), respectively. c Schematic representation of the binding model of the benzimidazole compound within the active site of IDO1