Heme binding to HutZ. (A) Docking result of HutZ dimer-heme complex. HutZ dimer is shown in surface charge representation, with positive charge in blue, and negative charge in red. Heme molecule is labeled in yellow stick, with iron atom in red sphere. His63 and Arg92 that coordinate with heme iron atom are represented in magenta stick. The distance (Å) between His63/Arg92 and iron atom is in black dash. (B) Absorbance spectra of HutZ and its mutants reconstituted with heme. DM: double mutant.