FIG 3.
The structure of HcbA1. (a) Overall structure of the HcbA1 dimer. Each subunit is shown in a different color (chain A, blue; chain B, green). (b) Five insertions (AI1 to AI5) of the HcbA1 subunit. AI1, AI2, AI3, AI4, AI5, and the C-extension are colored in wheat, yellow, green, cyan, pink, and blue, respectively. (c) Fo-Fc difference map calculated with the ligand omitted, contoured at 2.0 σ around modeled FMN. The hydrogen bond interactions of FMN with surrounding residues are shown as gray dashes. (d) The surface of HcbA1 features a substrate and flavin binding pocket. (e) The structure model of HcbA1·FMN docked with hexachlorobenzene (HCB). The orange dashed lines show the distances from the site of oxidation to the reactive N5 of FMN and from the target chlorine atom to the Nε2 of His17. The hydrogen bond network of the active center is shown as gray dashes. (f) A schematic of the active site of HcbA1.