Figure 2.

 Electron density corresponding to the dTDP-ligands. The substrate for WbtJ, dTDP-Qui4N, was observed binding in the active site of subunit A. The electron density map shown in (a) was calculated with coefficients of the form F_o − F_c, where F_o was the native structure factor amplitude and F_c was the calculated structure factor amplitude. The map was contoured at 3σ. The ligand coordinates were not included in the map calculation or in the initial model refinements. Shown in (b) is the electron density corresponding to the dTDP-Qui4NFo ligand bound to subunit B. The map was calculated as described above. All figures were prepared with the software package PyMOL.⁵