FIGURE 2.

Ferroxidase centers of PmFTN. Monomer A of the asymmetric unit is shown. Iron and zinc atoms are drawn as orange and gray spheres, respectively, and cyan spheres represent water molecules. Side chains of selected residues are drawn in sticks with carbon, nitrogen, and oxygen atoms in the backbone color, blue, and red, respectively. Solid lines are metal ligand bonds, and dashed lines are selected hydrogen bonds. A, crystal soaked for 75 min in ferrous iron under anaerobic conditions. One iron atom is bound at ferroxidase site A at 50% occupancy, and site B is occupied by a water molecule. The black mesh represents the anomalous map contoured at 5 σ. B, crystal soaked overnight in ferrous sulfate under aerobic conditions. Three iron atoms are bound at sites A, B, and C, and one further iron atom was found beyond site C. C, crystal soaked for 1 h in zinc sulfate. Three zinc atoms are bound at the ferroxidase sites A, B, and C. D, an omit map contoured at 1 σ around site A and site B of PmFTN soaked overnight in ferrous sulfate is shown as a gray mesh.