Figure 5.

Active sites of open and closed forms of nikD. (A) Close-up view of the active site in the open form of nikD. The chemical groups shown and the atom coloring scheme used are the same as in Fig. 3B, except for the addition of two water molecules (red spheres). Hydrogen bonds are represented by dashed lines. (B) Superimposition of the active sites in the open and closed forms of nikD. Carbon atoms are colored green and yellow in the open and closed forms, respectively. In each form, the same color is used for oxygen (red) or nitrogen (blue).