Figure 4.

Comparison of the open and closed forms of nikD. (A) Cα trace of the open form of nikD (blue) superimposed on that of the closed form (magenta). Included are stick figures of FAD and picolinate for the closed form only, colored as in Fig. 2. Carbon, nitrogen, oxygen and phosphorus atoms are colored green, blue, red and gold, respectively. (B) Surface representation of the closed form of nikD. There is a small channel visible that leads into the active site. (C) Open form surface representation of nikD. The indole ring of Trp355 (shown as a stick figure) is exposed to the solvent.