Figure 2.

Stereo views of the electron density of closed and open forms of nikD. The electron density surrounding the flavin ring of FAD, its covalent attachment to Cys321 and the endogenous ligand modeled as picolinate is shown. The atoms are colored with nitrogen blue, oxygen red, sulfur yellow and carbon green. (A) Refined |2Fo|-|Fc| electron density at 1.15 Å resolution of the closed form of nikD, contoured at 1 σ (cyan) and 3 σ (red). (B) Refined |2Fo|-|Fc| electron density at 1.90 Å resolution of the open form of nikD, contoured at 1 σ (cyan).