Figure 15.

Nif assembly machinery with corresponding crystal structures that are shown with β-strands and α-helices depicted in light yellow and blue, respectively; [FeS] clusters are represented as balls and sticks with Fe and S atoms colored in dark red and yellow, respectively. The crystal structures of NifS, NifB, NifEN ,and NifDK correspond to PDB 5WT2,⁸²7BI7,³⁰3PDI,⁸³ and 1M1N,¹⁴ respectively.