Cleaving the N,N Triple Bond: The Transformation of Dinitrogen to Ammonia by Nitrogenases - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 149

Figure 2 Crystal structures
of the MgADP-bound Fe
protein of Mo-nitrogenase
(a), the catalytically
important domains
(b), and the [Fe 4 S 4 ] cluster
(c) of the Fe protein.
The subunits of the Fe
protein are colored orange,
and the cluster is shown in
ball-and-stick presentation.
The P-loop is colored green,
the Switch I region is
colored blue, and
the Switch II region is
colored red. Atoms are
colored as follows: C,
white; O, red; N, blue; P,
green; Fe, orange; S,
yellow. The cysteinyl
ligands from the two
subunits are labeled Cys
and Cys*, respectively.
PYMOL was used
to generate this figure
(PDB entry 1FP6).