CO as a Substrate and Inhibitor of H+ Reduction for Mo-, V-, and Fe-Nitrogenase Isozymes

Alignment of α subunits of nitrogenase isozymes. Shown is
an alignment of α subunits of Mo-nitrogenase (PDB ID: 3U7Q), V-nitrogenase
(PDB ID: 5N6Y), and Fe-nitrogenase (sequence threaded
on to V-nitrogenase PDB ID: 5N6Y using Swiss-Model) highlighting
amino acid residues in the cofactor environment. The starting perspective is
looking down on the Fe2, 3, 6, 7 face of FeMoco and FeVco. S is in
yellow, Fe in orange, Mo in magenta, and V in pink with the homocitrate
to the right in grey. Side chains that are 100% conserved among the
isozymes are shown in green, whereas side chains where there is
variation in the residue in at least one isozyme are shown in red. The residue numbering refers
to Mo-nitrogenase. ChimeraX version 1.0 file.