This model represents the alpha chains of various forms of the nitrogen-fixing enzyme nitrogenase: vanadium-iron, iron-iron, and molybdenum-iron. Most examples of NifD, the molybdenum-iron type nitrogenase alpha chain, are excluded from this model and described instead by equivalog model TIGR01282. It appears by phylogenetic and UPGMA trees that this model represents a distinct clade of NifD homologs, in which arose several molybdenum-independent forms. [Central intermediary metabolism, Nitrogen fixation]
Jiyao W et al.(2023). "The conserved domain database in 2023.",