molybdopterin binding domain of eukaryotic nitrate reductase (NR). Assimilatory NRs catalyze the reduction of nitrate to nitrite which is subsequently converted to NH4+ by nitrite reductase. Eukaryotic assimilatory nitrate reductases are cytosolic homodimeric enzymes with three prosthetic groups, flavin adenine dinucleotide (FAD), cytochrome b557, and Mo cofactor, which are located in three functional domains. Common features of all known members of the sulfite oxidase (SO) family of molybdopterin binding domains are that they contain one single pterin cofactor and part of the coordination of the metal (Mo) is a cysteine ligand of the protein and that they catalyze the transfer of an oxygen to or from a lone pair of electrons on the substrate.
Jiyao W et al.(2023). "The conserved domain database in 2023.",