YedY_like molybdopterin cofactor (Moco) binding domain, a subgroup of the sulfite oxidase (SO) family of molybdopterin binding domains. Escherichia coli YedY has been proposed to form a heterodimer, consisting of a soluble catalytic subunit termed YedY, which is likely membrane-anchored by a heme-containing trans-membrane subunit YedZ. Preliminary results indicate that YedY may represent a new type of membrane-associated bacterial reductase. Common features of all known members of this family 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.