The key element of this family is the CX31-38CCX33-34CXXC sequence motif normally found at the C-terminus in archaeal and bacterial Hdr-like proteins [2]. There may be one or two copies, and the motif is probably an iron-sulfur binding cluster. In some instances one of the cysteines is replaced by an aspartate, and aspartate can in principle also function as a ligand of an iron-sulfur cluster [2]. The family includes a subunit from heterodisulphide reductase and a subunit from glycolate oxidase [1] Swiss:P52074 and glycerol-3-phosphate dehydrogenase.

1: glc locus of Escherichia coli: characterization of genes encoding the subunits of glycolate oxidase and the glc regulator protein. Pellicer MT, Badia J, Aguilar J, Baldoma L; J Bacteriol 1996;178:2051-2059. PMID:8606183

2: Purification and characterization of a membrane-bound enzyme complex from the sulfate-reducing archaeon Archaeoglobus fulgidus related to heterodisulfide reductase from methanogenic archaea. Mander GJ, Duin EC, Linder D, Stetter KO, Hedderich R; Eur J Biochem. 2002;269:1895-1904. PMID:11952791