This family consists of the small beta iron-sulfur (FeS) subunit of the DMSO Reductase (DMSOR) family. Members of this family also contain a large, periplasmic molybdenum-containing alpha subunit and may have a small gamma subunit as well. Examples of heterodimeric members with alpha and beta subunits include arsenite oxidase, and tungsten-containing formate dehydrogenase (FDH-T) while heterotrimeric members containing alpha, beta, and gamma subunits include formate dehydrogenase-N (FDH-N), and nitrate reductase (NarGHI). The beta subunit contains four Fe4/S4 and/or Fe3/S4 clusters which transfer the electrons from the alpha subunit to a hydrophobic integral membrane protein, presumably a cytochrome containing two b-type heme groups. The reducing equivalents are then transferred to menaquinone, which finally reduces the electron-accepting enzyme system.
Jiyao W et al.(2023). "The conserved domain database in 2023.",