Small subunit of Arsenite oxidase (ArOX) family, Rieske domain; ArOX is a molybdenum/iron protein involved in the detoxification of arsenic, oxidizing it to arsenate. It consists of two subunits, a large subunit similar to members of the DMSO reductase family of molybdenum enzymes and a small subunit with a Rieske-type [2Fe-2S] cluster. The large subunit of ArOX contains the molybdenum site at which the oxidation of arsenite occurs. The small subunit contains a domain homologous to the Rieske domains of the cytochrome bc(1) and cytochrome b6f complexes as well as naphthalene 1,2-dioxygenase. The Rieske domain is a [2Fe-2S] cluster binding domain involved in electron transfer.