This domain is comprised of the iron-sulphur cluster and Rieske subunit found in the large subunit of arsenite oxidase. Arsenite oxidase is a 100 kDa molybdenum- and iron-sulfur-containing protein located on the outer surface of the inner membrane of Gram-negative organisms. The large subunit of arsenite oxidase is similar to other members of the dimethylsulfoxide (DMSO) reductase family of molybdenum enzymes. The large subunit of arsenite oxidase is divided into four domains, with domain I binding the [3Fe-4S] cluster . Domain I, consists of three antiparallel beta sheets and six helices. The [3Fe-4S] cluster is coordinated by the motif Cys21-X2-Cys24-X3-Cys28 near the interface with domains III and IV. A large, flattened funnel-like cavity bounded by domains I, II, and III leads to the molybdenum center Pfam:PF00384 located near the center of the molecule [1].

1: Crystal structure of the 100 kDa arsenite oxidase from Alcaligenes faecalis in two crystal forms at 1.64 A and 2.03 A. Ellis PJ, Conrads T, Hille R, Kuhn P; Structure. 2001;9:125-132. PMID:11250197

2: The respiratory arsenite oxidase: structure and the role of residues surrounding the rieske cluster. Warelow TP, Oke M, Schoepp-Cothenet B, Dahl JU, Bruselat N, Sivalingam GN, Leimkuhler S, Thalassinos K, Kappler U, Naismith JH, Santini JM; PLoS One. 2013;8:e72535. PMID:24023621