This family includes a common region in the transmembrane proteins mammalian cytochrome B-245 heavy chain (gp91-phox), ferric reductase transmembrane component in yeast and respiratory burst oxidase from mouse-ear cress. This may be a family of flavocytochromes capable of moving electrons across the plasma membrane [1]. The Frp1 protein Swiss:Q04800 from S. pombe is a ferric reductase component and is required for cell surface ferric reductase activity, mutants in frp1 are deficient in ferric iron uptake [1]. Cytochrome B-245 heavy chain Swiss:P04839 is a FAD-dependent dehydrogenase it is also has electron transferase activity which reduces molecular oxygen to superoxide anion, a precursor in the production of microbicidal oxidants [2]. Mutations in the sequence of cytochrome B-245 heavy chain (gp91-phox) lead to the X-linked chronic granulomatous disease. The bacteriocidal ability of phagocytic cells is reduced and is characterised by the absence of a functional plasma membrane associated NADPH oxidase [3]. The chronic granulomatous disease gene codes for the beta chain of cytochrome B-245 and cytochrome B-245 is missing from patients with the disease [4].

1: The fission yeast ferric reductase gene frp1+ is required for ferric iron uptake and encodes a protein that is homologous to the gp91-phox subunit of the human NADPH phagocyte oxidoreductase. Roman DG, Dancis A, Anderson GJ, Klausner RD; Mol Cell Biol 1993;13:4342-4350. PMID:8321236

2: Cytochrome b558: the flavin-binding component of the phagocyte NADPH oxidase. Rotrosen D, Yeung CL, Leto TL, Malech HL, Kwong CH; Science 1992;256:1459-1462. PMID:1318579

3: The glycoprotein encoded by the X-linked chronic granulomatous disease locus is a component of the neutrophil cytochrome b complex. Dinauer MC, Orkin SH, Brown R, Jesaitis AJ, Parkos CA; Nature 1987;327:717-720. PMID:3600768

4: The X-linked chronic granulomatous disease gene codes for the beta- chain of cytochrome b-245. Teahan C, Rowe P, Parker P, Totty N, Segal AW; Nature 1987;327:720-721. PMID:3600769