InterPro domain: IPR013130

This domain represents 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. These proteins may be a family of flavocytochromes capable of moving electrons across the plasma membrane [ 1 ]. The Frp1 protein Q04800 from Schizosaccharomyces pombe is a ferric reductase component and is required for cell surface ferric reductase activity. Mutants in Frp1 are deficient in ferric iron uptake [ 2 ]. Cytochrome B-245 heavy chain 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. Mol. Cell. Biol. 13, 4342-50
2. Cytochrome b558: the flavin-binding component of the phagocyte NADPH oxidase. Science 256, 1459-62
3. The glycoprotein encoded by the X-linked chronic granulomatous disease locus is a component of the neutrophil cytochrome b complex. Nature 327, 717-20
4. The X-linked chronic granulomatous disease gene codes for the beta-chain of cytochrome b-245. Nature 327, 720-1