Cytochrome b245, heavy chain (IPR000778)

Short name: Cyt_b245_heavy_chain

Overlapping homologous superfamilies


Family relationships


Phagocytes form the first line of defence against invasion by micro-organisms. Engulfing of bacteria by neutrophils during phagocytosis is accompanied by a respiratory burst. Defects in phagocytosis involving the lack of a respiratory burst give rise to chronic granulomatous disease (CGD) [PMID: 8796870].

Regulation of the respiratory burst takes place at the phagocytic vacuole. The process is mediated by NADPH oxidase, which transports electrons across the plasma membrane to form superoxide in the vacuole interior. The electrons are carried across the membrane by a short electron transport chain in the form of an unusual flavocytochrome b.

The flavoprotein comprises two subunits, p21phox and gp91phox. Gp91phox has 2 major domains, an N-terminal, hydrophobic domain with a number of putative transmembrane helices that could associate to form a barrel-like pore in the membrane; and a more hydrophilic C-terminal domain, which probably lies on the cytosolic side of the membrane, capping the transmembrane structure [PMID: 8796870]. The C-terminal domain is similar to a number of electron-transport proteins, one of which, ferredoxin-NADP reductase, has provided a structural framework upon which to model this domain [PMID: 8251942].

Around two thirds of individuals with CGD inherit the disease in an X-linked, recessive manner. The gene responsible for X-linked CGD is that coding for the large subunit of flavocytochrome b, gp91phox.

GO terms

Biological Process

GO:0055114 oxidation-reduction process

Molecular Function

GO:0016491 oxidoreductase activity

Cellular Component

GO:0016020 membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.