Neutrophil cytosol factor P40 (IPR000919)

Short name: p40phox

Overlapping homologous superfamilies


Family relationships



Phagocytes form the first line of defence against invasion by microorganisms. Engulfing of bacteria by neutrophils is accompanied by the consumption of large amounts of oxygen, a so-called respiratory burst. Defects in phagocytosis involving the lack of a respiratory burst give rise to chronic granulomatous disease (CGD), in which patients are predisposed to infection, often from otherwise non-pathogenic bacteria. 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 (an oxygen molecule with an extra electron that is toxic to normal cells) 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 [PMID: 8796870]. To conserve NADPH and avoid the toxic effects of superoxide, the oxidase remains inactive until it receives an appropriate stimulus. Activation involves the participation of a number of cytosolic proteins, some of which attach to the flavocytochrome. P47phox, p67phox and p40phox are specialised components of phagocytic cells. All contain SH3 domains, by means of which they attach to proline-rich regions of other proteins. Upon activation, p40phox translocates to the region of the plasma membrane forming the phagocytic vacuole, where, with phosphorylated p47phox and p67phox, it associates with hydrophilic regions of the flavocytochrome

GO terms

Biological Process

GO:0006909 phagocytosis
GO:0045730 respiratory burst

Molecular Function

GO:0016176 superoxide-generating NADPH oxidase activator activity

Cellular Component

GO:0043020 NADPH oxidase complex

Contributing signatures

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