Functional epitope on human neutrophil flavocytochrome b558.

Gp91(phox) is the heme binding subunit of the superoxide-generating NADPH oxidase.

The phagocyte NADPH oxidase flavocytochrome b558 is a membrane-bound heterodimer comprised of a glycosylated subunit, gp91(phox), and a nonglycosylated subunit, p22(phox). It contains two nonidentical heme groups that mediate the final steps of electron transfer to molecular oxygen (O2), resulting in the generation of superoxide ion (O2-). However, the location of the hemes within the flavocyto...

Flavocytochrome Functional Epitope on Human Neutrophil

Stoichiometry of the subunits of flavocytochrome b558 of the NADPH oxidase of phagocytes.

Flavocytochrome b558, the membrane-spanning component of the NADPH oxidase system of phagocytic cells, is composed of two subunits, p22phox and gp91phox (where phox stands for phagocyte oxidase). The stoichiometry of the subunits has been determined for purified flavocytochrome b556 by: (1) densitometry of Coomassie Blue-stained proteins separated by SDS/PAGE, (2) aromatic absorbance at 280 mm ...

Mutation at histidine 338 of gp91(phox) depletes FAD and affects expression of cytochrome b558 of the human NADPH oxidase.

Defective NADPH oxidase components prevent superoxide (O-2) generation, causing chronic granulomatous disease (CGD). X-linked CGD patients have mutations in the gene encoding the gp91(phox) subunit of cytochrome b558 and usually lack gp91(phox) protein completely (X91(0)). gp91(phox) is considered to be a flavocytochrome that contains binding sites for NADPH, FAD, as well as heme. We here repor...

Fungal metabolite gliotoxin targets flavocytochrome b558 in the activation of the human neutrophil NADPH oxidase.

Fungal gliotoxin (GT) is a potent inhibitor of the O(2)(-)-generating NADPH oxidase of neutrophils. We reported that GT-treated neutrophils fail to phosphorylate p47(phox), a step essential for the enzyme activation, because GT prevents the colocalization of protein kinase C betaII with p47(phox) on the membrane. However, it remains unanswered whether GT directly affects any of NADPH oxidase co...