Cytochrome b-245 is a flavocytochrome containing FAD and the NADPH-binding site of the microbicidal oxidase of phagocytes

摘要: The NADPH oxidase of phagocytic cells is important for the efficient killing and digestion ingested microbes. A very unusual low-potential cytochrome b (b-245) only redox molecule to have been identified in this system. FAD-containing flavoprotein that binds transfers electrons has eluded identification three decades. We show here haem/FAD ratio membranes does not change significantly on activation oxidase, indicating FAD present from outset recruited cytosol. content patients with X-linked chronic granulomatous disease (CGD) lacking was roughly one-quarter normal subjects autosomal recessive CGD cytosolic protein p47-phox. Similar low amounts were uninduced promyelocytic (HL60) cells, suggesting amount X-CGD probably unrelated Cytochrome b-245 appears bind both haem FAD, a molar 2:1. e.p.r. signal purified weak had an asymmetric g(z) peak at g = 3.31. could be partially reflavinated (about 20%) presence lipid. Amino acid sequence homology detected between beta-subunit ferredoxin-NADP+ reductase (FNR) family reductases putative NADPH- FAD-binding sites. 32P-labelled 2-azido-NADP used as photoaffinity label NADPH-binding site. Labelling competed off NADP observed region cytochrome. No labelling seen whom missing third it but bore Pro-His transposition These studies indicate flavocytochrome, first described higher eukaryotic bearing complete electron-transporting apparatus oxidase.