A novel mutation at a probable heme-binding ligand in neutrophil cytochrome b(558) in atypical X-linked chronic granulomatous disease

A membrane-bound cytochrome b(558), a heterodimer consisting of gp91-phox a nd p22-phox, is a critical component of the superoxide (O-2(-))-generating reduced nicotinamide adenine dinucleotide phosphate (NAD PH) oxidase in pha gocytes. Chronic granulomatous disease (CGD) is characterized by recurrent bacterial infection caused by a defect of the oxidase. Both subunits are ab sent from phagocytes in typical X-linked recessive CGD patients who are pri marily defective in gp91-phox. We report here an atypical case of X-linked CGD in which neutrophils showed a complete absence of O-2(-)-forming NADPH oxidase activity, but a small amount (about 10% of control) of both subunit s was detected by immunoblot analysis. Spectrophotometric studies of the ne utrophils with a recently developed sensitive method gave no evidence for t he heme spectrum in the cytochrome b558 Of this CGD. Reverse transcription/ polymerase chain reaction and sequence analysis revealed a C to T transitio n replacing histidine at amino acid position 101 (His(101)) by tyrosine in gp91-phox. These results provide evidence that His(101) of gp91-phox is the one of the heme-binding ligands of cytochrome b(558).