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

Abstract

A membrane-bound cytochrome b ₅₅₈ , a heterodimer consisting of gp91-phox and p22-phox, is a critical component of the superoxide (O₂ ^-)-generating reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in phagocytes. Chronic granulomatous disease (CGD) is characterized by recurrent bacterial infection caused by a defect of the oxidase. Both subunits are absent from phagocytes in typical X-linked recessive CGD patients who are primarily defective in gp91-phox. We report here an atypical case of X-linked CGD in which neutrophils showed a complete absence of O₂ ^–-forming NADPH oxidase activity, but a small amount (about 10% of control) of both subunits was detected by immunoblot analysis. Spectrophotometric studies of the neutrophils with a recently developed sensitive method gave no evidence for the heme spectrum in the cytochrome b ₅₅₈ of this CGD. Reverse transcription/polymerase chain reaction and sequence analysis revealed a C to T transition replacing histidine at amino acid position 101 (His¹⁰¹) by tyrosine in gp91-phox. These results provide evidence that His¹⁰¹ of gp91-phox is the one of the heme-binding ligands of cytochrome b ₅₅₈ .