Cloning of murine gp91(phox) cDNA and functional expression in a human X-linked chronic granulomatous disease cell line

The phagocyte cytochrome b(558), a heterodimer comprised of gp91(phox) and p22(phox), is a flavocytochrome that mediates the transfer of electrons from NADPH to molecular oxygen in the respiratory burst oxidase. The human gene encoding the glycosylated gp91(phox) subunit is the site of mutations in X-linked chronic granulomatous disease (CGD). Reverse transcriptase-polymerase chain reaction was used to obtain a full-length clone for the murine gp91(phox) cDNA, which was 87% identical to the human gp91(phox) cDNA. The encoded murine protein had 39 amino acids out of 570 that differed from the human. many of which were conservative substitutions. Nonconservative replacements occurred in hydrophilic regions outside of domains previously implicated in binding to NADPH, flavin, and the cytosolic oxidase subunit p47(phox). Some substitutions altered potential N-glycosylation sites. which is likely to explain why the glycosylated murine protein migrates with an apparent molecular mass of 58 kD instead of 91 kD as seen for the human protein. Expression of murine gp91(phox) in a human myeloid cell line with a null gp91(phox) allele using a mammalian expression plasmid or a retroviral vector rescued stable expression of the p22(phox) subunit and fully reconstituted respiratory burst activity. This suggests that the murine gp91(phox) subunit forms a functional cytochrome b(558) heterodimer with human oxidase subunits, consistent with the high degree of identity between the mouse and human proteins in domains implicated in cytochrome function. (C) 1996 by The American Society of Hematology.