Mutation at Histidine 338 of gp91 phox Depletes FAD and Affects Expression of Cytochrome b 558 of the Human NADPH Oxidase

• Published in: The Journal of biological chemistry Vol. 273; no. 43; p. 27879
• Main Authors: Lucia S. Yoshida, Fumiko Saruta, Ken Yoshikawa, Osamu Tatsuzawa, Shohko Tsunawaki
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 23-10-1998
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.43.27879

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 b
558 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 report a rare
X-linked CGD patient whose neutrophils entirely failed to produce O⨪ 2 , but presented a diminished expression of gp91 phox containing about one-third of the heme present in normal individuals by Soret absorption. Translocation of cytosolic factors
p67 phox and p47 phox was normal. However, the FAD content in his neutrophil membranes was as low as that of X91 0 patients, suggesting complete depletion of FAD in his gp91 phox . This was in agreement with the finding that a single base substitution (C1024 to T) changed His-338 to Tyr in gp91 phox in a predicted FAD-binding domain of the flavocytochrome model. The loss of FAD could not be corrected even after addition
of reagent FAD or a FAD-rich dehydrogenase fraction isolated from normal neutrophils to the patient’s membranes, in a reconstitution
in vitro with normal cytosol. These results indicate that His-338 is a very critical residue for FAD incorporation into the NADPH
oxidase system. This is the first such mutation found in CGD.