(156)PRO-]GLN SUBSTITUTION IN THE LIGHT-CHAIN OF CYTOCHROME B(558) OFTHE HUMAN NADPH OXIDASE (P22-PHOX) LEADS TO DEFECTIVE TRANSLOCATION OF THE CYTOSOLIC PROTEINS P47-PHOX AND P67-PHOX

Src homology 3 (SH3) domains have been suggested to play an important role in the assembly of the superoxide-forming nicotinamide adenine di nucleotide phosphate (NADPH) oxidase upon activation of phagocytes, wh ich involves the association of membrane-bound and cytosolic component s. We studied the translocation of the cytosolic proteins to the plasm a membrane in neutrophils of a patient with a point mutation in the ge ne encoding the light chain of cytochrome b(558). This mutation leads to a substitution at residue 156 of a proline into a glutamine in a pu tative SH3 binding domain of p22-phox (Dinauer, M., E. A. Pierce, R. W . Erickson, T. Muhlebach, H. Messner, R. A. Seger, S. H. Orkin, and J. T. Curnutte. 1991. Proc, Natl. Acad. Sci. 88:11231). In PMA-stimulate d neutrophils and in a cell-free translocation assay with neutrophil m embranes and cytosol, association of the cytosolic proteins p47-phox a nd p67-phox with the membrane fraction of the patient's neutrophils wa s virtually absent. In contrast, when solubilized membranes of the pat ient's neutrophils were activated with phospholipids in the absence of cytosol (Koshkin, V., and E. Pick. 1993. FEBS[Fed. Eur. Biochem. Soc] Lett. 327:57), the rate of NADPH-dependent oxygen uptake was observed at a rate similar to that of control membranes. We suggest that the bi nding of an SH3 domain of p47-phox to p22-phox, and thus activation of the oxidase, does not occur in the neutrophils of this patient, altho ugh under artificial conditions, electron flow from NADPH to oxygen in cytochrome b(558) is possible.