p67-phox enhances the binding of p47-phox to the human neutrophil respiratory burst oxidase complex.
The neutrophil respiratory burst oxidase consists of both the plasma membrane-associated flavocytochrome b558 and cytosolic regulatory proteins including p47-phox, p67-phox, and a small GTP-binding protein (Rac1 and/or Rac2). Oxidase activation is thought to result from the assembly of the cytosolic components on the cytochrome. A model has been proposed in which p47-phox binds directly to the cytochrome, while p67-phox binding occurs indirectly by binding to p47-phox. We have carried out a steady state kinetic analysis using a cell-free semirecombinant activation system (isolated plasma membrane plus recombinant cytosolic factors) to analyze the effects of p47-phox and p67-phox on one another's association in the active oxidase complex. As predicted from the model, increasing p47-phox concentration markedly lowered the EC50 for p67-phox, indicating that p67-phox is dependent upon p47-phox for binding. Unexpectedly, increasing p67-phox concentration also produced a significant enhancement of p47-phox binding. Thus, a more complex binding model must be invoked in which p47-phox and p67-phox mutually enhance one another's binding.
Uhlinger
D J
DJ
Department of Biochemistry, Emory University Medical School, Atlanta, Georgia 30322.
Taylor
K L
KL
Lambeth
J D
JD
D003573:Cytochrome b Group / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D016897:Respiratory Burst
D003573:Cytochrome b Group; D010750:Phosphoproteins; C079789:neutrophil cytosol factor 67K; C036888:cytochrome b558; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; C022709:superoxide-forming enzyme; D009252:NADPH Dehydrogenase; D019204:GTP-Binding Proteins