Phosphorylation of p67phox in the neutrophil occurs in the cytosol and is independent of p47phox.

p67phox and p47phox are phosphorylated in the course of stimulation of the NADPH oxidase in neutrophils. Isolated neutrophil cytosol can phosphorylate both of these proteins in vitro. Phosphoamino acid analysis showed that isolated membranes can tyrosine-phosphorylate p67phox in vitro. Further experiments with anti-phosphotyrosine antibodies did not support a role for tyrosine phosphorylation of p67phox in the cell. A phosphopeptide analysis showed that the phosphorylation of p67phox is unchanged in the absence of p47phox. These results further characterise the phosphorylation of p67phox and provide evidence that this is a cytosolic event independent of interaction with p47phox and the membrane.