Phosphorylation of p67(phox) in the neutrophil occurs in the cytosol and is independent of p47(phox)

p67(phox) and p47(phox) are phosphorylated in the course of stimulation of the NADPH oxidase in neutrophils. Isolated neutrophil cytosol can phosphory late both of these proteins in vitro. Phosphoamino acid analysis showed tha t isolated membranes can tyrosine-phosphorylate p67(phox) in vitro. Further experiments with anti-phosphotyrosine antibodies did not support a role fo r tyrosine phosphorylation of p67(phox) in the cell. A phosphopeptide analy sis showed that the phosphorylation of p67(phox) is unchanged in the absenc e of p47(phox), These results further characterise the phosphorylation of p 67(phox) and provide evidence that this is a cytosolic event independent of interaction with p47(phox) and the membrane. (C) 1999 Federation of Europe an Biochemical Societies.