In a previous study, the S100A8/A9 protein, a Ca2+- and arachidonic acid-binding protein, abundant in neutrophil cytosol, was found to potentiate the activation of the redox component of the O2– generating oxidase in neutrophils, namely the membrane-bound flavocytochrome b, by the cytosolic phox proteins p67phox, p47phox and Rac ` (Doussiere J., Bouzidi F. and Vignais . (2001) Biochem. Biophys. Res. Commun. 285, 1317–1320). This led us to check by immunoprecipitation and protein fractionation whether the cytosolic phox proteins could bind to S100A8/A9. Following incubation of a cytosolic extract from nonactivated bovine neutrophil with protein A–Sepharose bound to antip67phox antibodies, the.
