A 260 kDa cytosolic complex (SP-1) was purified from guinea pig neutrophils. SP-1 was composed of 63 kDa, 47 kDa and 39 kDa proteins. The 63 kDa and 47 kDa proteins proved to correspond to human p67phox and p47phox by Western blot analysis, whereas Western blot and amino acid sequence analyses revealed that the 39 kDa protein was a novel protein. The 47 kDa protein was separated from the 63 kDa and 39 kDa proteins by dithiothreitol (DTT)-treatment. On the other hand, the 63 kDa and 39 kDa proteins were not separated with DTT, detergent and ethanol treatment. These results suggest that the 39 kDa protein tightly associates with the 63 kDa protein and may regulate the function of the 63 kDa protein.
