Combination of Arachidonic Acid and Guanosine 5′-O-(3-Thiotriphosphate) Induces Translocation of rac p21s to Membrane and Activation of NADPH Oxidase in a Cell-Free System

The superoxide-generating NADPH oxidase system in phagocytes consists of membrane-associated cytochrome b₅₅₈ and three cytosolic components named p67-phox, p47-phox, and rac p21s. In a cell-free system consisting of membrane and cytosol, the oxidase can be activated with guanosine 5′-O-(3-thiotriphosphate) (GTPγS) and an unsaturated fatty acid such as arachidonic acid (AA). Incubation of cytosol and membrane with AA alone caused clear translocation of p47-phox and p67-phox to the membrane, but only slight translocation of rac p21s. GTPγS alone did not significantly induce the iranslocation of rac p21s. However, GTPγS in combination with AA markedly augmented mac p21s translocation to the membrane. The translocation of rac p21s is not induced by GDP or GDPβS. These results indicate that the GTP-bound active form of mac p21s is the entity that is translocated to the membrane by the action of AA.