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pubmed:abstractText |
We recently characterized a "semirecombinant" cell-free NADPH-oxidase system, comprised of plasma membrane plus the recombinant cytosolic proteins p47-phox and p67-phox, wherein superoxide generation was activated by an anionic amphiphile plus guanosine 5'-O-(2-thiotriphosphate) (GTP gamma S) (Uhlinger, D. J., Inge, K. L., Kreck, M. L., Tyagi, S. R., Neckelmann, N., and Lambeth, J. D. (1992) Biochem. Biophys. Res. Commun. 186, 509-516). Based on preincubation with guanine nucleotides, we show that plasma membrane contains G protein(s) that support oxidase activation at submaximal rates. By varying p47-phox and p67-phox concentrations, kinetic parameters (EC50 and Vmax) for each were determined. For both, GTP gamma S increased the Vmax and decreased the EC50, whereas guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) produced the opposite effect, consistent with the participation of a G protein in an activation complex containing p47-phox and p67-phox. Using [35S]methionine-labeled p47-phox and p67-phox, we investigated the association of these components with both normal plasma membranes and chronic granulomatous disease membranes lacking cytochrome b558. p47-phox translocation was stimulated by arachidonate but not GTP gamma S, was about 50% cytochrome-dependent, and occurred independently of p67-phox. Arachidonate-stimulated translocation of p67-phox required both cytochrome and p47-phox and was enhanced by GTP gamma S. The mass of p47-phox and p67-phox which assembled with cytochrome b558 indicated a ternary complex with a 1:1:1 stoichiometry.
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