期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1994
卷号：91
期号：12
页码：5345-5349
DOI：10.1073/pnas.91.12.5345
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The phagocyte NADPH oxidase, dormant in resting cells, is activated during phagocytosis to produce superoxide, a precursor of microbicidal oxidants. The activated oxidase is a complex of membrane-integrated cytochrome b558, composed of 91-kDa (gp91phox) and 22-kDa (p22phox) subunits, and two cytosolic factors (p47phox and p67phox), each containing two Src homology 3 (SH3) domains. Here we show that the region of the tandem SH3 domains of p47phox (p47-SH3) expressed as a glutathione S-transferase fusion protein inhibits the superoxide production in a cell-free system, indicating involvement of the domains in the activation. Furthermore, we find that arachidonic acid and sodium dodecyl sulfate, activators of the oxidase in vitro, cause exposure of p47-SH3, which has probably been masked by the C-terminal region of this protein in a resting state. The unmasking of p47-SH3 appears to play a crucial role in the assembly of the oxidase components, because p47-SH3 binds to both p22phox and p67phox but fails to interact with a mutant p22phox carrying a Pro-156-->Gln substitution in a proline-rich region, which has been found in a patient with chronic granulomatous disease. Based on the observations, we propose a signal-transducing mechanism whereby normally inaccessible SH3 domains become exposed upon activation to interact with their target proteins.
