Assembly of the phagocyte NADPH oxidase complex: chimeric constructs derived from the cytosolic components as tools for exploring structure-function relationships.
Phagocytes generate superoxide (O2*-) by an enzyme complex known as reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Its catalytic component, responsible for the NADPH-driven reduction of oxygen to O2*-, is flavocytochrome b559, located in the membrane and consisting of gp91phox and p22phox subunits. NADPH oxidase activation is initiated by the translocation to the membrane of the cytosolic components p47phox, p67phox, and the GTPase Rac. Cytochrome b559 is converted to an active form by the interaction of gp91phox with p67phox, leading to a conformational change in gp91phox and the induction of electron flow. We designed a new family of NADPH oxidase activators, represented by chimeras comprising various segments of p67phox and Rac1. The prototype chimera p67phox (1-212)-Rac1 (1-192) is a potent activator in a cell-free system, also containing membrane p47phox and an anionic amphiphile. Chimeras behave like bona fide GTPases and can be prenylated, and prenylated (p67phox -Rac1) chimeras activate the oxidase in the absence of p47phox and amphiphile. Experiments involving truncations, mutagenesis, and supplementation with Rac1 demonstrated that the presence of intrachimeric bonds between the p67phox and Rac1 moieties is an absolute requirement for the ability to activate the oxidase. The presence or absence of intrachimeric bonds has a major impact on the conformation of the chimeras, as demonstrated by fluorescence resonance energy transfer, small angle X-ray scattering, and gel filtration. Based on this, a "propagated wave" model of NADPH oxidase activation is proposed in which a conformational change initiated in Rac is propagated to p67phox and from p67phox to gp91phox.
Mizrahi
Ariel
A
The Julius Friedrich Cohnheim-Minerva Center for Phagocyte Research and Ela Kodesz Institute of Host Defense against Infectious Diseases, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
Berdichevsky
Yevgeny
Y
Ugolev
Yelena
Y
Molshanski-Mor
Shahar
S
Nakash
Yael
Y
Dahan
Iris
I
Alloul
Nathalie
N
Gorzalczany
Yara
Y
Sarfstein
Rive
R
Hirshberg
Miriam
M
Pick
Edgar
E
D000818:Animals; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000502:physiology; D004793:Enzyme Reactivators / Q000138:chemical synthesis / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D010586:Phagocytes / Q000201:enzymology / Q000378:metabolism*; D011487:Protein Conformation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D004793:Enzyme Reactivators; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D019255:NADPH Oxidases; D020830:rac1 GTP-Binding Protein