Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.3.1 (NADPH oxidase)
 11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nicotinamide adenine dinucleotide phosphate (NADPH) binding site of the NADPH oxidase complex is believed to be located on the beta, subunit of cytochrome b558. However, our previous studies showed that p67PHOX also contains an NADPH binding site that is essential for normal oxidase activity and that p67PHOX is able to mediate a slow electron transfer from a reduced pyridine nucleotide to an artificial electron acceptor. Using both affinity labeling and fluorescence quenching, we have obtained further evidence that p67PHOX is able to bind NADPH. We have used a number of truncated forms of p67PHOX, including p67PHOX(1-243), p67PHOX(1-210), p67PHOX(1-199), and p67PHOX(244-526) (where the numbers represent the initial and final amino acids in the truncated p67PHOX) in order to localize the binding site. We found that NADPH could bind to p67PHOX(1-243), p67PHOX(1-210), and p67PHOX(1-199) but not to p67PHOX(244-526). The p67PHOX(1-199) fragment consists largely of four tetratricopeptide (TPR) domains. We showed further that Rac2-GTP gamma S and to a lesser extent Rac2-GDP beta S could modulate the binding of NADPH to p67PHOX.
 ...
PMID:Binding of nicotinamide adenine dinucleotide phosphate to the tetratricopeptide repeat domains at the N-terminus of p67PHOX, a subunit of the leukocyte nicotinamide adenine dinucleotide phosphate oxidase. 1071 28

p67phox is an essential part of the NADPH oxidase, a multiprotein enzyme complex that produces superoxide ions in response to microbial infection. Binding of the small GTPase Rac to p67phox is a key step in the assembly of the active enzyme complex. The structure of Rac.GTP bound to the N-terminal TPR (tetratricopeptide repeat) domain of p67phox reveals a novel mode of Rho family/effector interaction and explains the basis of GTPase specificity. Complex formation is largely mediated by an insertion between two TPR motifs, suggesting an unsuspected versatility of TPR domains in target recognition and in their more general role as scaffolds for the assembly of multiprotein complexes.
 ...
PMID:Structure of the TPR domain of p67phox in complex with Rac.GTP. 1109 Jun 27

Upon activation, the NADPH oxidase from neutrophils produces superoxide anions in response to microbial infection. This enzymatic complex is activated by association of its cytosolic factors p67(phox), p47(phox), and the small G protein Rac with a membrane-associated flavocytochrome b(558). Here we report the crystal structure of the active N-terminal fragment of p67(phox) at 1.8 A resolution, as well as functional studies of p67(phox) mutants. This N-terminal region (residues 1-213) consists mainly of four TPR (tetratricopeptide repeat) motifs in which the C terminus folds back into a hydrophobic groove formed by the TPR domain. The structure is very similar to that of the inactive truncated form of p67(phox) bound to the small G protein Rac previously reported, but differs by the presence of a short C-terminal helix (residues 187-193) that might be part of the activation domain. All p67(phox) mutants responsible for Chronic Granulomatous Disease (CGD), a severe defect of NADPH oxidase function, are localized in the N-terminal region. We investigated two CGD mutations, G78E and A128V. Surprisingly, the A128V CGD mutant is able to fully activate the NADPH oxidase in vitro at 25 degrees C. However, this point mutation represents a temperature-sensitive defect in p67(phox) that explains its phenotype at physiological temperature.
 ...
PMID:The active N-terminal region of p67phox. Structure at 1.8 A resolution and biochemical characterizations of the A128V mutant implicated in chronic granulomatous disease. 1126 7

The phagocyte NADPH oxidase, crucial for innate immunity, is dormant in resting cells, but becomes activated during phagocytosis to produce superoxide, a precursor of microbicidal oxidants. In activation of the oxidase, the multidomain protein p67(phox)plays a central role: it translocates to the membrane as a ternary complex with p47(phox)and p40(phox), and interacts with the small GTPase Rac to assemble with the membrane-integrated catalytic protein gp91(phox), leading to superoxide production. Here we show, using small-angle X-ray scattering (SAXS) analysis, that p67(phox)adopts an elongated conformation when it exists not only as a monomer but also as the heterotrimer. Although p67(phox)harbors an N-terminal TPR domain for binding to Rac and a p40(phox)-interacting PB1 domain, followed by an SH3 domain that associates with p47(phox), the present model suggests that no or few apparent associations occur between the domains. The positions of the protein-interaction domains in p67(phox)contribute to activation of the phagocyte NADPH oxidase: the first SH3 domain that is located between the TPR and PB1 domains positively regulates oxidase activation only when it is present at the correct position; the PB1 domain placed at this SH3 domain position inhibits the oxidase by interacting with p40(phox).
 ...
PMID:The domain organization of p67 phox, a protein required for activation of the superoxide-producing NADPH oxidase in phagocytes. 2037 10