Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.2 (NQO1)
 6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bacterial respiratory chain has two types of NADH-quinone reductase (NQR): one is energy-coupled (type-1) and the other had no energy-transducing capacity, that is, energy-uncoupled (type-2). Each of the NADH-reacting flavoprotein subunits of NQR-1 from Escherichia coli and the marine Vibrio alginolyticus reduced quinone to semiquinone radicals by the one-electron transfer pathway and was very sensitive to preincubation with NADH. On the other hand, the NQR-2 from these bacteria reduced quinone to quinol by the two-electron transfer pathway and was insensitive to preincubation with NADH. Since the NQR-1 from E. coli functions as a proton pump, whereas that from the marine V. alginolyticus functions as a sodium pump, the formation of semiquinone radicals as an intermediate is likely to be a common mechanism to functioning as either proton or sodium pump.
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PMID:Characteristic differences in the mode of quinone reduction and stability between energy-coupled and -uncoupled NADH-quinone reductases from bacterial respiratory chain. 162 43

The marine bacterium, Vibrio alginolyticus, has a respiratory chain-linked Na(+)-translocating NADH-quinone reductase (NQR). Among several mutant cells defective in Na+ pump activity, Nap1 was a very stable mutant and a spontaneous revertant could not be isolated from Nap1. Using genetic information from the recently sequenced nqr operon, the genetic defects in Nap1 were examined, and the sodium pump-defective mutant Nap1 was found to be caused by the insertion of a 1.2 kbp DNA fragment into the C-terminal region of nqr6 gene.
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PMID:Genetic defect of the sodium pump-defective mutant Nap-1 from the marine Vibrio alginolyticus. 904 33

Vibrio cholerae and many other marine and pathogenic bacteria possess a unique respiratory complex, the Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR), which pumps Na(+) across the cell membrane using the energy released by the redox reaction between NADH and ubiquinone. To function as a selective sodium pump, Na(+)-NQR must contain structures that (1) allow the sodium ion to pass through the hydrophobic core of the membrane and (2) provide cation specificity to the translocation system. In other sodium-transporting proteins, the structures that carry out these roles frequently include aspartate and glutamate residues. The negative charge of these residues facilitates binding and translocation of sodium. In this study, we have analyzed mutants of acid residues located in the transmembrane helices of subunits B, D, and E of Na(+)-NQR. The results are consistent with the participation of seven of these residues in the translocation process of sodium. Mutations at NqrB-D397, NqrD-D133, and NqrE-E95 produced a decrease of approximately >or=10-fold in the apparent affinity of the enzyme for sodium (Km(app)(Na+)), which suggests that these residues may form part of a sodium-binding site. Mutation at other residues, including NqrB-E28, NqrB-E144, NqrB-E346, and NqrD-D88, had a strong effect on the quinone reductase activity of the enzyme and its sodium sensitivity, but a weaker effect on the apparent sodium affinity, consistent with a possible role in sodium conductance pathways.
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PMID:Acid residues in the transmembrane helices of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae involved in sodium translocation. 1969 31