Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A c-type cytochrome, cytochrome c-552, from a soluble fraction of an extreme thermophile, Thermus thermophilus HB8, was highly purified and its properties investigated. The absorption peaks were at 552, 522, and 417 nm in the reduced form, and at 408 nm in the oxidized form. The isoelectric point was at PH 10.8, the midpoint redox potential was about +0.23 V, and the molecular weight was about 15,000. The cytochrome c-552 was highly thermoresistant. The cytochrome reacted rapidly with pseudomonas aeruginosa nitrite reductase [EC 1.9.3.2], but slowly with bovine cytochrome oxidase [EC 1.9.3.1], yeast cytochrome c peroxidase [EC 1.11.1.5], or Nitrosomonas europaea hydroxylamine-cytochrome c reductase [EC 1.7.3.4].
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PMID:Purification and some properties of cytochrome c-552 from an extreme thermophile, Thermus thermophilus HB8. 19 83

The Paracoccus denitrificans fnrP gene encoding a homologue of the Escherichia coli FNR protein was localized upstream of the gene cluster that encodes the high-affinity cbb3-type oxidase. FnrP harbours the invariant cysteine residues that are supposed to be the ligands of the redox-sensitive [4Fe-4S] cluster in FNR. NNR, another FNR-like transcriptional regulator in P. denitrificans, does not. Analysis of FnrP and NNR single and double mutants revealed that the two regulators each exert exclusive control on the expression of a discrete set of target genes. In FnrP mutants, the expression of cytochrome c peroxidase was blocked, that of membrane-bound nitrate reductase and the cbb3-type oxidase was significantly reduced, whilst the activity of the bb3-type quinol oxidase was increased. The amounts of the nitrite and nitric oxide reductases in these FnrP mutants were the same as in the wild type. NNR mutants, on the other hand, were disturbed exclusively in the concentrations of nitrite reductase and nitric oxide reductase. An FnrP.NNR double mutant combined the phenotypes of the single mutant strains. In all three mutants, the concentrations and/or activities of the aa3-type oxidase, cytochrome C550, cytochrome C552, and nitrous oxide reductase equalled those in the wild type. As the FNR boxes in front of the FnrP- and NNR-regulated genes are highly similar to or even identical to each other, the absence of cross-talk between the regulation by FnrP and NNR implies that as yet unidentified factors are important in the control. It is proposed that the redox state of an intracellular redox couple other than the oxygen/water couple is one of the factors that modulates the activity of FnrP.
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PMID:FnrP and NNR of Paracoccus denitrificans are both members of the FNR family of transcriptional activators but have distinct roles in respiratory adaptation in response to oxygen limitation. 907 27

Pseudomonas stutzeri is a facultative anaerobic bacterium with the capability of denitrification. In searching for regulators that control the expression of this trait in response to oxygen withdrawal, we have found an unprecedented multiplicity of four genes encoding transcription factors of the FNR family. The fnrA gene encodes a genuine FNR-type regulator, which is expressed constitutively and controls the cytochrome cbb3-type terminal oxidase (the cco operon), cytochrome c peroxidase (the ccp gene) and the oxygen-independent coproporphyrinogen III oxidase (the hemN gene), in addition to its previously demonstrated role in arginine catabolism (the arc operon). The fnr homologues dnrD, dnrE and dnrS encode regulators of a new subgroup within the FNR family. Their main distinctive feature is the lack of cysteine residues for complexing the [4Fe-4S] centre of redox-active FNR-type regulators. However, they form a phylogenetic lineage separate from the FixK branch of FNR proteins, which also lack this cysteine signature. We have studied the expression of the dnr genes under aerobic, oxygen-limited and denitrifying conditions. DnrD is a key regulator of denitrification by selective activation of the genes for cytochrome cd1 nitrite reductase and NO reductase. The dnrD gene is part of the 30 kb region carrying denitrification genes of P. stutzeri. Transcription of dnrD was activated in O2-limited cells and particularly strongly in denitrifying cells, but was not under the control of FnrA. In response to denitrifying growth conditions, dnrD was transcribed as part of an operon together with genes downstream and upstream of dnrD. dnrS was found about 9 kb upstream of dnrD, next to the nrdD gene for anaerobic ribonucleotide reductase. The transcription of dnrS required FnrA in O2-limited cells. Mutation of dnrS affected nrdD and the expression of ferredoxin I as an element of the oxidative stress response. The dnrE gene is part of the nar region encoding functions for respiratory nitrate reduction. We found the highest amount of dnrE transcripts in aerobically nitrate-challenged cells. The gene was transcribed from two promoters, P1 and P2, of which promoter P1 was under the control of the nitrate response regulator NarL. The multiplicity of FNR factors in P. stutzeri underlines the versatility of the FNR scaffold to serve for transcriptional regulation directed at anaerobic or nitrate-activated metabolic processes.
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PMID:Multiple transcription factors of the FNR family in denitrifying Pseudomonas stutzeri: characterization of four fnr-like genes, regulatory responses and cognate metabolic processes. 1020 42

Cyclic voltammetry shows that yeast iso-1-cytochrome c (YCC), chemisorbed on a bare gold electrode via Cys102, exhibits fast, reversible interfacial electron transfer (k(0) = 1.8 x 10(3) s(-1)) and retains its native functionality. Vectorially immobilized YCC relays electrons to yeast cytochrome c peroxidase, and to both cytochrome cd(1) nitrite reductase (NIR) and nitric oxide reductase from Paracoccus denitrificans, thereby revealing the mechanistic properties of these enzymes. On a microelectrode, we measured nitrite turnover by approximately 80 zmol (49 000 molecules) of NIR, coadsorbed on 0.65 amol (390 000 molecules) of YCC.
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PMID:Direct immobilization of native yeast iso-1 cytochrome C on bare gold: fast electron relay to redox enzymes and zeptomole protein-film voltammetry. 1533 97

Metalloenzymes control enzymatic activity by changing the characteristics of the metal centers where catalysis takes place. The conversion between inactive and active states can be tuned by altering the coordination number of the metal site, and in some cases by an associated conformational change. These processes will be illustrated using heme proteins (cytochrome c nitrite reductase, cytochrome c peroxidase and cytochrome cd1 nitrite reductase), non-heme proteins (superoxide reductase and [NiFe]-hydrogenase), and copper proteins (nitrite and nitrous oxide reductases) as examples. These examples catalyze electron transfer reactions that include atom transfer, abstraction and insertion.
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PMID:Enzymatic activity mastered by altering metal coordination spheres. 1871 50

Neisseria gonorrhoeae has been shown to form biofilms during cervical infection. Thus, biofilm formation may play an important role in the infection of women. The ability of N. gonorrhoeae to form membrane blebs is crucial to biofilm formation. Blebs contain DNA and outer membrane structures, which have been shown to be major constituents of the biofilm matrix. The organism expresses a DNA thermonuclease that is involved in remodeling of the biofilm matrix. Comparison of the transcriptional profiles of gonococcal biofilms and planktonic runoff indicate that genes involved in anaerobic metabolism and oxidative stress tolerance are more highly expressed in biofilm. The expression of aniA, ccp, and norB, which encode nitrite reductase, cytochrome c peroxidase, and nitric oxide reductase respectively, is required for mature biofilm formation over glass and human cervical cells. In addition, anaerobic respiration occurs in the substratum of gonococcal biofilms and disruption of the norB gene required for anaerobic respiration, results in a severe biofilm attenuation phenotype. It has been demonstrated that accumulation of nitric oxide (NO) contributes to the phenotype of a norB mutant and can retard biofilm formation. However, NO can also enhance biofilm formation, and this is largely dependent on the concentration and donation rate or steady-state kinetics of NO. The majority of the genes involved in gonococcal oxidative stress tolerance are also required for normal biofilm formation, as mutations in the following genes result in attenuated biofilm formation over cervical cells and/or glass: oxyR, gor, prx, mntABC, trxB, and estD. Overall, biofilm formation appears to be an adaptation for coping with the environmental stresses present in the female genitourinary tract. Therefore, this review will discuss the studies, which describe the composition and metabolic phenotype of gonococcal biofilms.
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PMID:The Composition and Metabolic Phenotype of Neisseria gonorrhoeae Biofilms. 2183 22