Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.7.1.2 (nitrate reductase)
3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have generated a chromosomal mutant of moeB (moeBA228T) that demonstrates limited molybdenum cofactor (molybdo-bis(molybdopterin guanine dinucleotide) (Mo-bisMGD)) availability in Escherichia coli and have characterized its effect on the maturation and physiological function of two well-characterized respiratory molybdoenzymes: the membrane-bound dimethylsulfoxide (DMSO) reductase (DmsABC) and the membrane-bound nitrate reductase A (NarGHI). In the moeBA228T mutant strain, E. coli F36, anaerobic respiratory growth is possible on nitrate but not on DMSO, indicating that cofactor insertion occurs into NarGHI but not into DmsABC. Fluorescence analyses of cofactor availability indicate little detectable cofactor in the moeBA228T mutant compared with the wild-type, suggesting that NarGHI is able to scavenge limiting cofactor, whereas DmsABC is not. MoeB functions to sulfurylate MoaD, and in the structure of the MoeB-MoaD complex, Ala-228 is located in the interface region between the two proteins. This suggests that the moeBA228T mutation disrupts the interaction between MoeB and MoaD. In the case of DmsABC, despite the absence of cofactor, the twin-arginine signal sequence of DmsA is cleaved in the moeBA228T mutant, indicating that maturation of the holoenzyme is not cofactor-insertion dependent.
...
PMID:Differential effects of a molybdopterin synthase sulfurylase (moeB) mutation on Escherichia coli molybdoenzyme maturation. 1223 97

In non-photosynthetic, yellow or colourless mutant cells of Chlorella kessleri, grown with nitrate as sole nitrogen source, blue light inhibited the uptake of the amino acids glycine, proline and arginine and of ammonia in growing cells, while it enhanced the uptake of these amino acids in resting cells. On the other hand, in cells grown with ammonia as the only nitrogen source without nitrate reductase activity, blue light did not influence the uptake of amino acids and of ammonia in growing cells, while it enhanced the uptake of amino acids in resting cells. Addition of methionine sulphoximine, a potent inhibitor of glutamine synthetase, to growing cells, resulted in intracellular ammonia-accumulation and inhibition of uptake of glycine and of ammonia. For the colourless mutant, blue light was shown to activate purified nitrate reductase. These results indicate that in the mutant cells of Chlorella examined, uptake of ammonia seems to be influenced by nitrate reductase and the uptake of amino acids was influenced by both nitrate reductase and an unknown blue-light-receptor(s). The uptake of urea in mutant cells is not influenced by the irradiation with blue light. Uptake of glycine was also increased after addition of glucose (hexose) in the dark. Because blue light is known to enhance the breakdown of starch, a reaction producing glucose for oxidative degradation in the algae used, the role of glucose (hexose) in the blue light-affected uptake of amino acids is discussed.
...
PMID:Blue-light-control of the uptake of amino acids and of ammonia in Chlorella mutants. 1235 2

Nap (periplasmic nitrate reductase) operons of many bacteria include four common, essential components, napD, napA, napB and napC (or a homologue of napC ). In Escherichia coli there are three additional genes, napF, napG and napH, none of which are essential for Nap activity. We now show that deletion of either napG or napH almost abolished Nap-dependent nitrate reduction by strains defective in naphthoquinone synthesis. The residual rate of nitrate reduction (approx. 1% of that of napG+ H+ strains) is sufficient to replace fumarate reduction in a redox-balancing role during growth by glucose fermentation. Western blotting combined with beta-galactosidase and alkaline phosphatase fusion experiments established that NapH is an integral membrane protein with four transmembrane helices. Both the N- and C-termini as well as the two non-haem iron-sulphur centres are located in the cytoplasm. An N-terminal twin arginine motif was shown to be essential for NapG function, consistent with the expectation that NapG is secreted into the periplasm by the twin arginine translocation pathway. A bacterial two-hybrid system was used to show that NapH interacts, presumably on the cytoplasmic side of, or within, the membrane, with NapC. As expected for a periplasmic protein, no NapG interactions with NapC or NapH were detected in the cytoplasm. An in vitro quinol dehydrogenase assay was developed to show that both NapG and NapH are essential for rapid electron transfer from menadiol to the terminal NapAB complex. These new in vivo and in vitro results establish that NapG and NapH form a quinol dehydrogenase that couples electron transfer from the high midpoint redox potential ubiquinone-ubiquinol couple via NapC and NapB to NapA.
...
PMID:NapGH components of the periplasmic nitrate reductase of Escherichia coli K-12: location, topology and physiological roles in quinol oxidation and redox balancing. 1467 86

Nitric oxide (NO) is an important signaling molecule in animals and plants. In mammals, NO is produced from Arg by the enzyme NO synthase. In plants, NO synthesis from Arg using an NO synthase-type enzyme and from nitrite using nitrate reductase has been demonstrated previously. The data presented in this report strongly support the hypothesis that plant tissues also synthesize NO via the nonenzymatic reduction of apoplastic nitrite. As measured by mass spectrometry or an NO-reactive fluorescent probe, Hordeum vulgare (barley) aleurone layers produce NO rapidly when nitrite is added to the medium in which they are incubated. NO production requires an acid apoplast and is accompanied by a loss of nitrite from the medium. Phenolic compounds in the medium can increase the rate of NO production. The possible significance of apoplastic NO production for germinating grain and for plant roots is discussed.
...
PMID:Apoplastic synthesis of nitric oxide by plant tissues. 1474 74

The ferredoxin-dependent nitrate reductase from the cyanobacterium Synechococcus sp. PCC 7942 has been shown to form a high-affinity complex with ferredoxin at low ionic strength. This complex, detected by changes in both the absorbance and circular dichroism (CD) spectra, did not form at high ionic strength. When reduced ferredoxin served as the electron donor for the reduction of nitrate to nitrite, the activity of the enzyme declined markedly as the ionic strength increased. In contrast, the activity of the enzyme with reduced methyl viologen (a non-physiological electron donor) was independent of ionic strength. These results suggest that an electrostatically stabilized complex between Synechococcus nitrate reductase and ferredoxin plays an important role in the mechanism of nitrate reduction catalyzed by this enzyme. Treatment of Synechococcus nitrate reductase with either an arginine-modifying reagent or a lysine-modifying reagent inhibited the ferredoxin-dependent activity of the enzyme but did not affect the methyl viologen-dependent activity. Treatment with these reagents also resulted in a large decrease in the affinity of the enzyme for ferredoxin. Formation of a nitrate reductase complex with ferredoxin prior to treatment with either reagent protected the enzyme against loss of ferredoxin-dependent activity. These results suggest that lysine and arginine residues are present at the ferredoxin-binding site of Synechococcus nitrate reductase. Results of experiments using site-specific, charge reversal variants of the ferredoxin from the cyanobacterium Anabaena sp. PCC 7119 as an electron donor to nitrate reductase were consistent with a role for negatively charged residues on ferredoxin in the interaction with Synechococcus nitrate reductase.
...
PMID:Complex formation between ferredoxin and Synechococcus ferredoxin: nitrate oxidoreductase. 1487 93

The twin-arginine protein transport (Tat) system is a remarkable molecular machine dedicated to the translocation of fully folded proteins across energy-transducing membranes. Complex cofactor-containing Tat substrates acquire their cofactors prior to export, and substrate proteins actually require to be folded before transport can proceed. Thus, it is very likely that mechanisms exist to prevent wasteful export of immature Tat substrates or to curb competition between immature and mature substrates for the transporter. Here we assess the primary sequence relationships between the accessory proteins implicated in this process during assembly of key respiratory enzymes in the model prokaryote Escherichia coli. For each respiratory enzyme studied, a redox enzyme maturation protein (REMP) was assigned. The main finding from this review was the hitherto unexpected link between the Tat-linked REMP DmsD and the nitrate reductase biosynthetic protein NarJ. The evolutionary link between Tat transport and cofactor insertion processes is discussed.
...
PMID:Sequence analysis of bacterial redox enzyme maturation proteins (REMPs). 1521 47

The -proteobacterium Wolinella succinogenes grows anaerobically by respiratory nitrite ammonification but not by denitrification. Nevertheless, it is capable of N(2)O reduction to N(2). Recently, the genome sequence of W. succinogenes revealed a nos gene cluster with intriguing features encoding a new type of N(2)O reductase. The predicted enzyme is similar to other N(2)O reductases exhibiting conservation of all residues ligating the two multinuclear copper centers but carries an unprecedented C-terminal monoheme cytochrome c domain. Notably, the N(2)O reductase pre-protein is synthesized with a Sec-dependent signal peptide, rather than the usually observed twin-arginine signal sequence, implying that the copper and heme cofactors are both incorporated in the periplasm. The nos gene cluster further consists of four adjacent open reading frames which are predicted to encode two monoheme c-type cytochromes as well as homologs of NapG and NapH. The latter proteins are thought to function in quinol oxidation coupled to cytochrome c reduction in electron transport to periplasmic nitrate reductase. While the accessory genes nosD, -F, -Y and -L are present in W. succinogenes, homologs of nosR and nosX are absent from the genome. We hypothesize that the nos gene cluster of W. succinogenes encodes a complete electron transport chain catalyzing N(2)O reduction by menaquinol, a pathway which might also be relevant to other bacteria.
...
PMID:The unprecedented nos gene cluster of Wolinella succinogenes encodes a novel respiratory electron transfer pathway to cytochrome c nitrous oxide reductase. 1522

Nitrate assimilation in autotrophs provides most of the reduced nitrogen on earth. In eukaryotes, reduction of nitrate to nitrite is catalyzed by the molybdenum-containing NAD(P)H:nitrate reductase (NR; EC 1.7.1.1-3). In addition to the molybdenum center, NR contains iron-heme and flavin adenine dinucleotide as redox cofactors involved in an internal electron transport chain from NAD(P)H to nitrate. Recombinant, catalytically active Pichia angusta nitrate-reducing, molybdenum-containing fragment (NR-Mo) was expressed in P. pastoris and purified. Crystal structures for NR-Mo were determined at 1.7 and 2.6 angstroms. These structures revealed a unique slot for binding nitrate in the active site and identified key Arg and Trp residues potentially involved in nitrate binding. Dimeric NR-Mo is similar in overall structure to sulfite oxidases, with significant differences in the active site. Sulfate bound in the active site caused conformational changes, as compared with the unbound enzyme. Four ordered water molecules located in close proximity to Mo define a nitrate binding site, a penta-coordinated reaction intermediate, and product release. Because yeast NAD(P)H:NR is representative of the family of eukaryotic NR, we propose a general mechanism for nitrate reduction catalysis.
...
PMID:Structural basis of eukaryotic nitrate reduction: crystal structures of the nitrate reductase active site. 1577 87

Many sulphate reducing bacteria can also reduce nitrite, but relatively few isolates are known to reduce nitrate. Although nitrate reductase genes are absent from Desulfovibrio vulgaris strain Hildenborough, for which the complete genome sequence has been reported, a single subunit periplasmic nitrate reductase, NapA, was purified from Desulfovibrio desulfuricans strain 27774, and the structural gene was cloned and sequenced. Chromosome walking methods have now been used to determine the complete sequence of the nap gene cluster from this organism. The data confirm the absence of a napB homologue, but reveal a novel six-gene organisation, napC-napM-napA-napD-napG-napH. The NapC polypeptide is more similar to the NrfH subgroup of tetraheme cytochromes than to NapC from other bacteria. NapM is predicted to be a tetra-heme c-type cytochrome with similarity to the small tetraheme cytochromes from Shewanella oneidensis. The operon is located close to a gene encoding a lysyl-tRNA synthetase that is also found in D. vulgaris. We suggest that electrons might be transferred to NapA either from menaquinol via NapC, or from other electron donors such as formate or hydrogen via the small tetraheme cytochrome, NapM. We also suggest that, despite the absence of a twin-arginine targeting sequence, NapG might be located in the periplasm where it would provide an alternative direct electron donor to NapA.
...
PMID:Nitrate reduction by Desulfovibrio desulfuricans: a periplasmic nitrate reductase system that lacks NapB, but includes a unique tetraheme c-type cytochrome, NapM. 1597 53

The origin of nitric oxide (*NO) in plants is unclear and an *NO synthase (NOS)-like enzyme and nitrate reductase (NR) are claimed as potential sources. Here we used wild-type and NR-defective double mutant plants to investigate *NO production in Arabidopsis thaliana in response to Pseudomonas syringae pv maculicola. NOS activity increased substantially in leaves inoculated with P. syringae. However, electron paramagnetic resonance experiments showed a much higher *NO formation that was dependent on nitrite and mitochondrial electron transport rather than on arginine or nitrate. Overall, these results indicate that NOS, NR and a mitochondrial-dependent nitrite-reducing activity cooperate to produce *NO during A. thaliana-P. syringae interaction.
...
PMID:Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae. 1597 83


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---