Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pterin cofactor in formate dehydrogenase isolated from Methanobacterium formicium is identified as molybdopterin guanine dinucleotide. The pterin, stabilized as the alkylated, dicarboxamidomethyl derivative, is shown to have absorption and chromatographic properties identical to those of the previously characterized authentic compound. Treatment with nucleotide pyrophosphatase produced the expected degradation products GMP and carboxyamidomethyl molybdopterin. The molybdopterin guanine dinucleotide released from the enzyme by treatment with 95% dimethyl sulfoxide is shown to be functional in the in vitro reconstitution of the cofactor-deficient nitrate reductase in extracts of the Neurospora crassa nit-1 mutant.
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PMID:Identification of molybdopterin guanine dinucleotide in formate dehydrogenase from Methanobacterium formicicum. 203 31

The napEDABC locus coding for the periplasmic nitrate reductase of Thiosphaera pantotropha has been cloned and sequenced. The large and small subunits of the enzyme are coded by napA and napB. The sequence of NapA indicates that this protein binds the GMP-conjugated form of the molybdopterin cofactor. Cysteine-181 is proposed to ligate the molybdenum atom. It is inferred that the active site of the periplasmic nitrate reductase is structurally related to those of the molybdenum-dependent formate dehydrogenases and bacterial assimilatory nitrate reductases, but is distinct from that of the membrane-bound respiratory nitrate reductases. A four-cysteine motif at the N-terminus of NapA binds a [4Fe-4S] cluster. The DNA- and protein-derived primary sequence of NapB confirm that this protein is a dihaem c-type cytochrome and, together with spectroscopic data, indicate that both NapB haems have bis-histidine ligation. napC is predicted to code for a membrane-anchored tetrahaem c-type cytochrome that shows sequence similarity to the NirT cytochrome c family. NapC may be the direct electron donor to the NapAB complex. napD is predicted to encode a soluble cytoplasmic protein and napE a monotopic integral membrane protein, napDABC genes can be discerned at the aeg-46.5 locus of Escherichia coli K-12, suggesting that this operon encodes a periplasmic nitrate reductase system, while napD and napC are identified adjacent to the napAB genes of Alcaligenes eutrophus H16.
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PMID:The napEDABC gene cluster encoding the periplasmic nitrate reductase system of Thiosphaera pantotropha. 763 19

A Mo(V) electron paramagnetic resonance (EPR) study of the periplasmic respiratory nitrate reductase of the denitrifying bacterium Thiosphaera pantotropha has revealed that the molybdenum centre of this enzyme is very similar to that in the assimilatory nitrate reductase of Azotobacter vinelandii but is somewhat different from that of the membrane-bound bacterial respiratory nitrate reductases such as those of Escherichia coli and Paracoccus denitrificans. We have identified the Mo(V) species most likely to be the catalytically relevant one and characterised two other sets of Mo(V) EPR signals. As well as exhibiting EPR signals with g values typical of bacterial molybdenum-containing reductases, molybdenum-hydroxylase-like EPR signals can be elicited in the nitrate reductase of T. pantotropha upon treatment with excess dithionite. The only other enzyme known to display this phenomenon is the periplasmic dimethylsulphoxide reductase of Rhodobacter capsulatus. A mechanism for the generation of these signals is proposed which invokes reduction of the pterin ring of the molybdenum cofactor linked to GMP from the dihydro to the tetrahydro state. The possibilities and implications of there being cysteine ligands to the molybdenum centres of these two enzymes are discussed.
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PMID:Mo(V) electron paramagnetic resonance signals from the periplasmic nitrate reductase of Thiosphaera pantotropha. 781 68

The mob mutants in Escherichia coli are pleiotropically defective in all molybdoenzyme activities. They synthesise molybdopterin, the unique core of the molybdenum cofactor, but are unable to attach the GMP moiety to molybdopterin to form molybdopterin guanine dinucleotide, the functional molybdenum cofactor in Escherichia coli. A partially purified preparation termed protein FA (protein factor d'association), is able to restore molybdoenzyme activities to broken cell preparations of mob mutants. A fragment of DNA capable of complementing mob mutants has been isolated from an E. coli genomic library. Strains carrying this DNA in a multicopy plasmid, express 30-fold more protein FA activity than the wild-type bacterium. Protein FA has been purified to homogeneity by a combination of ion-exchange, affinity and gel-filtration chromatography. Protein FA consists of a single polypeptide of molecular mass 22 kDa and is monomeric in solution. N-terminal amino acid sequencing confirmed that protein FA is a product of the first gene at the mob locus. The purified protein FA was required in stoichiometric rather than catalytic amounts in the process that leads to the activation of the precursor of the molybdoenzyme nitrate reductase, which is consistent with the requirement of a further component in the activation.
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PMID:Isolation of protein FA, a product of the mob locus required for molybdenum cofactor biosynthesis in Escherichia coli. 802 May 7

The opportunistic pathogen Burkholderia pseudomallei is a saprophytic bacterium and the causative agent of melioidosis, an emerging infectious disease associated with high morbidity and mortality. Although melioidosis is most prevalent during the rainy season in endemic areas, domestic gardens and farms can also serve as a reservoir for B. pseudomallei during the dry season, in part due to irrigation and fertilizer use. In the environment, B. pseudomallei forms biofilms and persists in soil near plant root zones. Biofilms are dynamic bacterial communities whose formation is regulated by extracellular cues and corresponding changes in the nearly universal secondary messenger cyclic dimeric GMP. Recent studies suggest B. pseudomallei loads are increased by irrigation and the addition of nitrate-rich fertilizers, whereby such nutrient imbalances may be linked to the transmission epidemiology of this important pathogen. We hypothesized that exogenous nitrate inhibits B. pseudomallei biofilms by reducing the intracellular concentration of c-di-GMP. Bioinformatics analyses revealed B. pseudomallei 1026b has the coding capacity for nitrate sensing, metabolism, and transport distributed on both chromosomes. Using a sequence-defined library of B. pseudomallei 1026b transposon insertion mutants, we characterized the role of denitrification genes in biofilm formation in response to nitrate. Our results indicate that the denitrification pathway is implicated in B. pseudomallei biofilm growth dynamics and biofilm formation is inhibited by exogenous addition of sodium nitrate. Genomics analysis identified transposon insertional mutants in a predicted two-component system (narX/narL), a nitrate reductase (narGH), and a nitrate transporter (narK-1) required to sense nitrate and alter biofilm formation. Additionally, the results presented here show that exogenous nitrate reduces intracellular levels of the bacterial second messenger c-di-GMP. These results implicate the role of nitrate sensing in the regulation of a c-di-GMP phosphodiesterase and the corresponding effects on c-di-GMP levels and biofilm formation in B. pseudomallei 1026b.
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PMID:Nitrate Sensing and Metabolism Inhibit Biofilm Formation in the Opportunistic Pathogen Burkholderia pseudomallei by Reducing the Intracellular Concentration of c-di-GMP. 2879 Sep 83