Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The phototrophic bacterium Rhodobacter sphaeroides DSM 158 has a periplasmic nitrate reductase which is induced by nitrate and it is not repressed by ammonium or oxygen. In a Tn5 mutant lacking nitrate reductase activity, transposon insertion is localized in a 1.2 kb EcoRI fragment. A 0.6 kb BamHI-EcoRI segment of this region was used as a probe to isolate, from the wild-type strain, a 6.8 kb PstI fragment carrying the putative genes coding for the periplasmic nitrate reductase. In vivo protein expression and DNA sequence analysis reveal the presence in this region of three genes, napABC, probably organized in an operon. These genes are required for nitrate reduction, as deduced by mutational and complementation studies. The napA gene codes for a protein with a high homology to the periplasmic nitrate reductase from Alcaligenes eutrophus and, to a lesser extent, to other prokaryotic nitrate reductases and molybdenum-containing enzymes. The napB gene product has two haem c-binding sites and shows a high homology with the cytochrome c-type subunit of the periplasmic nitrate reductase from A. eutrophus. NAPA and NAPB proteins appear to be translated with signal peptides of 29 and 24 residues, respectively, indicating that mature proteins are located in the periplasm. The napC gene codes for a 25 kDa protein with a transmembrane sequence of 17 hydrophobic residues. NAPC has four haem c-binding sites and is homologous to the membrane-bound c-type cytochromes encoded by Pseudomonas stutzeri nirT and Escherichia coli torC genes. The phenotypes of defined insertion mutants constructed for each gene also indicate that periplasmic nitrate reductase from R. sphaeroides DSM 158 is a dimeric complex of a 90 kDa catalytic subunit (NAPA) and a 15 kDa cytochrome c (NAPB), which receives electrons from a membrane-anchored tetrahaem protein (NAPC), thus allowing electron flow between membrane and periplasm. This nitrate-reducing system differs from the assimilatory and respiratory bacterial nitrate reductases at the level of cellular localization, regulatory properties, biochemical characteristics and gene organization.
Mol Microbiol 1996 Mar
PMID:Isolation of periplasmic nitrate reductase genes from Rhodobacter sphaeroides DSM 158: structural and functional differences among prokaryotic nitrate reductases. 873 Aug 72

The Escherichia coli mob locus is required for synthesis of active molybdenum cofactor, molybdopterin guanine dinucleotide. The mobB gene is not essential for molybdenum cofactor biosynthesis because a deletion of both mob genes can be fully complemented by just mobA. Inactive nitrate reductase, purified from a mob strain, can be activated in vitro by incubation with protein FA (the mobA gene product), GTP, MgCl2, and a further protein fraction, factor X. Factor X activity is present in strains that lack MobB, indicating that it is not an essential component of factor X, but over-expression of MobB increases the level of factor X. MobB, therefore, can participate in nitrate reductase activation. The narJ protein is not a component of mature nitrate reductase but narJ mutants cannot express active nitrate reductase A. Extracts from narJ strains are unable to support the in vitro activation of purified mob nitrate reductase: they lack factor X activity. Although the mob gene products are necessary for the biosynthesis of all E. coli molybdoenzymes as a result of their requirement for molybdopterin guanine dinucleotide, NarJ action is specific for nitrate reductase A. The inactive nitrate reductase A derivative in a narJ strain can be activated in vitro following incubation with cell extracts containing the narJ protein. NarJ acts to activate nitrate reductase after molybdenum cofactor biosynthesis is complete.
Mol Microbiol 1996 May
PMID:Involvement of the narJ and mob gene products in distinct steps in the biosynthesis of the molybdoenzyme nitrate reductase in Escherichia coli. 879 83

The objectives of this study were to find additional diagnostic information for the evaluation of xanthine dehydrogenase deficiency and molybdenum cofactor deficiency. Patients were given an oral loading test with 10 mg/kg 5,6,7,8-tetrahydrobiopterin. Urine excretion of pterin and isoxanthopterin was measured by HPLC. Control subjects had a fairly constant ratio of urinary pterin/isoxanthopterin before (0.57-5.32) and after (0.55-4.55) 5,6,7,8-tetrahydrobiopterin loading. These ratios were increased to 33 and 22 in a patient with hereditary xanthinuria and to 570 and 8030 in a patient with molybdenum cofactor deficiency. Obligate heterozygotes had an entirely normal test result. Evidence was obtained for the in vivo involvement of xanthine dehydrogenase in the conversion of pterin to isoxanthopterin. This test could be a sensitive marker for the establishment of residual enzyme activity.
Biochem Mol Med 1996 Aug
PMID:Tetrahydrobiopterin loading test in xanthine dehydrogenase and molybdenum cofactor deficiencies. 881 40

The periplasmic dimethyl sulfoxide reductase (DMSOR) from the photosynthetic purple bacterium Rhodobacter capsulatus functions as the terminal electron acceptor in its respiratory chain. The enzyme catalyzes the reduction of highly oxidized substrates like dimethyl sulfoxide to dimethyl sulfide. At a molybdenum redox center, two single electrons are transferred from cytochrome C556 to the substrate dimethyl sulfoxide, generating dimethyl sulfide and (with two protons) water. The enzyme was purified and crystallized in space group P4(1)2(1)2 with unit cell dimensions of a = b = 80.7 A and c = 229.2 A. The crystals diffract beyond 1.8 A with synchrotron radiation. The three-dimensional structure was solved by a combination of multiple isomorphous replacement and molecular replacement techniques. The atomic model was refined to an R-factor of 0.169 for 57,394 independent reflections. The spherical protein consists of four domains with a funnel-like cavity that leads to the freely accessible metal-ion redox center. The bis(molybdopterin guanine dinucleotide) molybdenum cofactor (1541 Da) of the single chain protein (85,033 Da) has the molybdenum ion bound to the cis-dithiolene group of only one molybdopterin guanine dinucleotide molecule. Three additional ligands, two oxo groups and the oxygen of a serine side-chain, are bound to the molybdenum ion. The second molybdopterin system is not part of the ligand sphere of the metal center with its sulfur atoms at distances of 3.5 A and 3.8 A away. It might be involved in electron shuttling from the protein surface to the molybdenum center.
J Mol Biol 1996 Oct 18
PMID:Crystal structure of dimethyl sulfoxide reductase from Rhodobacter capsulatus at 1.88 A resolution. 889 Sep 12

When used alone, both vanadate and hydrogen peroxide (H2O2) are weakly insulin-mimetic, while in combination they are strongly synergistic due to the formation of aqueous peroxovanadium species pV(aq). Administration of these pV(aq) species leads to activation of the insulin receptor tyrosine kinase (IRK), autophosphorylation at tyrosine residues and inhibition of phosphotyrosine phosphatases (PTPs). We therefore undertook to synthesize a series of peroxovanadium (pV) compounds containing one or two peroxo anions, an oxo anion and an ancillary ligand in the inner co-ordination sphere of vanadium, whose properties and insulin-mimetic potencies could be assessed. These pV compounds were shown to be the most potent inhibitors of PTPs yet described. Their PTP inhibitory potency correlated with their capacity to stimulate IRK activity. Some pV compounds showed much greater potency as inhibitors of insulin receptor (IR) dephosphorylation than epidermal growth factor receptor (EGFR) dephosphorylation, implying relative specificity as PTP inhibitors. Replacement of vanadium with either molybdenum or tungsten resulted in equally potent inhibition of IR dephosphorylation. However IRK activation was reduced by greater than 80% suggesting that these compounds did not access intracellular PTPs. The insulin-like activity of these pV compounds were demonstrable in vivo. Intra venous (i.v.) administration of bpV(pic) and bpV(phen) resulted in the lowering of plasma glucose concentrations in normal rats in a dose dependent manner. The greater potency of bpV(pic) compared to bpV(phen) was explicable, in part, by the capacity of the former but not the latter to act on skeletal muscle as well as liver. Finally administration of bpV(phen) and insulin led to a synergism, where tyrosine phosphorylation of the IR beta-subunit increased by 20-fold and led to the appearance of four insulin-dependent in vivo substrates. The insulin-mimetic properties of the pV compounds raises the possibility for their use as insulin replacements in the management of diabetes mellitus.
Mol Cell Biochem
PMID:Peroxovanadium compounds: biological actions and mechanism of insulin-mimesis. 892 47

The genome of Methanopyrus kandleri was found to harbour a gene, fwuB, predicted to encode the catalytic subunit of a tungsten formylmethanofuran dehydrogenase with an active site selenocysteine, and a second gene, fwcB, encoding a tungsten formylmethanofuran dehydrogenase with an active site cysteine. Northern blot and primer-extension analysis revealed that both genes were differentially transcribed. During growth of the methanogen on medium supplemented with selenium only fwuB was transcribed, whereas transcription of both fwuB and fwcB was observed on selenium-deprived medium. Growth of M. kandleri was stimulated by tungstate and selenite but not by molybdate. The findings indicate that the hyperthermophilic archaeon contains two tungsten isoenzymes of formylmethanofuran dehydrogenase, one of which is a novel selenium enzyme. They also indicate that the hyperthermophilic methanogen probably does not contain a molybdenum formylmethanofuran dehydrogenase which appears to be present only in thermophilic and mesophilic methanogens.
Mol Microbiol 1997 Mar
PMID:A selenium-dependent and a selenium-independent formylmethanofuran dehydrogenase and their transcriptional regulation in the hyperthermophilic Methanopyrus kandleri. 907 39

By the use of the universal EPR simulation program created by the author, spin S = 3/2 and S = 5/2 systems are studied and their simulated EPR spectra at high frequencies (Q-band for 35 GHz and W-band for 95 GHz) are presented here. The mononuclear Fe3+ in rubredoxin, isolated from Pseudomonas oleovorans (which is an S = 5/2 system with D = 1.76 cm-1 and E/D = 0.28), is extensively studied by EPR spectrum simulation at the Q-band, W-band, and "Z"-band. The molybdenum- and iron-containing protein (MoFe protein), which has g values at g = 4.32, 3.65, and 2.01 (S = 3/2, D = 6.0 cm-1, and E/D = 0.055) at the X-band, is also studied by EPR spectrum simulation at high frequencies.
J Mol Graph 1996 Dec
PMID:Prediction of high-frequency electron paramagnetic resonance spectra of spin S = 3/2, 5/2 systems. 919 86

A number of Tn5 mutants were isolated which were unable to fix nitrogen and showed enhanced ammonium repression of the nitrate/nitrite assimilation genes. They also had reduced nitrate reductase activity under fully inducing conditions. Insertions were localized within the nifB gene, and inability to fix nitrogen was shown to be due to disruption of the nifB gene. However, enhanced ammonium repression proved to be the result of constitutive expression of the downstream nifO gene from an 'out' promoter present in Tn5. Our results suggest that molybdenum metabolism might function as a regulatory factor that acts through the nitrate reductase.
Mol Gen Genet 1997 Jun
PMID:Ammonium repression of the nitrite-nitrate (nasAB) assimilatory operon of Azotobacter vinelandii is enhanced in mutants expressing the nifO gene at high levels. 923 74

Expression of the Escherichia coli dmsABC operon that encodes a molybdenum-containing DMSO/TMAO reductase is increased in response to anaerobiosis and repressed by nitrate. These changes are mediated by the transcription factors Fnr and NarL respectively. Interestingly, modC strains that are defective in molybdate uptake exhibit impaired anaerobic induction and no nitrate-dependent repression of the dmsABC operon. To determine if the molybdate-responsive transcription factor ModE is involved in this process, a set of dmsA-lacZ operon fusions were constructed and analysed. The pattern of dmsA-lacZ expression in response to anaerobiosis and nitrate addition was identical in both modC and modE strains, thus suggesting a regulatory role for ModE. In vitro studies confirmed that ModE bound the dmsA promoter at a high-affinity site typical of other E. coli ModE operator sites. Mutations in this site abolished ModE binding in vitro and displayed the same phenotype as a modE mutation. In contrast to previously characterized ModE operator sites, which either overlap or are located immediately upstream of the ModE-regulated promoter, the ModE site is centred 52.5 bp downstream of the major dmsA transcript start site. We identified a putative integration host factor (IHF) binding site in the intervening sequence, and in vitro studies confirmed that IHF bound this site with high affinity. Using himA mutants, we confirmed that IHF plays a role in the molybdate-dependent regulation of dmsA-lacZ expression in vivo. This study provides the first example in which ModE affects gene regulation in concert with another transcription factor.
Mol Microbiol 1998 Jan
PMID:Anaerobic regulation of the Escherichia coli dmsABC operon requires the molybdate-responsive regulator ModE. 946 67

The crystal structure of the molybdenum enzyme dimethylsulphoxide reductase (DMSOR) has been determined at 1.9 A resolution with substrate bound at the active site. DMSOR is an oxotransferase which catalyses the reduction of dimethylsulphoxide (DMSO) to dimethylsulphide (DMS) in a two stage reaction which is linked to oxygen atom transfer and electron transfer. In the first step, DMSO binds to reduced (Mo(IV)) enzyme, the enzyme is oxidised to Mo(VI) with an extra oxygen ligand and DMS is released. Regeneration of reduced enzyme is achieved by transfer of two electrons, successively from a specific cytochrome, and release of the oxygen as water. The enzyme, purified under aerobic conditions, is in the oxidised (Mo(VI)) state. Addition of a large excess of DMS to the oxidised enzyme in solution causes a change in the absorption spectrum of the enzyme. The same reaction occurs within crystals of the enzyme and the crystal structure reveals a complex with DMSO bound to the molybdenum via its oxygen atom. X-ray edge data indicate that the metal is in the Mo(IV) state. The DMSO ligand replaces one of the two oxo groups which ligate the oxidised form of the enzyme, suggesting very strongly that this is the oxygen which is transferred during catalysis. Residues 384 to 390, disordered in the oxidised enzyme, are now clearly seen in the cleft leading to the active site. The side-chain of Trp388 forms a lid trapping the substrate/product.
J Mol Biol 1998 Jan 30
PMID:The high resolution crystal structure of DMSO reductase in complex with DMSO. 946 35


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