51
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Yoshimatsu K, Sakurai T, Fujiwara T. Purification and characterization of dissimilatory nitrate reductase from a denitrifying halophilic archaeon, Haloarcula marismortui. FEBS Lett 2000; 470:216-20. [PMID: 10734237 DOI: 10.1016/s0014-5793(00)01321-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dissimilatory nitrate reductase was purified from a denitrifying halophilic archaeon, Haloarcula marismortui, to an electrophoretically homogeneous state. The purified enzyme was inferred to be a homotetramer composed of a 63 kDa polypeptide. The electron paramagnetic resonance spectrum of the purified enzyme revealed typical rhombic signals which were ascribed to Mo(V) in the Mo-molybdopterin complex. Like the bacterial membrane-bound (Nar-) enzyme, the purified enzyme supported the catalysis of chlorate. The enzyme was activated in extreme saline conditions and the values of k(cat) and K(m) toward nitrate were 145 s(-1) and 79 microM, respectively, in the presence of 2.0 M NaCl.
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Affiliation(s)
- K Yoshimatsu
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka, Japan
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52
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Hatton AD, Gibb SW. A technique for the determination of trimethylamine-N-oxide in natural waters and biological media. Anal Chem 1999; 71:4886-91. [PMID: 10565278 DOI: 10.1021/ac990366y] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Trimethylamine-N-oxide (TMAO) is a nitrogenous osmolyte widely distributed in marine organisms. The reduction of TMAO to TMA has long been implicated as characteristic reaction associated with fish and seafood spoilage. However, it is now apparent that, in the marine environment, TMAO can act as precursor to a range of reduced nitrogenous biogases that can play a significant role in the biogeochemical cycle of nitrogen and in the regulation of atmospheric pH. Although methods exist for the analysis of TMAO in some biological samples, they lack the sensitivity required for measurement of TMAO in natural waters. Here we present a new, safe and sensitive method for the determination of TMAO in aqueous and biological media, where TMAO is enzymatically reduced to TMA and subsequently quantified using Flow Injection Gas Diffusion-Ion Chromatography (Gibb et al. J. Autom. Chem. 1995, 17 (6), 205-212). The limit of detection was calculated to be 1.35 nmol dm-3 TMAO, and the response was linear for both fresh and seawater (R2 = 0.996 and 0.993, respectively). Precision (RSD) for standards in the range 40-600 nmol dm-3 was within 3%. The specificity and competitive inhibition of the enzyme are addressed and the applicability of the technique demonstrated through analysis of a number of natural water and biological samples.
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Affiliation(s)
- A D Hatton
- School of Environmental Sciences, University of East Anglia, Norwich, U.K
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53
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Wei Y, Miller CG. Characterization of a group of anaerobically induced, fnr-dependent genes of Salmonella typhimurium. J Bacteriol 1999; 181:6092-7. [PMID: 10498722 PMCID: PMC103637 DOI: 10.1128/jb.181.19.6092-6097.1999] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously reported the isolation of a group of anaerobically regulated, fnr-dependent lac fusions in Salmonella typhimurium and have grouped these oxd genes into classes based on map position. In order to identify these genes, we have replaced the original Mud-lac fusion in a member of each oxd class with the much smaller Mud-cam element, cloned the fusion, and determined DNA sequence sufficient to define the oxd gene. Several of the fusions correspond to previously known genes from S. typhimurium or Escherichia coli: oxd-4 = cbiA and oxd-11 = cbiK, oxd-5 = hybB, oxd-7 = dcuB, oxd-8 = moaB, oxd-12 = dmsA, and oxd-14 = napB (aeg-46. 5). Two other fusions correspond to previously unknown loci: oxd-2 encodes an acetate/propionate kinase, and oxd-6 encodes a putative ABC transporter present in S. typhimurium but not in E. coli.
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Affiliation(s)
- Y Wei
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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54
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Oremland RS, Blum JS, Bindi AB, Dowdle PR, Herbel M, Stolz JF. Simultaneous reduction of nitrate and selenate by cell suspensions of selenium-respiring bacteria. Appl Environ Microbiol 1999; 65:4385-92. [PMID: 10508064 PMCID: PMC91582 DOI: 10.1128/aem.65.10.4385-4392.1999] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Washed-cell suspensions of Sulfurospirillum barnesii reduced selenate [Se(VI)] when cells were cultured with nitrate, thiosulfate, arsenate, or fumarate as the electron acceptor. When the concentration of the electron donor was limiting, Se(VI) reduction in whole cells was approximately fourfold greater in Se(VI)-grown cells than was observed in nitrate-grown cells; correspondingly, nitrate reduction was approximately 11-fold higher in nitrate-grown cells than in Se(VI)-grown cells. However, a simultaneous reduction of nitrate and Se(VI) was observed in both cases. At nonlimiting electron donor concentrations, nitrate-grown cells suspended with equimolar nitrate and selenate achieved a complete reductive removal of nitrogen and selenium oxyanions, with the bulk of nitrate reduction preceding that of selenate reduction. Chloramphenicol did not inhibit these reductions. The Se(VI)-respiring haloalkaliphile Bacillus arsenicoselenatis gave similar results, but its Se(VI) reductase was not constitutive in nitrate-grown cells. No reduction of Se(VI) was noted for Bacillus selenitireducens, which respires selenite. The results of kinetic experiments with cell membrane preparations of S. barnesii suggest the presence of constitutive selenate and nitrate reduction, as well as an inducible, high-affinity nitrate reductase in nitrate-grown cells which also has a low affinity for selenate. The simultaneous reduction of micromolar Se(VI) in the presence of millimolar nitrate indicates that these organisms may have a functional use in bioremediating nitrate-rich, seleniferous agricultural wastewaters. Results with (75)Se-selenate tracer show that these organisms can lower ambient Se(VI) concentrations to levels in compliance with new regulations proposed for release of selenium oxyanions into the environment.
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Affiliation(s)
- R S Oremland
- U.S. Geological Survey, Menlo Park, California 94025, USA.
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55
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Rhee SK, Fuchs G. Phenylacetyl-CoA:acceptor oxidoreductase, a membrane-bound molybdenum-iron-sulfur enzyme involved in anaerobic metabolism of phenylalanine in the denitrifying bacterium Thauera aromatica. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 262:507-15. [PMID: 10336636 DOI: 10.1046/j.1432-1327.1999.00399.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Phenylacetic acids are common intermediates in the microbial metabolism of various aromatic substrates including phenylalanine. In the denitrifying bacterium Thauera aromatica phenylacetate is oxidized, under anoxic conditions, to the common intermediate benzoyl-CoA via the intermediates phenylacetyl-CoA and phenylglyoxylate (benzoylformate). The enzyme that catalyzes the four-electron oxidation of phenylacetyl-CoA has been purified from this bacterium and studied. The enzyme preparation catalyzes the reaction phenylacetyl-CoA + 2 quinone + 2 H2O --> phenylglyoxylate + 2 quinone H2 + CoASH. Phenylacetyl-CoA:acceptor oxidoreductase is a membrane-bound molybdenum-iron-sulfur protein. The purest preparations contained three subunits of 93, 27, and 26 kDa. Ubiquinone is most likely to act as the electron acceptor, and the oxygen atom introduced into the product is derived from water. The protein preparations contained 0.66 mol Mo, 30 mol Fe, and 25 mol acid-labile sulfur per mol of native enzyme, assuming a native molecular mass of 280 kDa. Phenylglyoxylyl-CoA, but not mandelyl-CoA, was observed as a free intermediate. All enzyme preparations also catalyzed the subsequent hydrolytic release of coenzyme A from phenylglyoxylyl-CoA but not from phenylacetyl-CoA. The enzyme is reversibly inactivated by a low concentration of cyanide, but is remarkably stable with respect to oxygen. This new member of the molybdoproteins represents the first example of an enzyme which catalyzes the alpha-oxidation of a CoA-activated carboxylic acid without utilizing molecular oxygen.
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Affiliation(s)
- S K Rhee
- Mikrobiologie, Institut Biologie II, Universität Freiburg, Germany
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56
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Hilton JC, Temple CA, Rajagopalan KV. Re-design of Rhodobacter sphaeroides dimethyl sulfoxide reductase. Enhancement of adenosine N1-oxide reductase activity. J Biol Chem 1999; 274:8428-36. [PMID: 10085074 DOI: 10.1074/jbc.274.13.8428] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The periplasmic DMSO reductase from Rhodobacter sphaeroides f. sp. denitrificans has been expressed in Escherichia coli BL21(DE3) cells in its mature form and with the R. sphaeroides or E. coli N-terminal signal sequence. Whereas the R. sphaeroides signal sequence prevents formation of active enzyme, addition of a 6x His-tag at the N terminus of the mature peptide maximizes production of active enzyme and allows for affinity purification. The recombinant protein contains 1.7-1.9 guanines and greater than 0.7 molybdenum atoms per molecule and has a DMSO reductase activity of 3.4-3.7 units/nmol molybdenum, compared with 3.7 units/nmol molybdenum for enzyme purified from R. sphaeroides. The recombinant enzyme differs from the native enzyme in its color and spectrum but is indistinguishable from the native protein after redox cycling with reduced methyl viologen and Me2SO. Substitution of Cys for the molybdenum-ligating Ser-147 produced a protein with DMSO reductase activity of 1.4-1.5 units/nmol molybdenum. The mutant protein differs from wild type in its color and absorption spectrum in both the oxidized and reduced states. This substitution leads to losses of 61-99% of activity toward five substrates, but the adenosine N1-oxide reductase activity increases by over 400%.
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Affiliation(s)
- J C Hilton
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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57
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Zhao Z, Weiner JH. Interaction of 2-n-heptyl-4-hydroxyquinoline-N-oxide with dimethyl sulfoxide reductase of Escherichia coli. J Biol Chem 1998; 273:20758-63. [PMID: 9694819 DOI: 10.1074/jbc.273.33.20758] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have studied the interaction of the menaquinol analog 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) with dimethyl sulfoxide reductase (DmsABC) and the effect of a mutation in the DmsC subunit (DmsABCH65R) using fluorescence titration and stopped-flow methods. The titration data show that the HOQNO fluorescence is quenched when HOQNO binds to DmsABC. The binding stoichiometry is determined to be about 1:1. The mutant DmsABCH65R blocks HOQNO binding to the protein. It is therefore proposed that there is one high-affinity HOQNO binding site per DmsABC molecule located in the DmsC subunit. Stopped-flow kinetic studies show that the interaction can be described by a two-step equilibrium model, a fast bimolecular step followed by a slow unimolecular step. The quenching of HOQNO fluorescence occurs in the bimolecular step. The rates for the forward and reverse reaction of the first equilibrium are determined to be k1 = (3.9 +/- 0.3) x 10(5) M-1 s-1 and k2 = 0. 10 +/- 0.01 s-1, respectively. The dissociation constant for the first equilibrium, Kd1 = k2/k1, is calculated to be about 260 nM. The upper limit of the overall dissociation constant is estimated to be 6 nM.
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Affiliation(s)
- Z Zhao
- Department of Biochemistry and the Medical Research Council Group in the Molecular Biology of Membranes, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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58
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Hanlon SP, Graham DL, Hogan PJ, Holt RA, Reeve CD, Shaw AL, McEwan AG. Asymmetric reduction of racemic sulfoxides by dimethyl sulfoxide reductases from Rhodobacter capsulatus, Escherichia coli and Proteus species. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 8):2247-2253. [PMID: 9720047 DOI: 10.1099/00221287-144-8-2247] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The enantioselective reduction of racemic sulfoxides by dimethyl sulfoxide reductases from Rhodobacter capsulatus, Escherichia coli, Proteus mirabilis and Proteus vulgaris was investigated. Purified dimethyl sulfoxide reductase from Rhodobacter capsulatus catalysed the selective removal of (S)-methyl p-tolyl sulfoxide from a racemic mixture of methyl p-tolyl sulfoxide and resulted in an 88% recovery of enantiomerically pure (R)-methyl p-tolyl sulfoxide. Rhodobacter capsulatus was shown to be able to grow photoheterotrophically in the presence of certain chiral sulfoxides under conditions where a sulfoxide is needed as an electron sink. Whole cells of Rhodobacter capsulatus were shown to catalyse the enantioselective reduction of methyl p-tolyl sulfoxide, ethyl 2-pyridyl sulfoxide, methylthiomethyl methyl sulfoxide and methoxymethyl phenyl sulfoxide. Similarly, whole cells of Escherichia coli, Proteus mirabilis and Proteus vulgaris reduced these sulfoxides but with opposite enantioselectivity.
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Affiliation(s)
- Steven P Hanlon
- School of Biological Sciences, University of East AngliaNorwich NR4 7TJUK
| | - Daniel L Graham
- Zeneca LifeScience MoleculesBelasis Avenue, Billingham, Cleveland TS23 1YNUK
| | - Philip J Hogan
- Zeneca PharmaceuticalsMacclesfield, Cheshire, SK10 2NAUK
| | - Robert A Holt
- Zeneca LifeScience MoleculesBelasis Avenue, Billingham, Cleveland TS23 1YNUK
| | - Christopher D Reeve
- Zeneca LifeScience MoleculesBelasis Avenue, Billingham, Cleveland TS23 1YNUK
| | - Anthony L Shaw
- Department of Microbiology, The University of QueenslandBrisbane 4072Australia
| | - Alastair G McEwan
- Department of Microbiology, The University of QueenslandBrisbane 4072Australia
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59
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Rothery RA, Chatterjee I, Kiema G, McDermott MT, Weiner JH. Hydroxylated naphthoquinones as substrates for Escherichia coli anaerobic reductases. Biochem J 1998; 332 ( Pt 1):35-41. [PMID: 9576848 PMCID: PMC1219448 DOI: 10.1042/bj3320035] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have used two hydroxylated naphthoquinol menaquinol analogues, reduced plumbagin (PBH2, 5-hydroxy-2-methyl-1,4-naphthoquinol) and reduced lapachol [LPCH2, 2-hydroxy-3-(3-methyl-2-butenyl)-1, 4-naphthoquinol], as substrates for Escherichia coli anaerobic reductases. These compounds have optical, solubility and redox properties that make them suitable for use in studies of the enzymology of menaquinol oxidation. Oxidized plumbagin and oxidized lapachol have well resolved absorbances at 419 nm (epsilon=3.95 mM-1. cm-1) and 481 nm (epsilon=2.66 mM-1.cm-1) respectively (in Mops/KOH buffer, pH 7.0). PBH2 is a good substrate for nitrate reductase A (Km=282+/-28 microM, kcat=120+/-6 s-1) and fumarate reductase (Km=155+/-24 microM, kcat=30+/-2 s-1), but not for DMSO reductase. LPCH2 is a good substrate for nitrate reductase A (Km=57+/-35 microM, kcat=68+/-13 s-1), fumarate reductase (Km=85+/-27 microM, kcat=74+/-6 s-1) and DMSO reductase (Km=238+/-30 microM, kcat=191+/-21 s-1). The sensitivity of enzymic LPCH2 and PBH2 oxidation to 2-n-heptyl-4-hydroxyquinoline N-oxide inhibition is consistent with their oxidation occurring at sites of physiological quinol binding.
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Affiliation(s)
- R A Rothery
- Department of Biochemistry and the Medical Research Council Group in the Molecular Biology of Membranes, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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60
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Abaibou H, Giordano G, Mandrand-Berthelot MA. Suppression of Escherichia coli formate hydrogenlyase activity by trimethylamine N-oxide is due to drainage of the inducer formate. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 8):2657-2664. [PMID: 9274019 DOI: 10.1099/00221287-143-8-2657] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of the addition of trimethylamine N-oxide (TMAO) in the growth medium on Escherichia coli anaerobic fermentative and respiratory pathways was examined. Formate dehydrogenase H (FDH-H) activity was totally repressed by the addition of 40 mM TMAO, whereas the overall hydrogenase (HYD) activity was reduced by 25%. Accordingly, expression of lacZ operon fusions with the fdhF and hycB structural genes specifying FDH-H and HYD3 was reduced sevenfold and eightfold, respectively, leading to suppression of an active formate hydrogenlyase system. In contrast, global respiratory formate-dependent phenazine methosulphate reductase (FDH-PMS) activity, which consists of both the major anaerobic FDH-N enzyme and the aerobic FDH-Z isoenzyme, was increased approximately twofold. This was corroborated by a 2.5-fold stimulation of the sole fdoG-uidA transcriptional fusion which reflects the synthesis of the respiratory aerobic FDH-Z enzyme. In fdhD, fdhE or torA mutants lacking either FDH-PMS activity or TMAO reductase (TOR) activity, the formate hydrogenlyase pathway was no longer inhibited by TMAO. In addition, introduction of 30 mM formate in the growth medium was found to relieve the repressive effect of TMAO in the wild-type strain. When TMAO was added as terminal electron acceptor a significant enhancement of anaerobic growth was observed with the wild-type strain and the fdoG mutant. It was associated with the concomitant suppression of the formate hydrogenlyase enzymes. This was in contrast to the fdnG and torA mutants whose growth pattern and fermentative enzymes remained unaffected. Taken together, these results strongly suggest that formate-dependent reduction of TMAO via FDH-N and TOR reduces the amount of formate available for induction of the formate hydrogenlyase pathway.
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Affiliation(s)
- Hafid Abaibou
- Laboratoire de Génétique Moléculaire des Micro-organismes et des Interactions Cellulaires CNRS UMR 5577, Institut National des Sciences Appliquées, 20 avenue A. Einstein, 69621 Villeurbanne Cedex, France
| | - Gérard Giordano
- Laboratoire de Chimie Bactérienne, CNRS UPR 9043, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Marie-Andrée Mandrand-Berthelot
- Laboratoire de Génétique Moléculaire des Micro-organismes et des Interactions Cellulaires CNRS UMR 5577, Institut National des Sciences Appliquées, 20 avenue A. Einstein, 69621 Villeurbanne Cedex, France
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61
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Affiliation(s)
- Russ Hille
- Department of Medical Biochemistry, The Ohio State University, Columbus, Ohio 43210-1218
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62
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Bogachev AV, Murtazina RA, Skulachev VP. H+/e- stoichiometry for NADH dehydrogenase I and dimethyl sulfoxide reductase in anaerobically grown Escherichia coli cells. J Bacteriol 1996; 178:6233-7. [PMID: 8892824 PMCID: PMC178495 DOI: 10.1128/jb.178.21.6233-6237.1996] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Anaerobically grown Escherichia coli cells were shown to acidify the reaction medium in response to oxygen or dimethyl sulfoxide (DMSO) pulses, with the H+/e- stoichiometry being close to 2.5 and 1.5, respectively. In the presence of the NADH dehydrogenase I (NDH-I) inhibitor 8-methyl-N-vanillyl-6-nonenamide (capsaicin) or in mutants lacking NDH-I, this ratio decreased to 1 for O2 and to 0 for DMSO. These data suggest that (i) the H+/e- stoichiometry for E. coli NDH-I is at least 1.5 and (ii) the DMSO reductase does not generate a proton motive force.
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Affiliation(s)
- A V Bogachev
- Department of Bioenergetics, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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63
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Trieber CA, Rothery RA, Weiner JH. Consequences of removal of a molybdenum ligand (DmsA-Ser-176) of Escherichia coli dimethyl sulfoxide reductase. J Biol Chem 1996; 271:27339-45. [PMID: 8910310 DOI: 10.1074/jbc.271.44.27339] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have used site-directed mutagenesis and EPR spectroscopy to examine the consequences of altering the molybdenum ligand in Escherichia coli dimethyl sulfoxide (Me2SO) reductase (DmsABC). Mutagenesis of DmsA-Ser-176 to Ala, Cys, or His abolishes both respiratory growth on Me2SO and in vitro benzyl viologen:Me2SO oxidoreductase activity. EPR spectroscopy reveals changes in the line shape and the gav of the Mo(V) signals of the S176A and S176C enzymes. The midpoint potentials (Em,7) of the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) couples in DmsABC are -15 and -175 mV. The Em,7 of the Mo(V)/Mo(IV) couple in the S176A mutant is 35 mV; however, the Mo(V) species could not be further oxidized with ferricyanide. Titration of the S176C mutant produced several overlapping Mo(V) species occurring at Eh > -150 mV, suggesting heterogeneity in the molybdenum environment. A Mo(V) spectrum was not visible in S176H membranes poised between -435 to 350 mV or oxidized with 200 microM ferricyanide. No differences were detected in the EPR spectra of the reduced [4Fe-4S] clusters of DmsABC and the S176A and S176H mutant enzymes; however, the S176C mutation altered the EPR line shape of one of the reduced [4Fe-4S] clusters.
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Affiliation(s)
- C A Trieber
- Department of Biochemistry and the Medical Research Council Group in the Molecular Biology of Membranes, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
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64
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Iobbi-Nivol C, Pommier J, Simala-Grant J, Méjean V, Giordano G. High substrate specificity and induction characteristics of trimethylamine-N-oxide reductase of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1294:77-82. [PMID: 8639717 DOI: 10.1016/0167-4838(95)00271-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using a wide variety of N- and S-oxide compounds we have shown by kinetic analysis that only two N-oxides, trimethylamine-N-oxide and 4-methylmorpholine-N-oxide, can be considered good substrates for trimethylamine-N-oxide (TMAO) reductase on the basis of their kcat/Km ratio. This result demonstrates that TMAO reductase possesses a high substrate specificity. Induction of the torCAD operon using the same S- and N-oxide compounds was also analyzed. We demonstrate that there is no correlation between the ability for a compound to be reduced by TMAO reductase and to induce TMAO reductase synthesis.
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Affiliation(s)
- C Iobbi-Nivol
- Laboratoire de Chimie Bactérienne, Institut Fédératif Biologie Structurale et Microbiologie, Marseille, France
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65
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Rothery RA, Weiner JH. Interaction of an engineered [3Fe-4S] cluster with a menaquinol binding site of Escherichia coli DMSO reductase. Biochemistry 1996; 35:3247-57. [PMID: 8605160 DOI: 10.1021/bi951584y] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have characterized by EPR the interaction of the Em,7 = -50 mV [4Fe-4S] cluster of Escherichia coli DMSO reductase (DmsABC) with a menaquinol (MQH2) binding site. Potentiometric titrations indicate that in DmsAB(C102S)C, the Em,7 = -50 mV [4Fe-4S] cluster is replaced by an Em,7 = +260 mV [3Fe-4S] cluster. The Q-pool coupling assay in combination with the MQH2 analog HOQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) was used to examine the effect of the DmsB(Cl02S) mutation on physiological electron transfer through DmsABC. Forward electron transfer through the mutant (MQH2 to DmsA) is blocked in the Q-pool coupling assay, but reverse electron transfer (DmsA to MQ) is not. HOQNO elicits a significant change in the EPR line shape of the oxidized DmsAB(Cl02S)C [3Fe-4S] cluster but has no effect on the line shape of the reduced [4Fe-4S] clusters. We have identified a residue in DmsC involved in MQH2 oxidation. DmsC(H65), and in a double mutant, DmsAB(C102S)C(H65R), the DmsC mutation blocks the HOQNO effect on the [3Fe-4S] EPR line shape, suggesting, that the DmsC(H65R) mutation either blocks HOQNO binding or blocks a conformational link between a HOQNO binding site and the DmsB(C102S) [3Fe-4S] cluster. These results suggest that the MQH2 binding site of DmsC is conformationally and functionally linked to the Em,7 = -50 mV [4Fe-4S] cluster of DmsB.
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Affiliation(s)
- R A Rothery
- MRC Group in the molecular Biology of Membranes, Department of Biochemistry, Edmonton, Alberta, Canada
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66
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Ueyama N, Oku H, Kondo M, Okamura TA, Yoshinaga N, Nakamura A. Trans Influence of Oxo and Dithiolene Coordination in Oxidized Models of Molybdenum Oxidoreductase: Synthesis, Structures, and Properties of Q2[MoVIO2(1,2-benzenedithiolato)2] (Q = NEt4, PPh4) and Related Complexes. Inorg Chem 1996. [DOI: 10.1021/ic950204u] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Norikazu Ueyama
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan
| | - Hiroyuki Oku
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan
| | - Mitsuru Kondo
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan
| | - Taka-aki Okamura
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan
| | - Naoto Yoshinaga
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan
| | - Akira Nakamura
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan
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67
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Lee SC, Renwick AG. Sulphoxide reduction by rat intestinal flora and by Escherichia coli in vitro. Biochem Pharmacol 1995; 49:1567-76. [PMID: 7786297 DOI: 10.1016/0006-2952(95)00093-f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The caecal microflora from female rats show a greater ability to reduce the sulphoxide group of sulindac than either the liver or kidneys. Studies on sulphoxide reduction by Escherichia coli showed that NADH, NADPH and dithiothreitol (DTT), but not acetaldehyde could act as cofactors. The cytosolic fraction was responsible for about 90%, 80% and 60% of the total reducing activity with sulindac, diphenyl sulphoxide and sulphinpyrazone, respectively. The main NADPH linked activity in the E. coli cytosol was dependent on thioredoxin, since the activity was essentially abolished by passing through a G50 column or by the addition of anti-thioredoxin anti-serum. Partial purification and separation of sulphoxide reducing activity by DEAE-cellulose chromatography separated two main protein bands, each of which possessed sulindac reducing activity. The importance of thioredoxin for much of the NADPH dependent activity was confirmed but the eluate fractions also showed the presence of other activities with NADH, NADPH and DTT that were independent of thioredoxin. Incubation of the DEAE-cellulose eluate fractions with flosequinan and sulphinpyrazone showed that the reducing activity in the two main protein peaks showed different substrate specificities and that there were multiple sulphoxide reductase systems present in E. coli cytosol.
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Affiliation(s)
- S C Lee
- University of Southampton, U.K
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68
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Heinzinger NK, Fujimoto SY, Clark MA, Moreno MS, Barrett EL. Sequence analysis of the phs operon in Salmonella typhimurium and the contribution of thiosulfate reduction to anaerobic energy metabolism. J Bacteriol 1995; 177:2813-20. [PMID: 7751291 PMCID: PMC176953 DOI: 10.1128/jb.177.10.2813-2820.1995] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The phs chromosomal locus of Salmonella typhimurium is essential for the dissimilatory anaerobic reduction of thiosulfate to hydrogen sulfide. Sequence analysis of the phs region revealed a functional operon with three open reading frames, designated phsA, phsB, and phsC, which encode peptides of 82.7, 21.3, and 28.5 kDa, respectively. The predicted products of phsA and phsB exhibited significant homology with the catalytic and electron transfer subunits of several other anaerobic molybdoprotein oxidoreductases, including Escherichia coli dimethyl sulfoxide reductase, nitrate reductase, and formate dehydrogenase. Simultaneous comparison of PhsA to seven homologous molybdoproteins revealed numerous similarities among all eight throughout the entire frame, hence, significant amino acid conservation among molybdoprotein oxidoreductases. Comparison of PhsB to six other homologous sequences revealed four highly conserved iron-sulfur clusters. The predicted phsC product was highly hydrophobic and similar in size to the hydrophobic subunits of the molybdoprotein oxidoreductases containing subunits homologous to phsA and phsB. Thus, phsABC appears to encode thiosulfate reductase. Single-copy phs-lac translational fusions required both anaerobiosis and thiosulfate for full expression, whereas multicopy phs-lac translational fusions responded to either thiosulfate or anaerobiosis, suggesting that oxygen and thiosulfate control of phs involves negative regulation. A possible role for thiosulfate reduction in anaerobic respiration was examined. Thiosulfate did not significantly augment the final densities of anaerobic cultures grown on any of the 18 carbon sources tested. on the other hand, washed stationary-phase cells depleted of ATP were shown to synthesize small amounts of ATP on the addition of the formate and thiosulfate, suggesting that the thiosulfate reduction plays a unique role in anaerobic energy conservation by S typhimurium.
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Affiliation(s)
- N K Heinzinger
- Department of Food Science and Technology, University of California, Davis 95616, USA
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69
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Rothery RA, Grant JL, Johnson JL, Rajagopalan KV, Weiner JH. Association of molybdopterin guanine dinucleotide with Escherichia coli dimethyl sulfoxide reductase: effect of tungstate and a mob mutation. J Bacteriol 1995; 177:2057-63. [PMID: 7721698 PMCID: PMC176849 DOI: 10.1128/jb.177.8.2057-2063.1995] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have identified the organic component of the molybdenum cofactor in Escherichia coli dimethyl sulfoxide reductase (DmsABC) to be molybdopterin (MPT) guanine dinucleotide (MGD) and have studied the effects of tungstate and a mob mutation on cofactor (Mo-MGD) insertion. Tungstate severely inhibits anaerobic growth of E. coli on a glycerol-dimethyl sulfoxide minimal medium, and this inhibition is partially overcome by overexpression of DmsABC. Isolation and characterization of an oxidized derivative of MGD (form A) from DmsABC overexpressed in cells grown in the presence of molybdate or tungstate indicate that tungstate inhibits insertion of Mo-MGD. No electron paramagnetic resonance evidence for the assembly of tungsten into DmsABC was found between Eh = -450 mV and Eh = +200 mV. The E. coli mob locus is responsible for the addition of a guanine nucleotide to molybdo-MPT (Mo-MPT) to form Mo-MGD. DmsABC does not bind Mo-MPT or Mo-MGD in a mob mutant, indicating that nucleotide addition must precede cofactor insertion. No electron paramagnetic resonance evidence for the assembly of molybdenum into DmsABC in a mob mutant was found between Eh = -450 mV and Eh = +200 mV. These data support a model for Mo-MGD biosynthesis and assembly into DmsABC in which both metal chelation and nucleotide addition to MPT precede cofactor insertion.
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Affiliation(s)
- R A Rothery
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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70
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Tseng CP, Hansen AK, Cotter P, Gunsalus RP. Effect of cell growth rate on expression of the anaerobic respiratory pathway operons frdABCD, dmsABC, and narGHJI of Escherichia coli. J Bacteriol 1994; 176:6599-605. [PMID: 7961411 PMCID: PMC197015 DOI: 10.1128/jb.176.21.6599-6605.1994] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The fumarate reductase (frdABCD), dimethyl sulfoxide (DMSO)-trimethylamine-N-oxide (TMAO) reductase (dmsABC), and nitrate reductase (narGHJI) operons in Escherichia coli encode enzymes involved in anaerobic respiration to the electron acceptors fumarate, DMSO or TMAO, and nitrate, respectively. They are regulated in response to anaerobiosis and nitrate availability. To determine how each operon is regulated in response to changes in cell growth rate and in oxygen availability, expression of frdA-lacZ, dmsA-lacZ, and narG-lacZ fusion genes was examined during continuous culture. After a change in the cell growth rate, each anaerobic electron transport pathway operon fusion responded somewhat differently. Whereas frdA-lacZ expression increased by fivefold as the growth rate decreased from 0.60 to 0.12/hour during aerobic growth, little change was seen under anaerobic conditions. In contrast, growth rate-dependent expression of narG-lacZ expression occurred under anaerobic conditions but not under aerobic conditions. Finally, dmsA-lacZ expression did not vary greatly for any of the growth rates tested. When cells were shifted from aerobic to anaerobic growth conditions, expression of each fusion increased at a moderate rate and peaked or "overshot" before reaching a new equilibrium value. This "overshoot" phenomenon was independent of the fnr gene product, which functions as a transcriptional activator of each respiratory operon during anaerobic conditions. In contrast to the moderate rate of anaerobic induction seen for narG-lacZ expression, the addition of nitrate caused a rapid induction response. The cell appears to have many ways to adjust cell respiration in response to changes in cell growth conditions.
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Affiliation(s)
- C P Tseng
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024
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71
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Lorenzen J, Steinwachs S, Unden G. DMSO respiration by the anaerobic rumen bacterium Wolinella succinogenes. Arch Microbiol 1994; 162:277-81. [PMID: 7802544 DOI: 10.1007/bf00301851] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The anaerobic rumen bacterium Wolinella succinogenes was able to grow by respiration with dimethylsulphoxide (DMSO) as electron acceptor and formate or H2 as electron donors. The growth yield amounted to 6.7 g and 6.4 g dry cells/mol DMSO with formate or H2 as the donors, respectively. This suggested an ATP yield of about 0.7 mol ATP/mol DMSO. Cell homogenates and the membrane fraction contained DMSO reductase activity with a high Km (43 mM) for DMSO. The electron transport from H2 to DMSO in the membranes was inhibited by 2-(heptyl)-4-hydroxyquinoline N-oxide, indicating the participation of menaquinone. Formation of DMSO reductase activity occurred only during growth on DMSO, presence of other electron acceptors (fumarate, nitrate, nitrite, N2O, and sulphur) repressed the DMSO reductase activity. DMSO can therefore be used by W. succinogenes as an acceptor for phosphorylative electron transport, but other electron acceptors are used preferentially.
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Affiliation(s)
- J Lorenzen
- Institut für Biochemie, Heinrich-Heine-Universität Düsseldorf, Germany
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72
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Kashiyama E, Yokoi T, Todaka T, Odomi M, Kamataki T. Chiral inversion of drug: role of intestinal bacteria in the stereoselective sulphoxide reduction of flosequinan. Biochem Pharmacol 1994; 48:237-43. [PMID: 8053920 DOI: 10.1016/0006-2952(94)90093-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Chiral inversion at a sulphoxide position of flosequinan enantiomers [(+/-)-7-fluoro-1-methyl-3-methylsulphinyl-4-quinolone] occurred in conventional rats but not in either germ-free rats or rats treated with antibiotics after an oral administration of each enantiomer. Thus, it was postulated that the chiral inversion occurred by mechanisms mediated by intestinal bacteria. The intestinal content isolated from conventional rats reduced R(+)- and S(-)-flosequinan to produce the sulphide, while intestinal content from rats treated with antibiotics did not reduce the drug. Several strains of facultative anaerobes possessed a high flosequinan reducing activity. Escherichia coli, Klebsiella oxytoca and Klebsiella pneumoniae reduced R(+)-flosequinan to the sulphide stereoselectively. On the other hand, Enterobacter aerogenes and Micrococcus agilis exclusively reduced S(-)-flosequinan. The sulphide, which could be produced by intestinal bacteria from R(+)- and S(-)-flosequinan, was readily absorbed upon an oral administration to rats, and was oxidized fairly rapidly to R(+)- and S(-)-flosequinan and further to the sulphone form. Based on these data, it has been confirmed that chiral inversion at the sulphoxide position of flosequinan enantiomers occur via stereoselective reduction of sulphoxide by intestinal bacteria to form the sulphide, followed by oxidation of the sulphide in the body to produce R(+)- and S(-)-flosequinan.
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Affiliation(s)
- E Kashiyama
- Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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73
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Gunsalus RP, Park SJ. Aerobic-anaerobic gene regulation in Escherichia coli: control by the ArcAB and Fnr regulons. Res Microbiol 1994; 145:437-50. [PMID: 7855430 DOI: 10.1016/0923-2508(94)90092-2] [Citation(s) in RCA: 160] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A variety of pathways for carbon and electron flow in the bacterium Escherichia coli and in other enteric bacteria are differentially expressed depending on whether molecular oxygen is present in the cell environment. This review briefly summarizes the metabolic pathways operative during aerobic versus anaerobic cell growth, and provides a regulatory overview for how the cell controls expression of the many genes involved in these processes. The cell has two distinctly different transcriptional regulators, consisting of the Fnr and the ArcA/ArcB regulatory proteins to accomplish this task. Together, they coordinate gene expression to adjust carbon flow with electron flow and energy generation so that cells can balance growth in an efficiently coupled manner.
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Affiliation(s)
- R P Gunsalus
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024
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74
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Méjean V, Iobbi-Nivol C, Lepelletier M, Giordano G, Chippaux M, Pascal MC. TMAO anaerobic respiration in Escherichia coli: involvement of the tor operon. Mol Microbiol 1994; 11:1169-79. [PMID: 8022286 DOI: 10.1111/j.1365-2958.1994.tb00393.x] [Citation(s) in RCA: 194] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The trimethylamine N-oxide (TMAO) respiratory system is subject to a strict positive control by the substrate. This property was exploited in the performance of miniMu replicon-mediated in vivo cloning of the promoter region of gene(s) positively regulated by TMAO. This region, located at 22 min on the chromosome, was shown to control the expression of a transcription unit composed of three open reading frames, designated torC, torA and torD, respectively. The presence of five putative c-type haem-binding sites within the TorC sequence, as well as the specific biochemical characterization, indicated that torC encodes a 43,300 Da c-type cytochrome. The second open reading frame, torA, was identified as the structural gene for TMAO reductase. A comparison of the predicted amino-terminal sequence of the torA gene product to that of the purified TMAO reductase indicated cleavage of a 39 amino acid signal peptide, which is in agreement with the periplasmic location of the enzyme. The predicted TorA protein contains the five molybdenum cofactor-binding motifs found in other molybdoproteins and displays extensive sequence homology with BisC and DmsA proteins. As expected, insertions in torA led to the loss of TMAO reductase. The 22,500 Da polypeptides encoded by the third open reading frame does not share any similarity with proteins listed in data banks.
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Affiliation(s)
- V Méjean
- Laboratoire de Chimie Bactérienne, CNRS, Marseille, France
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75
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Trieber C, Rothery R, Weiner J. Multiple pathways of electron transfer in dimethyl sulfoxide reductase of Escherichia coli. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37253-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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76
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Weiner J, Shaw G, Turner R, Trieber C. The topology of the anchor subunit of dimethyl sulfoxide reductase of Escherichia coli. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53684-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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77
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Gunsalus RP. Control of electron flow in Escherichia coli: coordinated transcription of respiratory pathway genes. J Bacteriol 1992; 174:7069-74. [PMID: 1331024 PMCID: PMC207394 DOI: 10.1128/jb.174.22.7069-7074.1992] [Citation(s) in RCA: 166] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- R P Gunsalus
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024
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78
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Weiner JH, Rothery RA, Sambasivarao D, Trieber CA. Molecular analysis of dimethylsulfoxide reductase: a complex iron-sulfur molybdoenzyme of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1102:1-18. [PMID: 1324728 DOI: 10.1016/0005-2728(92)90059-b] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J H Weiner
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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79
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Benson N, Farrar JA, McEwan AG, Thomson AJ. Detection of the optical bands of molybdenum(V) in DMSO reductase (Rhodobacter capsulatus) by low-temperature MCD spectroscopy. FEBS Lett 1992; 307:169-72. [PMID: 1644170 DOI: 10.1016/0014-5793(92)80760-e] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Dimethylsulphoxide (DMSO) reductase from R. capsulatus contains a molybdenum-pterin cofactor at its active site. As prepared the molybdenum is in the 6+ oxidation state, devoid of EPR signals. Stepwise reduction generates an EPR signal characteristic of Mo(V) having hyperfine coupling to a single proton and integrating to less than 25% of the total molybdenum. The low temperature MCD spectrum shows oppositely signed bands between approximately 550-700 nm. These bands are assigned as dithiolene-to-Mo(V) charge transitions. A simple theoretical model can satisfactorily account for the bands in the MCD spectrum. No evidence is found for cysteine coordination to Mo(V).
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Affiliation(s)
- N Benson
- Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences, University of East Anglia, Norwich, UK
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80
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Chiang RC, Cavicchioli R, Gunsalus RP. Identification and characterization of narQ, a second nitrate sensor for nitrate-dependent gene regulation in Escherichia coli. Mol Microbiol 1992; 6:1913-23. [PMID: 1508040 DOI: 10.1111/j.1365-2958.1992.tb01364.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In response to nitrate availability, Escherichia coli regulates the synthesis of a number of enzymes involved in anaerobic respiration and fermentation. When nitrate is present, nitrate reductase (narGHJI) gene expression is induced, while expression of the DMSO/TMAO reductase (dmsABC), fumarate reductase (frdABCD) and fermentation related genes are repressed. The narL and narX gene products are required for this nitrate-dependent control, and apparently function as members of a two-component regulatory system. NarX is a presumed sensor-transmitter for nitrate and possibly molybdenum detection. The presumed response-regulator, NarL, when activated by NarX then binds at the regulatory DNA sites of genes to modulate their expression. In this study a third nitrate regulatory gene, narQ, was identified that also participates in nitrate-dependent gene regulation. Strains defective in either narQ or narX alone exhibited no nitrate-dependent phenotype whereas mutants defective in both narQ and narX were fully inactive for nitrate-dependent repression or activation. In all conditions tested, this regulation required a functional narL gene product. These findings suggest that the narX and narQ products have complementary sensor-transmitter functions for nitrate detection, and can work independently to activate NarL, for eliciting nitrate-dependent regulation of anaerobic electron transport and fermentation functions. The narQ gene was cloned, sequenced, and compared with the narX gene. Both gene products are similar in size, hydrophobicity, and sequence, and contain a highly conserved histidine residue common to sensor-transmitter proteins.
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Affiliation(s)
- R C Chiang
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024
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81
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Krafft T, Bokranz M, Klimmek O, Schröder I, Fahrenholz F, Kojro E, Kröger A. Cloning and nucleotide sequence of the psrA gene of Wolinella succinogenes polysulphide reductase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 206:503-10. [PMID: 1597189 DOI: 10.1111/j.1432-1033.1992.tb16953.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The polysulphide reductase (formerly sulphur reductase) of Wolinella succinogenes is a component of the phosphorylative electron transport system with polysulphide as the terminal acceptor. Using an antiserum raised against the major subunit (PsrA, 85 kDa) of the enzyme, the corresponding gene (psrA) was cloned from a lambda-gene bank. The N-terminal amino acid sequence of PsrA mapped within the psrA gene product, which also contained an apparent signal peptide. Downstream of the psrA gene two more open reading frames (psrB and psrC) were found. The three genes may form a transcriptional unit with the transcription start site in front of psrA. The three genes were present only once on the genome. PsrA is a hydrophilic protein homologous to the largest subunits of six prokaryotic molybdoenzymes. PsrB is predicted to be hydrophilic, to contain ferredoxin-like cysteine clusters and to be homologous to the smaller hydrophilic subunits of four molybdoenzymes. PsrC is predicted to be a hydrophobic protein that could possibly serve as the membrane anchor of the enzyme.
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Affiliation(s)
- T Krafft
- Institut für Mikrobiologie, J.W. Goethe-Universität, Frankfurt am Main, Federal Republic of Germany
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82
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Reduction of N-oxides and sulfoxide by the same terminal reductase inProteus mirabilis. Curr Microbiol 1991. [DOI: 10.1007/bf02092029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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83
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Sambasivarao D, Weiner JH. Dimethyl sulfoxide reductase of Escherichia coli: an investigation of function and assembly by use of in vivo complementation. J Bacteriol 1991; 173:5935-43. [PMID: 1917829 PMCID: PMC208337 DOI: 10.1128/jb.173.19.5935-5943.1991] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Dimethyl sulfoxide (DMSO) reductase of Escherichia coli is a membrane-bound, terminal anaerobic electron transfer enzyme composed of three nonidentical subunits. The DmsAB subunits are hydrophilic and are localized on the cytoplasmic side of the plasma membrane. DmsC is the membrane-intrinsic polypeptide, proposed to anchor the extrinsic subunits. We have constructed a number of strains lacking portions of the chromosomal dmsABC operon. These mutant strains failed to grow anaerobically on glycerol minimal medium with DMSO as the sole terminal oxidant but exhibited normal growth with nitrate, fumarate, and trimethylamine N-oxide, indicating that DMSO reductase is solely responsible for growth on DMSO. In vivo complementation of the mutant with plasmids carrying various dms genes, singly or in combination, revealed that the expression of all three subunits is essential to restore anaerobic growth. Expression of the DmsAB subunits without DmsC results in accumulation of the catalytically active dimer in the cytoplasm. The dimer is thermolabile and catalyzes the reduction of various substrates in the presence of artificial electron donors. Dimethylnaphthoquinol (an analog of the physiological electron donor menaquinone) was oxidized only by the holoenzyme. These results suggest that the membrane-intrinsic subunit is necessary for anchoring, stability, and electron transport. The C-terminal region of DmsB appears to interact with the anchor peptide and facilitates the membrane assembly of the catalytic dimer.
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Affiliation(s)
- D Sambasivarao
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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84
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Daruwala R, Meganathan R. Dimethyl sulfoxide reductase is not required for trimethylamine N-oxide reduction inEscherichia chcoli. FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04473.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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85
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Differentiation of the multiple S- and N-oxide-reducing activities ofEscherichia coli. Curr Microbiol 1991. [DOI: 10.1007/bf02092258] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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86
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Yamamoto I, Hinakura M, Kondo H. Location of anaerobic respiratory enzyme trimethylamine N-oxide reductase in the cytoplasmic membrane ofEscherichia coli strain K10. Curr Microbiol 1991. [DOI: 10.1007/bf02092153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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87
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Wootton JC, Nicolson RE, Cock JM, Walters DE, Burke JF, Doyle WA, Bray RC. Enzymes depending on the pterin molybdenum cofactor: sequence families, spectroscopic properties of molybdenum and possible cofactor-binding domains. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1057:157-85. [PMID: 2015248 DOI: 10.1016/s0005-2728(05)80100-8] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- J C Wootton
- Department of Genetics, University of Leeds, U.K
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88
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Pascal MC, Lepelletier M, Giordano GÃ, Chippaux M. A regulatory mutant of the trimethylamineN-oxide reductase ofEscherichia coliK12. FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04459.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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89
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Purification and properties of dimethyl sulphoxide reductase from Rhodobacter capsulatus. A periplasmic molybdoenzyme. Biochem J 1991; 274 ( Pt 1):305-7. [PMID: 2001248 PMCID: PMC1149954 DOI: 10.1042/bj2740305] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Dimethyl sulphoxide reductase was purified from the photosynthetic bacterium Rhodobacter capsulatus. The enzyme is composed of a single polypeptide of Mr 82,000 and contains a pterin-type molybdenum cofactor as the only detectable prosthetic group. The oxidized molybdenum cofactor of dimethyl sulphoxide reductase is a weak chromophore and exhibits broad absorption bands in the u.v.-visible-absorption spectral region. A distinct spectrum was generated upon addition of dithionite.
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90
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Electron donors and the quinone involved in dimethyl sulfoxide reduction inEscherichia coli. Curr Microbiol 1991. [DOI: 10.1007/bf02105385] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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91
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Spectroscopic studies of the molybdenum-containing dimethyl sulfoxide reductase from Rhodobacter sphaeroides f. sp. denitrificans. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52399-1] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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92
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Karrasch M, Börner G, Enssle M, Thauer RK. The molybdoenzyme formylmethanofuran dehydrogenase from Methanosarcina barkeri contains a pterin cofactor. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 194:367-72. [PMID: 2125267 DOI: 10.1111/j.1432-1033.1990.tb15627.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Recently formylmethanofuran dehydrogenase from the archaebacterium Methanosarcina barkeri has been shown to be a novel molybdo-iron-sulfur protein. We report here that the enzyme contains one mol of a bound pterin cofactor/mol molybdenum, similar but not identical to the molybdopterin of milk xanthine oxidase. The two pterins, after oxidation with I2 at pH 2.5, showed identical fluorescence spectra and, after oxidation with permanganate at pH 13, yielded pterin 6-carboxylic acid. They differed, however, in their apparent molecular mass: the pterin of formylmethanofuran dehydrogenase was 400 Da larger than that of milk xanthine oxidase, a property also exhibited by the pterin cofactor of eubacterial molybdoenzymes. A homogeneous formylmethanofuran dehydrogenase preparation was used for these investigations. The enzyme, with a molecular mass of 220 kDa, contained 0.5-0.8 mol molybdenum, 0.6-0.9 mol pterin, 28 +/- 2 mol non-heme iron and 28 +/- 2 mol acid-labile sulfur/mol based on a protein determination with bicinchoninic acid. The specific activity was 175 mumol.min-1.mg-1 (kcat = 640 s-1) assayed with methylviologen (app. Km = 0.02 mM) as artificial electron acceptor. The apparent Km for formylmethanofuran was 0.02 mM.
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Affiliation(s)
- M Karrasch
- Laboratorium für Mikrobiologie, Philipps-Universität Marburg, FRG
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93
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Bauder R, Tshisuaka B, Lingens F. Microbial metabolism of quinoline and related compounds. VII. Quinoline oxidoreductase from Pseudomonas putida: a molybdenum-containing enzyme. BIOLOGICAL CHEMISTRY HOPPE-SEYLER 1990; 371:1137-44. [PMID: 2090161 DOI: 10.1515/bchm3.1990.371.2.1137] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The quinoline oxidoreductase from Pseudomonas putida was purified 50-fold to homogeneity with 21% recovery, using ammonium sulfate precipitation, hydrophobic interaction-, anion exchange-, and gel chromatography. The Mr of the native enzyme was calculated to be 300,000 by gel filtration. SDS-polyacrylamide gel electrophoresis of the enzyme revealed three protein bands corresponding to Mr 85,000, 30,000 and 20,000. The enzyme contained 8 atoms of iron, 8 atoms of acid-labile sulfide, 2 molecules of FAD, and the molybdenum cofactor, molybdopterin. Besides quinoline, the quinoline oxidoreductase also catalysed the conversion of 5-, 6-, 7- and 8-hydroxyquinoline and 8-chloroquinoline to the corresponding 2-oxo compounds. The incorporated oxygen atom was derived from water. Cyanide and methanol were effective inhibitors.
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Affiliation(s)
- R Bauder
- Institut für Mikrobiologie, Universität Hohenheim
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94
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Kalman LV, Gunsalus RP. Nitrate- and molybdenum-independent signal transduction mutations in narX that alter regulation of anaerobic respiratory genes in Escherichia coli. J Bacteriol 1990; 172:7049-56. [PMID: 2254274 PMCID: PMC210827 DOI: 10.1128/jb.172.12.7049-7056.1990] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Escherichia coli can respire anaerobically by reducing nitrate, trimethylamine-N-oxide, dimethyl sulfoxide, or fumarate. When nitrate is present, expression of the genes for fumarate (frdABCD), trimethylamine-N-oxide, and dimethyl sulfoxide (dmsABC) is repressed while expression of the nitrate reductase (narGHJI) gene is induced. This regulation requires molybdate and is mediated by the narX and narL gene products, which together form a two-component regulatory system. We provide evidence that NarX is a nitrate and molybdenum sensor which activates NarL when nitrate is available to cells. Mutants generated by hydroxylamine mutagenesis were repressed for frdA-lacZ expression even when cells were grown in the absence of nitrate. The mutations responsible for three of these nitrate independence (NarX*) phenotypes were localized to narX and further characterized in vivo for their ability to repress frdA-lacZ expression. Two of the mutants (the narX64 and narX71 mutants) had a greatly reduced requirement for molybdenum to function but still responded to nitrate. In contrast, a third mutant (the narX32 mutant) required molybdenum but did not exhibit full repression of frdA-lacZ expression even when nitrate was present. These narX* alleles also caused the induction of nitrate reductase gene expression and the repression of a dmsA-lacZ fusion in the absence of nitrate. Each narX* mutation was determined to lie in an 11-amino-acid region of the NarX polypeptide that follows a proposed transmembrane domain. We suggest that the conformation of the narX* gene products is altered such that even in the absence of nitrate each of these gene products more closely resembles the wild-type NarX protein when nitrate is present. These data establish a clear role for the narX gene product in gene regulation and strongly suggest its role in sensing nitrate and molybdenum.
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Affiliation(s)
- L V Kalman
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024
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95
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Karrasch M, Börner G, Thauer RK. The molybdenum cofactor of formylmethanofuran dehydrogenase from Methanosarcina barkeri is a molybdopterin guanine dinucleotide. FEBS Lett 1990; 274:48-52. [PMID: 2253782 DOI: 10.1016/0014-5793(90)81326-j] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The molybdenum cofactor of formylmethanofuran dehydrogenase from methanol-grown Methanosarcina barkeri was isolated as the [di(carboxamidomethyl)]-derivative. The alkylated factor showed an absorption spectrum and chemical properties identical to those recently reported for the molybdenum cofactor of dimethyl sulfoxide reductase from Rhodobacter sphaeroides. By treatment with nucleotide pyrophosphatase the factor was resolved into two components, which were identified as [di(carboxamidomethyl)]-molybdopterin and GMP by their absorption spectra, their retention times on Lichrospher RP-18, and by their conversion to dephospho-[di(carboxamidomethyl)]-molybdopterin and guanosine, respectively, in the presence of alkaline phosphatase. The GMP-moiety was sensitive to periodate, identifying it as the 5'-isomer. These results demonstrate that the molybdenum cofactor isolated from formylmethanofuran dehydrogenase contains the phosphoric anhydride of molybdopterin and 5'-GMP.
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Affiliation(s)
- M Karrasch
- Laboratorium für Mikrobiologie, Philipps-Universität Marburg, Marburg-Lahn, FRG
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96
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Steinberg NA, Oremland RS. Dissimilatory Selenate Reduction Potentials in a Diversity of Sediment Types. Appl Environ Microbiol 1990; 56:3550-7. [PMID: 16348359 PMCID: PMC185022 DOI: 10.1128/aem.56.11.3550-3557.1990] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We measured potential rates of bacterial dissimilatory reduction of
75
SeO
4
2−
to
75
Se
0
in a diversity of sediment types, with salinities ranging from freshwater (salinity = 1 g/liter) to hypersaline (salinity = 320 g/liter and with pH values ranging from 7.1 to 9.8. Significant biological selenate reduction occurred in all samples with salinities from 1 to 250 g/liter but not in samples with a salinity of 320 g/liter. Potential selenate reduction rates (25 nmol of SeO
4
2−
per ml of sediment added with isotope) ranged from 0.07 to 22 μmol of SeO
4
2−
reduced liter
−1
h
−1
. Activity followed Michaelis-Menten kinetics in relation to SeO
4
2−
concentration (
K
m
of selenate = 7.9 to 720 μM). There was no linear correlation between potential rates of SeO
4
2−
reduction and salinity, pH, concentrations of total Se, porosity, or organic carbon in the sediments. However, potential selenate reduction was correlated with apparent
K
m
for selenate and with potential rates of denitrification (
r
= 0.92 and 0.81, respectively). NO
3
−
, NO
2
−
, MoO
4
2−
, and WO
4
2−
inhibited selenate reduction activity to different extents in sediments from both Hunter Drain and Massie Slough, Nev. Sulfate partially inhibited activity in sediment from freshwater (salinity = 1 g/liter) Massie Slough samples but not from the saline (salinity = 60 g/liter) Hunter Drain samples. We conclude that dissimilatory selenate reduction in sediments is widespread in nature. In addition, in situ selenate reduction is a first-order reaction, because the ambient concentrations of selenium oxyanions in the sediments were orders of magnitude less than their
K
m
s.
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Affiliation(s)
- N A Steinberg
- Water Resources Division, U.S. Geological Survey, MS 465, 345 Middlefield Road, Menlo Park, California 94025
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97
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Sambasivarao D, Scraba DG, Trieber C, Weiner JH. Organization of dimethyl sulfoxide reductase in the plasma membrane of Escherichia coli. J Bacteriol 1990; 172:5938-48. [PMID: 2170332 PMCID: PMC526915 DOI: 10.1128/jb.172.10.5938-5948.1990] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Dimethyl sulfoxide reductase is a trimeric, membrane-bound, iron-sulfur molybdoenzyme induced in Escherichia coli under anaerobic growth conditions. The enzyme catalyzes the reduction of dimethyl sulfoxide, trimethylamine N-oxide, and a variety of S- and N-oxide compounds. The topology of dimethyl sulfoxide reductase subunits was probed by a combination of techniques. Immunoblot analysis of the periplasmic proteins from the osmotic shock and chloroform wash fluids indicated that the subunits were not free in the periplasm. The reductase was susceptible to proteases in everted membrane vesicles, but the enzyme in outer membrane-permeabilized cells became protease sensitive only after detergent solubilization of the E. coli plasma membrane. Lactoperoxidase catalyzed the iodination of each of the three subunits in an everted membrane vesicle preparation. Antibodies to dimethyl sulfoxide reductase and fumarate reductase specifically agglutinated the everted membrane vesicles. No TnphoA fusions could be found in the dmsA or -B genes, indicating that these subunits were not translocated to the periplasm. Immunogold electron microscopy of everted membrane vesicles and thin sections by using antibodies to the DmsABC, DmsA, DmsB subunits resulted in specific labeling of the cytoplasmic surface of the inner membrane. These results show that the DmsA (catalytic subunit) and DmsB (electron transfer subunit) are membrane-extrinsic subunits facing the cytoplasmic side of the plasma membrane.
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Affiliation(s)
- D Sambasivarao
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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98
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Cammack R, Weiner JH. Electron paramagnetic resonance spectroscopic characterization of dimethyl sulfoxide reductase of Escherichia coli. Biochemistry 1990; 29:8410-6. [PMID: 2174699 DOI: 10.1021/bi00488a030] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The electron transfer centers in dimethyl sulfoxide reductase were examined by EPR spectroscopy in membranes of the overproducing Escherichia coli strain HB101/pDMS159, and in purified enzyme. Iron-sulfur clusters of the [4Fe-4S] type and a molybdenum center were detected in the protein, which comprises three different subunits: DmsA, -B, and -C. The intensity of the reduced iron-sulfur clusters corresponded to 3.82 +/- 0.5 spins per molecule. The dithionite-reduced clusters were reoxidized by DMSO or TMAO. The enzyme, as prepared, showed a spectrum of Mo(V), which resembles the high-pH form of E. coli nitrate reductase. The Mo(V) detected by EPR was absent from a mutant which does not assemble the molybdenum cofactor. In these cases, the levels of EPR-detectable iron-sulfur clusters in the cells were increased. Extracts from HB101/pDMS159 enriched in DmsA showed more Mo(V) signals and considerably less iron-sulfur. These results are in agreement with predictions from amino acid sequence comparisons, that the molybdenum center is located in DmsA, while four iron-sulfur clusters are in DmsB. The midpoint potentials of the molybdenum and iron-sulfur clusters in the various preparations were determined by mediator titrations. The iron-sulfur signals could be best fitted by four clusters, with midpoint potentials spread between -50 and -330 mV. The midpoint potentials of the iron-sulfur clusters and Mo(V) species were pH dependent. In addition, all potentials became less negative in the presence of the detergent Triton X-100. Observation of relaxation enhancement of the Mo(V) species by the reduced [4Fe-4S] clusters indicated that the centers are in proximity within the protein.
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Affiliation(s)
- R Cammack
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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99
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Abstract
Bacteria which can grow in different environments have developed regulatory systems which allow them to exploit specific habitats to their best advantage. In the facultative anaerobe Escherichia coli two transcriptional regulators controlling independent networks of oxygen-regulated gene expression have been identified. One is a two-component sensor-regulator system (ArcB-A), which represses a wide variety of aerobic enzymes under anaerobic conditions. The other is FNR, the transcriptional regulator which is essential for expressing anaerobic respiratory processes. The purpose of this review is to summarize what is known about FNR. The fnr gene was initially defined by the isolation of some pleiotropic mutants which characteristically lacked the ability to use fumarate and nitrate as reducible substrates for supporting anaerobic growth and several other anaerobic respiratory functions. Its role as a transcriptional regulator emerged from genetic and molecular studies in which its homology with CRP (the cyclic AMP receptor protein which mediates catabolite repression) was established and has since been particularly important in identifying the structural basis of its regulatory specificities. FNR is a member of a growing family of CRP-related regulatory proteins which have a DNA-binding domain based on the helix-turn-helix structural motif, and a characteristic beta-roll that is involved in nucleotide-binding in CRP. The FNR protein has been isolated in a monomeric form (Mr 30,000) which exhibits a high but as yet non-specific affinity for DNA. Nevertheless, the DNA-recognition site and important residues conferring the functional specificity of FNR have been defined by site-directed mutagenesis. A consensus for the sequences that are recognized by FNR in the promoter regions of FNR-regulated genes, has likewise been identified. The basic features of the genes and operons regulated by FNR are reviewed, and examples in which FNR functions negatively as an anaerobic repressor as well as positively as an anaerobic activator, are included. Less is known about the way in which FNR senses anoxia and is thereby transformed into its 'active' form, but it seems likely that cysteine residues and possibly a metal ion are involved. Four of the five cysteine residues of FNR are clustered in an essential N-terminal 'domain' which is conserved in FNR and the HlyX protein of Actinobacillus pleuropneumoniae, but not in CRP or the FixK protein of Rhizobium meliloti. The relationships between FNR and other oxygen-related systems in E. coli are discussed, as well as parallel systems in other organisms.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- S Spiro
- Department of Molecular Biology and Biotechnology, University of Sheffield, U.K
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100
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Bell LC, Richardson DJ, Ferguson SJ. Periplasmic and membrane-bound respiratory nitrate reductases in Thiosphaera pantotropha. The periplasmic enzyme catalyzes the first step in aerobic denitrification. FEBS Lett 1990; 265:85-7. [PMID: 2365057 DOI: 10.1016/0014-5793(90)80889-q] [Citation(s) in RCA: 167] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The unusual ability of Thiosphaera pantotropha to catalyze respiratory nitrate reduction under aerobic conditions is shown to correlate with the activity of a periplasmic nitrate reductase that is expressed under both aerobic and anaerobic growth conditions. The organism also synthesizes, but only under anaerobic conditions, a membrane-bound nitrate reductase which resembles the corresponding enzyme in Paracoccus denitrificans in respect of both catalytic properties and inhibition of activity in intact cells in the presence of oxygen.
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Affiliation(s)
- L C Bell
- Department of Biochemistry, University of Oxford, UK
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