scholarly journals The Escherichia coli Azoreductase AzoR Is Involved in Resistance to Thiol-Specific Stress Caused by Electrophilic Quinones

2009 ◽  
Vol 191 (20) ◽  
pp. 6394-6400 ◽  
Author(s):  
Guangfei Liu ◽  
Jiti Zhou ◽  
Q. Shiang Fu ◽  
Jing Wang
Keyword(s):  
Escherichia Coli ◽  
Reduced Glutathione ◽  
Physiological Role ◽  
Quinone Reductase ◽  
Methyl Red ◽  
Transcription Start Point ◽  
Transcription Start ◽  
Translation Start

ABSTRACT The physiological role of Escherichia coli azoreductase AzoR was studied. It was found that AzoR was capable of reducing several benzo-, naphtho-, and anthraquinone compounds, which were better substrates for AzoR than the model azo substrate methyl red. The ΔazoR mutant displayed reduced viability when exposed to electrophilic quinones, which are capable of depleting cellular reduced glutathione (GSH). Externally added GSH can partially restore the impaired growth of the ΔazoR mutant caused by 2-methylhydroquinone. The transcription of azoR was induced by electrophiles, including 2-methylhydroquinone, catechol, menadione, and diamide. A transcription start point was identified 44 bp upstream from the translation start point. These data indicated that AzoR is a quinone reductase providing resistance to thiol-specific stress caused by electrophilic quinones.

scholarly journals Escherichia coli NsrR Regulates a Pathway for the Oxidation of 3-Nitrotyramine to 4-Hydroxy-3-Nitrophenylacetate

2008 ◽  
Vol 190 (18) ◽  
pp. 6170-6177 ◽  
Author(s):  
Linda D. Rankin ◽  
Diane M. Bodenmiller ◽  
Jonathan D. Partridge ◽  
Shirley F. Nishino ◽  
Jim C. Spain ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Physiological Role ◽  
Growth Conditions ◽  
Growth Defect ◽  
E Coli ◽  
Mutant Phenotypes ◽  
Culture Supernatants ◽  
Chip Chip

ABSTRACT Chromatin immunoprecipitation and microarray (ChIP-chip) analysis showed that the nitric oxide (NO)-sensitive repressor NsrR from Escherichia coli binds in vivo to the promoters of the tynA and feaB genes. These genes encode the first two enzymes of a pathway that is required for the catabolism of phenylethylamine (PEA) and its hydroxylated derivatives tyramine and dopamine. Deletion of nsrR caused small increases in the activities of the tynA and feaB promoters in cultures grown on PEA. Overexpression of nsrR severely retarded growth on PEA and caused a marked repression of the tynA and feaB promoters. Both the growth defect and the promoter repression were reversed in the presence of a source of NO. These results are consistent with NsrR mediating repression of the tynA and feaB genes by binding (in an NO-sensitive fashion) to the sites identified by ChIP-chip. E. coli was shown to use 3-nitrotyramine as a nitrogen source for growth, conditions which partially induce the tynA and feaB promoters. Mutation of tynA (but not feaB) prevented growth on 3-nitrotyramine. Growth yields, mutant phenotypes, and analyses of culture supernatants suggested that 3-nitrotyramine is oxidized to 4-hydroxy-3-nitrophenylacetate, with growth occurring at the expense of the amino group of 3-nitrotyramine. Accordingly, enzyme assays showed that 3-nitrotyramine and its oxidation product (4-hydroxy-3-nitrophenylacetaldehyde) could be oxidized by the enzymes encoded by tynA and feaB, respectively. The results suggest that an additional physiological role of the PEA catabolic pathway is to metabolize nitroaromatic compounds that may accumulate in cells exposed to NO.

Evidence against the physiological role of acetyl phosphate in the phosphorylation of the ArcA response regulator in Escherichia coli

2009 ◽  
Vol 47 (5) ◽  
pp. 657-662 ◽  
Author(s):  
Xueqiao Liu ◽  
Gabriela R. Peña Sandoval ◽  
Barry L. Wanner ◽  
Won Seok Jung ◽  
Dimitris Georgellis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Physiological Role ◽  
Acetyl Phosphate

The direct synthesis of phospho enol pyruvate from pyruvate by Escherichia coli

1967 ◽  
Vol 168 (1012) ◽  
pp. 263-280 ◽  
Keyword(s):  
Escherichia Coli ◽  
Inorganic Phosphate ◽  
Direct Synthesis ◽  
Physiological Role ◽  
Wild Type ◽  
Pyruvate Kinase Activity ◽  
Ph Values ◽  
Direct Formation ◽  
Pyruvate Synthase

Extracts of Escherichia coli are shown to contain an enzyme system which in the presence of Mg 2+ catalyses the direct formation of phospho enol pyruvate from pyruvate and ATP with concomitant formation of AMP and inorganic phosphate. This enzyme, which has been designated 'phospho enol pyruvate synthase' ( PEP -synthase) has been purified 80-fold and is free of pyruvate kinase activity; PEP synthesis proceeded most rapidly at pH 8 to 8.5. At pH values between 6.2 and 7.5 the enzyme can catalyse the formation of ATP and pyruvate from PEP , AMP and inorganic phosphate; if arsenate is used instead of phosphate, pyruvate and ADP are produced instead. Studies of the enzymic formation of PEP with ATP specifically labelled with 32 P, and of the reverse reaction with [U -14 C] AMP , suggest that the PEP -synthase reaction involves the transfer of a pyrophosphoryl-group. The physiological role of PEP -synthase has been demonstrated with mutants of E. coli devoid of the enzyme: in contrast to wild-type organisms, such mutants neither grow on pyruvate, lactate or alanine, nor form glycogen from lactate. It is thus concluded that PEP -synthase plays an important role in the anaplerotic and the biosynthetic reactions which enable the organisms to grow on pyruvate as sole carbon source.

Partial isolation and function of the prostacyclin regulating plasma factor

1985 ◽  
Vol 69 (4) ◽  
pp. 383-393 ◽  
Author(s):  
H. Deckmyn ◽  
C. Zoja ◽  
J. Arnout ◽  
A. Todisco ◽  
F. VANDEN Bulcke ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Reduced Glutathione ◽  
Physiological Role ◽  
Plasma Factor ◽  
High Concentrations ◽  
Partial Isolation ◽  
Glutathione Cycle ◽  
And Function ◽  
Plasma Activity

1. Rat aortic rings stop producing prostacyclin upon prolonged washing in buffer. This ‘exhaustion’ is caused by inhibition of cyclo-oxygenase, since these rings still convert cyclic endoperoxides but not arachidonic acid into prostacyclin, and most probably is due to high concentrations of peroxides: it can be accelerated by H2O2 or by interrupting the glutathione cycle, while it is delayed by reduced glutathione. 2. Incubation of exhausted rings in human plasma or in a plasma filtrate restores to some extent prostacyclin formation. This filtrate, in particular from uraemic subjects, also inhibits the H2O2 initiated oxidation of guaiacol by ram seminal vesicle microsomes or horseradish peroxidase. 3. The prostacyclin regulating plasma factor has been partially purified and identified as a stable and very polar molecule of mol. wt. 300–400, able to reactivate prostacyclin generation by exhausted rings. We suggest that one or more low mol. wt. plasma components prolong vascular prostacyclin formation by acting as reducing cofactor for cyclo-oxygenase peroxidase. 4. The main physiological role of this plasma activity is probably to protect the vascular prostacyclin forming system from exhaustion during persistent irritation.

scholarly journals Competition between Escherichia coli strains expressing either a periplasmic or a membrane-bound nitrate reductase: does Nap confer a selective advantage during nitrate-limited growth?

1999 ◽  
Vol 344 (1) ◽  
pp. 77-84 ◽  
Author(s):  
Laura C. POTTER ◽  
Paul MILLINGTON ◽  
Lesley GRIFFITHS ◽  
Gavin H. THOMAS ◽  
Jeffrey A. COLE
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Nitrate Reductase ◽  
Electron Acceptor ◽  
Physiological Role ◽  
Selective Advantage ◽  
Limited Growth ◽  
Terminal Electron Acceptor ◽  
Periplasmic Nitrate Reductase

The physiological role of the periplasmic nitrate reductase, Nap, one of the three nitrate reductases synthesized by Escherichia coli K-12, has been investigated. A series of double mutants that express only one nitrate reductase were grown anaerobically in batch cultures with glycerol as the non-fermentable carbon source and nitrate as the terminal electron acceptor. Only the strain expressing nitrate reductase A grew rapidly under these conditions. Introduction of a narL mutation severely decreased the growth rate of the nitrate reductase A strain, but enhanced the growth of the Nap+ strain. The ability to use nitrate as a terminal electron acceptor for anaerobic growth is therefore regulated primarily by the NarL protein at the level of transcription. Furthermore, the strain expressing nitrate reductase A had a substantial selective advantage in competition with the strain expressing only Nap during nitrate-sufficient continuous culture. However, the strain expressing Nap was preferentially selected during nitrate-limited continuous growth. The saturation constants for nitrate for the two strains (which numerically are equal to the nitrate concentrations at half of the maximum specific growth rate and therefore reflect the relative affinities for nitrate) were estimated using the integrated Monod equation to be 15 and 50 μM for Nap and nitrate reductase A respectively. This difference is sufficient to explain the selective advantage of the Nap+ strain during nitrate-limited growth. It is concluded that one physiological role of the periplasmic nitrate reductase of enteric bacteria is to enable bacteria to scavenge nitrate in nitrate-limited environments.

scholarly journals Escherichia coli abg Genes Enable Uptake and Cleavage of the Folate Catabolite p-Aminobenzoyl-Glutamate

2007 ◽  
Vol 189 (9) ◽  
pp. 3329-3334 ◽  
Author(s):  
Eric L. Carter ◽  
Lindsey Jager ◽  
Lars Gardner ◽  
Christel C. Hall ◽  
Stacey Willis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Copy Number ◽  
Physiological Role ◽  
Structural Protein ◽  
Rapid Loss ◽  
Endogenous Expression ◽  
Copy Number Plasmid ◽  
High Copy Number Plasmid ◽  
Low Levels

ABSTRACT Escherichia coli AbgT was first identified as a structural protein enabling the growth of p-aminobenzoate auxotrophs on exogenous p-aminobenzoyl-glutamate (M. J. Hussein, J. M. Green, and B. P. Nichols, J. Bacteriol. 180:6260-6268, 1998). The abg region includes abgA, abgB, abgT, and ogt; these genes may be regulated by AbgR, a divergently transcribed LysR-type protein. Wild-type cells transformed with a high-copy-number plasmid encoding abgT demonstrate saturable uptake of p-aminobenzoyl-glutamate (KT = 123 μM); control cells expressing vector demonstrate negligible uptake. The addition of metabolic poisons inhibited uptake of p-aminobenzoyl-glutamate, consistent with this process requiring energy. p-Aminobenzoyl-glutamate taken in by cells expressing large amounts of AbgT alone is not rapidly metabolized to a form that is trapped in the cell, as the addition of nonradioactive p-aminobenzoyl-glutamate to these cells results in a rapid loss of intracellular label. The addition of nonradioactive p-aminobenzoate has no effect. The abgA, abgB, and abgAB genes were cloned into the medium-copy-number plasmid pACYC184; p-aminobenzoate auxotrophs transformed with the clone encoding abgAB demonstrated enhanced ability to grow on low levels of p-aminobenzoyl-glutamate. When transformed with complementary plasmids encoding high-copy levels of abgT and medium-copy levels of abgAB, p-aminobenzoate auxotrophs grew on 50 nM p-aminobenzoyl-glutamate. Our data are consistent with a model of p-aminobenzoyl-glutamate utilization in which AbgT catalyzes transport of p-aminobenzoyl-glutamate, followed by cleavage to p-aminobenzoate by a protein composed of subunits encoded by abgA and abgB. While endogenous expression of these genes is very low under the conditions in which we performed our experiments, these genes may be induced by AbgR bound to an unknown molecule. The true physiological role of this region may be related to some molecule similar to p-aminobenzoyl-glutamate, such as a dipeptide.

Physiological role of GlpB of anaerobic glycerol-3-phosphate dehydrogenase ofEscherichia coli

1995 ◽  
Vol 73 (3-4) ◽  
pp. 147-153 ◽  
Author(s):  
Monica E. R. Varga ◽  
Joel H. Weiner
Keyword(s):  
Escherichia Coli ◽  
Physiological Role ◽  
Anaerobic Growth ◽  
Paramagnetic Resonance ◽  
Terminal Electron Acceptor ◽  
Iron Sulfur Center ◽  
Anaerobic Electron Transport ◽  
Membrane Bound ◽  
Glycerol 3 Phosphate Dehydrogenase

Anaerobic sn-glycerol-3-phosphate dehydrogenase of Escherichia coli is encoded by an operon of three genes, glpACB. The promoter distal gene, glpB, encodes a 44-kilodalton polypeptide that is not part of the purified soluble dehydrogenase. By recombinant plasmid complementation, in a strain harboring a chromosomal deletion of glpACB, we found that all three genes were essential for anaerobic growth on glycerol-3-phosphate (G3P). By isolation of inner membrane preparations we confirmed the cytoplasmic membrane localization of GlpB. GlpB displayed an electron paramagnetic resonance spectrum that suggested the presence of iron–sulfur center(s) within GlpB. We used this spectrum to show that the center(s) were reduced by the artificial reductant dithionite and by the physiological substrate G3P but not by lactate or formate. The center(s) were oxidized by fumarate. These data indicated that GlpB mediates electron transfer from the soluble GlpAC dimer to the terminal electron acceptor fumarate via the membrane-bound menaquinone pool.Key words: glycerol-3-phosphate dehydrogenase, anaerobic electron transport, membrane proteins, ferredoxin, Escherichia coli.

scholarly journals Thioesterase II of Escherichia coli Plays an Important Role in 3-Hydroxydecanoic Acid Production

2004 ◽  
Vol 70 (7) ◽  
pp. 3807-3813 ◽  
Author(s):  
Zhong Zheng ◽  
Qiang Gong ◽  
Tao Liu ◽  
Ying Deng ◽  
Jin-Chun Chen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Coenzyme A ◽  
Acyl Carrier Protein ◽  
Physiological Role ◽  
Carrier Protein ◽  
E Coli ◽  
Thioesterase Ii ◽  
Abnormal Accumulation ◽  
Acyl Coenzyme A

ABSTRACT 3-Hydroxydecanoic acid (3HD) was produced in Escherichia coli by mobilizing (R)-3-hydroxydecanoyl-acyl carrier protein-coenzyme A transacylase (PhaG, encoded by the phaG gene). By employing an isogenic tesB (encoding thioesterase II)-negative knockout E. coli strain, CH01, it was found that the expressions of tesB and phaG can up-regulate each other. In addition, 3HD was synthesized from glucose or fructose by recombinant E. coli harboring phaG and tesB. This study supports the hypothesis that the physiological role of thioesterase II in E. coli is to prevent the abnormal accumulation of intracellular acyl-coenzyme A.

scholarly journals Promoter Characterization and Constitutive Expression of the Escherichia coli gcvR Gene

1998 ◽  
Vol 180 (7) ◽  
pp. 1803-1807 ◽  
Author(s):  
Angela C. Ghrist ◽  
George V. Stauffer
Keyword(s):  
Escherichia Coli ◽  
Transcription Start Site ◽  
Promoter Region ◽  
Start Codon ◽  
Start Site ◽  
Transcription Start ◽  
Translation Start Codon ◽  
Translation Start ◽  
Glycine Cleavage ◽  
Extension Analysis

ABSTRACT The Escherichia coli glycine cleavage repressor protein (GcvR) negatively regulates expression of the glycine cleavage operon (gcv). In this study, the gcvR translational start site was determined by N-terminal amino acid sequence analysis of a GcvR-LacZ fusion protein. Primer extension analysis of thegcvR promoter region identified a primary transcription start site 27 bp upstream of the UUG translation start site and a minor transcription start site approximately 100 bp upstream of the translation start codon. The -10 and -35 promoter regions upstream of the primary transcription start site were defined by mutational analysis. Expression of a gcvR-lacZ fusion was unaltered in the presence of glycine or inosine, molecules known to induce or repress expression of gcv, respectively. In addition, it was shown that gcvR-lacZ expression is neither regulated by the glycine cleavage activator protein (GcvA) nor autogenously regulated by GcvR. From DNA sequence analysis, it was predicted that the translation start codon of the downstream bcp gene overlaps the gcvR stop codon, suggesting that these genes may form an operon. However, a down mutation in the -10 promoter region of gcvR had no effect on the expression of a downstreambcp-lacZ fusion, and primer extension analysis of thebcp promoter region demonstrated that bcp has its own promoter within the gcvR coding sequence. These results show that gcvR and bcp do not form an operon. Furthermore, the deletion of bcp from the chromosome had no effect on gcv-lacZ expression.

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