scholarly journals A haloarchaeal ferredoxin electron donor that plays an essential role in nitrate assimilation

2011 ◽  
Vol 39 (6) ◽  
pp. 1844-1848 ◽  
Author(s):  
Basilio Zafrilla ◽  
Rosa María Martínez-Espinosa ◽  
María José Bonete ◽  
Julea N. Butt ◽  
David J. Richardson ◽  
...  
Keyword(s):  
Essential Role ◽  
Inorganic Nitrogen ◽  
Nitrate Assimilation ◽  
Spectroscopic Characterization ◽  
Redox Properties ◽  
Nitrite Reduction ◽  
Plant Type ◽  
Uv Visible ◽  
Nitrate And Nitrite

In the absence of ammonium, many organisms, including the halophilic archaeon Haloferax volcanii DS2 (DM3757), may assimilate inorganic nitrogen from nitrate or nitrite, using a ferredoxin-dependent assimilatory NO3−/NO2− reductase pathway. The small acidic ferredoxin Hv-Fd plays an essential role in the electron transfer cascade required for assimilatory nitrate and nitrite reduction by the cytoplasmic NarB- and NirA-type reductases respectively. UV–visible absorbance and EPR spectroscopic characterization of purified Hv-Fd demonstrate that this protein binds a single [2Fe–2S] cluster, and potentiometric titration reveals that the cluster shares similar redox properties with those present in plant-type ferredoxins.

Nitrate and nitrite reduction by ferrous iron minerals in polluted groundwater: Isotopic characterization of batch experiments

2020 ◽  
Vol 548 ◽  
pp. 119691
Author(s):  
Rosanna Margalef-Marti ◽  
Raúl Carrey ◽  
José Antonio Benito ◽  
Vicenç Marti ◽  
Albert Soler ◽  
...  
Keyword(s):  
Ferrous Iron ◽  
Nitrite Reduction ◽  
Batch Experiments ◽  
Iron Minerals ◽  
Isotopic Characterization ◽  
Nitrate And Nitrite

Synthesis and NMR Spectroscopic Characterization of Some Fluoro-2H-1-Benzopyran Derivatives

2005 ◽  
Vol 58 (7) ◽  
pp. 517 ◽  
Author(s):  
Yannick Teral ◽  
Gabriel Roubaud ◽  
Claude Aubert ◽  
Robert Faure ◽  
Mylène Campredon
Keyword(s):  
Mass Spectra ◽  
Spectroscopic Characterization ◽  
Molecular Probe ◽  
Visible Spectroscopy ◽  
Chemical Shift Correlation ◽  
Photochemical Process ◽  
Fragment Ions ◽  
Complete Assignment ◽  
Uv Visible

The synthesis of some new fluoro-2H-1-benzopyran derivatives utilizing a reaction between titanium phenolates and β-phenylcinnamaldehydes in toluene is reported. These compounds were characterized by NMR and UV/visible spectroscopy as well as mass spectrometry. In solution all the compounds are photochromic. Complete assignment of the 1H and 13C resonances was achieved by concerted application of homonuclear (gs-COSY), proton-detected (C, H) one-bond (gs-HMQC), and long-range (gs-HMBC) heteronuclear two-dimensional chemical shift correlation experiments using a 500 MHz NMR spectrometer equipped with a cryoplatform and a 5 mm cryoprobe. The mass spectra of the different compounds were characterized by intense molecular and high fragment ions. The introduction of an atom of fluorine as a molecular probe is of interest in determining the mechanistic aspects of the photochemical process.

scholarly journals A recently evolved diflavin-containing monomeric nitrate reductase is responsible for highly efficient bacterial nitrate assimilation

2020 ◽  
Vol 295 (15) ◽  
pp. 5051-5066 ◽  
Author(s):  
Wei Tan ◽  
Tian-Hua Liao ◽  
Jin Wang ◽  
Yu Ye ◽  
Yu-Chen Wei ◽  
...  
Keyword(s):  
Nitrate Reductase ◽  
Biochemical Characterization ◽  
Catalytic Domain ◽  
Inorganic Nitrogen ◽  
Nitrate Assimilation ◽  
Nitrogen Sources ◽  
Electron Transfer Mechanism ◽  
Cofactor Binding ◽  
Environmental Mycobacteria

Nitrate is one of the major inorganic nitrogen sources for microbes. Many bacterial and archaeal lineages have the capacity to express assimilatory nitrate reductase (NAS), which catalyzes the rate-limiting reduction of nitrate to nitrite. Although a nitrate assimilatory pathway in mycobacteria has been proposed and validated physiologically and genetically, the putative NAS enzyme has yet to be identified. Here, we report the characterization of a novel NAS encoded by Mycolicibacterium smegmatis Msmeg_4206, designated NasN, which differs from the canonical NASs in its structure, electron transfer mechanism, enzymatic properties, and phylogenetic distribution. Using sequence analysis and biochemical characterization, we found that NasN is an NADPH-dependent, diflavin-containing monomeric enzyme composed of a canonical molybdopterin cofactor-binding catalytic domain and an FMN–FAD/NAD-binding, electron-receiving/transferring domain, making it unique among all previously reported hetero-oligomeric NASs. Genetic studies revealed that NasN is essential for aerobic M. smegmatis growth on nitrate as the sole nitrogen source and that the global transcriptional regulator GlnR regulates nasN expression. Moreover, unlike the NADH-dependent heterodimeric NAS enzyme, NasN efficiently supports bacterial growth under nitrate-limiting conditions, likely due to its significantly greater catalytic activity and oxygen tolerance. Results from a phylogenetic analysis suggested that the nasN gene is more recently evolved than those encoding other NASs and that its distribution is limited mainly to Actinobacteria and Proteobacteria. We observed that among mycobacterial species, most fast-growing environmental mycobacteria carry nasN, but that it is largely lacking in slow-growing pathogenic mycobacteria because of multiple independent genomic deletion events along their evolution.

scholarly journals Characterization of the Oxygen-Responsive NreABC Regulon of Staphylococcus aureus

2008 ◽  
Vol 190 (23) ◽  
pp. 7847-7858 ◽  
Author(s):  
Steffen Schlag ◽  
Stephan Fuchs ◽  
Christiane Nerz ◽  
Rosmarie Gaupp ◽  
Susanne Engelmann ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Transcriptional Activation ◽  
Nitrite Reduction ◽  
Anaerobic Growth ◽  
Regulation System ◽  
Anoxic Environments ◽  
Severe Impairment ◽  
Specific Regulation ◽  
Nitrate And Nitrite

ABSTRACT Here, we investigate the functionality of the oxygen-responsive nitrogen regulation system NreABC in the human pathogen Staphylococcus aureus and evaluate its role in anaerobic gene regulation and virulence factor expression. Deletion of nreABC resulted in severe impairment of dissimilatory nitrate and nitrite reduction and led to a small-colony phenotype in the presence of nitrate during anaerobic growth. For characterization of the NreABC regulon, comparative DNA microarray and proteomic analyses between the wild type and nreABC mutant were performed under anoxic conditions in the absence and presence of nitrate. A reduced expression of virulence factors was not observed in the mutant. However, both the transcription of genes involved in nitrate and nitrite reduction and the accumulation of corresponding proteins were highly decreased in the nreABC mutant, which was unable to utilize nitrate as a respiratory oxidant and, hence, was forced to use fermentative pathways. These data were corroborated by the quantification of the extracellular metabolites lactate and acetate. Using an Escherichia coli-compatible two-plasmid system, the activation of the promoters of the nitrate and nitrite reductase operons and of the putative nitrate/nitrite transporter gene narK by NreBC was confirmed. Overall, our data indicate that NreABC is very likely a specific regulation system that is essential for the transcriptional activation of genes involved in dissimilatory reduction and transport of nitrate and nitrite. The study underscores the importance of NreABC as a fitness factor for S. aureus in anoxic environments.

scholarly journals THE ISOLATION AND CHARACTERIZATION OF MUTANTS DEFECTIVE IN NITRATE ASSIMILATION IN NEUROSPORA CRASSA

Genetics ◽  
1980 ◽  
Vol 95 (3) ◽  
pp. 649-660
Author(s):  
A Brian Tomsett ◽  
Reginald H Garrett
Keyword(s):  
Nitrate Reductase ◽  
Neurospora Crassa ◽  
Nitrate Assimilation ◽  
Xanthine Dehydrogenase ◽  
Growth Patterns ◽  
Isolation And Characterization ◽  
Complex Locus ◽  
Complementation Groups ◽  
Nitrate And Nitrite

ABSTRACT The isolation and characterization of mutants altered for nitrate assimilation in Neurospora crassa is described, The mutants isolated can be subdivided into five classes on the basis of growth tests that correspond to the growth patterns of existing mutants at six distinct loci. Mutants with growth characteristics like those of nit-2, nit-3 and nit-6 are assigned to those loci on the basis of noncomplementation and lack of recombination. Mutants that, from their growth patterns, appear to lack the molybdenum-containing cofactor for both nitrate reductase and xanthine dehydrogenase subdivide into three loci (nit-7, nit4 and nit-9), all of which are genetically distinct from nit-1. nit-9 is a complex locus consisting of three complementation groups and thus appears similar to the cnxABC locus of Asperillus nidulans. Extensive complementational and recombinational analyses reveal that nit-4 and nit-5 are alleles of the same locus, and two new alleles of that locus have been isolated. The results indicate that, as in A. nidulans, nitrate assimilation in N. crassa requires at least four loci (nit-1,7,8 and 9) to produce the molybdenum co-factor for nitrate reductase (and xanthine dehydrogenase), one locus (nit-3) to code for the nitrate reductase apoprotein, one locus (nit-6) to code for the nitrite reductase approtein and only one locus (nit-4/5) for the regulation of induction of the pathway by nitrate and nitrite.

Thermodynamic characterization of the redox centres in a representative domain of a novel c-type multihaem cytochrome

2009 ◽  
Vol 420 (3) ◽  
pp. 485-492 ◽  
Author(s):  
Leonor Morgado ◽  
Ana P. Fernandes ◽  
Yuri Y. Londer ◽  
P. Raj Pokkuluri ◽  
Marianne Schiffer ◽  
...  
Keyword(s):  
Dominant Role ◽  
Redox Properties ◽  
Geobacter Sulfurreducens ◽  
Thermodynamic Characterization ◽  
Reduction Potentials ◽  
New Type ◽  
Uv Visible ◽  
Cytochrome C7 ◽  
The Individual

Multihaem cytochromes that could form protein “nanowires” were identified in the Geobacter sulfurreducens genome, and represent a new type of multihaem cytochrome. The sequences of these proteins, two with 12 haems (GSU1996, GSU0592) and one with 27 haems (GSU2210), suggest that they are formed with domains homologous to the trihaem cytochrome c7. Although all three haems have bis-His co-ordination in cytochromes c7, in each domain of the above polymers, the haem equivalent to haem IV has His-Met co-ordination. We previously determined the structure and measured the macroscopic redox potential of one representative domain (domain C) of a dodecahaem cytochrome (GSU1996). In the present study, the microscopic redox properties of the individual haem groups of domain C were determined using NMR and UV–visible spectroscopies. The reduction potentials of the haems for the fully reduced and protonated protein are different from each other (haem I, −106 mV; haem III, −136 mV; and haem IV, −125 mV) and are strongly modulated by redox interactions. This result is rather surprising since the His-Met co-ordinated haem IV does not have the highest potential as was expected. The polypeptide environment of each haem group and the strong haem pairwise redox interactions must play a dominant role in controlling the individual haem potentials. The strong redox interactions between the haems extend the range of their operating potentials at physiological pH (haem I, −71 mV, haem III, −146 mV and haem IV, −110 mV). Such a modulation in haem potentials is likely to have a functional significance in the metabolism of G. sulfurreducens.

Electrochemical, spectroelectrochemical and ESR spectroscopic characterization of 2,3- and 3,4-cobalt tetrapyridoporphyrazine isomers in non-aqueous media

2009 ◽  
Vol 13 (08n09) ◽  
pp. 876-887 ◽  
Author(s):  
Jianguo Shao ◽  
Juliette Commodore ◽  
Baocheng Han ◽  
Cynthia Pruente ◽  
Christopher A. Hansen
Keyword(s):  
Dimethyl Sulfoxide ◽  
Aqueous Media ◽  
Spectroscopic Characterization ◽  
Spectroscopic Properties ◽  
Axial Ligand ◽  
Electron Transfer Mechanism ◽  
Axial Ligands ◽  
Uv Visible ◽  
High Concentrations

Two cobalt porphyrazines, 2,3-tetrapyridoporphyrazine and 3,4-tetrapyridoporphyrazine, were examined in N,N-dimethylformamide, dimethyl sulfoxide and pyridine solutions as to their electrochemical, spectroelectrochemical and ESR spectroscopic properties. These results were compared with those of the unsubstituted cobalt phthalocyanine. At high concentrations, aggregation was observed for each investigated compound in the three solvents. The intensity of ESR signals of each derivative depends upon the extent of aggregation in its solution. The g values shift towards high field with an increase in the strength of the axial ligand and the number of axial ligands on the cobalt center. Both tetrapyridoporphyrazine complexes undergo one oxidation and three reductions in N,N-dimethylformamide, dimethyl sulfoxide or pyridine solution. Thin-layer UV-visible spectroelectrochemical results confirmed that the first oxidation and first reduction of both compounds are metal-centered while the second and third reductions are ring-centered. An overall electron transfer mechanism for both porphyrazine derivatives is proposed.

Modified Harrick reaction cell for in situ/operando fiber optics diffuse reflectance UV–visible spectroscopic characterization of catalysts

2018 ◽  
Vol 561 ◽  
pp. 7-18 ◽  
Author(s):  
Priya D. Srinivasan ◽  
Steven R. Nitz ◽  
Kyle J. Stephens ◽  
Ed Atchison ◽  
Juan J. Bravo-Suarez
Keyword(s):  
Fiber Optics ◽  
Diffuse Reflectance ◽  
Spectroscopic Characterization ◽  
Reaction Cell ◽  
Uv Visible
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