scholarly journals Modifications of the Aerobic Respiratory Chain of Paracoccus Denitrificans in Response to Superoxide Oxidative Stress

2019 ◽  
Vol 7 (12) ◽  
pp. 640 ◽  
Author(s):  
Vojtěch Sedláček ◽  
Igor Kučera
Keyword(s):  
Oxidative Stress ◽  
Respiratory Chain ◽  
Nadh Dehydrogenase ◽  
Paracoccus Denitrificans ◽  
Mrna Level ◽  
Oxygen Species ◽  
Stress Perception ◽  
Iron Sulfur Clusters ◽  
Iron Sulfur ◽  
Mammalian Mitochondria

Paracoccus denitrificans is a strictly respiring bacterium with a core respiratory chain similar to that of mammalian mitochondria. As such, it continuously produces and has to cope with superoxide and other reactive oxygen species. In this work, the effects of artificially imposed superoxide stress on electron transport were examined. Exposure of aerobically growing cells to paraquat resulted in decreased activities of NADH dehydrogenase, succinate dehydrogenase, and N,N,N’,N’-tetramethyl-p-phenylenediamine (TMPD) oxidase. Concomitantly, the total NAD(H) pool size in cells was approximately halved, but the NADH/NAD+ ratio increased twofold, thus partly compensating for inactivation losses of the dehydrogenase. The inactivation of respiratory dehydrogenases, but not of TMPD oxidase, also took place upon treatment of the membrane fraction with xanthine/xanthine oxidase. The decrease in dehydrogenase activities could be fully rescued by anaerobic incubation of membranes in a mixture containing 2-mercaptoethanol, sulfide and ferrous iron, which suggests iron–sulfur clusters as targets for superoxide. By using cyanide titration, a stress-sensitive contribution to the total TMPD oxidase activity was identified and attributed to the cbb3-type terminal oxidase. This response (measured by both enzymatic activity and mRNA level) was abolished in a mutant defective for the FnrP transcription factor. Therefore, our results provide evidence of oxidative stress perception by FnrP.

scholarly journals Identification of Streptococcus thermophilus CNRZ368 Genes Involved in Defense against Superoxide Stress

2004 ◽  
Vol 70 (4) ◽  
pp. 2220-2229 ◽  
Author(s):  
Annabelle Thibessard ◽  
Frédéric Borges ◽  
Annabelle Fernandez ◽  
Brigitte Gintz ◽  
Bernard Decaris ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Insertional Mutagenesis ◽  
Iron Homeostasis ◽  
Defense Mechanism ◽  
Streptococcus Thermophilus ◽  
Rna Modification ◽  
Cell Wall Metabolism ◽  
Iron Sulfur Clusters ◽  
Iron Sulfur ◽  
Oxidative Stress Defense

ABSTRACT To better understand the defense mechanism of Streptococcus thermophilus against superoxide stress, molecular analysis of 10 menadione-sensitive mutants, obtained by insertional mutagenesis, was undertaken. This analysis allowed the identification of 10 genes that, with respect to their putative functions, were classified into five categories: (i) those involved in cell wall metabolism, (ii) those involved in exopolysaccharide translocation, (iii) those involved in RNA modification, (iv) those involved in iron homeostasis, and (v) those whose functions are still unknown. The behavior of the 10 menadione-sensitive mutants exposed to heat shock was investigated. Data from these experiments allowed us to distinguish genes whose action might be specific to oxidative stress defense (tgt, ossF, and ossG) from those whose action may be generalized to other stressful conditions (mreD, rodA, pbp2b, cpsX, and iscU). Among the mutants, two harbored an independently inserted copy of pGh9:ISS1 in two loci close to each other. More precisely, these two loci are homologous to the sufD and iscU genes, which are involved in the biosynthesis of iron-sulfur clusters. This region, called the suf region, was further characterized in S. thermophilus CNRZ368 by sequencing and by construction of ΔsufD and iscU97 nonpolar mutants. The streptonigrin sensitivity levels of both mutants suggest that these two genes are involved in iron metabolism.

scholarly journals Structure-function studies of iron-sulfur clusters and semiquinones in the NADH-Q oxidoreductase segment of the respiratory chain

1998 ◽  
Vol 1365 (1-2) ◽  
pp. 301-308 ◽  
Author(s):  
Tomoko Ohnishi ◽  
Vladimir D. Sled ◽  
Takahiro Yano ◽  
Takao Yagi ◽  
Dosymzhan S. Burbaev ◽  
...  
Keyword(s):  
Structure Function ◽  
Respiratory Chain ◽  
Iron Sulfur Clusters ◽  
Iron Sulfur

scholarly journals The Di-iron RIC Protein (YtfE) ofEscherichia coliInteracts with the DNA-Binding Protein from Starved Cells (Dps) To Diminish RIC Protein-Mediated Redox Stress

2018 ◽  
Vol 200 (24) ◽  
Author(s):  
Liliana S. O. Silva ◽  
Joana M. Baptista ◽  
Charlotte Batley ◽  
Simon C. Andrews ◽  
Lígia M. Saraiva
Keyword(s):  
Double Mutant ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Redox Stress ◽  
Iron Sulfur Clusters ◽  
Iron Storage ◽  
Content Type ◽  
E Coli ◽  
Iron Sulfur ◽  
Two Hybrid

ABSTRACTThe RIC (repair of iron clusters) protein ofEscherichia coliis a di-iron hemerythrin-like protein that has a proposed function in repairing stress-damaged iron-sulfur clusters. In this work, we performed a bacterial two-hybrid screening to search for RIC-protein interaction partners inE. coli. As a result, theDNA-bindingprotein fromstarved cells (Dps) was identified, and its potential interaction with RIC was tested by bacterial adenylate cyclase-based two-hybrid (BACTH) system, bimolecular fluorescence complementation, and pulldown assays. Using the activity of two Fe-S-containing enzymes as indicators of cellular Fe-S cluster damage, we observed that strains with single deletions ofricordpshave significantly lower aconitase and fumarase activities. In contrast, theric dpsdouble mutant strain displayed no loss of aconitase and fumarase activity with respect to that of the wild type. Additionally, while complementation of theric dpsdouble mutant withricled to a severe loss of aconitase activity, this effect was no longer observed when a gene encoding a di-iron site variant of the RIC protein was employed. Thedpsmutant exhibited a large increase in reactive oxygen species (ROS) levels, but this increase was eliminated whenricwas also inactivated. Absence of other iron storage proteins, or of peroxidase and catalases, had no impact on RIC-mediated redox stress induction. Hence, we show that RIC interacts with Dps in a manner that serves to protectE. colifrom RIC protein-induced ROS.IMPORTANCEThe mammalian immune system produces reactive oxygen and nitrogen species that kill bacterial pathogens by damaging key cellular components, such as lipids, DNA, and proteins. However, bacteria possess detoxifying and repair systems that mitigate these deleterious effects. TheEscherichia coliRIC (repair of iron clusters) protein is a di-iron hemerythrin-like protein that repairs stress-damaged iron-sulfur clusters.E. coliDps is an iron storage protein of the ferritin superfamily with DNA-binding capacity that protects cells from oxidative stress. This work shows that theE. coliRIC and Dps proteins interact in a fashion that counters RIC protein-induced reactive oxygen species (ROS). Altogether, we provide evidence for the formation of a new bacterial protein complex and reveal a novel contribution for Dps in bacterial redox stress protection.

scholarly journals Mitochondria recycle nitrite back to the bioregulator nitric monoxide.

2000 ◽  
Vol 47 (4) ◽  
pp. 913-921 ◽  
Author(s):  
H Nohl ◽  
K Staniek ◽  
B Sobhian ◽  
S Bahrami ◽  
H Redl ◽  
...  
Keyword(s):  
Respiratory Chain ◽  
Paracoccus Denitrificans ◽  
Hypovolemic Shock ◽  
Heme Iron ◽  
Nitrite Reduction ◽  
No Donors ◽  
Mammalian Mitochondria ◽  
Membrane Bound ◽  
Chemical Sequestration ◽  
Nitric Monoxide

Nitric monoxide (NO) exerts a great variety of physiological functions. L-Arginine supplies amino groups which are transformed to NO in various NO-synthase-active isoenzyme complexes. NO-synthesis is stimulated under various conditions increasing the tissue of stable NO-metabolites. The major oxidation product found is nitrite. Elevated nitrite levels were reported to exist in a variety of diseases including HIV, reperfusion injury and hypovolemic shock. Denitrifying bacteria such as Paracoccus denitrificans have a membrane bound set of cytochromes (cyt cd1, cyt bc) which were shown to be involved in nitrite reduction activities. Mammalian mitochondria have similar cytochromes which form part of the respiratory chain. Like in bacteria quinols are used as reductants of these types of cytochromes. The observation of one-e- divergence from this redox-couple to external dioxygen made us to study whether this site of the respiratory chain may also recycle nitrite back to its bioactive form NO. Thus, the aim of the present study was therefore to confirm the existence of a reductive pathway which reestablishes the existence of the bioregulator NO from its main metabolite NO2-. Our results show that respiring mitochondria readily reduce added nitrite to NO which was made visible by nitrosylation of deoxyhemoglobin. The adduct gives characteristic triplet-ESR-signals. Using inhibitors of the respiratory chain for chemical sequestration of respiratory segments we were able to identify the site where nitrite is reduced. The results confirm the ubiquinone/cyt be1 couple as the reductant site where nitrite is recycled. The high affinity of NO to the heme-iron of cytochrome oxidase will result in an impairment of mitochondrial energy-production. "Nitrite tolerance" of angina pectoris patients using NO-donors may be explained in that way.

Mitochondrial oxidative injury: a key player in nonalcoholic fatty liver disease

2020 ◽  
Vol 319 (3) ◽  
pp. G400-G411
Author(s):  
Waleska Dornas ◽  
Detlef Schuppan
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Mitochondrial Dna ◽  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Respiratory Chain ◽  
Fatty Liver Disease ◽  
Oxygen Species ◽  
Nonalcoholic Fatty Liver

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. NAFLD is tightly linked to the metabolic syndrome, insulin resistance, and oxidative stress. Globally, its inflammatory form, nonalcoholic steatohepatitis (NASH), has become the main cause of liver-related morbidity and mortality, mainly due to liver cirrhosis and primary liver cancer. One hallmark of NASH is the presence of changes in mitochondrial morphology and function that are accompanied by a blocked flow of electrons in the respiratory chain, which increases formation of mitochondrial reactive oxygen species in a self-perpetuating vicious cycle. Consequences are oxidation of DNA bases and mitochondrial DNA depletion that are coupled with genetic and acquired mitochondrial DNA mutations, all impairing the resynthesis of respiratory chain polypeptides. In general, several maladaptations of pathways that usually maintain energy homeostasis occur with the early and late excess metabolic stress in NAFLD and NASH. We discuss the interplay between hepatocyte mitochondrial stress and inflammatory responses, focusing primarily on events initiated and maintained by mitochondrial free radical-induced damage in NAFLD. Importantly, mitochondrial oxidative stress and dysfunction are modulated by key pharmacological targets that are related to excess production of reactive oxygen species, mitochondrial turnover and the mitochondrial unfolded protein response, mitophagy, and mitochondrial biogenesis. However, the efficacy of such interventions depends on NAFLD/NASH disease stage.

scholarly journals Photobiomodulation and Oxidative Stress: 980 nm Diode Laser Light Regulates Mitochondrial Activity and Reactive Oxygen Species Production

2021 ◽  
Vol 2021 ◽  
pp. 1-11 ◽  
Author(s):  
Andrea Amaroli ◽  
Claudio Pasquale ◽  
Angelina Zekiy ◽  
Anatoliy Utyuzh ◽  
Stefano Benedicenti ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Oxygen Consumption ◽  
Respiratory Chain ◽  
Laser Light ◽  
Krebs Cycle ◽  
Mitochondrial Activity ◽  
Oxygen Species ◽  
Atp Production ◽  
And Oxidative Stress

Photobiomodulation with 808 nm laser light electively stimulates Complexes III and IV of the mitochondrial respiratory chain, while Complexes I and II are not affected. At the wavelength of 1064 nm, Complexes I, III, and IV are excited, while Complex II and some mitochondrial matrix enzymes seem to be not receptive to photons at that wavelength. Complex IV was also activated by 633 nm. The mechanism of action of wavelengths in the range 900–1000 nm on mitochondria is less understood or not described. Oxidative stress from reactive oxygen species (ROS) generated by mitochondrial activity is an inescapable consequence of aerobic metabolism. The antioxidant enzyme system for ROS scavenging can keep them under control. However, alterations in mitochondrial activity can cause an increment of ROS production. ROS and ATP can play a role in cell death, cell proliferation, and cell cycle arrest. In our work, bovine liver isolated mitochondria were irradiated for 60 sec, in continuous wave mode with 980 nm and powers from 0.1 to 1.4 W (0.1 W increment at every step) to generate energies from 6 to 84 J, fluences from 7.7 to 107.7 J/cm2, power densities from 0.13 to 1.79 W/cm2, and spot size 0.78 cm2. The control was equal to 0 W. The activity of the mitochondria’s complexes, Krebs cycle enzymes, ATP production, oxygen consumption, generation of ROS, and oxidative stress were detected. Lower powers (0.1–0.2 W) showed an inhibitory effect; those that were intermediate (0.3–0.7 W) did not display an effect, and the higher powers (0.8–1.1 W) induced an increment of ATP synthesis. Increasing the power (1.2–1.4 W) recovered the ATP production to the control level. The interaction occurred on Complexes III and IV, as well as ATP production and oxygen consumption. Results showed that 0.1 W uncoupled the respiratory chain and induced higher oxidative stress and drastic inhibition of ATP production. Conversely, 0.8 W kept mitochondria coupled and induced an increase of ATP production by increments of Complex III and IV activities. An augmentation of oxidative stress was also observed, probably as a consequence of the increased oxygen consumption and mitochondrial isolation experimental conditions. No effect was observed using 0.5 W, and no effect was observed on the enzymes of the Krebs cycle.

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