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Mariya Ostroukhova, Zhanneta Zalutskaya, Elena Ermilova
A feature of the mitochondrial electron transport chain in plants, some protists and many fungi is the presence of two terminal oxidases, the energy-conserving cytochrome oxidase and another termed alternative oxidase (AOX). AOX branches from the main respiratory chain, directly coupling the oxidation of ubiquinol with reduction of oxygen to water. The AOX genes can be divided into two discrete subfamilies, AOX1 and AOX2. Although AOX has been proposed to play essential roles in stress tolerance of organisms, the role of subfamily AOX2 is largely unknown...
December 13, 2016: European Journal of Protistology
Marten Szibor, Praveen K Dhandapani, Eric Dufour, Kira M Holmström, Yuan Zhuang, Isabelle Salwig, Ilka Wittig, Juliana Heidler, Zemfira Gizatullina, Timur Gainutdinov, German Mouse Clinic Consortium, Helmut Fuchs, Valérie Gailus-Durner, Martin Hrabě de Angelis, Jatin Nandania, Vidya Velagapudi, Astrid Wietelmann, Pierre Rustin, Frank N Gellerich, Howard T Jacobs, Thomas Braun
Plants and many lower organisms, but not mammals, express alternative oxidases (AOX) that branch the mitochondrial respiratory chain, transferring electrons directly from ubiquinol to oxygen without proton pumping. Thus, they maintain electron flow under conditions when the classical respiratory chain is impaired, limiting excess production of oxygen radicals and supporting redox and metabolic homeostasis. AOX from Ciona intestinalis has been used to study and mitigate mitochondrial impairments in mammalian cell-lines, Drosophila disease models and, most recently, in the mouse, where multiple, lentivector-AOX transgenes conferred substantial expression in specific tissues...
December 14, 2016: Disease Models & Mechanisms
Wilson Garcia-Neto, Alfredo Cabrera-Orefice, Salvador Uribe-Carvajal, Alicia J Kowaltowski, Luis Alberto Luévano-Martínez
The oleaginous yeast Debaryomyces hansenii is a good model to understand molecular mechanisms involved in halotolerance because of its impressive ability to survive under a wide range of salt concentrations. Several cellular adaptations are implicated in this response, including the presence of a cyanide-insensitive ubiquinol oxidase (Aox). This protein, which is present in several taxonomical orders, has been related to different stress responses. However, little is known about its role in mitochondria during transitions from low to high saline environments...
2017: PloS One
Nicole A Alber, Hampavi Sivanesan, Greg C Vanlerberghe
The plant mitochondrial electron transport chain (ETC) is bifurcated such that electrons from ubiquinol are passed to oxygen via the usual cytochrome path or through alternative oxidase (AOX). We previously showed that knockdown of AOX in transgenic tobacco increased leaf concentrations of nitric oxide (NO), implying that an activity capable of generating NO had been effected. Here we identify the potential source of this NO. Treatment of leaves with antimycin A (AA, Qi -site inhibitor of Complex III) increased NO amount more than treatment with myxothiazol (Myxo, Qo -site inhibitor) despite both being equally effective at inhibiting respiration...
December 16, 2016: Plant, Cell & Environment
Zhigang Qi, Kristina M Smith, Erin L Bredeweg, Natasa Bosnjak, Michael Freitag, Frank E Nargang
In Neurospora crassa, blocking the function of the standard mitochondrial electron transport chain results in the induction of an alternative oxidase (AOX). AOX transfers electrons directly from ubiquinol to molecular oxygen. AOX serves as a model of retrograde regulation since it is encoded by a nuclear gene that is regulated in response to signals from mitochondria. The N. crassa transcription factors AOD2 and AOD5 are necessary for the expression of the alternative oxidase gene. To gain insight into the mechanism by which these factors function, and to determine if they have roles in the expression of additional genes in N...
December 16, 2016: G3: Genes—Genomes—Genetics
Xingxing Jian, Ningchuan Li, Cheng Zhang, Qiang Hua
BACKGROUND: Succinic acid is a valuable product due to its wide-ranging utilities. To improve succinate production and reduce by-products formation, Escherichia coli NZN111 was constructed by insertional inactivation of lactate dehydrogenase (LDH) and pyruvate formate lyase (PFL) encoded by the genes ldhA and pflB, respectively. However, this double-deletion mutant is incapable of anaerobically growing on glucose in rich or minimal medium even with acetate supplementation. A widespread hold view is that the inactivation of NADH-dependent LDH limits the regeneration of NAD(+) and consequently disables proper growth under anaerobic conditions...
2016: Bioresources and Bioprocessing
Alexandra Fischer, Simone Onur, Petra Niklowitz, Thomas Menke, Matthias Laudes, Gerald Rimbach, Frank Döring
Aging is associated with sarcopenia, which is a loss of skeletal muscle mass and function. Coenzyme Q10 (CoQ10) is involved in several important functions that are related to bioenergetics and protection against oxidative damage; however, the role of CoQ10 as a determinant of muscular strength is not well documented. The aim of the present study was to evaluate the determinants of muscular strength by examining hand grip force in relation to CoQ10 status, gender, age and body mass index (BMI) in two independent cohorts (n = 334, n = 967)...
2016: PloS One
Jörg Ellinger, Arabella Gromes, Mirjam Poss, Maria Brüggemann, Doris Schmidt, Nadja Ellinger, Yuri Tolkach, Dimo Dietrich, Glen Kristiansen, Stefan C Müller
Mitochondrial dysfunction is common in cancer, and the mitochondrial electron transport chain is often affected in carcinogenesis. So far, few is known about the expression of the mitochondrial complex III (ubiquinol-cytochrome c reductase complex) subunits in clear cell renal cell carcinoma (ccRCC). In this study, the NextBio database was used to determine an expression profile of the mitochondrial complex III subunits based on published microarray studies. We observed that five out of 11 subunits of the complex III were downregulated in at least three microarray studies...
November 10, 2016: Oncotarget
Antonella Peduto, Maria Scuotto, Verena Krauth, Fiorentina Roviezzo, Antonietta Rossi, Veronika Temml, Veronica Esposito, Hermann Stuppner, Daniela Schuster, Bruno D'Agostino, Chiara Schiraldi, Mario de Rosa, Oliver Werz, Rosanna Filosa
Aiming to assess the biological activities of synthetic 1,4-benzoquinones, we previously synthesized different libraries of benzoquinones with lipophilic and bulky alkyl- or aryl-substituents that inhibited 5-lipoxygenase (5-LO). The high potency of 4,5-dimethoxy-3-alkyl-1,2-benzoquinones on 5-LO led to the idea to further modify the structures and thus to improve the inhibitory potential in vitro and in vivo as well as to investigate SARs. Systematic structural optimization through accurate structure-based design resulted in compound 30 (3-tridecyl-4,5-dimethoxybenzene-1,2-diol), an ubiquinol derivative that exhibited the strongest anti-inflammatory effect, with a 10-fold improved 5-LO inhibitory activity (IC50 = 28 nM) in activated neutrophils...
October 22, 2016: European Journal of Medicinal Chemistry
Hema P Narra, Casey L C Schroeder, Abha Sahni, Mark Rojas, Kamil Khanipov, Yuriy Fofanov, Sanjeev K Sahni
Small regulatory RNAs comprise critically important modulators of gene expression in bacteria, yet very little is known about their prevalence and functions in Rickettsia species. R. conorii, the causative agent of Mediterranean spotted fever, is a tick-borne pathogen that primarily infects microvascular endothelium in humans. We have determined the transcriptional landscape of R. conorii during infection of Human Microvascular Endothelial Cells (HMECs) by strand-specific RNA sequencing to identify 4 riboswitches, 13 trans-acting (intergenic), and 22 cis-acting (antisense) small RNAs (termed 'Rc_sR's)...
November 11, 2016: Scientific Reports
Aaron Robertson, Kyle Schaltz, Karina Neimanis, James F Staples, Allison E McDonald
Alternative oxidase (AOX) is a terminal oxidase within the inner mitochondrial membrane (IMM) present in many organisms where it functions in the electron transport system (ETS). AOX directly accepts electrons from ubiquinol and is therefore capable of bypassing ETS Complexes III and IV. The human genome does not contain a gene coding for AOX, so AOX expression has been suggested as a gene therapy for a range of human mitochondrial diseases caused by genetic mutations that render Complex III and/or IV dysfunctional...
October 2016: Journal of Bioenergetics and Biomembranes
Vera G Grivennikova, Vladimir S Kozlovsky, Andrei D Vinogradov
Bovine heart mitochondrial respiratory complex II generates ROS, mostly as superoxide, at the rate of about 20% of that detected during simultaneous operation of complex I and II when oxidation of ubiquinol is prevented by myxothiazol. ROS generating activity at different fumarate/succinate concentrations ratio implies that an enzyme component with a midpoint potential 40mV more positive than that of fumarate/succinate couple is the donor for one-electron reduction of oxygen. This suggests that the iron-sulfur cluster(s) is(are) involved in superoxide formation...
February 2017: Biochimica et Biophysica Acta
D Wang, A Fu
Mitochondria possess oxygen-consuming respiratory electron transfer chains (RETCs), and the oxygen-evolving photosynthetic electron transfer chain (PETC) resides in chloroplasts. Evolutionarily mitochondria and chloroplasts are derived from ancient α-proteobacteria and cyanobacteria, respectively. However, cyanobacteria harbor both RETC and PETC on their thylakoid membranes. It is proposed that chloroplasts could possess a RETC on the thylakoid membrane, in addition to PETC. Identification of a plastid terminal oxidase (PTOX) in the chloroplast from the Arabidopsis variegation mutant immutans (im) demonstrated the presence of a RETC in chloroplasts, and the PTOX is the committed oxidase...
2016: Enzymes
Lothar Esser, Fei Zhou, Yihui Zhou, Yumei Xiao, Wai-Kwan Tang, Chang-An Yu, Zhaohai Qin, Di Xia
Complex III or the cytochrome (cyt) bc1 complex constitutes an integral part of the respiratory chain of most aerobic organisms and of the photosynthetic apparatus of anoxygenic purple bacteria. The function of cyt bc1 is to couple the reaction of electron transfer from ubiquinol to cytochrome c to proton pumping across the membrane. Mechanistically, the electron transfer reaction requires docking of its Rieske iron-sulfur protein (ISP) subunit to the quinol oxidation site (QP) of the complex. Formation of an H-bond between the ISP and the bound substrate was proposed to mediate the docking...
November 25, 2016: Journal of Biological Chemistry
Xue-Jiao Chang, Chao-Qun Zheng, Yu-Wei Wang, Chuang Meng, Xiao-Lu Xie, Hai-Peng Liu
Gradually increasing atmospheric CO2 partial pressure (pCO2) has caused an imbalance in carbonate chemistry and resulted in decreased seawater pH in marine ecosystems, termed seawater acidification. Anthropogenic seawater acidification is postulated to affect the physiology of many marine calcifying organisms. To understand the possible effects of seawater acidification on the proteomic responses of a marine crustacean brine shrimp (Artemia sinica) three groups of cysts were hatched and further raised in seawater at different pH levels (8...
November 2016: Fish & Shellfish Immunology
Rich Boden, Lee P Hutt, Marcel Huntemann, Alicia Clum, Manoj Pillay, Krishnaveni Palaniappan, Neha Varghese, Natalia Mikhailova, Dimitrios Stamatis, Tatiparthi Reddy, Chew Yee Ngan, Chris Daum, Nicole Shapiro, Victor Markowitz, Natalia Ivanova, Tanja Woyke, Nikos Kyrpides
Thermithiobacillus tepidarius DSM 3134(T) was originally isolated (1983) from the waters of a sulfidic spring entering the Roman Baths (Temple of Sulis-Minerva) at Bath, United Kingdom and is an obligate chemolithoautotroph growing at the expense of reduced sulfur species. This strain has a genome size of 2,958,498 bp. Here we report the genome sequence, annotation and characteristics. The genome comprises 2,902 protein coding and 66 RNA coding genes. Genes responsible for the transaldolase variant of the Calvin-Benson-Bassham cycle were identified along with a biosynthetic horseshoe in lieu of Krebs' cycle sensu stricto...
2016: Standards in Genomic Sciences
Chang Sun, Alexander T Taguchi, Josh V Vermaas, Nathan J Beal, Patrick J O'Malley, Emad Tajkhorshid, Robert B Gennis, Sergei A Dikanov
The respiratory cytochrome bo3 ubiquinol oxidase from Escherichia coli has a high-affinity ubiquinone binding site that stabilizes the one-electron reduced ubisemiquinone (SQH), which is a transient intermediate during the electron-mediated reduction of O2 to water. It is known that SQH is stabilized by two strong hydrogen bonds from R71 and D75 to ubiquinone carbonyl oxygen O1 and weak hydrogen bonds from H98 and Q101 to O4. In this work, SQH was investigated with orientation-selective Q-band (∼34 GHz) pulsed (1)H electron-nuclear double resonance (ENDOR) spectroscopy on fully deuterated cytochrome (cyt) bo3 in a H2O solvent so that only exchangeable protons contribute to the observed ENDOR spectra...
October 11, 2016: Biochemistry
Huan Zhang, Lulu Shi, Xinlei Mao, Jinping Lin, Dongzhi Wei
Membrane-bound alcohol dehydrogenase (mADH) was overexpressed in Gluconobacter oxydans DSM 2003, and the effects on cell growth and glycolic acid production were investigated. The transcription levels of two terminal ubiquinol oxidases (bo3 and bd) in the respiratory chain of the engineered strain G. oxydans-adhABS were up-regulated by 13.4- and 3.8-fold, respectively, which effectively enhanced the oxygen uptake rate, resulting in higher resistance to acid. The cell biomass of G. oxydans-adhABS could increase by 26%-33% when cultivated in a 7L bioreactor...
November 10, 2016: Journal of Biotechnology
A Kamali Sangani, A A Masoudi, R Vaez Torshizi
The objectives of the current study were to investigate the activity of the electron transport chain (ETC) complexes, adenosine triphosphate (ATP), and reactive oxygen species (ROS) in the sperm mitochondria of 2 Iranian slow- and fast-growing chickens, namely native and Aryan strains. In this study, semen of 133 roosters was analyzed by computer-assisted sperm analysis (CASA). The roosters were categorized by sperm progressivity, as a low or high sperm motility phenotype. Mitochondrial complex I (NADH ubiquinone oxidoreductase), II (succinate dehydrogenase), III (ubiquinol cytochrome C reductase), IV (cytochrome C oxidase) activity, ATP, and ROS production in sperm were assayed...
January 1, 2017: Poultry Science
Francesco Francia, Marco Malferrari, Pascal Lanciano, Stefan Steimle, Fevzi Daldal, Giovanni Venturoli
The ubiquinol:cytochrome (cyt) c oxidoreductase (or cyt bc1) is an important membrane protein complex in photosynthetic and respiratory energy transduction. In bacteria such as Rhodobacter capsulatus it is constituted of three subunits: the iron-sulfur protein, cyt b and cyt c1, which form two catalytic domains, the Qo (hydroquinone (QH2) oxidation) and Qi (quinone (Q) reduction) sites. At the Qo site, the pathways of bifurcated electron transfers emanating from QH2 oxidation are known, but the associated proton release routes are not well defined...
November 2016: Biochimica et Biophysica Acta
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