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Electron Transport Chain (electron + transport_chain)
Kinds of Electron Transport Chain Selected AbstractsIntegrated regulation in response to aromatic compounds: from signal sensing to attractive behaviourENVIRONMENTAL MICROBIOLOGY, Issue 12 2003Victoria Shingler Summary Deciphering the complex interconnecting bacterial responses to the presence of aromatic compounds is required to gain an integrated understanding of how aromatic catabolic processes function in relation to their genome and environmental context. In addition to the properties of the catabolic enzymes themselves, regulatory responses on at least three different levels are important. At a primary level, aromatic compounds control the activity of specific members of many families of transcriptional regulators to direct the expression of the specialized enzymes for their own catabolism. At a second level, dominant global regulation in response to environmental and physiological cues is incorporated to subvert and couple transcription levels to the energy status of the bacteria. Mediators of these global regulatory responses include the alarmone (p)ppGpp, the DNA-bending protein IHF and less well-defined systems that probably sense the energy status through the activity of the electron transport chain. At a third level, aromatic compounds can also impact on catabolic performance by provoking behavioural responses that allow the bacteria to seek out aromatic growth substrates in their environment. [source] Oxygen sensing in hypoxic pulmonary vasoconstriction: using new tools to answer an age-old questionEXPERIMENTAL PHYSIOLOGY, Issue 1 2008Gregory B. Waypa Hypoxic pulmonary vasoconstriction (HPV) becomes activated in response to alveolar hypoxia and, although the characteristics of HPV have been well described, the underlying mechanism of O2 sensing which initiates the HPV response has not been fully established. Mitochondria have long been considered as a putative site of oxygen sensing because they consume O2 and therefore represent the intracellular site with the lowest oxygen tension. However, two opposing theories have emerged regarding mitochondria-dependent O2 sensing during hypoxia. One model suggests that there is a decrease in mitochondrial reactive oxygen species (ROS) levels during the transition from normoxia to hypoxia, resulting in the shift in cytosolic redox to a more reduced state. An alternative model proposes that hypoxia paradoxically increases mitochondrial ROS signalling in pulmonary arterial smooth muscle. Experimental resolution of the question of whether the mitochondrial ROS levels increase or decrease during hypoxia has been problematic owing to the technical limitations of the tools used to assess oxidant stress as well as the pharmacological agents used to inhibit the mitochondrial electron transport chain. However, recent developments in genetic techniques and redox-sensitive probes may allow us eventually to reach a consensus concerning the O2 sensing mechanism underlying HPV. [source] Transcription of mammalian cytochrome c oxidase subunit IV-2 is controlled by a novel conserved oxygen responsive elementFEBS JOURNAL, Issue 21 2007Maik Hüttemann Subunit 4 of cytochrome c oxidase (CcO) is a nuclear-encoded regulatory subunit of the terminal complex of the mitochondrial electron transport chain. We have recently discovered an isoform of CcO 4 (CcO4-2) which is specific to lung and trachea, and is induced after birth. The role of CcO as the major cellular oxygen consumer, and the lung-specific expression of CcO4-2, led us to investigate CcO4-2 gene regulation. We cloned the CcO4-2 promoter regions of cow, rat and mouse and compared them with the human promoter. Promoter activity is localized within a 118-bp proximal region of the human promoter and is stimulated by hypoxia, reaching a maximum (threefold) under 4% oxygen compared with normoxia. CcO4-2 oxygen responsiveness was assigned by mutagenesis to a novel promoter element (5,-GGACGTTCCCACG-3,) that lies within a 24-bp region that is 79% conserved in all four species. This element is able to bind protein, and competition experiments revealed that, within the element, the four core bases 5,-TCNCA-3, are obligatory for transcription factor binding. CcO isolated from lung showed a 2.5-fold increased maximal turnover compared with liver CcO. We propose that CcO4-2 expression in highly oxygenated lung and trachea protects these tissues from oxidative damage by accelerating the last step in the electron transport chain, leading to a decrease in available electrons for free radical formation. [source] Isolation and structural characterization of the Ndh complex from mesophyll and bundle sheath chloroplasts of Zea maysFEBS JOURNAL, Issue 11 2005Costel C. Darie Complex I (NADH: ubiquinone oxidoreductase) is the first complex in the respiratory electron transport chain. Homologs of this complex exist in bacteria, mitochondria and chloroplasts. The minimal complex I from mitochondria and bacteria contains 14 different subunits grouped into three modules: membrane, connecting, and soluble subcomplexes. The complex I homolog (NADH dehydrogenase or Ndh complex) from chloroplasts from higher plants contains genes for two out of three modules: the membrane and connecting subcomplexes. However, there is not much information about the existence of the soluble subcomplex (which is the electron input device in bacterial complex I) in the composition of the Ndh complex. Furthermore, there are contrasting reports regarding the subunit composition of the Ndh complex and its molecular mass. By using blue native (BN)/PAGE and Tricine/PAGE or colorless-native (CN)/PAGE, BN/PAGE and Tricine/PAGE, combined with mass spectrometry, we attempted to obtain more information about the plastidal Ndh complex from maize (Zea mays). Using antibodies, we detected the expression of a new ndh gene (ndhE) in mesophyll (MS) and bundle sheath (BS) chloroplasts and in ethioplasts (ET). We determined the molecular mass of the Ndh complex (550 kDa) and observed that it splits into a 300 kDa membrane subcomplex (containing NdhE) and a 250 kDa subcomplex (containing NdhH, -J and -K). The Ndh complex forms dimers at 1000,1100 kDa in both MS and BS chloroplasts. Native/PAGE of the MS and BS chloroplasts allowed us to determine that the Ndh complex contains at least 14 different subunits. The native gel electrophoresis, western blotting and mass spectrometry allowed us to identify five of the Ndh subunits. We also provide a method that allows the purification of large amounts of Ndh complex for further structural, as well as functional studies. [source] Respiratory protection of nitrogenase in Azotobacter species: is a widely held hypothesis unequivocally supported by experimental evidence?FEMS MICROBIOLOGY REVIEWS, Issue 4 2000Jürgen Oelze Abstract The hypothesis of respiratory protection, originally formulated on the basis of results obtained with Azotobacter species, postulates that consumption of O2 at the surface of diazotrophic prokaryotes protects nitrogenase from inactivation by O2. Accordingly, it is assumed that, at increased ambient O2 concentrations, nitrogenase activity depends on increased activities of a largely uncoupled respiratory electron transport system. The present review compiles evidence indicating that cellular O2 consumption as well as both the activity and the formation of the respiratory system of Azotobacter vinelandii are controlled by the C/N ratio, that is to say the ratio at which the organism consumes the substrate (i.e. the source of carbon, reducing equivalents and ATP) per source of compound nitrogen. The maximal respiratory capacity which can be attained at increased C/N ratios, however, is controlled, within limits, by the ambient O2 concentration. When growth becomes N-limited at increased C/N ratios, cells synthesize nitrogenase and fix N2. Under these diazotrophic conditions, cellular O2 consumption remains constant at a level controlled by the O2 concentration. Control by O2 has been studied on the basis of both whole cell respiration and defined segments of the respiratory electron transport chain. The results demonstrate that the effect of O2 on the respiratory system is restricted to the lower range of O2 concentrations up to about 70 ,M. Nevertheless, azotobacters are able to grow diazotrophically at dissolved O2 concentrations of up to about 230 ,M indicating that respiratory protection is not warranted at increased ambient O2 concentrations. This conclusion is supported and extended by a number of results largely excluding an obvious relationship between nitrogenase activity and the actual rate of cellular O2 consumption. On the basis of theoretical calculations, it is assumed that the rate of O2 diffusion into the cells is not significantly affected by respiration. All of these results lead to the conclusion that, in the protection of nitrogenase from O2 damage, O2 consumption at the cell surface is less effective than generally assumed. It is proposed that alternative factors like the supply of ATP and reducing equivalents are more important. [source] Maternal high-fat feeding primes steatohepatitis in adult mice offspring, involving mitochondrial dysfunction and altered lipogenesis gene expression,HEPATOLOGY, Issue 6 2009Kimberley D. Bruce Nonalcoholic fatty liver disease (NAFLD) describes an increasingly prevalent spectrum of liver disorders associated with obesity and metabolic syndrome. It is uncertain why steatosis occurs in some individuals, whereas nonalcoholic steatohepatitis (NASH) occurs in others. We have generated a novel mouse model to test our hypothesis: that maternal fat intake contributes to the development of NAFLD in adult offspring. Female mice were fed either a high-fat (HF) or control chow (C) diet before and during gestation and lactation. Resulting offspring were fed either a C or a HF diet after weaning, to generate four offspring groups; HF/HF, HF/C, C/HF, C/C. At 15 weeks of age, liver histology was normal in both the C/C and HF/C offspring. Kleiner scoring showed that although the C/HF offspring developed nonalcoholic fatty liver, the HF/HF offspring developed NASH. At 30 weeks, histological analysis and Kleiner scoring showed that both the HF/C and C/HF groups had NAFLD, whereas the HF/HF had a more severe form of NASH. Therefore, exposure to a HF diet in utero and during lactation contributes toward NAFLD progression. We investigated the mechanisms by which this developmental priming is mediated. At 15 weeks of age, hepatic mitochondrial electron transport chain (ETC) enzyme complex activity (I, II/III, and IV) was reduced in both groups of offspring from HF-fed mothers (HF/C and HF/HF). In addition, measurement of hepatic gene expression indicated that lipogenesis, oxidative stress, and inflammatory pathways were up-regulated in the 15-week-old HF/C and HF/HF offspring. Conclusion: Maternal fat intake contributes toward the NAFLD progression in adult offspring, which is mediated through impaired hepatic mitochondrial metabolism and up-regulated hepatic lipogenesis. (HEPATOLOGY 2009.) [source] Functional connections and pathways of coenzyme Q10-inducible genes: An in-silico studyIUBMB LIFE, Issue 10 2007Frank Döring Abstract Coenzyme Q10 (CoQ10, ubiquinone) is an essential cofactor in the electron transport chain, serves as a potent antioxidant in mitochondria and lipid membranes, and is often used as a dietary supplement for a number of diseases including cardiovascular diseases. Recently, we obtained evidence that CoQ10 (Kaneka Q10Ō) affects the expression of hundreds of human genes. To decipher the functional and regulatory connections of these genes, a literature search combined with transcription factor binding site analysis was performed using Genomatix BiblioSphere and MatInspector. This in-silico analysis revealed 17 CoQ10-inducible genes which are functionally connected by signalling pathways of G-protein coupled receptors, JAK/STAT, integrin, and beta-arrestin. Promoter analysis of these CoQ10-inducible genes showed one group of NF, B-regulated genes, namely IL5, thrombin, vitronectin receptor and C-reactive protein (CRP). Furthermore, a common promoter framework containing binding sites of the transcription factor families EVI1, HOXF, HOXC, and CLOX was identified in the promoters of IL5, CRP, and vitronectin receptor. The identified CoQ10-inducible genes and pathways play an important role in inflammatory response. Since these effects are based on an in-vitro study, the effect of CoQ10 on vascular health in vivo needs to be addressed in further animal and/or human intervention studies. IUBMB Life, 59: 628-633, 2007 [source] Sevoflurane and propofol depolarize mitochondria in rat and human cerebrocortical synaptosomes by different mechanismsACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009R. BAINS Background and objectives: The mitochondrial membrane potential drives the main functions of the mitochondria. Sevoflurane depolarizes neural mitochondria. There is still, however, limited information concerning the effect of anaesthetics on neural mitochondria in humans. The effect of sevoflurane and propofol on the intracellular Ca2+ concentration [Ca2+]i and the mitochondrial membrane potential (,,m) was therefore compared in rat and human synaptosomes, and the changes were related to interventions in the electron transport chain. Methods: Synaptosomes from rat and human cerebral cortex were loaded with the fluorescent probes fura-2 ([Ca2+]i) and JC-1 (,,m) before exposure to sevoflurane 1 and 2 minimum alveolar concentration (MAC), and propofol 30 and 100 ,M. The effect on the electron transport chain was investigated by blocking complex V. Results: Sevoflurane and propofol decreased ,,m in rat synaptosomes in a dose-dependent manner, and to the same extent by equipotent doses. Inhibition of complex V enhanced the depolarizing effect of sevoflurane 2 MAC, but not of propofol 100 ,M. Neither sevoflurane nor propofol affected [Ca2+]i significantly. Sevoflurane and propofol decreased ,,m in human synaptosomes to the same extent as in the rat experiments. Conclusions: Sevoflurane and propofol at equipotent doses depolarize the mitochondria in rat and human nerve terminals to the same extent. The depolarizing effect of propofol on ,m was more rapid in onset than that of sevoflurane. Whereas sevoflurane inhibits the respiratory chain sufficiently to cause ATP synthase reversal, the depolarizing effect of propofol seems to be related to inhibition of the respiratory chain from complex I to V. [source] Catechin as an antioxidant in liver mitochondrial toxicity: Inhibition of tamoxifen-Induced protein oxidation and lipid peroxidation,JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 3 2007Heena Tabassum Abstract Tamoxifen (TAM) is a nonsteroidal triphenylethylene antiestrogenic drug widely used in the treatment and prevention of breast cancer. TAM brings about a collapse of the mitochondrial membrane potential. It acts both as an uncoupling agent and as a powerful inhibitor of mitochondrial electron transport chain. The effect of catechin pretreatment on the mitochondrial toxicity of TAM was studied in liver mitochondria of Swiss albino mice. TAM treatment caused a significant increase in the mitochondrial lipid peroxidation (LPO) and the protein carbonyls (PCs). It also caused a significant increase in superoxide radical production. Pretreatment of mice with catechin (40 mg/kg) showed significant protection as demonstrated by marked attenuation of increased oxidative stress parameters such LPO, PCs, and superoxide production. It also restored the decreased nonenzymatic and enzymatic antioxidants of mitochondria. The inhibitory effect of catechin on TAM-induced oxidative damage suggests that it may have potential benefits in prevention of human diseases where reactive oxygen species have some role as causative agents. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:110,117, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20167 [source] Metabolic syndrome and mitochondrial function: Molecular replacement and antioxidant supplements to prevent membrane peroxidation and restore mitochondrial function,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2007Garth L. Nicolson Abstract Metabolic syndrome consists of a cluster of metabolic conditions, such as hypertriglyeridemia, hyper-low-density lipoproteins, hypo-high-density lipoproteins, insulin resistance, abnormal glucose tolerance and hypertension, that,in combination with genetic susceptibility and abdominal obesity,are risk factors for type 2 diabetes, vascular inflammation, atherosclerosis, and renal, liver and heart disease. One of the defects in metabolic syndrome and its associated diseases is excess cellular oxidative stress (mediated by reactive oxygen and nitrogen species, ROS/RNS) and oxidative damage to mitochondrial components, resulting in reduced efficiency of the electron transport chain. Recent evidence indicates that reduced mitochondrial function caused by ROS/RNS membrane oxidation is related to fatigue, a common complaint of MS patients. Lipid replacement therapy (LRT) administered as a nutritional supplement with antioxidants can prevent excess oxidative membrane damage, restore mitochondrial and other cellular membrane functions and reduce fatigue. Recent clinical trials have shown the benefit of LRT plus antioxidants in restoring mitochondrial electron transport function and reducing moderate to severe chronic fatigue. Thus LRT plus antioxidant supplements should be considered for metabolic syndrome patients who suffer to various degrees from fatigue. J. Cell. Biochem. 100: 1352,1369, 2007. © 2007 Wiley-Liss, Inc. [source] Respiratory chain deficiency slows down cell-cycle progression via reduced ROS generation and is associated with a reduction of p21CIP1/WAF1JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2006Matthias Schauen We have used HeLa cells without mitochondrial DNA (,0 -cells) and transient ,0 -phenocopies, obtained from wild-type cells by short-term treatment with ethidium bromide, to analyze how the absence of a functional mitochondrial respiratory chain slows down proliferation. We ruled out an energetic problem (ATP/ADP content) as well as defective synthesis of pyrimidine, iron-sulfur clusters or heme as important causes for the proliferative defect. Flow cytometric analysis revealed that reactive oxygen species were reduced in ,0 -cells and in ,0 -phenocopies, and that, quite unusually, all stages of the cell cycle were slowed down. Specific quenching of mitochondrial ROS with the ubiquinone analog MitoQ also resulted in slower growth. Some important cell-cycle regulators were reduced in ,0 -cells: cyclin D3, cdk6, p18INK4C, p27KIP1, and p21CIP1/WAF1. In the ,0 -phenocopies, the expression pattern did not fully duplicate the complex response observed in ,0 -cells, and mainly p21CIP1/WAF1 was downregulated. Activities of the growth regulatory PKB/Akt and MAPK/ERK-signaling pathways did not correlate with proliferation rates of ,0 -cells and ,0 -phenocopies. Our study demonstrates that loss of a functional mitochondrial electron transport chain inhibits cell-cycle progression, and we postulate that this occurs through the decreased concentration of reactive oxygen species, leading to downregulation of p21CIP1/WAF1. J. Cell. Physiol. 209: 103,112, 2006. © 2006 Wiley-Liss, Inc. [source] Oxidative stress: A cause and therapeutic target of diabetic complicationsJOURNAL OF DIABETES INVESTIGATION, Issue 3 2010Eiichi Araki Abstract Oxidative stress is defined as excessive production of reactive oxygen species (ROS) in the presence of diminished anti-oxidant substances. Increased oxidative stress could be one of the common pathogenic factors of diabetic complications. However, the mechanisms by which hyperglycemia increases oxidative stress are not fully understood. In this review, we focus on the impact of mitochondrial derived ROS (mtROS) on diabetic complications and suggest potential therapeutic approaches to suppress mtROS. It has been shown that hyperglycemia increases ROS production from mitochondrial electron transport chain and normalizing mitochondrial ROS ameliorates major pathways of hyperglycemic damage, such as activation of polyol pathway, activation of PKC and accumulation of advanced glycation end-products (AGE). Additionally, in subjects with type 2 diabetes, we found a positive correlation between HbA1c and urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG), which reflects mitochondrial oxidative damage, and further reported that 8-OHdG was elevated in subjects with diabetic micro- and macro- vascular complications. We recently created vascular endothelial cell-specific manganese superoxide dismutase (MnSOD) transgenic mice, and clarified that overexpression of MnSOD in endothelium could prevent diabetic retinopathy in vivo. Furthermore, we found that metformin and pioglitazone, both of which have the ability to reduce diabetic vascular complications, could ameliorate hyperglycemia-induced mtROS production by the induction of PPAR, coactivator-1, (PGC-1,) and MnSOD and/or activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK). We also found that metformin and pioglitazone promote mitochondrial biogenesis through the same AMPK,PGC-1, pathway. Taking these results, mtROS could be the key initiator of and a therapeutic target for diabetic vascular complications. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00013.x, 2010) [source] Perturbation of mitochondrial complex V alters the response to dietary restriction in DrosophilaAGING CELL, Issue 1 2010Sepehr Bahadorani Summary Studies in a broad spectrum of model organisms have reported that dietary restriction (DR) is associated with an increase in mitochondrial electron transport chain (ETC) function. However, the question of whether ETC function is required for DR-mediated longevity remains controversial. Here, we report that genetic and pharmacological interventions that target mitochondrial complex V affect Drosophila lifespan in a nutrient-dependent manner. These findings support a requirement for mitochondrial complex V in DR-mediated longevity in flies. [source] The efficiency of mitochondrial electron transport chain is increased in the long-lived mrg19 Saccharomyces cerevisiaeAGING CELL, Issue 6 2009Nitish Mittal Summary Integrity of mitochondrial functionality is a key determinant of longevity in several organisms. In particular, reduced mitochondrial ROS (mtROS) production leading to decreased mtDNA damage is believed to be a crucial aspect of longevity. The generation of low mtROS was thought to be due to low mitochondrial oxygen consumption. However, recent studies have shown that higher mitochondrial oxygen consumption could still result in low mtROS and contribute to longevity. This increased mitochondrial efficiency (i.e. low mtROS generated despite high oxygen consumption) was explained as a result of mitochondrial biogenesis, which provides more entry points for the electrons to the electron transport chain (ETC), thereby resulting in low mtROS production. In this study, we provide evidence for the existence of an alternative pathway to explain the observed higher mitochondrial efficiency in the long-lived mrg19 mutant of Saccharomyces cerevisiae. Although we observe similar amounts of mitochondria in mrg19 and wild-type (wt) yeast, we find that mrg19 mitochondria have higher expression of ETC components per mitochondria in comparison with the wt. These findings demonstrate that more efficient mitochondria because of increased ETC per mitochondria can also produce less mtROS. Taken together, our findings provide evidence for an alternative explanation for the involvement of higher mitochondrial activity in prolonging lifespan. We anticipate that similar mechanisms might also exist in eukaryotes including human. [source] Isoflurane-induced depolarization of neural mitochondria increases with ageACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2009RAVI BAINS Background and objectives: The mitochondrial membrane potential (,,m) drives the three fundamental functions of mitochondria, namely adenosine triphosphate (ATP) generation, Ca2+ uptake/storage, and generation/detoxification of ROS. Isoflurane depolarizes neural mitochondria. The sensitivity for general anesthetics increases with age, but the mechanism for this age-related sensitivity is still unknown. We compared the effect of isoflurane on [Ca2+]i and ,,m in isolated pre-synaptic terminals (synaptosomes) from neonatal, adolescent, and adult rats and the influence of interventions in the respiratory chain was assessed. Methods: Synaptosomes were loaded with the fluorescent probes fura-2 ([Ca2+]i) and JC-1 (,,m) and exposed to isoflurane 1 and 2 minimum alveolar concentration (MAC). The effect on the electron transport chain was investigated by blocking complexes I and V. Results: In neonatal rats isoflurane had no significant effect on ,,m. In adolescent and adult synaptosomes, however, isoflurane 1 and 2 MAC decreased ,,m. Isoflurane 2 MAC increased [Ca2+]i in neonatal and adolescent rats, but not in adult synaptosomes. In Ca2+ -depleted medium, isoflurane still decreased ,,m, while [Ca2+]i remained unaltered. By blocking complex V of the respiratory chain, the isoflurane-induced mitochondrial depolarization was enhanced in all age groups. Blocking complex I depolarized the mitochondria to the same extent as isoflurane 2 MAC, but without any additive effect. Conclusions: The depolarizing effect of isoflurane on neural mitochondria is more pronounced in the adolescent and adult than in neonatal synaptosomes. The increased mitochondrial sensitivity with age seems to be related to the reversed function of the ATP synthase of the electron transport chain. [source] Effects of non-steady-state iron limitation on nitrogen assimilatory enzymes in the marine diatom thalassiosira weissflogii (BACILLARIOPHYCEAE)JOURNAL OF PHYCOLOGY, Issue 1 2000Allen J. Milligan Since the recognition of iron-limited high nitrate (or nutrient) low chlorophyll (HNLC) regions of the ocean, low iron availability has been hypothesized to limit the assimilation of nitrate by diatoms. To determine the influence of non-steady-state iron availability on nitrogen assimilatory enzymes, cultures of Thalassiosira weissflogii (Grunow) Fryxell et Hasle were grown under iron-limited and iron-replete conditions using artificial seawater medium. Iron-limited cultures suffered from decreased efficiency of PSII as indicated by the DCMU-induced variable fluorescence signal (Fv/Fm). Under iron-replete conditions, in vitro nitrate reductase (NR) activity was rate limiting to nitrogen assimilation and in vitro nitrite reductase (NiR) activity was 50-fold higher. Under iron limitation, cultures excreted up to 100 fmol NO2,·cell,1·d,1 (about 10% of incorporated N) and NiR activities declined by 50-fold while internal NO2, pools remained relatively constant. Activities of both NR and NiR remained in excess of nitrogen incorporation rates throughout iron-limited growth. One possible explanation is that the supply of photosynthetically derived reductant to NiR may be responsible for the limitation of nitrogen assimilation at the NO2, reduction step. Urease activity showed no response to iron limitation. Carbon:nitrogen ratios were equivalent in both iron conditions, indicating that, relative to carbon, nitrogen was assimilated at similar rates whether iron was limiting growth or not. We hypothesize that, diatoms in HNLC regions are not deficient in their ability to assimilate nitrate when they are iron limited. Rather, it appears that diatoms are limited in their ability to process photons within the photosynthetic electron transport chain which results in nitrite reduction becoming the rate-limiting step in nitrogenassimilation. [source] A Mutation in Mitochondrial Complex I Increases Ethanol Sensitivity in Caenorhabditis elegansALCOHOLISM, Issue 4 2003Ernst-Bernhard Kayser Background: The gene gas-1 encodes the 49-kDa subunit of complex I of the mitochondrial electron transport chain in Caenorhabditis elegans. A mutation in gas-1 profoundly increases sensitivity to ethanol and decreases complex I-dependent metabolism in mitochondria. Methods: Mitochondria were isolated from wild-type and gas-1 strains of C. elegans. The effects of ethanol on complex I-, II-, and III-dependent oxidative phosphorylation were measured for mitochondria from each strain. Reversibility of the effects of ethanol was determined by measuring oxidative phosphorylation after removal of mitochondria from 1.5 M ethanol. The effects of ethanol on mitochondrial structure were visualized with electron microscopy. Results: We found that ethanol inhibited complex I,, II,, and III,dependent oxidative phosphorylation in isolated wild-type mitochondria at concentrations that immobilize intact worms. It is important to note that the inhibitory effects of ethanol on mitochondria from either C. elegans or rat skeletal muscle were reversible even at molar concentrations. Complex I activity was lower in mitochondria from gas-1 animals than in mitochondria from wild-type animals at equal ethanol concentrations. Complex II activity was higher in gas-1 than in wild-type mitochondria at all concentrations of ethanol. No difference was seen between the strains in the sensitivity of complex III to ethanol. Conclusions: The difference in ethanol sensitivities between gas-1 and wild-type nematodes results solely from altered complex I function. At the respective concentrations of ethanol that immobilize whole animals, mitochondria from each strain of worms displayed identical rates of complex I-dependent state 3 respiration. We conclude that a threshold value of complex I activity controls the transition from mobility to immobility of C. elegans. [source] Volatile anaesthetics depolarize neural mitochondria by inhibiton of the electron transport chainACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2006R. Bains Background:, The mitochondrial membrane potential (,,m) controls the generation of adenosine triphosphate (ATP) and reactive oxygen species, and sequesteration of intracellular Ca2+[Ca2+]i. Clinical concentrations of sevoflurane affect the ,,m in neural mitochondria, but the mechanisms remain elusive. The aim of the present study was to compare the effect of isoflurane and sevoflurane on ,,m in rat pre-synaptic terminals (synaptosomes), and to investigate whether these agents affect ,,m by inhibiting the respiratory chain. Methods:, Synaptosomes were loaded with the fluorescent probes JC-1 (,,m) and Fura-2 ([Ca2+]i) and exposed to isoflurane or sevoflurane. The effect of the anaesthetics on the electron transport chain was investigated by blocking complex I and complex V. Results:, Isoflurane 1 and 2 minimum alveolar concentration (MAC) decreased the normalized JC-1 ratio from 0.92 ± 0.03 in control to 0.86 ± 0.02 and 0.81 ± 0.01, respectively, reflecting a depolarization of the mitochondrial membrane (n = 9). Isoflurane 2 MAC increased [Ca2+]i. In Ca2+ -depleted medium, isoflurane still decreased ,,m while [Ca2+]i remained unaltered. The effect of isoflurane was more pronounced than for sevoflurane. Blocking complex V of the respiratory chain enhanced the isoflurane- and sevoflurane-induced mitochondrial depolarization, whereas blocking complex I and V decreased ,,m to the same extent in control, isoflurane and sevoflurane experiments. Conclusions:, Isoflurane and sevoflurane may act as metabolic inhibitors by depolarizing pre-synaptic mitochondria through inhibition of the electron transport chain, although isoflurane seems to inhibit mitochondrial function more significantly than sevoflurane. Both agents inhibit the respiratory chain sufficiently to cause ATP synthase reversal. [source] QSAR modeling of photosynthesis-inhibiting nostoclide derivativesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2010Róbson Ricardo Teixeira Abstract BACKGROUND: A statistical model, built using the CODESSA software package, was developed to describe the relationship between the structure of nostoclide derivatives and their ability to interfere with the electron transport chain in the Hill reaction. RESULTS: A QSAR treatment was carried out on a series of compounds designed using the naturally occurring toxin nostoclides to correlate molecular descriptors with their in vitro biological activity (the ability to interfere with light-driven reduction of ferricyanide by isolated spinach chloroplast thylakoid membranes). The treatment using the CODESSA software package resulted in a three-parameter model with n = 19, R2 = 0.83, F = 23.8 and R2cv = 0.72. In the proposed model, the Image of Onsager Kirkwood solvation energy, which gives a measure of the polarity of a given compound, is the most important descriptor. The model was internally validated. CONCLUSIONS: The results obtained in this study indicate that polarity, as expressed by the dipole moment, is the most relevant molecular property determining efficiency of photosynthetic inhibitory activity. Copyright © 2009 Society of Chemical Industry [source] Phosphorus alleviates aluminum-induced inhibition of growth and photosynthesis in Citrus grandis seedlingsPHYSIOLOGIA PLANTARUM, Issue 3 2009Huan-Xin Jiang Limited data are available on the effects of phosphorus (P) and aluminum (Al) interactions on Citrus spp. growth and photosynthesis. Sour pummelo (Citrus grandis) seedlings were irrigated for 18 weeks with nutrient solution containing 50, 100, 250 and 500 ,M KH2PO4× 0 and 1.2 mM AlCl3· 6H2O. Thereafter, P and Al in roots, stems and leaves, and leaf chlorophyll (Chl), CO2 assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and Chl a fluorescence (OJIP) transients were measured. Under Al stress, P increased root Al, but decreased stem and leaf Al. Shoot growth is more sensitive to Al than root growth, CO2 assimilation and OJIP transients. Al decreased CO2 assimilation, Rubisco activity and Chl content, whereas it increased or did not affect intercellular CO2 concentration. Al affected CO2 assimilation more than Rubisco and Chl under 250 and 500 ,M P. Al decreased root, stem and leaf P, leaf maximum quantum yield of primary photochemistry (Fv/Fm) and total performance index (PItot,abs), but increased leaf minimum fluorescence (Fo), relative variable fluorescence at K- and I-steps. P could alleviate Al-induced increase or decrease for all these parameters. We conclude that P alleviated Al-induced inhibition of growth and impairment of the whole photosynthetic electron transport chain from photosystem II (PSII) donor side up to the reduction of end acceptors of photosystem I (PSI), thus preventing photosynthesis inhibition through increasing Al immobilization in roots and P level in roots and shoots. Al-induced impairment of the whole photosynthetic electron transport chain may be associated with growth inhibition. [source] Kinetics of leaf oxygen uptake represent in planta activities of respiratory electron transport and terminal oxidasesPHYSIOLOGIA PLANTARUM, Issue 1 2007Agu Laisk We present, for the first time, the oxygen response kinetics of mitochondrial respiration measured in intact leaves (sunflower and aspen). Low O2 concentrations in N2 (9,1500 ppm) were preset in a flow-through gas exchange measurement system, and the decrease in O2 concentration and the increase in CO2 concentration as result of leaf respiration were measured by a zirconium cell O2 analyser and infrared-absorption CO2 analyser, respectively. The low O2 concentrations little influenced the rate of CO2 evolution during the 60-s exposure. The initial slope of the O2 uptake curve on the dissolved O2 concentration basis was relatively constant in leaves of a single species, 1.5 mm s,1 in sunflower and 1.8 mm s,1 in aspen. The apparent K0.5(O2) values ranged from 0.33 to 0.67 ,M in sunflower and from 0.33 to 1.1 ,M in aspen, mainly because of the variation of the maximum rate, Vmax (leaf temperature 22°C). The initial slope of the O2 response of respiration characterizes the catalytic efficiency of terminal oxidases, an important parameter of the respiratory machinery in leaves. The plateau of the response characterizes the activity of the mitochondrial electron transport chain and is subject to regulations in accordance with the necessity for ATP production. The relatively low oxygen conductivity of terminal oxidases means that in leaves, less than 10% of the photosynthetic oxygen can be reassimilated by mitochondria. [source] Alterations of Mitochondria in Peripheral Blood Mononuclear Cells of Vitiligo PatientsPIGMENT CELL & MELANOMA RESEARCH, Issue 5 2003Maria Lucia Dell'Anna The possible role for a defective mitochondrial functionality in the pathogenesis of vitiligo was investigated by measuring intracellular levels of reactive oxygen species and of antioxidants, the activity of Krebs cycle enzymes, as well as the effects of inhibitors of the electron transport chain, in peripheral blood mononuclear cells from patients with active or stable disease vs. normal subjects. Plasma glyoxal levels were also determined in the same groups of subjects as an index of systemic oxidative stress. In patients with vitiligo in active phase, we observed an increased intracellular production of reactive oxygen species with a consequent imbalance of the prooxidant/antioxidant equilibrium, whereas plasma did not show apparent alterations in glyoxal levels, ruling out a systemic oxidative stress. In patients with stable disease, the balance between pro-oxidants and anti-oxidants seems to be maintained. Moreover, a marked increase in the expression of mitochondrial malate dehydrogenase activity and a specific sensitivity to electron transport chain complex I inhibitor were observed. Overall, these data provide further evidence for an altered mitochondrial functionality in vitiligo patients. [source] Light-to-dark transitions trigger a transient increase in intracellular Ca2+ modulated by the redox state of the photosynthetic electron transport chain in the cyanobacterium Anabaena sp.PLANT CELL & ENVIRONMENT, Issue 7 2004PCC7120 ABSTRACT Light-to-dark transitions represent one of the most crucial environmental stresses that photosynthetic organisms must cope with, since substantial metabolism adaptations are required in order to utilize alternative energy and carbon sources. Although signal transduction systems for changing light regimes are not sufficiently understood, calcium has been implicated in plants as a second messenger in light-on and light-off events. Much less is known about light signalling in cyanobacteria, but it has been shown that calcium probably performs similar signalling roles in these organisms and other prokaryotes. Herein it is reported that light-to-dark transitions trigger a calcium transient in aequorin expressing Anabaena sp. PCC7120. The magnitude of this transient depends on the fluence rate previously irradiated and can reach a peak height over 2 µm free calcium when the fluence rate of light is around 400 µmol photons s,1 m,2. The use of increasing calcium concentration, ethylene glycol-bis (, -aminoethylether) N,N,N,,N,-tetraacetic acid (EGTA), verapamil and trifluoperazine indicated that these transients are originated by a calcium influx probably through verapamil-sensitive Ca2+ channels and are probably modulated by calcium-binding proteins. Experiments with different light spectral qualities and the photosynthetic inhibitors 3-(3,4 dichlorophenyl)1,1,dimelthylurea (DCMU) and 3,5-dibromo-3-methyl-b-isopropyl-p-benzoquinone (DBMIB) indicate that the calcium transient triggered by the light-to-dark transition is not coupled to a specific photoreceptor but rather to changes in the redox state of photosynthetic electron transport chain components other than the plastoquinone pool. [source] Would transformation of C3 crop plants with foreign Rubisco increase productivity?PLANT CELL & ENVIRONMENT, Issue 2 2004A computational analysis extrapolating from kinetic properties to canopy photosynthesis ABSTRACT Genetic modification of Rubisco to increase the specificity for CO2 relative to O2 (,) would decrease photorespiration and in principle should increase crop productivity. When the kinetic properties of Rubisco from different photosynthetic organisms are compared, it appears that forms with high , have low maximum catalytic rates of carboxylation per active site (kcc). If it is assumed that an inverse relationship between kcc and , exists, as implied from measurements, and that an increased concentration of Rubisco per unit leaf area is not possible, will increasing , result in increased leaf and canopy photosynthesis? A steady-state biochemical model for leaf photosynthesis was coupled to a canopy biophysical microclimate model and used to explore this question. C3 photosynthetic CO2 uptake rate (A) is either limited by the maximum rate of Rubisco activity (Vcmax) or by the rate of regeneration of ribulose-1,5-bisphosphate, in turn determined by the rate of whole chain electron transport (J). Thus, if J is limiting, an increase in , will increase net CO2 uptake because more products of the electron transport chain will be partitioned away from photorespiration into photosynthesis. The effect of an increase in , on Rubisco-limited photosynthesis depends on both kcc and the concentration of CO2 ([CO2]). Assuming a strict inverse relationship between kcc and ,, the simulations showed that a decrease, not an increase, in , increases Rubisco-limited photosynthesis at the current atmospheric [CO2], but the increase is observed only in high light. In crop canopies, significant amounts of both light-limited and light-saturated photosynthesis contribute to total crop carbon gain. For canopies, the present average , found in C3 terrestrial plants is supra-optimal for the present atmospheric [CO2] of 370 µmol mol,1, but would be optimal for a CO2 concentration of around 200 µmol mol,1, a value close to the average of the last 400 000 years. Replacing the average Rubisco of terrestrial C3 plants with one having a lower and optimal , would increase canopy carbon gain by 3%. Because there are significant deviations from the strict inverse relationship between kcc and ,, the canopy model was also used to compare the rates of canopy photosynthesis for several Rubiscos with well-defined kinetic constants. These simulations suggest that very substantial increases (> 25%) in crop carbon gain could result if specific Rubiscos having either a higher , or higher kcc were successfully expressed in C3 plants. [source] Sensitivity of Botrytis cinerea from vegetable greenhouses to boscalidPLANT PATHOLOGY, Issue 4 2007C. Q. Zhang Between 2004 and 2006, 228 isolates of Botrytis cinerea from two regions in China were characterized for baseline sensitivity to boscalid, a new active ingredient that interferes with succinate ubiquinone reductase in the electron transport chain. The isolates showed similar sensitivity in different years and regions. Baseline sensitivities were distributed as unimodal curves with mean EC50 values of 1·07 (± 0·11) and 0·42 (± 0·05) mg L,1 for inhibition of mycelial growth and conidial germination, respectively. Laboratory studies were conducted to evaluate the risk of development of resistance to boscalid. Boscalid-resistant mutants were obtained by UV-treatment at lower frequencies and with smaller resistance factors than pyrimethanil-resistant mutants. All boscalid-resistant mutants were also significantly more sensitive to Qo inhibitors than their wild-type parents and showed reduced sporulation in vitro and pathogenicity on aubergine leaves. The results suggested that the risk of resistance developing for boscalid was lower than for pyrimethanil. However, as B. cinerea is a high-risk pathogen, appropriate precautions against resistance development should be taken. Synergism between the activity of boscalid and that of kresoxim-methyl was observed. [source] Staphylococcus aureus ClpC ATPase is a late growth phase effector of metabolism and persistencePROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 5 2009Indranil Chatterjee Dr. Abstract Staphylococcus aureus Clp ATPases (molecular chaperones) alter normal physiological functions including an aconitase-mediated effect on post-stationary growth, acetate catabolism, and entry into death phase (Chatterjee et al., J. Bacteriol. 2005, 187, 4488,4496). In the present study, the global function of ClpC in physiology, metabolism, and late-stationary phase survival was examined using DNA microarrays and 2-D PAGE followed by MALDI-TOF MS. The results suggest that ClpC is involved in regulating the expression of genes and/or proteins of gluconeogenesis, the pentose-phosphate pathway, pyruvate metabolism, the electron transport chain, nucleotide metabolism, oxidative stress, metal ion homeostasis, stringent response, and programmed cell death. Thus, one major function of ClpC is balancing late growth phase carbon metabolism. Furthermore, these changes in carbon metabolism result in alterations of the intracellular concentration of free NADH, the amount of cell-associated iron, and fatty acid metabolism. This study provides strong evidence for ClpC as a critical factor in staphylococcal energy metabolism, stress regulation, and late-stationary phase survival; therefore, these data provide important insight into the adaptation of S. aureus toward a persister state in chronic infections. [source] Proteomic analysis of hearts from frataxin knockout mice: Marked rearrangement of energy metabolism, a response to cellular stress and altered expression of proteins involved in cell structure, motility and metabolismPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2008Robert Sutak Abstract A frequent cause of death in Friedreich's ataxia patients is cardiomyopathy, but the molecular alterations underlying this condition are unknown. We performed 2-DE to characterize the changes in protein expression of hearts using the muscle creatine kinase frataxin conditional knockout (KO) mouse. Pronounced changes in protein expression profile were observed in 9,week-old KO mice with severe cardiomyopathy. In contrast, only several proteins showed altered expression in asymptomatic 4,week-old KO mice. In hearts from frataxin KO mice, components of the iron-dependent complex-I and -II of the mitochondrial electron transport chain and enzymes involved in ATP homeostasis (creatine kinase, adenylate kinase) displayed decreased expression. Interestingly, the KO hearts exhibited increased expression of enzymes involved in the citric acid cycle, catabolism of branched-chain amino acids, ketone body utilization and pyruvate decarboxylation. This constitutes evidence of metabolic compensation due to decreased expression of electron transport proteins. There was also pronounced up-regulation of proteins involved in stress protection, such as a variety of chaperones, as well as altered expression of proteins involved in cellular structure, motility and general metabolism. This is the first report of the molecular changes at the protein level which could be involved in the cardiomyopathy of the frataxin KO mouse. [source] Differential expression of cardiac mitochondrial proteinsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2008Julia R. Smith Abstract Mitochondria were isolated from whole hearts of Dahl salt sensitive (SS) and chromosome 13 consomic control (SS.13BN/Mcwi) rats using a mechanical homogenization process followed by density centrifugation. The proteins present in the two mitochondria preparations were quantified; equal amounts of protein from each sample were taken and trypsinized in the presence of either 16O or 18O before pooling. Incorporation of one or two 18O atoms at the C-terminus of the peptide cleaved by trypsin allows the distinction between the two samples. The proteins were identified by automated MS/MS sequencing and relative amounts of each protein assessed by comparison of the intensities of the constituent peptides. Relative quantification was performed using the ZoomQuant (v1.24) software. Nine proteins were found to be differentially expressed. Electron transfer flavoprotein alpha (P13803, ETFA) protein expression was two-fold lower in the SS compared to the SS.13BN. This was confirmed by Western blot and 2-DE gel quantification. Potential functional implications of this differential expression include an impaired capacity of the heart to oxidize fatty acids in the SS strain compared to the control. Mathematical modeling of mitochondrial electron transport predicted that the observed change in ETFA expression may result in decreased activity of the electron transport chain. [source] Proteomic profiling reveals comprehensive insights into adrenergic receptor-mediated hypertrophy in neonatal rat cardiomyocytesPROTEOMICS - CLINICAL APPLICATIONS, Issue 12 2009Zijian Li Abstract Myocardial adrenergic receptors (ARs) play important roles in cardiac hypertrophy. However, the detailed molecular mechanism of AR-mediated cardiac hypertrophy remains elusive to date. To gain full insight into how ARs are involved in the regulation of cardiac hypertrophy, protein expression profiling was performed with comparative proteomics approach on neonatal rat cardiomyocytes. Forty-six proteins were identified as differentially expressed in hypertrophic cardiomyocytes induced by AR stimulation. To better understand the biological significance of the obtained proteomic data, we utilized the ingenuity pathway analysis tool to construct biological networks and analyze function and pathways that might associate with AR-mediated cardiac hypertrophy. Pathway analysis strongly suggested that ROS may be involved in the development of AR-mediated cardiac hypertrophy, which was then confirmed by further experimentation. The results showed that a marked increase in ROS production was detected in AR-mediated cardiac hypertrophy and blocking of ROS production significantly inhibited AR-mediated cardiac hypertrophy. We further proved that the ROS production was through NADPH oxidase or the mitochondrial electron transport chain and this ROS accumulation resulted in activation of extracellular signal-regulated kinase 1/2 leading to AR-mediated cardiac hypertrophy. These experimental results support the hypothesis, from the ingenuity pathway analysis, that AR-mediated cardiac hypertrophy is associated with the dysregulation of a complicated oxidative stress-regulatory network. In conclusion, our results provide a basis for understanding the detailed molecular mechanisms of AR-mediated cardiac hypertrophy. [source] Impact of oxidative stress on lung diseasesRESPIROLOGY, Issue 1 2009Hee Sun PARK ABSTRACT Reactive oxygen species (ROS) are products of normal cellular metabolism and are known to act as second messengers. Under physiological conditions, ROS participate in maintenance of cellular ,redox homeostasis' in order to protect cells against oxidative stress through various redox-regulatory mechanisms. Overproduction of ROS, most frequently due to excessive stimulation of either reduced nicotinamide adenine dinucleotide phosphate by cytokines or the mitochondrial electron transport chain and xanthine oxidase, results in oxidative stress. Oxidative stress is a deleterious process that leads to lung damage and consequently to various disease states. Knowledge of the mechanisms of ROS regulation could lead to the pharmacological manipulation of antioxidants in lung inflammation and injury. [source] | ||||||||||||||||||||||||||||||||||