Jesús Tejero

University of Pittsburgh, Pittsburgh, Pennsylvania, United States

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Publications (59)287.03 Total impact

  • Paola Corti · Matthew Ieraci · Jesús Tejero
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    ABSTRACT: Neuroglobin (Ngb) and cytoglobin (Cygb) are two six-coordinate heme proteins of unknown physiological function. Although studies on the mammalian proteins have elucidated aspects of Ngb and Cygb biophysics and indicated potential functions, the properties of non-mammalian Ngbs and Cygbs are largely uncharacterized. We have expressed the recombinant zebrafish proteins Ngb, Cygb1, and Cygb2 in E. coli and characterized their nitrite reduction rates, spectral properties, autoxidation rate constants, redox potentials and lipid binding properties. The three zebrafish proteins can catalyze the reduction of nitrite to nitric oxide with a broad range of reaction rate constants (Ngb, 0.68 ± 0.04 M(-1)s(-1); Cygb1, 28.6 ± 3.1 M(-1)s(-1); Cygb2, 0.94 ± 0.18 M(-1)s(-1)).We observe that zebrafish Ngb and Cygb2 have comparable spectral features to those of human Ngb and Cygb, consistent with a six-coordinate heme, whereas unexpectedly Cygb1 has a five-coordinate heme, a slower autoxidation and in general has properties more akin to oxygen transport proteins. In agreement with a possible oxygen carrier and nitrite reductase role, we detect mRNA transcript for Cygb1 but not Cygb2 or Ngb in zebrafish blood. Unlike human Cygb, neither of the zebrafish globins binds oleic acid with high affinity. This finding suggests that lipid binding may be a trait acquired later during evolution and not an ancestral property of cytoglobins. Altogether, our results uncover unexpected properties of zebrafish globins and reveal the pivotal role of cytoglobins in the transition of heme globins from six-coordinate to five-coordinate oxygen carriers and nitrite reductases.
    No preview · Article · Dec 2015 · Nitric Oxide
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    ABSTRACT: Nitrite acts as an endocrine source of bioactive nitric oxide, impacting vascular reactivity, angiogenesis, and cytoprotection. Nitrite has recently been shown to have a metabolic role although its effects and mechanisms of action in the obese insulin-resistant state are unknown. We examined glucose tolerance and insulin secretion using the frequently sampled intravenous glucose tolerance test and insulin sensitivity using the hyperinsulinemic euglycemic clamp in obese male ob(lep) mice administered nitrite (100 mg/kg/day) or saline (control) for seven days and compared responses to the known insulin-sensitizing effects of rosiglitazone (6 mg/kg/day). Under weight-matched conditions, nitrite lowered blood pressure relative to saline and rosiglitazone, whereas only rosiglitazone was effective at reducing hepatic glucose output and basal blood glucose. Both nitrite and rosiglitazone produced improvements, relative to saline, in glucose tolerance (12524 ± 602, 12811 ± 692 vs14428 ± 335 mg/dl*min, respectively; p < 0.05) and insulin sensitivity (8.6 ± 0.7, 7.9 ± 0.3 vs 6.6 ± 0.5 mg/kg/min, respectively; p < 0.001), but there was no effect on insulin secretion. Nitrite exhibited an uncoupling of mitochondrial respiration and decrease in ATP generation in muscle that was independent of mitochondrial biogenesis or activation of uncoupling proteins. There was no insulin-stimulated phosphorylation of Akt, but nitrite increased phosphorylation of AMPK. We conclude that nitrite improves two key components of the metabolic syndrome, blood pressure and insulin sensitivity, independent of weight and with effectiveness comparable to rosiglitazone. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    No preview · Article · May 2015 · The Journal of Physiology
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    ABSTRACT: Neuroglobin (Ngb) is a six-coordinate globin that can catalyze the reduction of nitrite to nitric oxide. Although this reaction is common to heme proteins, the molecular interactions in the heme pocket that regulate this reaction are largely unknown. We have shown that the H64L Ngb mutation increases the rate of nitrite reduction by 2000-fold compared to the wild-type Ngb (Tiso, M. et al. (2011) J. Biol. Chem. 286, 18277-18289). Here we explore the effect of distal heme pocket mutations on nitrite reduction. For this purpose, we have generated mutations of the Ngb residues Phe28(B10), His64(E7) and Val68(E11). Our results indicate a dichotomy in the reactivity of deoxy five- and six-coordinate globins towards nitrite. In hemoglobin and myoglobin there is a correlation between faster rates and more negative potentials. However, in Ngb, reaction rates are apparently related to the distal pocket volume, and redox potential shows a poor relationship with the rate constants. This suggests a relationship between the nitrite reduction rate and heme accessibility in Ngb, particularly marked for His64(E7) mutants. In five-coordinate globins His(E7) facilitates nitrite reduction, likely through proton donation. Conversely, in Ngb the reduction mechanism does not rely on proton delivery from the histidine side chain, as His64 mutants show the fastest reduction rates. In fact, the rate observed for the H64A Ngb (1120 M-1s-1) is to our knowledge the fastest reported for a heme nitrite reductase. These differences may be related to a differential stabilization of the iron-nitrite complexes in five- and six-coordinate globins.
    Full-text · Article · Jan 2015 · Biochemistry

  • No preview · Article · Nov 2014 · Nitric Oxide

  • No preview · Article · Nov 2014 · Nitric Oxide

  • No preview · Article · Nov 2014 · Nitric Oxide
  • Paola Corti · Matthew Ieraci · Mark Gladwin · Jesus Tejero

    No preview · Article · Nov 2014 · Nitric Oxide

  • No preview · Article · Nov 2014
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    ABSTRACT: Molybdenum enzymes xanthine oxidase and aldehyde oxidase exhibit nitrite reductase activity. A third molybdenum enzyme, sulfite oxidase (SO), catalyzes the oxidation of sulfite to sulfate. Given the structural and functional homology of SO to plant nitrate reductase, SO was investigated as a candidate nitrite reductase. Using gas-phase NO detection and physiological concentrations of enzyme, nitrite, and sulfite, we find that SO functions as a mammalian nitrite reductase, coupling sulfite oxidation and nitrite reduction to form NO. Studies with recombinant heme and molybdenum domains of SO showed that nitrite reduction occurs at the fully reduced molybdenum IV center. Reaction rates of nitrite to NO are decreased in the presence of a functional heme domain, mediated by both direct steric and redox effects of the heme domain. Nitrite treatment of human fibroblasts activated soluble guanylate cyclase to form cGMP, which was abrogated in fibroblasts from patients with genetic deficiencies of molybdenum cofactor and SO. These data in aggregate identify SO as a new mammalian nitrite reductase that may contribute to nitrite–NO signaling. Disclosure NIH Grants R01HL098032, RO1HL096973, and PO1HL103455; the German Sciency Foundation (DFG) and the Fonds der Chemischen Industrie.
    No preview · Article · Oct 2014 · Nitric Oxide
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    ABSTRACT: Multi-domain enzymes often rely on large conformational motions to function. However, the conformational setpoints, rates of domain motions, and relationships between these parameters and catalytic activity is not well understood. To address this, we determined and compared the conformational setpoints and the rates of conformational switching between closed unreactive and open reactive states in four mammalian di-flavin NADPH oxidoreductases that catalyze important biological electron transfer reactions: cytochrome P450 reductase (CPR), methionine synthase reductase (MSR), and endothelial and neuronal NO synthase (eNOS & nNOS). We used stopped-flow spectroscopy, single turnover methods, and a kinetic model that relates electron flux through each enzyme to its conformational setpoint and its rates of conformational switching. Results show that the four flavoproteins, when fully-reduced, have a broad range of conformational setpoints (from 12 to 72% open state) and also vary 100-fold regarding their rates of conformational switching between unreactive closed and reactive open states (CPR > nNOS > MSR > eNOS). Furthermore, simulations of the kinetic model could explain how each flavoprotein can support its given rate of electron flux (cytochrome c reductase activity) based on its unique conformational setpoint and switching rates. Our study is the first to quantify these conformational parameters among the di-flavin enzymes, and suggests how the parameters might be manipulated to speed or slow biological electron flux.This article is protected by copyright. All rights reserved.
    No preview · Article · Sep 2014 · FEBS Journal
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    ABSTRACT: mARC (mitochondrial Amidoxime Reducing Component) proteins are molybdopterin-containing enzymes of unclear physiological function. Both human isoforms mARC-1 and mARC-2 are able to catalyze the reduction of nitrite when they are in the reduced form. Moreover, our results indicate that mARC can generate nitric oxide (NO) from nitrite when forming an electron transfer chain with NADH, cytochrome b5, and NADH-dependent cytochrome b5 reductase. The rate of NO formation increases almost 3-fold when pH was lowered from 7.5 to 6.5. To determine if nitrite reduction is catalyzed by molybdenum in the active site of mARC-1, we mutated the putative active site cysteine residue (Cys273), known to coordinate molybdenum binding. NO formation was abolished by the C273A mutation in mARC-1. Supplementation of transformed E. coli with tungsten facilitated the replacement of molybdenum in recombinant mARC-1 and abolished NO formation. Therefore, we conclude that human mARC-1 and mARC-2 are capable of catalyzing reduction of nitrite to NO through reaction with its molybdenum cofactor. Finally, expression of mARC-1 in HEK cells using a lentivirus vector was used to confirm cellular nitrite reduction to NO. The reduction of nitrite by mARC in the mitochondria may represent a new signaling pathway for NADH-dependent hypoxic NO production. A comparison of NO formation profiles between mARC and xanthine oxidase reveals similar Kcat and Vmax values but more sustained NO formation from mARC, likely because it is not vulnerable to auto-inhibition via molybdenum desulfuration.
    Full-text · Article · Feb 2014 · Journal of Biological Chemistry
  • Jesús Tejero · Mark T Gladwin
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    ABSTRACT: Abstract Globin proteins are ubiquitous in living organisms and carry out a variety of functions related to the ability of their prosthetic heme group to bind gaseous ligands such as O2, NO and CO. Moreover, they catalyze important reactions with nitrogen oxide species, such as NO dioxygenation and nitrite reduction. The formation of NO from nitrite is a reaction catalyzed by globins that has received increasing attention due to its potential as an hypoxic NO signaling mechanism. In this review we revisit the current knowledge about the role of globins in NO formation and its physiological implications.
    No preview · Article · Jan 2014 · Biological Chemistry
  • Paola Corti · Jesús Tejero · Mark T Gladwin

    No preview · Article · Oct 2013 · Free Radical Biology and Medicine
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    ABSTRACT: NO synthase (NOS) enzymes convert L-arginine to NO in two sequential reactions whose rates (kcat1 and kcat2 ) are both limited by the rate of ferric heme reduction (kr ). An enzyme ferric heme-NO complex forms as an immediate product complex and then undergoes either dissociation (at a rate that we denote as kd ) to release NO in a productive manner, or reduction (kr ) to form a ferrous heme-NO complex (Fe(II) NO) that must react with O2 (at a rate that we denote as kox ) in a NO dioxygenase reaction that regenerates the ferric enzyme. The interplay of these five kinetic parameters (kcat1 , kcat2 , kr , kd , and kox ) determine NOS specific activity, O2 concentration response, and pulsatile versus steady-state NO generation. Here we utilized stopped-flow spectroscopy and single catalytic turnover methods to characterize the individual temperature dependencies of the five kinetic parameters of rat neuronal NOS (nNOS). We then incorporated the measured kinetic values into computer simulations of the nNOS reaction using a global kinetic model to comprehensively model its temperature-dependent catalytic behaviors. Our results provide new mechanistic insights and also reveal that the different temperature dependencies of the five kinetic parameters significantly alter nNOS catalytic behaviors and NO release efficiency as a function of temperature. This article is protected by copyright. All rights reserved.
    Preview · Article · Jun 2013 · FEBS Journal
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    ABSTRACT: Aims: Hemoglobin-based oxygen carriers (HBOC) provide a potential alternative to red blood cell (RBC) transfusion. Their clinical application has been limited by adverse effects, in large part thought to be mediated by the intravascular scavenging of the vasodilator nitric oxide (NO) by cell-free plasma oxy-hemoglobin. Free hemoglobin may also cause endothelial dysfunction and platelet activation in hemolytic diseases and after transfusion of aged stored RBCs. The new soluble guanylate cyclase (sGC) stimulator Bay 41-8543 and sGC activator Bay 60-2770 directly modulate sGC, independent of NO bioavailability, providing a potential therapeutic mechanism to bypass hemoglobin-mediated NO inactivation. Results: Infusions of human hemoglobin solutions and the HBOC Oxyglobin into rats produced a severe hypertensive response, even at low plasma heme concentrations approaching 10 μM. These reactions were only observed for ferrous oxy-hemoglobin and not analogs that do not rapidly scavenge NO. Infusions of L-NG-Nitroarginine methyl ester (L-NAME), a competitive NO synthase inhibitor, after hemoglobin infusion did not produce additive vasoconstriction, suggesting that vasoconstriction is related to scavenging of vascular NO. Open-chest hemodynamic studies confirmed that hypertension occurred secondary to direct effects on increasing vascular resistance, with limited negative cardiac inotropic effects. Intravascular hemoglobin reduced the vasodilatory potency of sodium nitroprusside (SNP) and sildenafil, but had no effect on vasodilatation by direct NO-independent activation of sGC by BAY 41-8543 and BAY 60-2770. Innovation and conclusion: These data suggest that both sGC stimulators and sGC activators could be used to restore cyclic guanosine monophosphate-dependent vasodilation in conditions where cell-free plasma hemoglobin is sufficient to inhibit endogenous NO signaling.
    No preview · Article · May 2013 · Antioxidants & Redox Signaling
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    ABSTRACT: Airway lining fluid contains relatively high concentrations of nitrite and arterial blood levels of nitrite are higher than venous levels, suggesting the lung epithelium may represent an important source of nitrite in vivo. To investigate whether lung epithelial cells possess the ability to convert NO to nitrite by oxidation, and the effect of oxygen reactions on nitrite formation, the NO donor DETA NONOate was incubated with or without A549 cells or primary human bronchial epithelial (HBE) cells for 24hrs under normoxic (21% O2) and hypoxic (1% O2) conditions. Nitrite production was significantly increased under all conditions in the presence of A549 or HBE cells, suggesting that both A549 and HBE cells have the capacity to oxidize NO to nitrite even under low oxygen conditions. The addition of oxy-hemoglobin (oxy-Hb) to the A549 cell media decreased the production of nitrite, consistent with NO scavenging limiting nitrite formation. Heat-denatured A549 cells produced much lower nitrite and bitrate, suggesting an enzymatic activity is required. This NO oxidation activity was found to be highest in membrane bound proteins with molecular sizes < 100 kDa. In addition, 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one] (ODQ) and cyanide inhibited formation of nitrite in A549 cells. It has been shown that ceruloplasmin (Cp) possesses an NO oxidase and nitrite synthase activity in plasma based on NO oxidation to nitrosonium cation (NO(+)). We observed that Cp is expressed intracellularly in lung epithelial A549 cells and secreted into medium under basal conditions and during cytokine stimulation. However, an analysis of Cp expression level and activity measured via ρ-phenylenediamine oxidase activity assay revealed very low activity compared with plasma, suggesting that there is insufficient Cp to contribute to detectable NO oxidation to nitrite in A549 cells. Additionally, Cp levels were knocked down using siRNA by more than 75% in A549 cells, with no significant change in either nitrite or cellular S-nitrosothiol (SNO) formation compared to scrambled siRNA control under basal conditions or cytokine stimulation. These data suggest that lung epithelial cells possess NO oxidase activity, which is enhanced in cell membrane associated proteins and not regulated by intracellular or secreted Cp, indicating that alternative NO oxidases determine hypoxic and normoxic nitrite formation from NO in human lung epithelial cells.
    Preview · Article · Apr 2013 · Free Radical Biology and Medicine
  • Paola Corti · Jesus Tejero · Michael Tsang · Mark Gladwin
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    ABSTRACT: Myocardial infarction is a leading cause of death in developed countries. It is now apparent that nitrite has remarkable cytoprotective and anti-apoptotic effects on the cardiac muscle cells following injury. Reduction of nitrite to nitric oxide during ischemia protects the heart against injury from ischemia/reperfusion by reducing apoptosis and necrosis at the infarct site. Yet in mammals there is little or no significant cardiac muscle regeneration after an injury such as acute myocardial infarction and the scar persists throughout the entire adult life. In contrast adult zebrafish possess a remarkable ability to replace damaged or lost tissue after injury, providing a model for understanding heart regeneration. After resection or cryoinjury of the ventricular apex, pre-existing cardiomyocytes re-enter the cell cycle to generate new cardiac muscle. We investigated the effects of hypoxia and nitrite on zebrafish heart regeneration and found that low concentrations (10 μM) of nitrite reduced scar tissue at 5 and 10 days post cryoinjury. Exposure to nitrite under normoxia or to hypoxia alone had no positive effects on regeneration. However simultaneous exposure to nitrite and hypoxia resulted in an increase of cell proliferation showing a positive interaction of hypoxia and nitrite. A specific increase in proliferating cardiomyocytes is detectable at 5 days after cryoinjury and amputation. These studies show that physiological levels of nitrite improve cardiomyocyte proliferation and cardiac regeneration following cardiac injury in the zebrafish. Disclosure Nothing to disclose.
    No preview · Article · Apr 2013 · Nitric Oxide
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    ABSTRACT: Neuroglobin is a highly conserved hemoprotein of uncertain physiological function that evolved from a common ancestor to hemoglobin and myoglobin. Unlike hemoglobin or myoglobin, which show a five-coordinate heme iron, neuroglobin shows a six-coordinate heme with proximal and distal histidines in the heme pocket directly bound to the heme iron. Previous work from our lab has shown that neuroglobin can reduce nitrite to nitric oxide. In order to assess the role in this reaction of the distal Histidine His64(E7) and other heme pocket residues-Phe28 (B10) and Val68 (E11), we studied the nitrite reductase activity of wild-type neuroglobin and mutations of the three aforementioned residues. The mutants H64Q, H64L, H64A, H64W, F28W, F28L, F28V, F28H, V68A, V68F and V68I were studied in terms of nitrite reductase activity, redox potential and autoxidation rates. All mutants except Val68Ala showed increases in nitrite reductase rates (1.5 to 25-fold increases for F28/V68 mutants; 60- to 10,000-fold increases for H64 mutants). Most His64 and Val68 mutations caused modest decreases in the autoxidation, except the V68A mutants which shows very fast autoxidation rates (half life of the oxy complex 26 s). The Phe28 mutations caused marked increases in the autoxidation rates (with half life of the oxy complexes below 1 min), indicating that only the Phe residue in the position B10 can stabilize the oxy-complex against autoxidation. His64 and Phe28 mutations caused a small decrease (10–20 mV) in the redox potential, with the exception of the H64Q mutation that increased the potential by about 45 mV. Val68 mutants showed slight increases. Nitrite reductase activity of neuroglobin appears to be more related to nitrite access to the heme than to other factors such as redox potential. It must be noted that the redox potentials of wt and mutant neuroglobins are in all cases significantly lower than those of hemoglobin or myoglobin. The similarities and differences between myoglobin and neuroglobin mutants will be discussed. Disclosure Supported by the Institute for Transfusion Medicine and the Hemophilia Center of Western Pennsylvania and grants from NIH (R01 HL096973-02 to M.G.) and the Competitive Medical Research Fund of the UPMC Health System (to J.T.).
    No preview · Article · Apr 2013 · Nitric Oxide
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    ABSTRACT: Endogenous metabolism of nitrate to nitrite to nitric oxide (NO) affects numerous biological events in humans, such as blood pressure control and hypoxic vasodilation, yet the molecular mechanism of this transformation remains uncertain and controversial. Nitrate and nitrite conversion to NO are reductive processes, requiring electron and proton transfer reactions, suggesting that oxidoreductase enzymes are involved. Nitrate reduction may occur through a combination of endogenous (i.e. human enzymes) and exogenous (i.e. commensal bacteria) nitrate reductase enzymes, while nitrite reduction to nitric oxide is likely catalyzed by endogenous nitrite reductase enzymes. Several mechanisms have been investigated, yet no conclusive data are available to support a single enzyme as an indispensable component for reduction of nitrite to NO in human tissue. It is likely that different enzyme systems are active in specific tissues under differential hypoxia, pH and co-factor regulatory control. We have identified a novel human nitrite reductase enzyme, which we hypothesize may contribute to mitochondrial reduction of nitrite to NO. The mitochondria amidoxime reducing component (mARC) enzyme is widely expressed in human tissue, but has an undefined physiological function. We hypothesize that mARC catalyzes the NADH-dependent reduction of nitrite to NO. To test this hypothesis the kinetics of nitrite reduction to NO by human mARC was investigated. Recombinant mARC was generated using standard molecular biology techniques, and then isolated using metal affinity chromatography. Site directed mutagenesis was used to change the active site cysteine into alanine. Human cytochrome b5 and cytochrome b5 reductase were also isolated to determine if mARC can utilize NADH as an electron source in conjunction with these enzymes. Nitric oxide chemiluminescence spectroscopy was used to measure NO-formation rates under anaerobic conditions. Our study established that mARC can generate NO from nitrite in the presence of NADH, cytochrome b5, and cytochrome b5 reductase at pH 7.4. The maximum velocity (Vmax) of NO-formation measured was 5 nmoles NO s−1 mg−1 protein. Moreover, mutation of the putative active site cysteine residue to alanine, and substitution of tungsten for molybdenum, completely abolished enzyme activity. The kinetic data supports our hypothesis and establishes that human mARC is capable of catalyzing reduction of nitrite to NO. Moreover, these data suggest that cysteine 270 and molybdenum are important in the transformation of nitrite to NO. Disclosure Supported by institution training grant (T32).
    No preview · Article · Apr 2013 · Nitric Oxide
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    Jesús Tejero · Dennis Stuehr
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    ABSTRACT: Nitric oxide synthase (NOS) is a critical enzyme for the production of the messenger molecule nitric oxide (NO) from L-arginine. NOS enzymes require tetrahydrobiopterin as a cofactor for NO synthesis. Besides being one of the few enzymes to use this cofactor, the role of tetrahydrobiopterin in NOS catalytic mechanism is different from other enzymes: during the catalytic cycle of NOS, tetrahydrobiopterin forms a radical species that is again reduced, thus effectively regenerating after each NO synthesis cycle. In this review, we summarize our current knowledge about the role of tetrahydrobiopterin in the structure, function, and catalytic mechanism of NOS enzymes. © 2013 IUBMB Life, 2013.
    Preview · Article · Apr 2013 · International Union of Biochemistry and Molecular Biology Life

Publication Stats

1k Citations
287.03 Total Impact Points


  • 2010-2015
    • University of Pittsburgh
      • • Department of Medicine
      • • Vascular Medicine Institute
      Pittsburgh, Pennsylvania, United States
  • 2014
    • Kent State University
      • Department of Chemistry and Biochemistry
      Кент, Ohio, United States
  • 2007-2011
    • Lerner Research Institute
      • Department of Cellular and Molecular Medicine
      Cleveland, Ohio, United States
    • Case Western Reserve University
      • Department of Anthropology
      Cleveland, OH, United States
  • 2006-2007
    • University of Zaragoza
      • Department of Biochemistry and Molecular and Cellular Biology
      Caesaraugusta, Aragon, Spain