51
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Bahadur V, Mastronicola D, Singh AK, Tiwari HK, Pucillo LP, Sarti P, Singh BK, Giuffrè A. Antigiardial activity of novel triazolyl-quinolone-based chalcone derivatives: when oxygen makes the difference. Front Microbiol 2015; 6:256. [PMID: 25904901 PMCID: PMC4389562 DOI: 10.3389/fmicb.2015.00256] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/16/2015] [Indexed: 01/25/2023] Open
Abstract
Giardiasis is a common diarrheal disease worldwide caused by the protozoan parasite Giardia intestinalis. It is urgent to develop novel drugs to treat giardiasis, due to increasing clinical resistance to the gold standard drug metronidazole (MTZ). New potential antiparasitic compounds are usually tested for their killing efficacy against G. intestinalis under anaerobic conditions, in which MTZ is maximally effective. On the other hand, though commonly regarded as an ‘anaerobic pathogen,’ G. intestinalis is exposed to relatively high O2 levels in vivo, living attached to the mucosa of the proximal small intestine. It is thus important to test the effect of O2 when searching for novel potential antigiardial agents, as outlined in a previous study [Bahadur et al. (2014) Antimicrob. Agents Chemother. 58, 543]. Here, 45 novel chalcone derivatives with triazolyl-quinolone scaffold were synthesized, purified, and characterized by high resolution mass spectrometry, 1H and 13C nuclear magnetic resonance and infrared spectroscopy. Efficacy of the compounds against G. intestinalis trophozoites was tested under both anaerobic and microaerobic conditions, and selectivity was assessed in a counter-screen on human epithelial colorectal adenocarcinoma cells. MTZ was used as a positive control in the assays. All the tested compounds proved to be more effective against the parasite in the presence of O2, with the exception of MTZ that was less effective. Under anaerobiosis eighteen compounds were found to be as effective as MTZ or more (up to three to fourfold); the same compounds proved to be up to >100-fold more effective than MTZ under microaerobic conditions. Four of them represent potential candidates for the design of novel antigiardial drugs, being highly selective against Giardia trophozoites. This study further underlines the importance of taking O2 into account when testing novel potential antigiardial compounds.
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Affiliation(s)
- Vijay Bahadur
- Bio-Organic Laboratory, Department of Chemistry, University of Delhi Delhi, India
| | - Daniela Mastronicola
- CNR Institute of Molecular Biology and Pathology Rome, Italy ; Department of Biochemical Sciences and Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University of Rome Rome, Italy
| | - Amit K Singh
- Bio-Organic Laboratory, Department of Chemistry, University of Delhi Delhi, India
| | - Hemandra K Tiwari
- Bio-Organic Laboratory, Department of Chemistry, University of Delhi Delhi, India
| | - Leopoldo P Pucillo
- L. Spallanzani National Institute for Infectious Diseases, Istituto di Ricovero e Cura a Carattere Scientifico Rome, Italy
| | - Paolo Sarti
- CNR Institute of Molecular Biology and Pathology Rome, Italy ; Department of Biochemical Sciences and Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University of Rome Rome, Italy
| | - Brajendra K Singh
- Bio-Organic Laboratory, Department of Chemistry, University of Delhi Delhi, India
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52
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Frederick RE, Caranto JD, Masitas CA, Gebhardt LL, MacGowan CE, Limberger RJ, Kurtz DM. Dioxygen and nitric oxide scavenging by Treponema denticola flavodiiron protein: a mechanistic paradigm for catalysis. J Biol Inorg Chem 2015; 20:603-13. [PMID: 25700637 PMCID: PMC4768905 DOI: 10.1007/s00775-015-1248-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 02/13/2015] [Indexed: 10/24/2022]
Abstract
Flavodiiron proteins (FDPs) contain a unique active site consisting of a non-heme diiron carboxylate site proximal to a flavin mononucleotide (FMN). FDPs serve as the terminal components for reductive scavenging of dioxygen (to water) or nitric oxide (to nitrous oxide), which combats oxidative or nitrosative stress in many bacteria. Characterizations of FDPs from spirochetes or from any oral microbes have not been previously reported. Here, we report characterization of an FDP from the anaerobic spirochete, Treponema (T.) denticola, which is associated with chronic periodontitis. The isolated T. denticola FDP exhibited efficient four-electron dioxygen reductase activity and lower but significant anaerobic nitric oxide reductase activity. A mutant T. denticola strain containing the inactivated FDP-encoding gene was significantly more air-sensitive than the wild-type strain. Single turnover reactions of the four-electron-reduced FDP (FMNH2-Fe(II)Fe(II)) (FDPred) with O2 monitored on the milliseconds to seconds time scale indicated initial rapid formation of a spectral feature consistent with a cis-μ-1,2-peroxo-diferric intermediate, which triggered two-electron oxidation of FMNH2. Reaction of FDPred with NO showed apparent cooperativity between binding of the first and second NO to the diferrous site. The resulting diferrous dinitrosyl complex triggered two-electron oxidation of the FMNH2. Our cumulative results on this and other FDPs indicate that smooth two-electron FMNH2 oxidation triggered by the FDPred/substrate complex and overall four-electron oxidation of FDPred to FDPox constitutes a mechanistic paradigm for both dioxygen and nitric oxide reductase activities of FDPs. Four-electron reductive O2 scavenging by FDPs could contribute to oxidative stress protection in many other oral bacteria.
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Affiliation(s)
- Rosanne E. Frederick
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Jonathan D. Caranto
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Cesar A. Masitas
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Linda L. Gebhardt
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Charles E. MacGowan
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Ronald J. Limberger
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
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53
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Allahverdiyeva Y, Isojärvi J, Zhang P, Aro EM. Cyanobacterial Oxygenic Photosynthesis is Protected by Flavodiiron Proteins. Life (Basel) 2015; 5:716-43. [PMID: 25761262 PMCID: PMC4390876 DOI: 10.3390/life5010716] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/04/2015] [Accepted: 02/25/2015] [Indexed: 12/13/2022] Open
Abstract
Flavodiiron proteins (FDPs, also called flavoproteins, Flvs) are modular enzymes widely present in Bacteria and Archaea. The evolution of cyanobacteria and oxygenic photosynthesis occurred in concert with the modulation of typical bacterial FDPs. Present cyanobacterial FDPs are composed of three domains, the β-lactamase-like, flavodoxin-like and flavin-reductase like domains. Cyanobacterial FDPs function as hetero- and homodimers and are involved in the regulation of photosynthetic electron transport. Whilst Flv2 and Flv4 proteins are limited to specific cyanobacterial species (β-cyanobacteria) and function in photoprotection of Photosystem II, Flv1 and Flv3 proteins, functioning in the "Mehler-like" reaction and safeguarding Photosystem I under fluctuating light conditions, occur in nearly all cyanobacteria and additionally in green algae, mosses and lycophytes. Filamentous cyanobacteria have additional FDPs in heterocyst cells, ensuring a microaerobic environment for the function of the nitrogenase enzyme under the light. Here, the evolution, occurrence and functional mechanisms of various FDPs in oxygenic photosynthetic organisms are discussed.
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Affiliation(s)
- Yagut Allahverdiyeva
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
| | - Janne Isojärvi
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
| | - Pengpeng Zhang
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
| | - Eva-Mari Aro
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
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54
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Khatua S, Majumdar A. Flavodiiron nitric oxide reductases: Recent developments in the mechanistic study and model chemistry for the catalytic reduction of NO. J Inorg Biochem 2015; 142:145-53. [DOI: 10.1016/j.jinorgbio.2014.09.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/26/2014] [Accepted: 09/29/2014] [Indexed: 11/24/2022]
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55
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Niculescu VF. The stem cell biology of the protist pathogen entamoeba invadens in the context of eukaryotic stem cell evolution. ACTA ACUST UNITED AC 2015. [DOI: 10.7243/2054-717x-2-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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56
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Isolation, characterization and functional annotation of the salt tolerance genes through screening the high-quality cDNA library of the halophytic green alga Dunaliella salina (Chlorophyta). ANN MICROBIOL 2014. [DOI: 10.1007/s13213-014-0967-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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57
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Caranto JD, Weitz A, Giri N, Hendrich MP, Kurtz DM. A diferrous-dinitrosyl intermediate in the N2O-generating pathway of a deflavinated flavo-diiron protein. Biochemistry 2014; 53:5631-7. [PMID: 25144650 PMCID: PMC4159209 DOI: 10.1021/bi500836z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
![]()
Flavo-diiron proteins (FDPs) function
as anaerobic nitric oxide
scavengers in some microorganisms, catalyzing reduction of nitric
to nitrous oxide. The FDP from Thermotoga maritima can be prepared in a deflavinated form with an intact diferric site
(deflavo-FDP). Hayashi et al. [(2010) Biochemistry 49, 7040–7049] reported that reaction of NO with reduced deflavo-FDP
produced substoichiometric N2O. Here we report a multispectroscopic
approach to identify the iron species in the reactions of deflavo-FDP
with NO. Mössbauer spectroscopy identified two distinct ferrous
species after reduction of the antiferromagnetically coupled diferric
site. Approximately 60% of the total ferrous iron was assigned to
a diferrous species associated with the N2O-generating
pathway. This pathway proceeds through successive diferrous-mononitrosyl
(S = 1/2 FeII{FeNO}7) and diferrous-dinitrosyl (S = 0 [{FeNO}7]2) species that form within ∼100 ms of
mixing of the reduced protein with NO. The diferrous-dinitrosyl intermediate
converted to an antiferromagnetically coupled diferric species that
was spectroscopically indistinguishable from that in the starting
deflavinated protein. These diiron species closely resembled those
reported for the flavinated FDP [Caranto et al. (2014) J.
Am. Chem. Soc. 136, 7981–7992], and
the time scales of their formation and decay were consistent with
the steady state turnover of the flavinated protein. The remaining
∼40% of ferrous iron was inactive in N2O generation
but reversibly bound NO to give an S = 3/2 {FeNO}7 species. The results demonstrate
that N2O formation in FDPs can occur via conversion of S = 0 [{FeNO}7]2 to a diferric form
without participation of the flavin cofactor.
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Affiliation(s)
- Jonathan D Caranto
- Department of Chemistry, University of Texas at San Antonio , San Antonio, Texas 78249, United States
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58
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Gonçalves VL, Vicente JB, Pinto L, Romão CV, Frazão C, Sarti P, Giuffrè A, Teixeira M. Flavodiiron oxygen reductase from Entamoeba histolytica: modulation of substrate preference by tyrosine 271 and lysine 53. J Biol Chem 2014; 289:28260-70. [PMID: 25151360 DOI: 10.1074/jbc.m114.579086] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Flavodiiron proteins (FDPs) are a family of enzymes endowed with bona fide oxygen- and/or nitric-oxide reductase activity, although their substrate specificity determinants remain elusive. After a comprehensive comparison of available three-dimensional structures, particularly of FDPs with a clear preference toward either O2 or NO, two main differences were identified near the diiron active site, which led to the construction of site-directed mutants of Tyr(271) and Lys(53) in the oxygen reducing Entamoeba histolytica EhFdp1. The biochemical and biophysical properties of these mutants were studied by UV-visible and electron paramagnetic resonance (EPR) spectroscopies coupled to potentiometry. Their reactivity with O2 and NO was analyzed by stopped-flow absorption spectroscopy and amperometric methods. These mutations, whereas keeping the overall properties of the redox cofactors, resulted in increased NO reductase activity and faster inactivation of the enzyme in the reaction with O2, pointing to a role of the mutated residues in substrate selectivity.
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Affiliation(s)
- Vera L Gonçalves
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República (EAN), 2781-901 Oeiras, Portugal, the Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal
| | - João B Vicente
- the Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal, the Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal,
| | - Liliana Pinto
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República (EAN), 2781-901 Oeiras, Portugal
| | - Célia V Romão
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República (EAN), 2781-901 Oeiras, Portugal
| | - Carlos Frazão
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República (EAN), 2781-901 Oeiras, Portugal
| | - Paolo Sarti
- the Department of Biochemical Sciences and Istituto Pasteur, Fondazione Cenci Bolognetti, Sapienza University of Rome, Piazzale Aldo Moro 5, I-00185 Rome, Italy, and the CNR Institute of Biology, Molecular Medicine and Nanobiotechnology, Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Alessandro Giuffrè
- the CNR Institute of Biology, Molecular Medicine and Nanobiotechnology, Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Miguel Teixeira
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República (EAN), 2781-901 Oeiras, Portugal,
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59
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Antioxidant defences of Spironucleus vortens: Glutathione is the major non-protein thiol. Mol Biochem Parasitol 2014; 196:45-52. [DOI: 10.1016/j.molbiopara.2014.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/21/2014] [Accepted: 07/28/2014] [Indexed: 11/17/2022]
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60
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Caranto J, Weitz A, Hendrich MP, Kurtz DM. The nitric oxide reductase mechanism of a flavo-diiron protein: identification of active-site intermediates and products. J Am Chem Soc 2014; 136:7981-92. [PMID: 24828196 PMCID: PMC4063189 DOI: 10.1021/ja5022443] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Indexed: 11/30/2022]
Abstract
The unique active site of flavo-diiron proteins (FDPs) consists of a nonheme diiron-carboxylate site proximal to a flavin mononucleotide (FMN) cofactor. FDPs serve as the terminal components for reductive scavenging of dioxygen or nitric oxide to combat oxidative or nitrosative stress in bacteria, archaea, and some protozoan parasites. Nitric oxide is reduced to nitrous oxide by the four-electron reduced (FMNH2-Fe(II)Fe(II)) active site. In order to clarify the nitric oxide reductase mechanism, we undertook a multispectroscopic presteady-state investigation, including the first Mössbauer spectroscopic characterization of diiron redox intermediates in FDPs. A new transient intermediate was detected and determined to be an antiferromagnetically coupled diferrous-dinitrosyl (S = 0, [{FeNO}(7)]2) species. This species has an exchange energy, J ≥ 40 cm(-1) (JS1 ° S2), which is consistent with a hydroxo or oxo bridge between the two irons. The results show that the nitric oxide reductase reaction proceeds through successive formation of diferrous-mononitrosyl (S = ½, Fe(II){FeNO}(7)) and the S = 0 diferrous-dinitrosyl species. In the rate-determining process, the diferrous-dinitrosyl converts to diferric (Fe(III)Fe(III)) and by inference N2O. The proximal FMNH2 then rapidly rereduces the diferric site to diferrous (Fe(II)Fe(II)), which can undergo a second 2NO → N2O turnover. This pathway is consistent with previous results on the same deflavinated and flavinated FDP, which detected N2O as a product (Hayashi Biochemistry 2010, 49, 7040). Our results do not support other proposed mechanisms, which proceed either via "super-reduction" of [{FeNO}(7)]2 by FMNH2 or through Fe(II){FeNO}(7) directly to a diferric-hyponitrite intermediate. The results indicate that an S = 0 [{FeNO}(7)}]2 complex is a proximal precursor to N-N bond formation and N-O bond cleavage to give N2O and that this conversion can occur without redox participation of the FMN cofactor.
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Affiliation(s)
- Jonathan
D. Caranto
- Department
of Chemistry, University of Texas at San
Antonio, San Antonio, Texas 78249, United
States
| | - Andrew Weitz
- Department
of Chemistry, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Michael P. Hendrich
- Department
of Chemistry, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Donald M. Kurtz
- Department
of Chemistry, University of Texas at San
Antonio, San Antonio, Texas 78249, United
States
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61
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Hayashi R, Shimakawa G, Shaku K, Shimizu S, Akimoto S, Yamamoto H, Amako K, Sugimoto T, Tamoi M, Makino A, Miyake C. O2-dependent large electron flow functioned as an electron sink, replacing the steady-state electron flux in photosynthesis in the cyanobacterium Synechocystis sp. PCC 6803, but not in the cyanobacterium Synechococcus sp. PCC 7942. Biosci Biotechnol Biochem 2014; 78:384-93. [PMID: 25036824 DOI: 10.1080/09168451.2014.882745] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
To determine whether alternative electron flow (AEF) can replace the photosynthetic electron flow in cyanobacteria, we used an open O2-electrode system to monitor O2-exchange over a long period. In air-grown Synechocystis sp. PCC 6803 (S. 6803(WT)), the quantum yield of PSII, Y(II), held even after photosynthesis was suppressed by CO2 shortage. The S. 6803 mutant, deficient in flavodiiron (FLV) proteins 1 and 3, showed the same phenotype as S. 6803(WT). In contrast, Y(II) decreased in Synechococcus sp. PCC 7942 (S. 7942). These results suggest that AEF functioned as the Y(II) in S. 6803 and replaced the photosynthetic electron flux. In contrast, the activity of AEF in S. 7942 was lower. The affinity of AEF for O2 in S. 6803 did not correspond to those of FLVs in bacteria or terminal oxidases in respiration. AEF might be driven by photorespiration.
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Affiliation(s)
- Ryosuke Hayashi
- a Department of Biological and Environmental Sciences, Faculty of Agriculture , Graduate School of Agricultural Science, Kobe University , Kobe , Japan
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62
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Peroxynitrite and peroxiredoxin in the pathogenesis of experimental amebic liver abscess. BIOMED RESEARCH INTERNATIONAL 2014; 2014:324230. [PMID: 24822193 PMCID: PMC4009108 DOI: 10.1155/2014/324230] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 03/12/2014] [Indexed: 12/21/2022]
Abstract
The molecular mechanisms by which Entamoeba histolytica causes amebic liver abscess (ALA) are still not fully understood. Amebic mechanisms of adherence and cytotoxic activity are pivotal for amebic survival but apparently do not directly cause liver abscess. Abundant evidence indicates that chronic inflammation (resulting from an inadequate immune response) is probably the main cause of ALA. Reports referring to inflammatory mechanisms of liver damage mention a repertoire of toxic molecules by the immune response (especially nitric oxide and reactive oxygen intermediates) and cytotoxic substances released by neutrophils and macrophages after being lysed by amoebas (e.g., defensins, complement, and proteases). Nevertheless, recent evidence downplays these mechanisms in abscess formation and emphasizes the importance of peroxynitrite (ONOO−). It seems that the defense mechanism of amoebas against ONOO−, namely, the amebic thioredoxin system (including peroxiredoxin), is superior to that of mammals. The aim of the present text is to define the importance of ONOO− as the main agent of liver abscess formation during amebic invasion, and to explain the superior capacity of amoebas to defend themselves against this toxic agent through the peroxiredoxin and thioredoxin system.
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63
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Novel functions of an iron-sulfur flavoprotein from Trichomonas vaginalis hydrogenosomes. Antimicrob Agents Chemother 2014; 58:3224-32. [PMID: 24663020 DOI: 10.1128/aac.02320-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Iron-sulfur flavoproteins (Isf) are flavin mononucleotide (FMN)- and FeS cluster-containing proteins commonly encountered in anaerobic prokaryotes. However, with the exception of Isf from Methanosarcina thermophila, which participates in oxidative stress management by removing oxygen and hydrogen peroxide, none of these proteins has been characterized in terms of function. Trichomonas vaginalis, a sexually transmitted eukaryotic parasite of humans, was found to express several iron-sulfur flavoprotein (TvIsf) homologs in its hydrogenosomes. We show here that in addition to having oxygen-reducing activity, the recombinant TvIsf also functions as a detoxifying reductase of metronidazole and chloramphenicol, both of which are antibiotics effective against a variety of anaerobic microbes. TvIsf can utilize both NADH and reduced ferredoxin as electron donors. Given the prevalence of Isf in anaerobic prokaryotes, we propose that these proteins are central to a novel defense mechanism against xenobiotics.
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64
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Mastronicola D, Falabella M, Testa F, Pucillo LP, Teixeira M, Sarti P, Saraiva LM, Giuffrè A. Functional characterization of peroxiredoxins from the human protozoan parasite Giardia intestinalis. PLoS Negl Trop Dis 2014; 8:e2631. [PMID: 24416465 PMCID: PMC3886907 DOI: 10.1371/journal.pntd.0002631] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 11/26/2013] [Indexed: 01/03/2023] Open
Abstract
The microaerophilic protozoan parasite Giardia intestinalis, causative of one of the most common human intestinal diseases worldwide, infects the mucosa of the proximal small intestine, where it has to cope with O2 and nitric oxide (NO). Elucidating the antioxidant defense system of this pathogen lacking catalase and other conventional antioxidant enzymes is thus important to unveil novel potential drug targets. Enzymes metabolizing O2, NO and superoxide anion (O2−•) have been recently reported for Giardia, but it is yet unknown how the parasite copes with H2O2 and peroxynitrite (ONOO−). Giardia encodes two yet uncharacterized 2-cys peroxiredoxins (Prxs), GiPrx1a and GiPrx1b. Peroxiredoxins are peroxidases implicated in virulence and drug resistance in several parasitic protozoa, able to protect from nitroxidative stress and repair oxidatively damaged molecules. GiPrx1a and a truncated form of GiPrx1b (deltaGiPrx1b) were expressed in Escherichia coli, purified and functionally characterized. Both Prxs effectively metabolize H2O2 and alkyl-hydroperoxides (cumyl- and tert-butyl-hydroperoxide) in the presence of NADPH and E. coli thioredoxin reductase/thioredoxin as the reducing system. Stopped-flow experiments show that both proteins in the reduced state react with ONOO− rapidly (k = 4×105 M−1 s−1 and 2×105 M−1 s−1 at 4°C, for GiPrx1a and deltaGiPrx1b, respectively). Consistent with a protective role against oxidative stress, expression of GiPrx1a (but not deltaGiPrx1b) is induced in parasitic cells exposed to air O2 for 24 h. Based on these results, GiPrx1a and deltaGiPrx1b are suggested to play an important role in the antioxidant defense of Giardia, possibly contributing to pathogenesis. Giardia intestinalis causes one of the most common human intestinal diseases worldwide, called giardiasis. This microorganism infects the small intestine where it has to cope with O2, nitric oxide (NO) and related reactive species that are toxic for Giardia as it lacks most of the conventional antioxidant enzymes. Understanding how this pathogen survives oxidative stress is thus important because it may help to identify novel drug targets to combat giardiasis. Some enzymes playing a role in the antioxidant defense of Giardia have been recently reported, but it is yet unknown how the parasite copes with two well-known oxidants, hydrogen peroxide (H2O2) and peroxynitrite (ONOO−). In this study, the Authors show that Giardia expresses two enzymes (called peroxiredoxins), yet uncharacterized, that are able not only to degrade both H2O2 and ONOO−, but also to repair damaged molecules (called hydroperoxides) that accumulate in the cell under oxidative stress conditions. These results are totally unprecedented because no enzymes with these types of functions have been reported for Giardia to date. If these two enzymes will prove to be essential for Giardia virulence in future studies, a new way will be paved towards the discovery of novel drugs to treat giardiasis.
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Affiliation(s)
| | - Micol Falabella
- Department of Biochemical Sciences and Istituto Pasteur – Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy
| | - Fabrizio Testa
- Department of Biochemical Sciences and Istituto Pasteur – Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy
| | | | - Miguel Teixeira
- Instituto de Tecnologia Quimica e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Paolo Sarti
- CNR Institute of Molecular Biology and Pathology, Rome, Italy
- Department of Biochemical Sciences and Istituto Pasteur – Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy
| | - Lígia M. Saraiva
- Instituto de Tecnologia Quimica e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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65
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O(2)-dependent efficacy of novel piperidine- and piperazine-based chalcones against the human parasite Giardia intestinalis. Antimicrob Agents Chemother 2013; 58:543-9. [PMID: 24217695 DOI: 10.1128/aac.00990-13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Giardia intestinalis is the most frequent protozoan agent of intestinal diseases worldwide. Though commonly regarded as an anaerobic pathogen, it preferentially colonizes the fairly oxygen-rich mucosa of the proximal small intestine. Therefore, when testing new potential antigiardial drugs, O2 should be taken into account, since it also reduces the efficacy of metronidazole, the gold standard drug against giardiasis. In this study, 46 novel chalcones were synthesized by microwave-assisted Claisen-Schmidt condensation, purified, characterized by high-resolution mass spectrometry, (1)H and (13)C nuclear magnetic resonance, and infrared spectroscopy, and tested for their toxicity against G. intestinalis under standard anaerobic conditions. As a novel approach, compounds showing antigiardial activity under anaerobiosis were also assayed under microaerobic conditions, and their selectivity against parasitic cells was assessed in a counterscreen on human epithelial colorectal adenocarcinoma cells. Among the tested compounds, three [30(a), 31(e), and 33] were more effective in the presence of O2 than under anaerobic conditions and killed the parasite 2 to 4 times more efficiently than metronidazole under anaerobiosis. Two of them [30(a) and 31(e)] proved to be selective against parasitic cells, thus representing potential candidates for the design of novel antigiardial drugs. This study highlights the importance of testing new potential antigiardial agents not only under anaerobic conditions but also at low, more physiological O2 concentrations.
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66
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Millet COM, Williams CF, Hayes AJ, Hann AC, Cable J, Lloyd D. Mitochondria-derived organelles in the diplomonad fish parasite Spironucleus vortens. Exp Parasitol 2013; 135:262-73. [PMID: 23867147 DOI: 10.1016/j.exppara.2013.07.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/02/2013] [Accepted: 07/03/2013] [Indexed: 11/15/2022]
Abstract
In some eukaryotes, mitochondria have become modified during evolution to yield derived organelles (MDOs) of a similar size (hydrogenosomes), or extremely reduced to produce tiny cellular vesicles (mitosomes). The current study provides evidence for the presence of MDOs in the highly infectious fish pathogen Spironucleus vortens, an organism that produces H₂ and is shown here to have no detectable cytochromes. Transmission electron microscopy (TEM) reveals that S. vortens trophozoites contain electron-dense, membranous structures sometimes with an electron-dense core (200 nm-1 μm), resembling the hydrogenosomes previously described in other protists from habitats deficient in O₂. Confocal microscopy establishes that these organelles exhibit autofluorescence emission spectra similar to flavoprotein constituents previously described for mitochondria and also present in hydrogenosomes. These organelles possess a membrane potential and are labelled by a fluorescently labeled antibody against Fe-hydrogenase from Blastocystis hominis. Heterologous antibodies raised to mitochondrial proteins frataxin and Isu1, also exhibit a discrete punctate pattern of localization in S. vortens; however these labelled structures are distinctly smaller (90-150 nm) than hydrogenosomes as observed previously in other organisms. TEM confirms the presence of double-membrane bounded organelles of this smaller size. In addition, strong background immunostaining occurs in the cytosol for frataxin and Isu1, and labelling by anti-ferredoxin antibody is generally distributed and not specifically localized except for at the anterior polar region. This suggests that some of the functions traditionally attributed to such MDOs may also occur elsewhere. The specialized parasitic life-style of S. vortens may necessitate more complex intracellular compartmentation of redox reactions than previously recognized. Control of infection requires biochemical characterization of redox-related organelles.
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Fang H, Caranto JD, Mendoza R, Taylor AB, Hart PJ, Kurtz DM. Histidine ligand variants of a flavo-diiron protein: effects on structure and activities. J Biol Inorg Chem 2012; 17:1231-9. [PMID: 22990880 DOI: 10.1007/s00775-012-0938-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 09/10/2012] [Indexed: 11/30/2022]
Abstract
Flavo-diiron proteins (FDPs) contain non-heme diiron and proximal flavin mononucleotide (FMN) active sites and function as terminal components of a nitric oxide reductase (NOR) and/or a four-electron dioxygen reductase (O(2)R). While most FDPs show similar structural, spectroscopic, and redox properties, O(2)R and NOR activities vary significantly among FDPs. A potential source of this variability is the iron ligation status of a conserved His residue that provides an iron ligand in all known FDP structures but one, where this His residue is rotated away from iron and replaced by a solvent ligand. In order to test the effect of this His ligation status, we changed this ligating His residue (H90) in Thermotoga maritima (Tm) FDP to either Asn or Ala. The wild-type Tm FDP shows significantly higher O(2)R than NOR activity. Single crystal X-ray crystallography revealed a remarkably conserved diiron site structure in the H90N and -A variants, differing mainly by either Asn or solvent coordination, respectively, in place of H90. The steady-state activities were minimally affected by the H90 substitutions, remaining significantly higher for O(2)R versus NOR. The pre-steady-state kinetics of the fully reduced FDP with O(2) were also minimally affected by the H90 substitutions. The results indicate that the coordination status of this His ligand does not significantly modulate the O(2)R or NOR activities, and that FDPs can retain these activities when the individual iron centers are differentiated by His ligand substitution. This differentiation may have implications for the O(2)R and NOR mechanisms of FDPs.
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Affiliation(s)
- Han Fang
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
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Abstract
SIGNIFICANCE Parasitic infections continue to be a major problem for global human health. Vaccines are practically not available and chemotherapy is highly unsatisfactory. One approach toward a novel antiparasitic drug development is to unravel pathways that may be suited as future targets. Parasitic organisms show a remarkable diversity with respect to the nature and functions of their main low-molecular-mass antioxidants and many of them developed pathways that do not have a counterpart in their mammalian hosts. RECENT ADVANCES Work of the last years disclosed the individual antioxidants employed by parasites and their distinct pathways. Entamoeba, Trichomonas, and Giardia directly use cysteine as main low-molecular-mass thiol but have divergent cysteine metabolisms. Malarial parasites rely exclusively on cysteine uptake and generate glutathione (GSH) as main free thiol as do metazoan parasites. Trypanosomes and Leishmania have a unique trypanothione-based thiol metabolism but employ individual mechanisms for their cysteine supply. In addition, some trypanosomatids synthesize ovothiol A and/or ascorbate. Various essential parasite enzymes such as trypanothione synthetase and trypanothione reductase in Trypanosomatids and the Schistosoma thioredoxin GSH reductase are currently intensively explored as drug target molecules. CRITICAL ISSUES Essentiality is a prerequisite but not a sufficient property of an enzyme to become a suited drug target. The availability of an appropriate in vivo screening system and many other factors are equally important. FUTURE DIRECTIONS The current organism-wide RNA-interference and proteome analyses are supposed to reveal many more interesting candidates for future drug development approaches directed against the parasite antioxidant defense systems.
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69
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A detoxifying oxygen reductase in the anaerobic protozoan Entamoeba histolytica. EUKARYOTIC CELL 2012; 11:1112-8. [PMID: 22798391 DOI: 10.1128/ec.00149-12] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We report the characterization of a bacterial-type oxygen reductase abundant in the cytoplasm of the anaerobic protozoan parasite Entamoeba histolytica. Upon host infection, E. histolytica is confronted with various oxygen tensions in the host intestine, as well as increased reactive oxygen and nitrogen species at the site of local tissue inflammation. Resistance to oxygen-derived stress thus plays an important role in the pathogenic potential of E. histolytica. The genome of E. histolytica has four genes that encode flavodiiron proteins, which are bacterial-type oxygen or nitric oxide reductases and were likely acquired by lateral gene transfer from prokaryotes. The EhFdp1 gene has higher expression in virulent than in nonvirulent Entamoeba strains and species, hinting that the response to oxidative stress may be one correlate of virulence potential. We demonstrate that EhFdp1 is abundantly expressed in the cytoplasm of E. histolytica and that the protein levels are markedly increased (up to ~5-fold) upon oxygen exposure. Additionally, we produced fully functional recombinant EhFdp1 and demonstrated that this enzyme is a specific and robust oxygen reductase but has poor nitric oxide reductase activity. This observation represents a new mechanism of oxygen resistance in the anaerobic protozoan pathogen E. histolytica.
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70
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Müller M, Mentel M, van Hellemond JJ, Henze K, Woehle C, Gould SB, Yu RY, van der Giezen M, Tielens AGM, Martin WF. Biochemistry and evolution of anaerobic energy metabolism in eukaryotes. Microbiol Mol Biol Rev 2012; 76:444-95. [PMID: 22688819 PMCID: PMC3372258 DOI: 10.1128/mmbr.05024-11] [Citation(s) in RCA: 505] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Major insights into the phylogenetic distribution, biochemistry, and evolutionary significance of organelles involved in ATP synthesis (energy metabolism) in eukaryotes that thrive in anaerobic environments for all or part of their life cycles have accrued in recent years. All known eukaryotic groups possess an organelle of mitochondrial origin, mapping the origin of mitochondria to the eukaryotic common ancestor, and genome sequence data are rapidly accumulating for eukaryotes that possess anaerobic mitochondria, hydrogenosomes, or mitosomes. Here we review the available biochemical data on the enzymes and pathways that eukaryotes use in anaerobic energy metabolism and summarize the metabolic end products that they generate in their anaerobic habitats, focusing on the biochemical roles that their mitochondria play in anaerobic ATP synthesis. We present metabolic maps of compartmentalized energy metabolism for 16 well-studied species. There are currently no enzymes of core anaerobic energy metabolism that are specific to any of the six eukaryotic supergroup lineages; genes present in one supergroup are also found in at least one other supergroup. The gene distribution across lineages thus reflects the presence of anaerobic energy metabolism in the eukaryote common ancestor and differential loss during the specialization of some lineages to oxic niches, just as oxphos capabilities have been differentially lost in specialization to anoxic niches and the parasitic life-style. Some facultative anaerobes have retained both aerobic and anaerobic pathways. Diversified eukaryotic lineages have retained the same enzymes of anaerobic ATP synthesis, in line with geochemical data indicating low environmental oxygen levels while eukaryotes arose and diversified.
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Affiliation(s)
| | - Marek Mentel
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Jaap J. van Hellemond
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Katrin Henze
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Christian Woehle
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Sven B. Gould
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Re-Young Yu
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
| | - Mark van der Giezen
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Aloysius G. M. Tielens
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, Netherlands
| | - William F. Martin
- Institute of Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
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71
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Hayashi T, Caranto JD, Matsumura H, Kurtz DM, Moënne-Loccoz P. Vibrational analysis of mononitrosyl complexes in hemerythrin and flavodiiron proteins: relevance to detoxifying NO reductase. J Am Chem Soc 2012; 134:6878-84. [PMID: 22449095 PMCID: PMC3335888 DOI: 10.1021/ja301812p] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Flavodiiron proteins (FDPs) play important roles in the microbial nitrosative stress response in low-oxygen environments by reductively scavenging nitric oxide (NO). Recently, we showed that FMN-free diferrous FDP from Thermotoga maritima exposed to 1 equiv NO forms a stable diiron-mononitrosyl complex (deflavo-FDP(NO)) that can react further with NO to form N(2)O [Hayashi, T.; Caranto, J. D.; Wampler, D. A; Kurtz, D. M., Jr.; Moënne-Loccoz, P. Biochemistry 2010, 49, 7040-7049]. Here we report resonance Raman and low-temperature photolysis FTIR data that better define the structure of this diiron-mononitrosyl complex. We first validate this approach using the stable diiron-mononitrosyl complex of hemerythrin, Hr(NO), for which we observe a ν(NO) at 1658 cm(-1), the lowest ν(NO) ever reported for a nonheme {FeNO}(7) species. Both deflavo-FDP(NO) and the mononitrosyl adduct of the flavinated FPD (FDP(NO)) show ν(NO) at 1681 cm(-1), which is also unusually low. These results indicate that, in Hr(NO) and FDP(NO), the coordinated NO is exceptionally electron rich, more closely approaching the Fe(III)(NO(-)) resonance structure. In the case of Hr(NO), this polarization may be promoted by steric enforcement of an unusually small FeNO angle, while in FDP(NO), the Fe(III)(NO(-)) structure may be due to a semibridging electrostatic interaction with the second Fe(II) ion. In Hr(NO), accessibility and steric constraints prevent further reaction of the diiron-mononitrosyl complex with NO, whereas in FDP(NO) the increased nucleophilicity of the nitrosyl group may promote attack by a second NO to produce N(2)O. This latter scenario is supported by theoretical modeling [Blomberg, L. M.; Blomberg, M. R.; Siegbahn, P. E. J. Biol. Inorg. Chem. 2007, 12, 79-89]. Published vibrational data on bioengineered models of denitrifying heme-nonheme NO reductases [Hayashi, T.; Miner, K. D.; Yeung, N.; Lin, Y.-W.; Lu, Y.; Moënne-Loccoz, P. Biochemistry 2011, 50, 5939-5947 ] support a similar mode of activation of a heme {FeNO}(7) species by the nearby nonheme Fe(II).
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Affiliation(s)
- Takahiro Hayashi
- Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health and Science University, 20,000 NW Walker Road, Beaverton, Oregon 97006-8921, USA
| | - Jonathan D. Caranto
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, USA
| | - Hirotoshi Matsumura
- Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health and Science University, 20,000 NW Walker Road, Beaverton, Oregon 97006-8921, USA
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, USA
| | - Pierre Moënne-Loccoz
- Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health and Science University, 20,000 NW Walker Road, Beaverton, Oregon 97006-8921, USA
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Testa F, Mastronicola D, Cabelli DE, Bordi E, Pucillo LP, Sarti P, Saraiva LM, Giuffrè A, Teixeira M. The superoxide reductase from the early diverging eukaryote Giardia intestinalis. Free Radic Biol Med 2011; 51:1567-74. [PMID: 21839165 DOI: 10.1016/j.freeradbiomed.2011.07.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 06/02/2011] [Accepted: 07/20/2011] [Indexed: 12/13/2022]
Abstract
Unlike superoxide dismutases (SODs), superoxide reductases (SORs) eliminate superoxide anion (O(2)(•-)) not through its dismutation, but via reduction to hydrogen peroxide (H(2)O(2)) in the presence of an electron donor. The microaerobic protist Giardia intestinalis, responsible for a common intestinal disease in humans, though lacking SOD and other canonical reactive oxygen species-detoxifying systems, is among the very few eukaryotes encoding a SOR yet identified. In this study, the recombinant SOR from Giardia (SOR(Gi)) was purified and characterized by pulse radiolysis and stopped-flow spectrophotometry. The protein, isolated in the reduced state, after oxidation by superoxide or hexachloroiridate(IV), yields a resting species (T(final)) with Fe(3+) ligated to glutamate or hydroxide depending on pH (apparent pK(a)=8.7). Although showing negligible SOD activity, reduced SOR(Gi) reacts with O(2)(•-) with a pH-independent second-order rate constant k(1)=1.0×10(9) M(-1) s(-1) and yields the ferric-(hydro)peroxo intermediate T(1); this in turn rapidly decays to the T(final) state with pH-dependent rates, without populating other detectable intermediates. Immunoblotting assays show that SOR(Gi) is expressed in the disease-causing trophozoite of Giardia. We propose that the superoxide-scavenging activity of SOR in Giardia may promote the survival of this air-sensitive parasite in the fairly aerobic proximal human small intestine during infection.
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Affiliation(s)
- Fabrizio Testa
- Department of Biochemical Sciences, CNR Institute of Molecular Biology and Pathology, Sapienza Università di Roma, I-00185 Rome, Italy
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Leitsch D, Burgess AG, Dunn LA, Krauer KG, Tan K, Duchêne M, Upcroft P, Eckmann L, Upcroft JA. Pyruvate:ferredoxin oxidoreductase and thioredoxin reductase are involved in 5-nitroimidazole activation while flavin metabolism is linked to 5-nitroimidazole resistance in Giardia lamblia. J Antimicrob Chemother 2011; 66:1756-65. [PMID: 21602576 DOI: 10.1093/jac/dkr192] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES The mechanism of action of, and resistance to, metronidazole in the anaerobic (or micro-aerotolerant) protozoan parasite Giardia lamblia has long been associated with the reduction of ferredoxin (Fd) by the enzyme pyruvate:ferredoxin oxidoreductase (PFOR) and the subsequent activation of metronidazole by Fd to toxic radical species. Resistance to metronidazole has been associated with down-regulation of PFOR and Fd. The aim of this study was to determine whether the PFOR/Fd couple is the only pathway involved in metronidazole activation in Giardia. METHODS PFOR and Fd activities were measured in extracts of highly metronidazole-resistant (MTR(r)) lines and activities of recombinant G. lamblia thioredoxin reductase (GlTrxR) and NADPH oxidase were assessed for their involvement in metronidazole activation and resistance. RESULTS We demonstrated that several lines of highly MTR(r) G. lamblia have fully functional PFOR and Fd indicating that PFOR/Fd-independent mechanisms are involved in metronidazole activation and resistance in these cells. Flavin-dependent GlTrxR, like TrxR of other anaerobic protozoa, reduces 5-nitroimidazole compounds including metronidazole, although expression of TrxR is not decreased in MTR(r) Giardia. However, reduction of flavins is suppressed in highly MTR(r) cells, as evidenced by as much as an 80% decrease in NADPH oxidase flavin mononucleotide reduction activity. This suppression is consistent with generalized impaired flavin metabolism in highly MTR(r) Trichomonas vaginalis. CONCLUSIONS These data add to the mounting evidence against the dogma that PFOR/Fd is the only couple with a low enough redox potential to reduce metronidazole in anaerobes and point to the multi-factorial nature of metronidazole resistance.
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Affiliation(s)
- David Leitsch
- Institute of Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
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74
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Allahverdiyeva Y, Ermakova M, Eisenhut M, Zhang P, Richaud P, Hagemann M, Cournac L, Aro EM. Interplay between flavodiiron proteins and photorespiration in Synechocystis sp. PCC 6803. J Biol Chem 2011; 286:24007-14. [PMID: 21602273 DOI: 10.1074/jbc.m111.223289] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Flavodiiron (Flv) proteins are involved in detoxification of O(2) and NO in anaerobic bacteria and archaea. Cyanobacterial Flv proteins, on the contrary, function in oxygenic environment and possess an extra NAD(P)H:flavin oxidoreductase module. Synechocystis sp. PCC 6803 has four genes (sll1521, sll0219, sll0550, and sll0217) encoding Flv proteins (Flv1, Flv2, Flv3, and Flv4). Previous in vitro studies with recombinant Flv3 protein from Synechocystis provided evidence that it functions as a NAD(P)H:oxygen oxidoreductase, and subsequent in vivo studies with Synechocystis confirmed the role of Flv1 and Flv3 proteins in the Mehler reaction (photoreduction of O(2) to H(2)O). Interestingly, homologous proteins to Flv1 and Flv3 can be found also in green algae, mosses, and Selaginella. Here, we addressed the function of Flv1 and Flv3 in Synechocystis using the Δflv1, Δflv3, and Δflv1/Δflv3 mutants and applying inorganic carbon (C(i))-deprivation conditions. We propose that only the Flv1/Flv3 heterodimer form is functional in the Mehler reaction in vivo. (18)O(2) labeling was used to discriminate between O(2) evolution in photosynthetic water splitting and O(2) consumption. In wild type, ∼20% of electrons originated from water was targeted to O(2) under air level CO(2) conditions but increased up to 60% in severe limitation of C(i). Gas exchange experiments with Δflv1, Δflv3, and Δflv1/Δflv3 mutants demonstrated that a considerable amount of electrons in these mutants is directed to photorespiration under C(i) deprivation. This assumption is in line with increased transcript abundance of photorespiratory genes and accumulation of photorespiratory intermediates in the WT and to a higher extent in mutant cells under C(i) deprivation.
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Affiliation(s)
- Yagut Allahverdiyeva
- Laboratory of Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku, FI-20014 Turku, Finland
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75
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Mastronicola D, Giuffrè A, Testa F, Mura A, Forte E, Bordi E, Pucillo LP, Fiori PL, Sarti P. Giardia intestinalis escapes oxidative stress by colonizing the small intestine: A molecular hypothesis. IUBMB Life 2011; 63:21-5. [PMID: 21280173 DOI: 10.1002/iub.409] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 11/28/2010] [Indexed: 11/07/2022]
Abstract
Giardia intestinalis is the microaerophilic protozoon causing giardiasis, a common infectious intestinal disease. Giardia possesses an O(2) -scavenging activity likely essential for survival in the host. We report that Giardia trophozoites express the O(2) -detoxifying flavodiiron protein (FDP), detected by immunoblotting, and are able to reduce O(2) to H(2) O rapidly (∼3 μM O(2) × min × 10(6) cells at 37 °C) and with high affinity (C(50) = 3.4 ± 0.7 μM O(2)). Following a short-term (minutes) exposure to H(2) O(2) ≥ 100 μM, the O(2) consumption by the parasites is irreversibly impaired, and the FDP undergoes a degradation, prevented by the proteasome-inhibitor MG132. Instead, H(2) O(2) does not cause degradation or inactivation of the isolated FDP. On the basis of the elevated susceptibility of Giardia to oxidative stress, we hypothesize that the parasite preferentially colonizes the small intestine since, compared with colon, it is characterized by a greater capacity for redox buffering and a lower propensity to oxidative stress.
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Affiliation(s)
- Daniela Mastronicola
- Department of Biochemical Sciences, CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, Rome, Italy
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76
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Schopfer MP, Wang J, Karlin KD. Bioinspired heme, heme/nonheme diiron, heme/copper, and inorganic NOx chemistry: *NO((g)) oxidation, peroxynitrite-metal chemistry, and *NO((g)) reductive coupling. Inorg Chem 2010; 49:6267-82. [PMID: 20666386 DOI: 10.1021/ic100033y] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The focus of this Forum Article highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide [nitrogen monoxide, *NO((g))] and its biological roles and reactions. The latter focus is on (i) oxidation of *NO((g)) to nitrate by nitric oxide dioxygenases (NODs) and (ii) reductive coupling of two molecules of *NO((g)) to give N(2)O(g). In the former case, NODs are described, and the highlighting of possible peroxynitrite/heme intermediates and the consequences of this are given by a discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with *NO((g)) and O(2)(g), leading to peroxynitrite species, are given. The coverage of biological reductive coupling of *NO((g)) deals with bacterial nitric oxide reductases (NORs) with heme/nonheme diiron active sites and on heme/copper oxidases such as cytochrome c oxidase, which can mediate the same chemistry. Recently designed protein and synthetic model compounds (heme/nonheme/diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, that describe the oxidation of *NO((g)) to nitrate (or nitrite) and possible peroxynitrite intermediates or reductive coupling of *NO((g)) to give nitrous oxide.
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Affiliation(s)
- Mark P Schopfer
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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Hayashi T, Caranto JD, Wampler DA, Kurtz DM, Moënne-Loccoz P. Insights into the nitric oxide reductase mechanism of flavodiiron proteins from a flavin-free enzyme. Biochemistry 2010; 49:7040-9. [PMID: 20669924 PMCID: PMC2923256 DOI: 10.1021/bi100788y] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Flavodiiron proteins (FDPs) catalyze reductive scavenging of dioxygen and nitric oxide in air-sensitive microorganisms. FDPs contain a distinctive non-heme diiron/flavin mononucleotide (FMN) active site. Alternative mechanisms for the nitric oxide reductase (NOR) activity consisting of either protonation of a diiron-bridging hyponitrite or "super-reduction" of a diferrous-dinitrosyl by the proximal FMNH(2) in the rate-determining step have been proposed. To test these alternative mechanisms, we examined a deflavinated FDP (deflavo-FDP) from Thermotoga maritima. The deflavo-FDP retains an intact diiron site but does not exhibit multiturnover NOR or O(2) reductase (O(2)R) activity. Reactions of the reduced (diferrous) deflavo-FDP with nitric oxide were examined by UV-vis absorption, EPR, resonance Raman, and FTIR spectroscopies. Anaerobic addition of nitric oxide up to one NO per diferrous deflavo-FDP results in formation of a diiron-mononitrosyl complex characterized by a broad S = (1)/(2 )EPR signal arising from antiferromagnetic coupling of an S = (3)/(2) {FeNO}(7) with an S = 2 Fe(II). Further addition of NO results in two reaction pathways, one of which produces N(2)O and the diferric site and the other of which produces a stable diiron-dinitrosyl complex. Both NO-treated and as-isolated deflavo-FDPs regain full NOR and O(2)R activities upon simple addition of FMN. The production of N(2)O upon addition of NO to the mononitrosyl deflavo-FDP supports the hyponitrite mechanism, but the concomitant formation of a stable diiron-dinitrosyl complex in the deflavo-FDP is consistent with a super-reduction pathway in the flavinated enzyme. We conclude that a diiron-mononitrosyl complex is an intermediate in the NOR catalytic cycle of FDPs.
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Affiliation(s)
- Takahiro Hayashi
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, 20,000 NW Walker Road, Beaverton, Oregon 97006, USA
| | - Jonathan D. Caranto
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, USA
| | - David A. Wampler
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, USA
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, USA
| | - Pierre Moënne-Loccoz
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, 20,000 NW Walker Road, Beaverton, Oregon 97006, USA
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78
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Mastronicola D, Testa F, Forte E, Bordi E, Pucillo LP, Sarti P, Giuffrè A. Flavohemoglobin and nitric oxide detoxification in the human protozoan parasite Giardia intestinalis. Biochem Biophys Res Commun 2010; 399:654-8. [PMID: 20691663 DOI: 10.1016/j.bbrc.2010.07.137] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 07/30/2010] [Indexed: 11/18/2022]
Abstract
Flavohemoglobins (flavoHbs), commonly found in bacteria and fungi, afford protection from nitrosative stress by degrading nitric oxide (NO) to nitrate. Giardia intestinalis, a microaerophilic parasite causing one of the most common intestinal human infectious diseases worldwide, is the only pathogenic protozoon as yet identified coding for a flavoHb. By NO amperometry we show that, in the presence of NADH, the recombinant Giardia flavoHb metabolizes NO with high efficacy under aerobic conditions (TN=116+/-10s(-1) at 1microM NO, T=37 degrees C). The activity is [O(2)]-dependent and characterized by an apparent K(M,O2)=22+/-7microM. Immunoblotting analysis shows that the protein is expressed at low levels in the vegetative trophozoites of Giardia; accordingly, these cells aerobically metabolize NO with low efficacy. Interestingly, in response to nitrosative stress (24-h incubation with 5mM nitrite) flavoHb expression is enhanced and the trophozoites thereby become able to metabolize NO efficiently, the activity being sensitive to both cyanide and carbon monoxide. The NO-donors S-nitrosoglutathione (GSNO) and DETA-NONOate mimicked the effect of nitrite on flavoHb expression. We propose that physiologically flavoHb contributes to NO detoxification in G. intestinalis.
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Affiliation(s)
- Daniela Mastronicola
- Department of Biochemical Sciences, CNR Institute of Molecular Biology and Pathology and Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University of Rome, I-00185 Rome, Italy
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79
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Mogi T, Kita K. Diversity in mitochondrial metabolic pathways in parasitic protists Plasmodium and Cryptosporidium. Parasitol Int 2010; 59:305-12. [PMID: 20433942 DOI: 10.1016/j.parint.2010.04.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 09/24/2009] [Accepted: 09/25/2009] [Indexed: 01/29/2023]
Abstract
Apicomplexans are obligate intracellular parasites and occupy diverse niches. They have remodeled mitochondrial carbon and energy metabolism through reductive evolution. Plasmodium lacks mitochondrial pyruvate dehydrogenase and H(+)-translocating NADH dehydrogenase (Complex I, NDH1). The mitochondorion contains a minimal mtDNA ( approximately 6kb) and carries out oxidative phosphorylation in the insect vector stages, by using 2-oxoglutarate as an alternative means of entry into the TCA cycle and a single-subunit flavoprotein as an alternative NADH dehydrogenase (NDH2). In the blood stages of mammalian hosts, mitochondrial enzymes are down-regulated and parasite energy metabolism relies mainly on glycolysis. Mitosomes of Cryptosporidium parvum and Cryptosporidium hominis (human intestine parasites) lack mtDNA, pyruvate dehydrogenase, TCA cycle enzymes except malate-quinone oxidoreductase (MQO), and ATP synthase subunits except alpha and beta. In contrast, mitosomes of Cryptosporidium muris (a rodent gastric parasite) retain all TCA cycle enzymes and functional ATP synthase and carry out oxidative phosphorylation with pyruvate-NADP(+) oxidoreductase (PNO) and a simple and unique respiratory chain consisting of NDH2 and alternative oxidase (AOX). Cryptosporidium and Perkinsus are early branching groups of chromoalveolates (apicomplexa and dinoflagellates, respectively), and both Cryptosporidium mitosome and Perkinsus mitochondrion use PNO, MQO, and AOX. All apicomplexan parasites and dinoflagellates share MQO, which has been acquired from epsilon-proteobacteria via lateral gene transfer. By genome data mining on Plasmodium, Cryptosporidium and Perkinsus, here we summarized their mitochondrial metabolic pathways, which are varied largely from those of mammalian hosts. We hope that our findings will help in understanding the apicomplexan metabolism and development of new chemotherapeutics with novel targets.
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Affiliation(s)
- Tatsushi Mogi
- Department of Biomedical Chemistry, Graduate School of Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan.
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80
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Alaleona F, Franceschini S, Ceci P, Ilari A, Chiancone E. Thermosynechococcus elongatus DpsA binds Zn(II) at a unique three histidine-containing ferroxidase center and utilizes O2 as iron oxidant with very high efficiency, unlike the typical Dps proteins. FEBS J 2010; 277:903-17. [PMID: 20088882 DOI: 10.1111/j.1742-4658.2009.07532.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The cyanobacterium Thermosynechococcus elongatus is one the few bacteria to possess two Dps proteins, DpsA-Te and Dps-Te. The present characterization of DpsA-Te reveals unusual structural and functional features that differentiate it from Dps-Te and the other known Dps proteins. Notably, two Zn(II) are bound at the ferroxidase center, owing to the unique substitution of a metal ligand at the A-site (His78 in place of the canonical aspartate) and to the presence of a histidine (His164) in place of a hydrophobic residue at a metal-coordinating distance in the B-site. Only the latter Zn(II) is displaced by incoming iron, such that Zn(II)-Fe(III) complexes are formed upon oxidation, as indicated by absorbance and atomic emission spectroscopy data. In contrast to the typical behavior of Dps proteins, where Fe(II) oxidation by H(2)O(2) is about 100-fold faster than by O(2), in DpsA-Te the ferroxidation efficiency of O(2) is very high and resembles that of H(2)O(2). Oxygraphic experiments show that two Fe(II) are required to reduce O(2), and that H(2)O(2) is not released into solution at the end of the reaction. On this basis, a reaction mechanism is proposed that also takes into account the formation of Zn(II)-Fe(III) complexes. The physiological significance of the DpsA-Te behavior is discussed in the framework of a possible localization of the protein at the thylakoid membranes, where photosynthesis takes place, with the consequent increased formation of reactive oxygen species.
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Affiliation(s)
- Flaminia Alaleona
- C.N.R. Institute of Molecular Biology and Pathology, Department of Biochemical Sciences A. Rossi-Fanelli, University of Rome La Sapienza, Italy
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81
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Vicente JB, Testa F, Mastronicola D, Forte E, Sarti P, Teixeira M, Giuffrè A. Redox properties of the oxygen-detoxifying flavodiiron protein from the human parasite Giardia intestinalis. Arch Biochem Biophys 2009; 488:9-13. [PMID: 19545535 DOI: 10.1016/j.abb.2009.06.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 06/17/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
Flavodiiron proteins (FDPs) are enzymes identified in prokaryotes and a few pathogenic protozoa, which protect microorganisms by reducing O(2) to H(2)O and/or NO to N(2)O. Unlike most prokaryotic FDPs, the protozoan enzymes from the human pathogens Giardia intestinalis and Trichomonas vaginalis are selective towards O(2). UV/vis and EPR spectroscopy showed that, differently from the NO-consuming bacterial FDPs, the Giardia FDP contains an FMN with reduction potentials for the formation of the single and the two-electron reduced forms very close to each other (E(1)=-66+/-15mV and E(2)=-83+/-15mV), a condition favoring destabilization of the semiquinone radical. Giardia FDP contains also a non-heme diiron site with significantly up-shifted reduction potentials (E(1)=+163+/-20mV and E(2)=+2+/-20mV). These properties are common to the Trichomonas hydrogenosomal FDP, and likely reflect yet undetermined subtle structural differences in the protozoan FDPs, accounting for their marked O(2) specificity.
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Affiliation(s)
- João B Vicente
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
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82
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Victor BL, Baptista AM, Soares CM. Dioxygen and nitric oxide pathways and affinity to the catalytic site of rubredoxin:oxygen oxidoreductase from Desulfovibrio gigas. J Biol Inorg Chem 2009; 14:853-62. [PMID: 19337761 DOI: 10.1007/s00775-009-0497-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 03/13/2009] [Indexed: 11/29/2022]
Abstract
Rubredoxin:oxygen oxidoreductase (ROO) is the terminal oxidase of a soluble electron transfer chain found in Desulfovibrio gigas. This protein belongs to the flavodiiron family and was initially described as an oxygen reductase, converting this substrate to water and acting as an oxygen-detoxifying system. However, more recent studies evidenced also the ability for this protein to act as a nitric oxide reductase, suggesting an alternative physiological role. To clarify the apparent bifunctional nature of this protein, we performed molecular dynamics simulations of the protein, in different redox states, together with O(2) and NO molecules in aqueous solution. The two small molecules were parameterized using free-energy calculations of the hydration process. With these simulations we were able to identify specific protein paths that allow the diffusion of both these molecules through the protein towards the catalytic centers. Also, we have tried to characterize the preference of ROO towards the presence of O(2) and/or NO at the active site. By using free-energy simulations, we did not find any significant preference for ROO to accommodate both O(2) and NO. Also, from our molecular dynamics simulations we were able to identify similar diffusion profiles for both O(2) and NO molecules. These two conclusions are in good agreement with previous experimental works stating that ROO is able to catalyze both O(2) and NO.
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Affiliation(s)
- Bruno L Victor
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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83
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Reductive dioxygen scavenging by flavo-diiron proteins of Clostridium acetobutylicum. FEBS Lett 2008; 583:241-5. [PMID: 19084524 DOI: 10.1016/j.febslet.2008.12.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Revised: 12/01/2008] [Accepted: 12/02/2008] [Indexed: 11/22/2022]
Abstract
Two flavo-diiron proteins (FDPs), FprA1 and FprA2, are up-regulated when the strictly anaerobic solvent producer, Clostridium acetobutylicum, is exposed to dioxygen. These two FDPs were purified following heterologous overexpression in Escherichia coli as N-terminal Strep-tag fusion proteins. The recombinant FprA1 and FprA2 were found to be homodimeric and homotetrameric, respectively, and both FDPs functioned as terminal components of NADH oxidases (NADH:O(2) oxidoreductases) when using C. acetobutylicum NADH:rubredoxin oxidoreductase (NROR) and rubredoxin (Rd) as electron transport intermediaries. Both FDPs catalyzed the four-electron reduction of molecular oxygen to water with similar specific activities. The results are consistent with these FDPs functioning as efficient scavengers of intracellular dioxygen under aerobic or microoxic growth conditions.
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84
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Petoukhov MV, Vicente JB, Crowley PB, Carrondo MA, Teixeira M, Svergun DI. Quaternary structure of flavorubredoxin as revealed by synchrotron radiation small-angle X-ray scattering. Structure 2008; 16:1428-36. [PMID: 18786405 DOI: 10.1016/j.str.2008.06.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 06/01/2008] [Accepted: 06/03/2008] [Indexed: 10/21/2022]
Abstract
Flavodiiron proteins (FDP) are modular enzymes which function as NO and/or O(2) reductases. Although the majority is composed of two structural domains, the homolog found in Escherichia coli, flavorubredoxin, possesses an extra C-terminal module consisting of a linker and a rubredoxin (Rd) domain necessary for interprotein redox processes. In order to investigate the location of the Rd domain with respect to the flavodiiron structural core, small-angle X-ray scattering was used to construct low-resolution structural models of flavorubredoxin. Scattering patterns from the Rd domain, the FDP core, and full-length flavorubredoxin were collected. The latter two species were found to be tetrameric in solution. Ab initio shape reconstruction and rigid-body modeling indicate a peripheral location for the Rd domains, which appear to have weak contacts with the FDP core. This finding suggests that Rd behaves as an independent domain and is freely available to participate in redox reactions with protein partners.
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Affiliation(s)
- Maxim V Petoukhov
- European Molecular Biology Laboratory, Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany
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85
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Flavodiiron protein from Trichomonas vaginalis hydrogenosomes: the terminal oxygen reductase. EUKARYOTIC CELL 2008; 8:47-55. [PMID: 19011120 DOI: 10.1128/ec.00276-08] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Trichomonas vaginalis is one of a few eukaryotes that have been found to encode several homologues of flavodiiron proteins (FDPs). Widespread among anaerobic prokaryotes, these proteins are believed to function as oxygen and/or nitric oxide reductases to provide protection against oxidative/nitrosative stresses and host immune responses. One of the T. vaginalis FDP homologues is equipped with a hydrogenosomal targeting sequence and is expressed in the hydrogenosomes, oxygen-sensitive organelles that participate in carbohydrate metabolism and assemble iron-sulfur clusters. The bacterial homologues characterized thus far have been dimers or tetramers; the trichomonad protein is a dimer of identical 45-kDa subunits, each noncovalently binding one flavin mononucleotide. The protein reduces dioxygen to water but is unable to utilize nitric oxide as a substrate, similarly to its closest homologue from another human parasite Giardia intestinalis and related archaebacterial proteins. T. vaginalis FDP is able to accept electrons derived from pyruvate or NADH via ferredoxin and is proposed to play a role in the protection of hydrogenosomes against oxygen.
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86
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Vicente JB, Ehrenkaufer GM, Saraiva LM, Teixeira M, Singh U. Entamoeba histolytica modulates a complex repertoire of novel genes in response to oxidative and nitrosative stresses: implications for amebic pathogenesis. Cell Microbiol 2008; 11:51-69. [PMID: 18778413 DOI: 10.1111/j.1462-5822.2008.01236.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Upon host infection, the protozoan parasite Entamoeba histolytica is confronted with reactive oxygen and nitrogen species and must survive these stresses in order to cause invasive disease. We analysed the parasite's response to oxidative and nitrosative stresses, probing the transcriptional changes of trophozoites of a pathogenic strain after a 60 min exposure to H2O2 (1 mM) or a NO donor (dipropylenetriamine-NONOate, 200 microM), using whole-genome DNA microarrays. Genes encoding reactive oxygen and nitrogen species detoxification enzymes had high transcriptional levels under basal conditions and upon exposure to both stresses. On a whole-genome level, there was significant modulation of gene expression by H2O2 (286 genes regulated) and dipropylenetriamine-NONOate (1036 genes regulated) with a significant overlap of genes modulated under both conditions (164 genes). A number of transcriptionally regulated genes were in signalling/regulatory and repair/metabolic pathways. However, the majority of genes with altered transcription encode unknown proteins, suggesting as yet unraveled response pathways in E. histolytica. Trophozoites of a non-pathogenic E. histolytica strain had a significantly muted transcriptional response to H2O2 compared with the pathogenic strain, hinting that differential response to oxidative stress may be one factor that contributes to the pathogenic potential of E. histolytica.
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Affiliation(s)
- João B Vicente
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305-5107, USA
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87
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Fallah E, Nahavandi KH, Jamali R, Mahdavi B, Asgharzade M. Genetic Characterization of Giardia intestinalis Strains from Patients Having Sporadic Giardiasis by Using PCR Assay. JOURNAL OF MEDICAL SCIENCES 2008. [DOI: 10.3923/jms.2008.310.315] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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