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Demircan N, Sonmez MC, Akyol TY, Ozgur R, Turkan I, Dietz KJ, Uzilday B. Alternative electron sinks in chloroplasts and mitochondria of halophytes as a safety valve for controlling ROS production during salinity. PHYSIOLOGIA PLANTARUM 2024; 176:e14397. [PMID: 38894507 DOI: 10.1111/ppl.14397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 05/07/2024] [Accepted: 05/12/2024] [Indexed: 06/21/2024]
Abstract
Electron flow through the electron transport chain (ETC) is essential for oxidative phosphorylation in mitochondria and photosynthesis in chloroplasts. Electron fluxes depend on environmental parameters, e.g., ionic and osmotic conditions and endogenous factors, and this may cause severe imbalances. Plants have evolved alternative sinks to balance the reductive load on the electron transport chains in order to avoid overreduction, generation of reactive oxygen species (ROS), and to cope with environmental stresses. These sinks act primarily as valves for electron drainage and secondarily as regulators of tolerance-related metabolism, utilizing the excess reductive energy. High salinity is an environmental stressor that stimulates the generation of ROS and oxidative stress, which affects growth and development by disrupting the redox homeostasis of plants. While glycophytic plants are sensitive to high salinity, halophytic plants tolerate, grow, and reproduce at high salinity. Various studies have examined the ETC systems of glycophytic plants, however, information about the state and regulation of ETCs in halophytes under non-saline and saline conditions is scarce. This review focuses on alternative electron sinks in chloroplasts and mitochondria of halophytic plants. In cases where information on halophytes is lacking, we examined the available knowledge on the relationship between alternative sinks and gradual salinity resilience of glycophytes. To this end, transcriptional responses of involved components of photosynthetic and respiratory ETCs were compared between the glycophyte Arabidopsis thaliana and the halophyte Schrenkiella parvula, and the time-courses of these transcripts were examined in A. thaliana. The observed regulatory patterns are discussed in the context of reactive molecular species formation in halophytes and glycophytes.
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Affiliation(s)
- Nil Demircan
- Department of Biology, Faculty of Science, Ege University, Izmir, Türkiye
| | | | - Turgut Yigit Akyol
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Rengin Ozgur
- Department of Biology, Faculty of Science, Ege University, Izmir, Türkiye
| | - Ismail Turkan
- Department of Soil and Plant Nutrition, Faculty of Agricultural Sciences and Technologies, Yasar University, İzmir, Türkiye
| | - Karl-Josef Dietz
- Faculty of Biology, Department of Biochemistry and Physiology of Plants, University of Bielefeld, Bielefeld, Germany
| | - Baris Uzilday
- Department of Biology, Faculty of Science, Ege University, Izmir, Türkiye
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2
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Speijer D. How mitochondrial cristae illuminate the important role of oxygen during eukaryogenesis. Bioessays 2024; 46:e2300193. [PMID: 38449346 DOI: 10.1002/bies.202300193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 02/15/2024] [Accepted: 02/19/2024] [Indexed: 03/08/2024]
Abstract
Inner membranes of mitochondria are extensively folded, forming cristae. The observed overall correlation between efficient eukaryotic ATP generation and the area of internal mitochondrial inner membranes both in unicellular organisms and metazoan tissues seems to explain why they evolved. However, the crucial use of molecular oxygen (O2) as final acceptor of the electron transport chain is still not sufficiently appreciated. O2 was an essential prerequisite for cristae development during early eukaryogenesis and could be the factor allowing cristae retention upon loss of mitochondrial ATP generation. Here I analyze illuminating bacterial and unicellular eukaryotic examples. I also discuss formative influences of intracellular O2 consumption on the evolution of the last eukaryotic common ancestor (LECA). These considerations bring about an explanation for the many genes coming from other organisms than the archaeon and bacterium merging at the start of eukaryogenesis.
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Affiliation(s)
- Dave Speijer
- Medical Biochemistry, Amsterdam UMC location, University of Amsterdam, Amsterdam, The Netherlands
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3
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Lukeš J, Speijer D, Zíková A, Alfonzo JD, Hashimi H, Field MC. Trypanosomes as a magnifying glass for cell and molecular biology. Trends Parasitol 2023; 39:902-912. [PMID: 37679284 DOI: 10.1016/j.pt.2023.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/08/2023] [Accepted: 08/09/2023] [Indexed: 09/09/2023]
Abstract
The African trypanosome, Trypanosoma brucei, has developed into a flexible and robust experimental model for molecular and cellular parasitology, allowing us to better combat these and related parasites that cause worldwide suffering. Diminishing case numbers, due to efficient public health efforts, and recent development of new drug treatments have reduced the need for continued study of T. brucei in a disease context. However, we argue that this pathogen has been instrumental in revolutionary discoveries that have widely informed molecular and cellular biology and justifies continuing research as an experimental model. Ongoing work continues to contribute towards greater understanding of both diversified and conserved biological features. We discuss multiple examples where trypanosomes pushed the boundaries of cell biology and hope to inspire researchers to continue exploring these remarkable protists as tools for magnifying the inner workings of cells.
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Affiliation(s)
- Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic.
| | - Dave Speijer
- Medical Biochemistry, University of Amsterdam, AMC, Amsterdam, The Netherlands
| | - Alena Zíková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Juan D Alfonzo
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA
| | - Hassan Hashimi
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Mark C Field
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; School of Life Sciences, University of Dundee, Dundee, UK
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4
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Sendra KM, Watson AK, Kozhevnikova E, Moore AL, Embley TM, Hirt RP. Inhibition of mitosomal alternative oxidase causes lifecycle arrest of early-stage Trachipleistophora hominis meronts during intracellular infection of mammalian cells. PLoS Pathog 2022; 18:e1011024. [PMID: 36538568 PMCID: PMC9767352 DOI: 10.1371/journal.ppat.1011024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/24/2022] [Indexed: 12/24/2022] Open
Abstract
Mitosomes are highly reduced forms of mitochondria which have lost two of the 'defining' features of the canonical organelle, the mitochondrial genome, and the capacity to generate energy in the form of ATP. Mitosomes are found in anaerobic protists and obligate parasites and, in most of the studied organisms, have a conserved function in the biosynthesis of iron-sulfur clusters (ISC) that are indispensable cofactors of many essential proteins. The genomes of some mitosome-bearing human pathogenic Microsporidia encode homologues of an alternative oxidase (AOX). This mitochondrial terminal respiratory oxidase is absent from the human host, and hence is a potential target for the development of new antimicrobial agents. Here we present experimental evidence for the mitosomal localization of AOX in the microsporidian Trachipleistophora hominis and demonstrate that it has an important role during the parasite's life cycle progression. Using a recently published methodology for synchronising T. hominis infection of mammalian cell lines, we demonstrated specific inhibition of T. hominis early meront growth and replication by an AOX inhibitor colletochlorin B. Treatment of T. hominis-infected host cells with the drug also inhibited re-infection by newly formed dispersive spores. Addition of the drug during the later stages of the parasite life cycle, when our methods suggest that AOX is not actively produced and T. hominis mitosomes are mainly active in Fe/S cluster biosynthesis, had no inhibitory effects on the parasites. Control experiments with the AOX-deficient microsporidian species Encephalitozoon cuniculi, further demonstrated the specificity of inhibition by the drug. Using the same methodology, we demonstrate effects of two clinically used anti-microsporidian drugs albendazole and fumagillin on the cell biology and life cycle progression of T. hominis infecting mammalian host cells. In summary, our results reveal that T. hominis mitosomes have an active role to play in the progression of the parasite life cycle as well as an important role in the biosynthesis of essential Fe/S clusters. Our work also demonstrates that T. hominis is a useful model for testing the efficacy of therapeutic agents and for studying the physiology and cell biology of microsporidian parasites growing inside infected mammalian cells.
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Affiliation(s)
- Kacper M. Sendra
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Andrew K. Watson
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | | | - Anthony L. Moore
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - T. Martin Embley
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Robert P. Hirt
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
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5
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Cantoni D, Osborne A, Taib N, Thompson G, Martín‐Escolano R, Kazana E, Edrich E, Brown IR, Gribaldo S, Gourlay CW, Tsaousis AD. Localization and functional characterization of the alternative oxidase in Naegleria. J Eukaryot Microbiol 2022; 69:e12908. [PMID: 35322502 PMCID: PMC9540462 DOI: 10.1111/jeu.12908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The alternative oxidase (AOX) is a protein involved in supporting enzymatic reactions of the Krebs cycle in instances when the canonical (cytochrome-mediated) respiratory chain has been inhibited, while allowing for the maintenance of cell growth and necessary metabolic processes for survival. Among eukaryotes, alternative oxidases have dispersed distribution and are found in plants, fungi, and protists, including Naegleria ssp. Naegleria species are free-living unicellular amoeboflagellates and include the pathogenic species of N. fowleri, the so-called "brain-eating amoeba." Using a multidisciplinary approach, we aimed to understand the evolution, localization, and function of AOX and the role that plays in Naegleria's biology. Our analyses suggest that AOX was present in last common ancestor of the genus and structure prediction showed that all functional residues are also present in Naegleria species. Using cellular and biochemical techniques, we also functionally characterize N. gruberi's AOX in its mitochondria, and we demonstrate that its inactivation affects its proliferation. Consequently, we discuss the benefits of the presence of this protein in Naegleria species, along with its potential pathogenicity role in N. fowleri. We predict that our findings will spearhead new explorations to understand the cell biology, metabolism, and evolution of Naegleria and other free-living relatives.
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Affiliation(s)
- Diego Cantoni
- Laboratory of Molecular & Evolutionary Parasitology, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
| | - Ashley Osborne
- Laboratory of Molecular & Evolutionary Parasitology, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
| | - Najwa Taib
- Unit Evolutionary Biology of the Microbial CellDepartment of MicrobiologyInstitut Pasteur, UMR CNRS 2001ParisFrance
- Hub Bioinformatics and BiostatisticsDepartment of Computational BiologyInstitut Pasteur, USR 3756 CNRSParisFrance
| | - Gary Thompson
- NMR FacilitySchool of BiosciencesUniversity of KentCanterburyUK
| | - Rubén Martín‐Escolano
- Laboratory of Molecular & Evolutionary Parasitology, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
| | - Eleanna Kazana
- Laboratory of Molecular & Evolutionary Parasitology, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
| | - Elizabeth Edrich
- Kent Fungal Group, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
| | - Ian R. Brown
- Bioimaging FacilitySchool of BiosciencesUniversity of KentCanterburyUK
| | - Simonetta Gribaldo
- Unit Evolutionary Biology of the Microbial CellDepartment of MicrobiologyInstitut Pasteur, UMR CNRS 2001ParisFrance
| | - Campbell W. Gourlay
- Kent Fungal Group, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
| | - Anastasios D. Tsaousis
- Laboratory of Molecular & Evolutionary Parasitology, RAPID GroupSchool of BiosciencesUniversity of KentCanterburyUK
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Sankar TV, Saharay M, Santhosh D, Vishwakarma A, Padmasree K. Structural and Biophysical Characterization of Purified Recombinant Arabidopsis thaliana's Alternative Oxidase 1A (rAtAOX1A): Interaction With Inhibitor(s) and Activator. FRONTIERS IN PLANT SCIENCE 2022; 13:871208. [PMID: 35783971 PMCID: PMC9243770 DOI: 10.3389/fpls.2022.871208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/27/2022] [Indexed: 05/14/2023]
Abstract
In higher plants, alternative oxidase (AOX) participates in a cyanide resistant and non-proton motive electron transport pathway of mitochondria, diverging from the ubiquinone pool. The physiological significance of AOX in biotic/abiotic stress tolerance is well-documented. However, its structural and biophysical properties are poorly understood as its crystal structure is not yet revealed in plants. Also, most of the AOX purification processes resulted in a low yield/inactive/unstable form of native AOX protein. The present study aims to characterize the purified rAtAOX1A protein and its interaction with inhibitors, such as salicylhydroxamic acid (SHAM) and n-propyl gallate (n-PG), as well as pyruvate (activator), using biophysical/in silico studies. The rAtAOX1A expressed in E. coli BL21(DE3) cells was functionally characterized by monitoring the respiratory and growth sensitivity of E. coli/pAtAOX1A and E. coli/pET28a to classical mitochondrial electron transport chain (mETC) inhibitors. The rAtAOX1A, which is purified through affinity chromatography and confirmed by western blotting and MALDI-TOF-TOF studies, showed an oxygen uptake activity of 3.86 μmol min-1 mg-1 protein, which is acceptable in non-thermogenic plants. Circular dichroism (CD) studies of purified rAtAOX1A revealed that >50% of the protein content was α-helical and retained its helical absorbance signal (ellipticity) at a wide range of temperature and pH conditions. Further, interaction with SHAM, n-PG, or pyruvate caused significant changes in its secondary structural elements while retaining its ellipticity. Surface plasmon resonance (SPR) studies revealed that both SHAM and n-PG bind reversibly to rAtAOX1A, while docking studies revealed that they bind to the same hydrophobic groove (Met191, Val192, Met195, Leu196, Phe251, and Phe255), to which Duroquinone (DQ) bind in the AtAOX1A. In contrast, pyruvate binds to a pocket consisting of Cys II (Arg174, Tyr175, Gly176, Cys177, Val232, Ala233, Asn294, and Leu313). Further, the mutational docking studies suggest that (i) the Met195 and Phe255 of AtAOX1A are the potential candidates to bind the inhibitor. Hence, this binding pocket could be a 'potential gateway' for the oxidation-reduction process in AtAOX1A, and (ii) Arg174, Gly176, and Cys177 play an important role in binding to the organic acids like pyruvate.
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Affiliation(s)
- Tadiboina Veera Sankar
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Moumita Saharay
- Department of Systems and Computational Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Dharawath Santhosh
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Abhaypratap Vishwakarma
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
- Department of Botany, Deshbandhu College, University of Delhi, New Delhi, India
| | - Kollipara Padmasree
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India
- *Correspondence: Kollipara Padmasree
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7
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Flores-Cotera LB, Chávez-Cabrera C, Martínez-Cárdenas A, Sánchez S, García-Flores OU. Deciphering the mechanism by which the yeast Phaffia rhodozyma responds adaptively to environmental, nutritional, and genetic cues. J Ind Microbiol Biotechnol 2021; 48:kuab048. [PMID: 34302341 PMCID: PMC8788774 DOI: 10.1093/jimb/kuab048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/16/2021] [Indexed: 11/13/2022]
Abstract
Phaffia rhodozyma is a basidiomycetous yeast that synthesizes astaxanthin (ASX), which is a powerful and highly valuable antioxidant carotenoid pigment. P. rhodozyma cells accrue ASX and gain an intense red-pink coloration when faced with stressful conditions such as nutrient limitations (e.g., nitrogen or copper), the presence of toxic substances (e.g., antimycin A), or are affected by mutations in the genes that are involved in nitrogen metabolism or respiration. Since cellular accrual of ASX occurs under a wide variety of conditions, this yeast represents a valuable model for studying the growth conditions that entail oxidative stress for yeast cells. Recently, we proposed that ASX synthesis can be largely induced by conditions that lead to reduction-oxidation (redox) imbalances, particularly the state of the NADH/NAD+ couple together with an oxidative environment. In this work, we review the multiple known conditions that elicit ASX synthesis expanding on the data that we formerly examined. When considered alongside the Mitchell's chemiosmotic hypothesis, the study served to rationalize the induction of ASX synthesis and other adaptive cellular processes under a much broader set of conditions. Our aim was to propose an underlying mechanism that explains how a broad range of divergent conditions converge to induce ASX synthesis in P. rhodozyma. The mechanism that links the induction of ASX synthesis with the occurrence of NADH/NAD+ imbalances may help in understanding how other organisms detect any of a broad array of stimuli or gene mutations, and then adaptively respond to activate numerous compensatory cellular processes.
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Affiliation(s)
- Luis B Flores-Cotera
- Department of Biotechnology and Bioengineering, Cinvestav-IPN, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, México city 07360, México
| | - Cipriano Chávez-Cabrera
- Department of Biotechnology and Bioengineering, Cinvestav-IPN, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, México city 07360, México
| | - Anahi Martínez-Cárdenas
- Department of Biotechnology and Bioengineering, Cinvestav-IPN, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, México city 07360, México
| | - Sergio Sánchez
- Department of Molecular Biology and Biotechnology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México city 04510, México
| | - Oscar Ulises García-Flores
- Department of Biotechnology and Bioengineering, Cinvestav-IPN, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, México city 07360, México
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8
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Xu F, Copsey AC, Young L, Barsottini MRO, Albury MS, Moore AL. Comparison of the Kinetic Parameters of Alternative Oxidases From Trypanosoma brucei and Arabidopsis thaliana-A Tale of Two Cavities. FRONTIERS IN PLANT SCIENCE 2021; 12:744218. [PMID: 34745175 PMCID: PMC8569227 DOI: 10.3389/fpls.2021.744218] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 09/21/2021] [Indexed: 05/27/2023]
Abstract
The alternative oxidase (AOX) is widespread in plants, fungi, and some protozoa. While the general structure of the AOX remains consistent, its overall activity, sources of kinetic activation and their sensitivity to inhibitors varies between species. In this study, the recombinant Trypanosoma brucei AOX (rTAO) and Arabidopsis thaliana AOX1A (rAtAOX1A) were expressed in the Escherichia coli ΔhemA mutant FN102, and the kinetic parameters of purified AOXs were compared. Results showed that rTAO possessed the highest V max and K m for quinol-1, while much lower V max and K m were observed in the rAtAOX1A. The catalytic efficiency (k cat/K m) of rTAO was higher than that of rAtAOX1A. The rTAO also displayed a higher oxygen affinity compared to rAtAOX1A. It should be noted that rAtAOX1a was sensitive to α-keto acids while rTAO was not. Nevertheless, only pyruvate and glyoxylate can fully activate Arabidopsis AOX. In addition, rTAO and rAtAOX1A showed different sensitivity to AOX inhibitors, with ascofuranone (AF) being the best inhibitor against rTAO, while colletochlorin B (CB) appeared to be the most effective inhibitor against rAtAOX1A. Octylgallate (OG) and salicylhydroxamic acid (SHAM) are less effective than the other inhibitors against protist and plant AOX. A Caver analysis indicated that the rTAO and rAtAOX1A differ with respect to the mixture of polar residues lining the hydrophobic cavity, which may account for the observed difference in kinetic and inhibitor sensitivities. The data obtained in this study are not only beneficial for our understanding of the variation in the kinetics of AOX within protozoa and plants but also contribute to the guidance for the future development of phytopathogenic fungicides.
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9
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Wojciechowska D, Roszkowska M, Kaczmarek Ł, Jarmuszkiewicz W, Karachitos A, Kmita H. The tardigrade Hypsibius exemplaris has the active mitochondrial alternative oxidase that could be studied at animal organismal level. PLoS One 2021; 16:e0244260. [PMID: 34424897 PMCID: PMC8382173 DOI: 10.1371/journal.pone.0244260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 08/09/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial alternative oxidase (AOX) is predicted to be present in mitochondria of several invertebrate taxa including tardigrades. Independently of the reason concerning the enzyme occurrence in animal mitochondria, expression of AOX in human mitochondria is regarded as a potential therapeutic strategy. Till now, relevant data were obtained due to heterologous AOX expression in cells and animals without natively expressed AOX. Application of animals natively expressing AOX could importantly contribute to the research. Thus, we decided to investigate AOX activity in intact specimens of the tardigrade Hypsibius exemplaris. We observed that H. exemplaris specimens’ tolerance to the blockage of the mitochondrial respiratory chain (MRC) cytochrome pathway was diminished in the presence of AOX inhibitor and the inhibitor-sensitive respiration enabled the tardigrade respiration under condition of the blockage. Importantly, these observations correlated with relevant changes of the mitochondrial inner membrane potential (Δψ) detected in intact animals. Moreover, detection of AOX at protein level required the MRC cytochrome pathway blockage. Overall, we demonstrated that AOX activity in tardigrades can be monitored by the animals’ behavior observation as well as by measurement of intact specimens’ whole-body respiration and Δψ. Furthermore, it is also possible to check the impact of the MRC cytochrome pathway blockage on AOX level as well as AOX inhibition in the absence of the blockage on animal functioning. Thus, H. exemplaris could be consider as a whole-animal model suitable to study AOX.
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Affiliation(s)
- Daria Wojciechowska
- Faculty of Physics, Department of Macromolecular Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
| | - Milena Roszkowska
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
| | - Łukasz Kaczmarek
- Department of Animal Taxonomy and Ecology, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
| | - Wiesława Jarmuszkiewicz
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
| | - Andonis Karachitos
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
| | - Hanna Kmita
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University, Uniwersytetu Poznańskiego, Poznań, Poland
- * E-mail:
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10
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Wojciechowska D, Karachitos A, Roszkowska M, Rzeźniczak W, Sobkowiak R, Kaczmarek Ł, Kosicki JZ, Kmita H. Mitochondrial alternative oxidase contributes to successful tardigrade anhydrobiosis. Front Zool 2021; 18:15. [PMID: 33794934 PMCID: PMC8015188 DOI: 10.1186/s12983-021-00400-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 03/15/2021] [Indexed: 12/14/2022] Open
Abstract
Anhydrobiosis can be described as an adaptation to lack of water that enables some organisms, including tardigrades, to survive extreme conditions, even some that do not exist on Earth. The cellular mechanisms underlying anhydrobiosis are still not completely explained including the putative contribution of mitochondrial proteins. Since mitochondrial alternative oxidase (AOX), described as a drought response element in plants, was recently proposed for various invertebrates including tardigrades, we investigated whether AOX is involved in successful anhydrobiosis of tardigrades. Milnesium inceptum was used as a model for the study. We confirmed functionality of M. inceptum AOX and estimated its contribution to the tardigrade revival after anhydrobiosis of different durations. We observed that AOX activity was particularly important for M. inceptum revival after the long-term tun stage but did not affect the rehydration stage specifically. The results may contribute to our understanding and then application of anhydrobiosis underlying mechanisms.
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Affiliation(s)
- Daria Wojciechowska
- Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland.,Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Andonis Karachitos
- Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Milena Roszkowska
- Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland.,Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Wiktor Rzeźniczak
- Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Robert Sobkowiak
- Department of Cell Biology, Institute of Experimental Biology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Łukasz Kaczmarek
- Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Jakub Z Kosicki
- Department of Avian Biology and Ecology, Institute of Experimental Biology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland
| | - Hanna Kmita
- Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland.
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11
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Degradation of mitochondrial alternative oxidase in the appendices of Arum maculatum. Biochem J 2021; 477:3417-3431. [PMID: 32856714 PMCID: PMC7505559 DOI: 10.1042/bcj20200515] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/25/2020] [Accepted: 08/27/2020] [Indexed: 01/09/2023]
Abstract
Cyanide-resistant alternative oxidase (AOX) is a nuclear-encoded quinol oxidase located in the inner mitochondrial membrane. Although the quality control of AOX proteins is expected to have a role in elevated respiration in mitochondria, it remains unclear whether thermogenic plants possess molecular mechanisms for the mitochondrial degradation of AOX. To better understand the mechanism of AOX turnover in mitochondria, we performed a series of in organello AOX degradation assays using mitochondria from various stages of the appendices of Arum maculatum. Our analyses clearly indicated that AOX proteins at certain stages in the appendices are degraded at 30°C, which is close to the maximum appendix temperature observed during thermogenesis. Interestingly, such temperature-dependent protease activities were specifically inhibited by E-64, a cysteine protease inhibitor. Moreover, purification and subsequent nano LC–MS/MS analyses of E-64-sensitive and DCG-04-labeled active mitochondrial protease revealed an ∼30 kDa protein with an identical partial peptide sequence to the cysteine protease 1-like protein from Phoenix dactylifera. Our data collectively suggest that AOX is a potential target for temperature-dependent E-64-sensitive cysteine protease in the appendices of A. maculatum. A possible retrograde signalling cascade mediated by specific degradation of AOX proteins and its physiological significance are discussed.
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12
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Rosell-Hidalgo A, Young L, Moore AL, Ghafourian T. QSAR and molecular docking for the search of AOX inhibitors: a rational drug discovery approach. J Comput Aided Mol Des 2020; 35:245-260. [PMID: 33289903 PMCID: PMC7904559 DOI: 10.1007/s10822-020-00360-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 11/12/2020] [Indexed: 11/24/2022]
Abstract
The alternative oxidase (AOX) is a monotopic diiron carboxylate protein that catalyses the oxidation of ubiquinol and the reduction of oxygen to water. Although a number of AOX inhibitors have been discovered, little is still known about the ligand–protein interaction and essential chemical characteristics of compounds required for a potent inhibition. Furthermore, owing to the rapidly growing resistance to existing inhibitors, new compounds with improved potency and pharmacokinetic properties are urgently required. In this study we used two computational approaches, ligand–protein docking and Quantitative Structure–Activity Relationships (QSAR) to investigate binding of AOX inhibitors to the enzyme and the molecular characteristics required for inhibition. Docking studies followed by protein–ligand interaction fingerprint (PLIF) analysis using the AOX enzyme and the mutated analogues revealed the importance of the residues Leu 122, Arg 118 and Thr 219 within the hydrophobic cavity. QSAR analysis, using stepwise regression analysis with experimentally obtained IC50 values as the response variable, resulted in a multiple regression model with a good prediction accuracy. The model highlighted the importance of the presence of hydrogen bonding acceptor groups on specific positions of the aromatic ring of ascofuranone derivatives, acidity of the compounds, and a large linker group on the compounds on the inhibitory effect of AOX.
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Affiliation(s)
- Alicia Rosell-Hidalgo
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Luke Young
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Anthony L Moore
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Taravat Ghafourian
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK. .,School of Life Sciences, Faculty of Creative Arts, Technologies and Science, University of Bedfordshire, Luton, Bedfordshire, LU1 3JU, UK.
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13
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Molecular characterization and gene expression modulation of the alternative oxidase in a scuticociliate parasite by hypoxia and mitochondrial respiration inhibitors. Sci Rep 2020; 10:11880. [PMID: 32681023 PMCID: PMC7367826 DOI: 10.1038/s41598-020-68791-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 07/01/2020] [Indexed: 12/26/2022] Open
Abstract
Philasterides dicentrarchi is a marine benthic microaerophilic scuticociliate and an opportunistic endoparasite that can infect and cause high mortalities in cultured turbot (Scophthalmus maximus). In addition to a cytochrome pathway (CP), the ciliate can use a cyanide-insensitive respiratory pathway, which indicates the existence of an alternative oxidase (AOX) in the mitochondrion. Although AOX activity has been described in P. dicentrarchi, based on functional assay results, genetic evidence of the presence of AOX in the ciliate has not previously been reported. In this study, we conducted genomic and transcriptomic analysis of the ciliate and identified the AOX gene and its corresponding mRNA. The AOX gene (size 1,106 bp) contains four exons and three introns that generate an open reading frame of 915 bp and a protein with a predicted molecular weight of 35.6 kDa. The amino acid (aa) sequence of the AOX includes an import signal peptide targeting the mitochondria and the protein is associated with the inner membrane of the mitochondria. Bioinformatic analysis predicted that the peptide is a homodimeric glycoprotein, although monomeric forms may also appear under native conditions, with EXXH motifs associated with the diiron active centers. The aa sequences of the AOX of different P. dicentrarchi isolates are highly conserved and phylogenetically closely related to AOXs of other ciliate species, especially scuticociliates. AOX expression increased significantly during infection in the host and after the addition of CP inhibitors. This confirms the important physiological roles of AOX in respiration under conditions of low levels of O2 and in protecting against oxidative stress generated during infection in the host.
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14
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Ebiloma GU, Balogun EO, Cueto-Díaz EJ, de Koning HP, Dardonville C. Alternative oxidase inhibitors: Mitochondrion-targeting as a strategy for new drugs against pathogenic parasites and fungi. Med Res Rev 2019; 39:1553-1602. [PMID: 30693533 DOI: 10.1002/med.21560] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 11/07/2018] [Accepted: 12/08/2018] [Indexed: 12/11/2022]
Abstract
The alternative oxidase (AOX) is a ubiquitous terminal oxidase of plants and many fungi, catalyzing the four-electron reduction of oxygen to water alongside the cytochrome-based electron transfer chain. Unlike the classical electron transfer chain, however, the activity of AOX does not generate adenosine triphosphate but has functions such as thermogenesis and stress response. As it lacks a mammalian counterpart, it has been investigated intensely in pathogenic fungi. However, it is in African trypanosomes, which lack cytochrome-based respiration in their infective stages, that trypanosome alternative oxidase (TAO) plays the central and essential role in their energy metabolism. TAO was validated as a drug target decades ago and among the first inhibitors to be identified was salicylhydroxamic acid (SHAM), which produced the expected trypanocidal effects, especially when potentiated by coadministration with glycerol to inhibit anaerobic energy metabolism as well. However, the efficacy of this combination was too low to be of practical clinical use. The antibiotic ascofuranone (AF) proved a much stronger TAO inhibitor and was able to cure Trypanosoma vivax infections in mice without glycerol and at much lower doses, providing an important proof of concept milestone. Systematic efforts to improve the SHAM and AF scaffolds, aided with the elucidation of the TAO crystal structure, provided detailed structure-activity relationship information and reinvigorated the drug discovery effort. Recently, the coupling of mitochondrion-targeting lipophilic cations to TAO inhibitors has dramatically improved drug targeting and trypanocidal activity while retaining target protein potency. These developments appear to have finally signposted the way to preclinical development of TAO inhibitors.
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Affiliation(s)
- Godwin U Ebiloma
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan.,Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Emmanuel O Balogun
- Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria.,Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | | | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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15
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Zhu T, Zou L, Li Y, Yao X, Xu F, Deng X, Zhang D, Lin H. Mitochondrial alternative oxidase-dependent autophagy involved in ethylene-mediated drought tolerance in Solanum lycopersicum. PLANT BIOTECHNOLOGY JOURNAL 2018; 16:2063-2076. [PMID: 29729068 PMCID: PMC6230944 DOI: 10.1111/pbi.12939] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 04/01/2018] [Accepted: 04/04/2018] [Indexed: 05/02/2023]
Abstract
Mitochondrial alternative oxidase (AOX) is involved in a large number of plant physiological processes, such as growth, development and stress responses; however, the exact role of AOX in response to drought remains unclear. In our study, we provide solid evidences that the activated AOX capacity positively involved in ethylene-induced drought tolerance, in tomato (Solanum lycopersicum), accompanied by the changing level of hydrogen peroxide (H2 O2 ) and autophagy. In AOX1a-RNAi plants, the ethylene-induced drought tolerance was aggravated and associated with decreasing level of autophagy. The H2 O2 level was relatively higher in AOX1a-RNAi plants, whereas it was lower in AOX1a-overexpressing (35S-AOX1a-OE) plants after 1-(aminocarbonyl)-1-cyclopropanecarboxylic acid (ACC) pretreatment in the 14th day under drought stress. Interestingly, the accumulation of autophagosome was accompanied by the changing level of reactive oxygen species (ROS) in AOX transgenic tomato under drought stress whether or not pretreated with ACC. Pharmacological scavenging of H2 O2 accumulation in AOX1a-RNAi (aox19) stimulated autophagy acceleration under drought stress, and it seems that AOX-dependent ROS signalling is critical in triggering autophagy. Lower levels of ROS signalling positively induce autophagy activity, whereas higher ROS level would lead to rapid programmed cell death (PCD), especially in ethylene-mediated drought tolerance. Moreover, ethylene-induced autophagy during drought stress also can be through ERF5 binding to the promoters of ATG8d and ATG18h. These results demonstrated that AOX plays an essential role in ethylene-induced drought tolerance and also played important roles in mediating autophagy generation via balancing ROS level.
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Affiliation(s)
- Tong Zhu
- Key Laboratory of Bio‐Resources and Eco‐Environment of Ministry of EducationCollege of Life SciencesSichuan UniversityChengduSichuanChina
| | - Lijuan Zou
- Life Science and Technology College and Ecological Security and Protection Key Laboratory of Sichuan ProvinceMianyang Normal UniversityMianyangChina
| | - Yan Li
- Key Laboratory of Bio‐Resources and Eco‐Environment of Ministry of EducationCollege of Life SciencesSichuan UniversityChengduSichuanChina
| | - Xiuhong Yao
- Key Laboratory of Bio‐Resources and Eco‐Environment of Ministry of EducationCollege of Life SciencesSichuan UniversityChengduSichuanChina
| | - Fei Xu
- Life Science and BiotechnologyWuhan Bioengineering InstituteWuhanChina
| | - Xingguang Deng
- Key Laboratory of Bio‐Resources and Eco‐Environment of Ministry of EducationCollege of Life SciencesSichuan UniversityChengduSichuanChina
| | - Dawei Zhang
- Key Laboratory of Bio‐Resources and Eco‐Environment of Ministry of EducationCollege of Life SciencesSichuan UniversityChengduSichuanChina
| | - Honghui Lin
- Key Laboratory of Bio‐Resources and Eco‐Environment of Ministry of EducationCollege of Life SciencesSichuan UniversityChengduSichuanChina
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16
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Gong H, Li J, Xu A, Tang Y, Ji W, Gao R, Wang S, Yu L, Tian C, Li J, Yen HY, Man Lam S, Shui G, Yang X, Sun Y, Li X, Jia M, Yang C, Jiang B, Lou Z, Robinson CV, Wong LL, Guddat LW, Sun F, Wang Q, Rao Z. An electron transfer path connects subunits of a mycobacterial respiratory supercomplex. Science 2018; 362:science.aat8923. [PMID: 30361386 DOI: 10.1126/science.aat8923] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 10/10/2018] [Indexed: 11/02/2022]
Abstract
We report a 3.5-angstrom-resolution cryo-electron microscopy structure of a respiratory supercomplex isolated from Mycobacterium smegmatis. It comprises a complex III dimer flanked on either side by individual complex IV subunits. Complex III and IV associate so that electrons can be transferred from quinol in complex III to the oxygen reduction center in complex IV by way of a bridging cytochrome subunit. We observed a superoxide dismutase-like subunit at the periplasmic face, which may be responsible for detoxification of superoxide formed by complex III. The structure reveals features of an established drug target and provides a foundation for the development of treatments for human tuberculosis.
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Affiliation(s)
- Hongri Gong
- State Key Laboratory of Medicinal Chemical Biology and College of Life Science, Nankai University, Tianjin 300353, China
| | - Jun Li
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences (CAS), 320 Yueyang Road, Shanghai 200031, China
| | - Ao Xu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Science, Nankai University, Tianjin 300353, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China
| | - Yanting Tang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Science, Nankai University, Tianjin 300353, China
| | - Wenxin Ji
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ruogu Gao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Shuhui Wang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences (CAS), 320 Yueyang Road, Shanghai 200031, China
| | - Lu Yu
- High Magnetic Field Laboratory, CAS, Hefei 230031, China
| | - Changlin Tian
- High Magnetic Field Laboratory, CAS, Hefei 230031, China.,Hefei National Laboratory of Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Jingwen Li
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Rd, Oxford, OX1 3QZ, UK
| | - Hsin-Yung Yen
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Rd, Oxford, OX1 3QZ, UK.,OMass Technologies, Begbroke Science Park, Woodstock Rd, Yarnton, Kidlington OX5 1PF, UK
| | - Sin Man Lam
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, CAS, Beijing 100101, China
| | - Guanghou Shui
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, CAS, Beijing 100101, China
| | - Xiuna Yang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences (CAS), 320 Yueyang Road, Shanghai 200031, China
| | - Yuna Sun
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China
| | - Xuemei Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China
| | - Minze Jia
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China
| | - Cheng Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Science, Nankai University, Tianjin 300353, China
| | - Biao Jiang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China
| | - Zhiyong Lou
- Laboratory of Structural Biology, Tsinghua University, Beijing 100084, China
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Rd, Oxford, OX1 3QZ, UK
| | - Luet-Lok Wong
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
| | - Luke W Guddat
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, 4072 Queensland, Australia
| | - Fei Sun
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China. .,University of Chinese Academy of Sciences, Beijing, China
| | - Quan Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China.
| | - Zihe Rao
- State Key Laboratory of Medicinal Chemical Biology and College of Life Science, Nankai University, Tianjin 300353, China. .,Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences (CAS), 320 Yueyang Road, Shanghai 200031, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, CAS, Beijing 100101, China.,Laboratory of Structural Biology, Tsinghua University, Beijing 100084, China
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17
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Tsaousis AD, Hamblin KA, Elliott CR, Young L, Rosell-Hidalgo A, Gourlay CW, Moore AL, van der Giezen M. The Human Gut Colonizer Blastocystis Respires Using Complex II and Alternative Oxidase to Buffer Transient Oxygen Fluctuations in the Gut. Front Cell Infect Microbiol 2018; 8:371. [PMID: 30406045 PMCID: PMC6204527 DOI: 10.3389/fcimb.2018.00371] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 10/03/2018] [Indexed: 12/12/2022] Open
Abstract
Blastocystis is the most common eukaryotic microbe in the human gut. It is linked to irritable bowel syndrome (IBS), but its role in disease has been contested considering its widespread nature. This organism is well-adapted to its anoxic niche and lacks typical eukaryotic features, such as a cytochrome-driven mitochondrial electron transport. Although generally considered a strict or obligate anaerobe, its genome encodes an alternative oxidase. Alternative oxidases are energetically wasteful enzymes as they are non-protonmotive and energy is liberated in heat, but they are considered to be involved in oxidative stress protective mechanisms. Our results demonstrate that the Blastocystis cells themselves respire oxygen via this alternative oxidase thereby casting doubt on its strict anaerobic nature. Inhibition experiments using alternative oxidase and Complex II specific inhibitors clearly demonstrate their role in cellular respiration. We postulate that the alternative oxidase in Blastocystis is used to buffer transient oxygen fluctuations in the gut and that it likely is a common colonizer of the human gut and not causally involved in IBS. Additionally the alternative oxidase could act as a protective mechanism in a dysbiotic gut and thereby explain the absence of Blastocystis in established IBS environments.
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Affiliation(s)
- Anastasios D. Tsaousis
- RAPID Group, Laboratory of Molecular & Evolutionary Parasitology, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Karleigh A. Hamblin
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
- Biosciences, University of Exeter, Exeter, United Kingdom
| | - Catherine R. Elliott
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Luke Young
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Alicia Rosell-Hidalgo
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Campbell W. Gourlay
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Anthony L. Moore
- Department of Biochemistry and Biomedicine, School of Life Sciences, University of Sussex, Brighton, United Kingdom
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18
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Hartmann SK, Stockdreher Y, Wandrey G, Hosseinpour Tehrani H, Zambanini T, Meyer AJ, Büchs J, Blank LM, Schwarzländer M, Wierckx N. Online in vivo monitoring of cytosolic NAD redox dynamics in Ustilago maydis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1015-1024. [DOI: 10.1016/j.bbabio.2018.05.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 04/06/2018] [Accepted: 05/20/2018] [Indexed: 12/20/2022]
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19
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Brew-Appiah RAT, York ZB, Krishnan V, Roalson EH, Sanguinet KA. Genome-wide identification and analysis of the ALTERNATIVE OXIDASE gene family in diploid and hexaploid wheat. PLoS One 2018; 13:e0201439. [PMID: 30074999 PMCID: PMC6075773 DOI: 10.1371/journal.pone.0201439] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/16/2018] [Indexed: 11/19/2022] Open
Abstract
A comprehensive understanding of wheat responses to environmental stress will contribute to the long-term goal of feeding the planet. ALERNATIVE OXIDASE (AOX) genes encode proteins involved in a bypass of the electron transport chain and are also known to be involved in stress tolerance in multiple species. Here, we report the identification and characterization of the AOX gene family in diploid and hexaploid wheat. Four genes each were found in the diploid ancestors Triticum urartu, and Aegilops tauschii, and three in Aegilops speltoides. In hexaploid wheat (Triticum aestivum), 20 genes were identified, some with multiple splice variants, corresponding to a total of 24 proteins for those with observed transcription and translation. These proteins were classified as AOX1a, AOX1c, AOX1e or AOX1d via phylogenetic analysis. Proteins lacking most or all signature AOX motifs were assigned to putative regulatory roles. Analysis of protein-targeting sequences suggests mixed localization to the mitochondria and other organelles. In comparison to the most studied AOX from Trypanosoma brucei, there were amino acid substitutions at critical functional domains indicating possible role divergence in wheat or grasses in general. In hexaploid wheat, AOX genes were expressed at specific developmental stages as well as in response to both biotic and abiotic stresses such as fungal pathogens, heat and drought. These AOX expression patterns suggest a highly regulated and diverse transcription and expression system. The insights gained provide a framework for the continued and expanded study of AOX genes in wheat for stress tolerance through breeding new varieties, as well as resistance to AOX-targeted herbicides, all of which can ultimately be used synergistically to improve crop yield.
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Affiliation(s)
- Rhoda A. T. Brew-Appiah
- Department of Crop and Soil Sciences, Washington State University, Pullman, Washington, United States of America
| | - Zara B. York
- Department of Crop and Soil Sciences, Washington State University, Pullman, Washington, United States of America
| | - Vandhana Krishnan
- Stanford Center for Genomics and Personalized Medicine, Department of Genetics, Stanford University, Stanford, United States of America
| | - Eric H. Roalson
- School of Biological Sciences, Washington State University, Pullman, Washington, United States of America
| | - Karen A. Sanguinet
- Department of Crop and Soil Sciences, Washington State University, Pullman, Washington, United States of America
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20
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Liu M, Guo X. A novel and stress adaptive alternative oxidase derived from alternative splicing of duplicated exon in oyster Crassostrea virginica. Sci Rep 2017; 7:10785. [PMID: 28883650 PMCID: PMC5589949 DOI: 10.1038/s41598-017-10976-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 08/17/2017] [Indexed: 12/25/2022] Open
Abstract
Alternative oxidase (AOX) is a mitochondrial inner-membrane oxidase that accepts electrons directly from ubiquinol and reduces oxygen to water without involving cytochrome-linked electron transport chain. It is highly conserved in many non-vertebrate taxa and may protect cells against hypoxia and oxidative stress. We identified two AOX mRNAs in eastern oyster Crassostrea virginica, CvAOXA and CvAOXB, which differ by 170 bp but encode AOXs of the same size. Sequence analyses indicate that CvAOX has 10 exons with a tandem duplication of exon 10, and 3' alternative splicing using either the first or second exon 10 produces the two variants CvAOXB or CvAOXA, respectively. The second exon 10 in CvAOXA is more conserved across taxa, while the first exon 10 in CvAOXB contains novel mutations surrounding key functional sites. Both variants are expressed in all organs with the expression of CvAOXA higher than that of CvAOXB under normal condition. Under stress by air exposure, CvAOXB showed significantly higher expression than CvAOXA and became the dominant variant. This is the first case of alternative splicing of duplicated exon in a mollusc that produces a novel variant adaptive to stress, highlighting genome's versatility in generating diversity and phenotypic plasticity.
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Affiliation(s)
- Ming Liu
- Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, NJ, 08349, USA
| | - Ximing Guo
- Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, NJ, 08349, USA.
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21
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Cárdenas-Monroy CA, Pohlmann T, Piñón-Zárate G, Matus-Ortega G, Guerra G, Feldbrügge M, Pardo JP. The mitochondrial alternative oxidase Aox1 is needed to cope with respiratory stress but dispensable for pathogenic development in Ustilago maydis. PLoS One 2017; 12:e0173389. [PMID: 28273139 PMCID: PMC5342259 DOI: 10.1371/journal.pone.0173389] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 02/20/2017] [Indexed: 12/22/2022] Open
Abstract
The mitochondrial alternative oxidase is an important enzyme that allows respiratory activity and the functioning of the Krebs cycle upon disturbance of the respiration chain. It works as a security valve in transferring excessive electrons to oxygen, thereby preventing potential damage by the generation of harmful radicals. A clear biological function, besides the stress response, has so far convincingly only been shown for plants that use the alternative oxidase to generate heat to distribute volatiles. In fungi it was described that the alternative oxidase is needed for pathogenicity. Here, we investigate expression and function of the alternative oxidase at different stages of the life cycle of the corn pathogen Ustilago maydis (Aox1). Interestingly, expression of Aox1 is specifically induced during the stationary phase suggesting a role at high cell density when nutrients become limiting. Studying deletion strains as well as overexpressing strains revealed that Aox1 is dispensable for normal growth, for cell morphology, for response to temperature stress as well as for filamentous growth and plant pathogenicity. However, during conditions eliciting respiratory stress yeast-like growth as well as hyphal growth is strongly affected. We conclude that Aox1 is dispensable for the normal biology of the fungus but specifically needed to cope with respiratory stress.
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Affiliation(s)
| | - Thomas Pohlmann
- Institute for Microbiology, Cluster of Excellence on Plant Sciences, Department of Biology, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany
| | - Gabriela Piñón-Zárate
- Departamento de Biología Celular y Tisular, Facultad de Medicina, UNAM. Ciudad de México, México
| | - Genaro Matus-Ortega
- Departamento de Bioquímica, Facultad de Medicina, UNAM. Ciudad de México, México
| | - Guadalupe Guerra
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional. Ciudad de México, México
| | - Michael Feldbrügge
- Institute for Microbiology, Cluster of Excellence on Plant Sciences, Department of Biology, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany
| | - Juan Pablo Pardo
- Departamento de Bioquímica, Facultad de Medicina, UNAM. Ciudad de México, México
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22
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Zhu T, Deng XG, Tan WR, Zhou X, Luo SS, Han XY, Zhang DW, Lin HH. Nitric oxide is involved in brassinosteroid-induced alternative respiratory pathway in Nicotiana benthamiana seedlings' response to salt stress. PHYSIOLOGIA PLANTARUM 2016; 156:150-163. [PMID: 26419322 DOI: 10.1111/ppl.12392] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/26/2015] [Indexed: 05/20/2023]
Abstract
Recent studies reported that brassinosteroids (BRs) can induce plant tolerance to different environmental stresses via the nitric oxide (NO) signaling pathway. Previous reports have indicated that alternative oxidase (AOX) plays an important role in plants under various stresses. The mechanisms governing how NO is involved as a signal molecule which connects BR with AOX in regulating stress tolerance are still unknown. Recently, we found that Nicotiana benthamiana seedlings which were pretreated with BR have more tolerance to salt stress, accompanied with an increase of CN-resistant respiration. Our results suggested that pretreatment with 0.1 μM brassinolide (BL, the most active brassinosteroid) alleviated salt-induced oxidative damage and increased the NbAOX1 transcript level. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-1-oxyl-3-oxide (cPTIO, an NO scavenger) or virus-induced gene silencing of nitrate reductase (NR) and nitric oxide synthase (NOS)-like enzyme compromised the BRs-induced alternative respiratory pathway. Furthermore, pretreatment with specific chemical inhibitors of NR and NOS or gene silencing experiments decreased plant resistance to salt stress which also compromised BRs-induced salt stress tolerance. In conclusion, NO is involved in BRs-induced AOX capability which plays essential roles in salt tolerance in N. benthamiana seedlings.
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Affiliation(s)
- Tong Zhu
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Xing-Guang Deng
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Wen-Rong Tan
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Xue Zhou
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Shi-Shuai Luo
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Xue-Ying Han
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Da-Wei Zhang
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
| | - Hong-Hui Lin
- Ministry of Education, Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, China
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23
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Unraveling the evolution and regulation of the alternative oxidase gene family in plants. Dev Genes Evol 2015; 225:331-9. [DOI: 10.1007/s00427-015-0515-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 08/20/2015] [Indexed: 12/19/2022]
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24
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Abstract
Philasterides dicentrarchi causes a severe disease in turbot, and at present there are no drugs available to treat infected fish. We have previously demonstrated that, in addition to the classical respiratory pathway, P. dicentrarchi possesses an alternative mitochondrial respiratory pathway that is cyanide-insensitive and salicylhydroxamic acid (SHAM)-sensitive. In this study, we found that during the initial phase of growth in normoxia, ciliate respiration is sensitive to the natural polyphenol resveratrol (RESV) and to Antimycin A (AMA). However, under hypoxic conditions, the parasite utilizes AMA-insensitive respiration, which is completely inhibited by RESV and by the antioxidant propyl gallate (PG), an alternative oxidase (AOX) inhibitor. PG caused significantly dose-dependent inhibition of the in vitro growth of the parasite under normoxia and hypoxia and an over-expression of heat shock proteins of the Hsp70 subfamily. RESV and PG may affect the protective role of the AOX against mitochondrial oxidative stress, leading to an impaired mitochondrial membrane potential and mitochondrial dysfunction, which the parasite attempts to neutralize by increasing the expression of Hsp70. In view of the antiparasitic effects induced by AOX inhibitors and the absence of AOX in their host, this enzyme constitutes a potential target for the development of new drugs against scuticociliatosis.
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25
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Antos-Krzeminska N, Jarmuszkiewicz W. Functional expression of the Acanthamoeba castellanii alternative oxidase in Escherichia coli; regulation of the activity and evidence for Acaox gene function. Biochem Cell Biol 2014; 92:235-41. [PMID: 24860925 DOI: 10.1139/bcb-2014-0014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To evidence Acanthamoeba castellanii alternative oxidase (AcAOX) gene product function, we studied alterations in the levels of mRNA and protein and AcAOX activity during growth in amoeba batch culture. Moreover, heterologous expression of AcAOX in AOX-deficient Escherichia coli confirmed by the protein immunodetection and functional studies was performed. Despite the presence of native bo and bd quinol oxidases in E. coli membrane, from which the latter is known to be cyanide-resistant, functional expression of AcAOX in E. coli conferred cyanide-resistant benzohydroxamate-sensitive respiration on the bacteria. Moreover, AcAOX activity in transformed bacteria was stimulated by GMP and inhibited by ATP, indicating that AcAOX is regulated by mutual exclusion of purine nucleotides, which was previously demonstrated in the mitochondria of A. castellanii.
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Affiliation(s)
- Nina Antos-Krzeminska
- Department of Bioenergetics, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
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26
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Highly divergent mitochondrion-related organelles in anaerobic parasitic protozoa. Biochimie 2014; 100:3-17. [DOI: 10.1016/j.biochi.2013.11.018] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 11/24/2013] [Indexed: 11/20/2022]
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27
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Neimanis K, Staples JF, Hüner NP, McDonald AE. Identification, expression, and taxonomic distribution of alternative oxidases in non-angiosperm plants. Gene 2013; 526:275-86. [DOI: 10.1016/j.gene.2013.04.072] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/23/2013] [Accepted: 04/24/2013] [Indexed: 10/26/2022]
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29
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Engineering plant alternative oxidase function in mammalian cells: substitution of the motif-like sequence ENV for QDT diminishes catalytic activity of Arum concinnatum AOX1a expressed in HeLa cells. Appl Biochem Biotechnol 2013; 170:1229-40. [PMID: 23653140 DOI: 10.1007/s12010-013-0235-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 04/09/2013] [Indexed: 10/26/2022]
Abstract
Alternative oxidase (AOX) is a nonproton motive quinol-oxygen oxidoreductase which is a component of the mitochondrial respiratory chain in higher plants. In this study, we have characterized the catalytic activity and regulatory behaviors of Arum concinnatum AOX isoforms, namely AcoAOX1a and AcoAOX1b, and their artificial mutants in HeLa cells. We demonstrated that substitution of the motif-like sequence ENV on the C-terminal half of AcoAOX1a for QDT diminishes its activity and proposed that the innate inactivity of AcoAOX1b in HeLa cells is, at least in part, attributable to its QDT motif. Furthermore, we show that introduction of F130L in the hydrophilic N-terminal extension of AcoAOX1a resulted in greater activity in the presence of pyruvate. This result indicates that functional significance of the N-terminal extension is not particular to the conventional regulatory cysteine. On the basis of these findings, we discuss new insights into the structural integrity of AOX in HeLa cells and the applicability of mammalian cells for functional analysis of this enzyme.
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30
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Vanlerberghe GC. Alternative oxidase: a mitochondrial respiratory pathway to maintain metabolic and signaling homeostasis during abiotic and biotic stress in plants. Int J Mol Sci 2013; 14:6805-47. [PMID: 23531539 PMCID: PMC3645666 DOI: 10.3390/ijms14046805] [Citation(s) in RCA: 405] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Revised: 03/08/2013] [Accepted: 03/12/2013] [Indexed: 02/07/2023] Open
Abstract
Alternative oxidase (AOX) is a non-energy conserving terminal oxidase in the plant mitochondrial electron transport chain. While respiratory carbon oxidation pathways, electron transport, and ATP turnover are tightly coupled processes, AOX provides a means to relax this coupling, thus providing a degree of metabolic homeostasis to carbon and energy metabolism. Beside their role in primary metabolism, plant mitochondria also act as "signaling organelles", able to influence processes such as nuclear gene expression. AOX activity can control the level of potential mitochondrial signaling molecules such as superoxide, nitric oxide and important redox couples. In this way, AOX also provides a degree of signaling homeostasis to the organelle. Evidence suggests that AOX function in metabolic and signaling homeostasis is particularly important during stress. These include abiotic stresses such as low temperature, drought, and nutrient deficiency, as well as biotic stresses such as bacterial infection. This review provides an introduction to the genetic and biochemical control of AOX respiration, as well as providing generalized examples of how AOX activity can provide metabolic and signaling homeostasis. This review also examines abiotic and biotic stresses in which AOX respiration has been critically evaluated, and considers the overall role of AOX in growth and stress tolerance.
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Affiliation(s)
- Greg C Vanlerberghe
- Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C1A4, Canada.
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31
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Shiba T, Kido Y, Sakamoto K, Inaoka DK, Tsuge C, Tatsumi R, Takahashi G, Balogun EO, Nara T, Aoki T, Honma T, Tanaka A, Inoue M, Matsuoka S, Saimoto H, Moore AL, Harada S, Kita K. Structure of the trypanosome cyanide-insensitive alternative oxidase. Proc Natl Acad Sci U S A 2013; 110:4580-5. [PMID: 23487766 PMCID: PMC3607012 DOI: 10.1073/pnas.1218386110] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In addition to haem copper oxidases, all higher plants, some algae, yeasts, molds, metazoans, and pathogenic microorganisms such as Trypanosoma brucei contain an additional terminal oxidase, the cyanide-insensitive alternative oxidase (AOX). AOX is a diiron carboxylate protein that catalyzes the four-electron reduction of dioxygen to water by ubiquinol. In T. brucei, a parasite that causes human African sleeping sickness, AOX plays a critical role in the survival of the parasite in its bloodstream form. Because AOX is absent from mammals, this protein represents a unique and promising therapeutic target. Despite its bioenergetic and medical importance, however, structural features of any AOX are yet to be elucidated. Here we report crystal structures of the trypanosomal alternative oxidase in the absence and presence of ascofuranone derivatives. All structures reveal that the oxidase is a homodimer with the nonhaem diiron carboxylate active site buried within a four-helix bundle. Unusually, the active site is ligated solely by four glutamate residues in its oxidized inhibitor-free state; however, inhibitor binding induces the ligation of a histidine residue. A highly conserved Tyr220 is within 4 Å of the active site and is critical for catalytic activity. All structures also reveal that there are two hydrophobic cavities per monomer. Both inhibitors bind to one cavity within 4 Å and 5 Å of the active site and Tyr220, respectively. A second cavity interacts with the inhibitor-binding cavity at the diiron center. We suggest that both cavities bind ubiquinol and along with Tyr220 are required for the catalytic cycle for O2 reduction.
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Affiliation(s)
- Tomoo Shiba
- Department of Biomedical Chemistry, Graduate School of Medicine, and
| | - Yasutoshi Kido
- Department of Biomedical Chemistry, Graduate School of Medicine, and
| | | | - Daniel Ken Inaoka
- Department of Biomedical Chemistry, Graduate School of Medicine, and
| | - Chiaki Tsuge
- Department of Biomedical Chemistry, Graduate School of Medicine, and
| | - Ryoko Tatsumi
- Department of Biomedical Chemistry, Graduate School of Medicine, and
| | - Gen Takahashi
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Emmanuel Oluwadare Balogun
- Department of Biomedical Chemistry, Graduate School of Medicine, and
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
- Department of Biochemistry, Ahmadu Bello University, Zaria 2222, Nigeria
| | - Takeshi Nara
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Takashi Aoki
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Teruki Honma
- Systems and Structural Biology Center, RIKEN, Tsurumi, Yokohama 230-0045, Japan;
| | - Akiko Tanaka
- Systems and Structural Biology Center, RIKEN, Tsurumi, Yokohama 230-0045, Japan;
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeru Matsuoka
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroyuki Saimoto
- Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, Tottori 680-8552, Japan; and
| | - Anthony L. Moore
- Biochemistry and Molecular Biology, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom
| | - Shigeharu Harada
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, and
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32
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Moore AL, Shiba T, Young L, Harada S, Kita K, Ito K. Unraveling the heater: new insights into the structure of the alternative oxidase. ANNUAL REVIEW OF PLANT BIOLOGY 2013; 64:637-63. [PMID: 23638828 DOI: 10.1146/annurev-arplant-042811-105432] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The alternative oxidase is a membrane-bound ubiquinol oxidase found in the majority of plants as well as many fungi and protists, including pathogenic organisms such as Trypanosoma brucei. It catalyzes a cyanide- and antimycin-A-resistant oxidation of ubiquinol and the reduction of oxygen to water, short-circuiting the mitochondrial electron-transport chain prior to proton translocation by complexes III and IV, thereby dramatically reducing ATP formation. In plants, it plays a key role in cellular metabolism, thermogenesis, and energy homeostasis and is generally considered to be a major stress-induced protein. We describe recent advances in our understanding of this protein's structure following the recent successful crystallization of the alternative oxidase from T. brucei. We focus on the nature of the active site and ubiquinol-binding channels and propose a mechanism for the reduction of oxygen to water based on these structural insights. We also consider the regulation of activity at the posttranslational and retrograde levels and highlight challenges for future research.
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Affiliation(s)
- Anthony L Moore
- Biochemistry and Molecular Biology, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
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33
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Saimoto H, Kido Y, Haga Y, Sakamoto K, Kita K. Pharmacophore identification of ascofuranone, potent inhibitor of cyanide-insensitive alternative oxidase of Trypanosoma brucei. ACTA ACUST UNITED AC 2012. [DOI: 10.1093/jb/mvs135] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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34
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Xu F, Zhang DW, Zhu F, Tang H, Lv X, Cheng J, Xie HF, Lin HH. A novel role for cyanide in the control of cucumber (Cucumis sativus L.) seedlings response to environmental stress. PLANT, CELL & ENVIRONMENT 2012; 35:1983-97. [PMID: 22554042 DOI: 10.1111/j.1365-3040.2012.02531.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The effects of potassium cyanide (KCN) pretreatment on the response of cucumber (Cucumis sativus L.) plants to salt, polyethylene glycol (PEG) and cold stress were investigated in the present study. Here, we found that KCN pretreatment improved cucumber seedlings tolerance to stress conditions with maximum efficiency at a concentration of 20 µM. The results showed that pretreatment with 20 µM KCN alleviated stress-induced oxidative damage in plant cells and clearly induced the activity of alternative oxidase (AOX) and the ethylene production. Furthermore, the structures of thylakoids and mitochondria in the KCN-pretreated seedlings were less damaged by the stress conditions, which maintained higher total chlorophyll content, photosynthetic rate and photosystem II (PSII) proteins levels than the control. Importantly, the addition of the AOX inhibitor salicylhydroxamic acid (1 mm; SHAM) decreased plant resistance to environmental stress and even compromised the cyanide (CN)-enhanced stress tolerance. Therefore, our findings provide a novel role of CN in plant against environmental stress and indicate that the CN-enhanced AOX might contribute to the reactive oxygen species (ROS) scavenging and the protection of photosystem by maintaining energy charge homoeostasis from chloroplast to mitochondria.
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Affiliation(s)
- Fei Xu
- Plant Physiology Laboratory Key Laboratory of Bio-resources & Eco-environment (Ministry of Education), College of Life Science, Sichuan University, Chengdu 610064, China
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35
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Martins VDP, Dinamarco TM, Curti C, Uyemura SA. Classical and alternative components of the mitochondrial respiratory chain in pathogenic fungi as potential therapeutic targets. J Bioenerg Biomembr 2011; 43:81-8. [PMID: 21271279 DOI: 10.1007/s10863-011-9331-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The frequency of opportunistic fungal infection has increased drastically, mainly in patients who are immunocompromised due to organ transplant, leukemia or HIV infection. In spite of this, only a few classes of drugs with a limited array of targets, are available for antifungal therapy. Therefore, more specific and less toxic drugs with new molecular targets is desirable for the treatment of fungal infections. In this context, searching for differences between mitochondrial mammalian hosts and fungi in the classical and alternative components of the mitochondrial respiratory chain may provide new potential therapeutic targets for this purpose.
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Affiliation(s)
- Vicente de Paulo Martins
- Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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36
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Interaction of purified alternative oxidase from thermogenic Arum maculatum with pyruvate. FEBS Lett 2010; 585:397-401. [PMID: 21187094 DOI: 10.1016/j.febslet.2010.12.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Revised: 12/06/2010] [Accepted: 12/16/2010] [Indexed: 10/18/2022]
Abstract
Plant alternative oxidase (AOX) activity in isolated mitochondria is regulated by carboxylic acids, but reaction and regulatory mechanisms remain unclear. We show that activity of AOX protein purified from thermogenic Arum maculatum spadices is sensitive to pyruvate and glyoxylate but not succinate. Rapid, irreversible AOX inactivation occurs in the absence of pyruvate, whether or not duroquinol oxidation has been initiated, and is insensitive to duroquinone. Our data indicate that pyruvate stabilises an active conformation of AOX, increasing the population of active protein in a manner independent of reducing substrate and product, and are thus consistent with an exclusive effect of pyruvate on the enzyme's apparent V(max).
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37
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Albury MS, Elliott C, Moore AL. Ubiquinol-binding site in the alternative oxidase: Mutagenesis reveals features important for substrate binding and inhibition. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1933-9. [DOI: 10.1016/j.bbabio.2010.01.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 01/11/2010] [Accepted: 01/12/2010] [Indexed: 11/16/2022]
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38
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Crichton PG, Albury MS, Affourtit C, Moore AL. Mutagenesis of the Sauromatum guttatum alternative oxidase reveals features important for oxygen binding and catalysis. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1797:732-7. [PMID: 20026041 DOI: 10.1016/j.bbabio.2009.12.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 12/10/2009] [Accepted: 12/14/2009] [Indexed: 11/19/2022]
Abstract
The alternative oxidase (AOX) is a non-protonmotive ubiquinol oxidase that is found in mitochondria of all higher plants studied to date. To investigate the role of highly conserved amino acid residues in catalysis we have expressed site-directed mutants of Cys-172, Thr-179, Trp-206, Tyr-253, and Tyr-299 in AOX in the yeast Schizosaccharomyces pombe. Assessment of AOX activity in isolated yeast mitochondria reveals that mutagenesis of Trp-206 to phenylalanine or tyrosine abolishes activity, in contrast to that observed with either Tyr-253 or 299 both mutants of which retained activity. None of the mutants exhibited sensitivity to Q-like inhibitors that differed significantly from the wild type AOX. Interestingly, however, mutagenesis of Thr-179 or Cys-172 (a residue implicated in AOX regulation by alpha-keto acids) to alanine not only resulted in a decrease of maximum AOX activity but also caused a significant increase in the enzyme's affinity for oxygen (4- and 2-fold, respectively). These results provide important new insights in the mechanism of AOX catalysis and regulation by pyruvate.
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Affiliation(s)
- Paul G Crichton
- Department of Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
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39
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Lenaz G, Genova ML. Structure and organization of mitochondrial respiratory complexes: a new understanding of an old subject. Antioxid Redox Signal 2010; 12:961-1008. [PMID: 19739941 DOI: 10.1089/ars.2009.2704] [Citation(s) in RCA: 186] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The enzymatic complexes of the mitochondrial respiratory chain have been extensively investigated in their structural and functional properties. A clear distinction is possible today between three complexes in which the difference in redox potential allows proton translocation (complexes I, III, and IV) and those having the mere function to convey electrons to the respiratory chain. We also have a clearer understanding of the structure and function of most respiratory complexes, of their biogenesis and regulation, and of their capacity to generate reactive oxygen species. Past investigations led to the conclusion that the complexes are randomly dispersed and functionally connected by diffusion of smaller redox components, coenzyme Q and cytochrome c. More-recent investigations by native gel electrophoresis and single-particle image processing showed the existence of supramolecular associations. Flux-control analysis demonstrated that complexes I and III in mammals and I, III, and IV in plants kinetically behave as single units, suggesting the existence of substrate channeling. This review discusses conditions affecting the formation of supercomplexes that, besides kinetic advantage, have a role in the stability and assembly of the individual complexes and in preventing excess oxygen radical formation. Disruption of supercomplex organization may lead to functional derangements responsible for pathologic changes.
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Affiliation(s)
- Giorgio Lenaz
- Dipartimento di Biochimica "G. Moruzzi," Alma Mater Studiorum, Università di Bologna, Bologna, Italy.
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40
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Kido Y, Sakamoto K, Nakamura K, Harada M, Suzuki T, Yabu Y, Saimoto H, Yamakura F, Ohmori D, Moore A, Harada S, Kita K. Purification and kinetic characterization of recombinant alternative oxidase from Trypanosoma brucei brucei. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:443-50. [DOI: 10.1016/j.bbabio.2009.12.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 12/23/2009] [Accepted: 12/25/2009] [Indexed: 10/20/2022]
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41
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Kido Y, Shiba T, Inaoka DK, Sakamoto K, Nara T, Aoki T, Honma T, Tanaka A, Inoue M, Matsuoka S, Moore A, Harada S, Kita K. Crystallization and preliminary crystallographic analysis of cyanide-insensitive alternative oxidase from Trypanosoma brucei brucei. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:275-8. [PMID: 20208159 PMCID: PMC2833035 DOI: 10.1107/s1744309109054062] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Accepted: 12/15/2009] [Indexed: 04/24/2023]
Abstract
Cyanide-insensitive alternative oxidase (AOX) is a mitochondrial membrane protein and a non-proton-pumping ubiquinol oxidase that catalyzes the four-electron reduction of dioxygen to water. In the African trypanosomes, trypanosome alternative oxidase (TAO) functions as a cytochrome-independent terminal oxidase that is essential for survival in the mammalian host; hence, the enzyme is considered to be a promising drug target for the treatment of trypanosomiasis. In the present study, recombinant TAO (rTAO) overexpressed in haem-deficient Escherichia coli was purified and crystallized at 293 K by the hanging-drop vapour-diffusion method using polyethylene glycol 400 as a precipitant. X-ray diffraction data were collected at 100 K and were processed to 2.9 A resolution with 93.1% completeness and an overall R(merge) of 9.5%. The TAO crystals belonged to the orthorhombic space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 63.11, b = 136.44, c = 223.06 A. Assuming the presence of two rTAO molecules in the asymmetric unit (2 x 38 kDa), the calculated Matthews coefficient (V(M)) was 3.2 A(3) Da(-1), which corresponds to a solvent content of 61.0%. This is the first report of a crystal of the membrane-bound diiron proteins, which include AOXs.
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Affiliation(s)
- Yasutoshi Kido
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Tomoo Shiba
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Daniel Ken Inaoka
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kimitoshi Sakamoto
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Takeshi Nara
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Takashi Aoki
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
| | - Teruki Honma
- Systems and Structural Biology Center, RIKEN, Tsurumi, Yokohama 230-0045, Japan
| | - Akiko Tanaka
- Systems and Structural Biology Center, RIKEN, Tsurumi, Yokohama 230-0045, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeru Matsuoka
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Anthony Moore
- Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton, England
| | - Shigeharu Harada
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
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Williams BAP, Elliot C, Burri L, Kido Y, Kita K, Moore AL, Keeling PJ. A broad distribution of the alternative oxidase in microsporidian parasites. PLoS Pathog 2010; 6:e1000761. [PMID: 20169184 PMCID: PMC2820529 DOI: 10.1371/journal.ppat.1000761] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 01/11/2010] [Indexed: 11/19/2022] Open
Abstract
Microsporidia are a group of obligate intracellular parasitic eukaryotes that were considered to be amitochondriate until the recent discovery of highly reduced mitochondrial organelles called mitosomes. Analysis of the complete genome of Encephalitozoon cuniculi revealed a highly reduced set of proteins in the organelle, mostly related to the assembly of iron-sulphur clusters. Oxidative phosphorylation and the Krebs cycle proteins were absent, in keeping with the notion that the microsporidia and their mitosomes are anaerobic, as is the case for other mitosome bearing eukaryotes, such as Giardia. Here we provide evidence opening the possibility that mitosomes in a number of microsporidian lineages are not completely anaerobic. Specifically, we have identified and characterized a gene encoding the alternative oxidase (AOX), a typically mitochondrial terminal oxidase in eukaryotes, in the genomes of several distantly related microsporidian species, even though this gene is absent from the complete genome of E. cuniculi. In order to confirm that these genes encode functional proteins, AOX genes from both A. locustae and T. hominis were over-expressed in E. coli and AOX activity measured spectrophotometrically using ubiquinol-1 (UQ-1) as substrate. Both A. locustae and T. hominis AOX proteins reduced UQ-1 in a cyanide and antimycin-resistant manner that was sensitive to ascofuranone, a potent inhibitor of the trypanosomal AOX. The physiological role of AOX microsporidia may be to reoxidise reducing equivalents produced by glycolysis, in a manner comparable to that observed in trypanosomes.
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Affiliation(s)
- Bryony A. P. Williams
- School of Biosciences, Geoffrey Pope Building, University of Exeter, Exeter, Devon, United Kingdom
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Catherine Elliot
- Department of Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Lena Burri
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yasutoshi Kido
- Department of Biomedical Chemistry, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Anthony L. Moore
- Department of Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Patrick J. Keeling
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
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Albury MS, Elliott C, Moore AL. Towards a structural elucidation of the alternative oxidase in plants. PHYSIOLOGIA PLANTARUM 2009; 137:316-27. [PMID: 19719482 DOI: 10.1111/j.1399-3054.2009.01270.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In addition to the conventional cytochrome c oxidase, mitochondria of all plants studied to date contain a second cyanide-resistant terminal oxidase or alternative oxidase (AOX). The AOX is located in the inner mitochondrial membrane and branches from the cytochrome pathway at the level of the quinone pool. It is non-protonmotive and couples the oxidation of ubiquinone to the reduction of oxygen to water. For many years, the AOX was considered to be confined to plants, fungi and a small number of protists. Recently, it has become apparent that the AOX occurs in wide range of organisms including prokaryotes and a moderate number of animal species. In this paper, we provide an overview of general features and current knowledge available about the AOX with emphasis on structure, the active site and quinone-binding site. Characterisation of the AOX has advanced considerably over recent years with information emerging about the role of the protein, regulatory regions and functional sites. The large number of sequences available is now enabling us to obtain a clearer picture of evolutionary origins and diversity.
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Affiliation(s)
- Mary S Albury
- Division of Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton BN19QG, UK
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44
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McDonald AE. Alternative oxidase: what information can protein sequence comparisons give us? PHYSIOLOGIA PLANTARUM 2009; 137:328-341. [PMID: 19493309 DOI: 10.1111/j.1399-3054.2009.01242.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The finding that alternative oxidase (AOX) is present in most kingdoms of life has resulted in a large number of AOX sequences that are available for analyses. Multiple sequence alignments of AOX proteins from evolutionarily divergent organisms represent a valuable tool and can be used to identify amino acids and domains that may play a role in catalysis, membrane association and post-translational regulation, especially when these data are coupled with the structural model for the enzyme. I validate the use of this approach by demonstrating that it detects the conserved glutamate and histidine residues in AOX that initially led to its identification as a di-iron carboxylate protein and the generation of a structural model for the protein. A comparative analysis using a larger dataset identified 35 additional amino acids that are conserved in all AOXs examined, 30 of which have not been investigated to date. I hypothesize that these residues will be involved in the quinol terminal oxidase activity or membrane association of AOX. Major differences in AOX protein sequences between kingdoms are revealed, and it is hypothesized that two angiosperm-specific domains may be responsible for the non-covalent dimerization of AOX, whereas two indels in the aplastidic AOXs may play a role in their post-translational regulation. A scheme for predicting whether a particular AOX protein will be recognized by the alternative oxidase monoclonal antibody generated against the AOX of Sauromatum guttatum (Voodoo lily) is presented. The number of functional sites in AOX is greater than expected, and determining the structure of AOX will prove extremely valuable to future research.
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Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, 1151 Richmond St. N., London, Ontario N6A5B7, Canada.
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45
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Ito-Inaba Y, Hida Y, Inaba T. What is critical for plant thermogenesis? Differences in mitochondrial activity and protein expression between thermogenic and non-thermogenic skunk cabbages. PLANTA 2009; 231:121-130. [PMID: 19859730 DOI: 10.1007/s00425-009-1034-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 10/06/2009] [Indexed: 05/28/2023]
Abstract
Thermogenesis during the blooming of inflorescence is found in several but not all aroids. To understand what is critical for thermogenesis, we investigated the difference between thermogenic and non-thermogenic skunk cabbages (Symplocarpus renifolius and Lysichiton camtschatcensis), which are closely related in morphology and phylogeny. Critical parameters of mitochondrial biogenesis, including density, respiratory activity, and protein expression were compared between these two species. Mitochondrial density, respiratory activity, and the amount of alternative oxidase (AOX) in L. camtschatcensis spadix mitochondria were lower than in S. renifolius spadix mitochondria, while the level of uncoupling protein (UCP) was higher. AOX and UCP mRNAs in L. camtschatcensis were constitutively expressed in various tissues, such as the spadix, the spathe, the stalk, and the leaves. cDNA encoding two putative thermogenic proteins, AOX and UCP were isolated from L. camtschatcensis, and their primary structure was analyzed by multiple alignment and phylogenetic tree reconstruction. AOX and UCP protein of two the skunk cabbage species are closely related in structure, compared with other isoforms in thermogenic plants. Our results suggest that mitochondrial density, respiratory activity, and protein expression, rather than the primary structure of AOX or UCP proteins, may play critical roles in thermogenesis in plants.
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Affiliation(s)
- Yasuko Ito-Inaba
- Cryobiofrontier Research Center, Iwate University, Morioka, 020-8550, Japan.
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46
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Dassa EP, Dufour E, Goncalves S, Jacobs HT, Rustin P. The alternative oxidase, a tool for compensating cytochrome c oxidase deficiency in human cells. PHYSIOLOGIA PLANTARUM 2009; 137:427-434. [PMID: 19493305 DOI: 10.1111/j.1399-3054.2009.01248.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In plants as well as in a number of micro-organisms, and in several animal phyla, but not in mammals, the alternative oxidase (AOX) possibly by-passes the cytochrome segment of the respiratory chain. The AOX is located at the inner surface of the inner mitochondrial membrane, being activated by over-reduction of the quinone pool and accumulation of keto-acids such as pyruvate. Since these conditions are frequently encountered in patients with mitochondrial diseases, we hypothesized that the expression of the ascidian Ciona intestinalis AOX might alleviate the consequences of a blockade of the cytochrome segment of the respiratory chain in human cells. We previously expressed the C. intestinalis AOX in human embryonic kidney (HEK 293-T-derived) cells conferring cyanide-resistance to cell respiration without any detectable detrimental effect (Hakkaart et al. 2006). We have now expressed the AOX in human cultured fibroblasts either with a functional respiratory chain (foreskin immortalized fibroblasts, BJ1-htert) or presenting a cytochrome c oxidase deficiency resulting from an impaired heme aa3 biogenesis. We used immortalized COX15-deficient skin fibroblasts from a patient who died from an early fatal cardiomyopathy. We found that the expression of the AOX in these cells was well tolerated and corrected for the various consequences of the cytochrome c oxidase deficiency in COX15-mutant cells, i.e. decreased cell respiration, glucose and pyruvate dependency. We thus validated our hypothesis that AOX could compensate for cytochrome c oxidase deficiency in human cells.
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Affiliation(s)
- Emmanuel P Dassa
- Inserm, U676 and Université Paris 7, Faculté de Médecine Denis Diderot, Paris, France
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47
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Maréchal A, Kido Y, Kita K, Moore AL, Rich PR. Three redox states of Trypanosoma brucei alternative oxidase identified by infrared spectroscopy and electrochemistry. J Biol Chem 2009; 284:31827-33. [PMID: 19767647 DOI: 10.1074/jbc.m109.059980] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Electrochemistry coupled with Fourier transform infrared (IR) spectroscopy was used to investigate the redox properties of recombinant alternative ubiquinol oxidase from Trypanosoma brucei, the organism responsible for African sleeping sickness. Stepwise reduction of the fully oxidized resting state of recombinant alternative ubiquinol oxidase revealed two distinct IR redox difference spectra. The first of these, signal 1, titrates in the reductive direction as an n = 2 Nernstian component with an apparent midpoint potential of 80 mV at pH 7.0. However, reoxidation of signal 1 in the same potential range under anaerobic conditions did not occur and only began with potentials in excess of 500 mV. Reoxidation by introduction of oxygen was also unsuccessful. Signal 1 contained clear features that can be assigned to protonation of at least one carboxylate group, further perturbations of carboxylic and histidine residues, bound ubiquinone, and a negative band at 1554 cm(-1) that might arise from a radical in the fully oxidized protein. A second distinct IR redox difference spectrum, signal 2, appeared more slowly once signal 1 had been reduced. This component could be reoxidized with potentials above 100 mV. In addition, when both signals 1 and 2 were reduced, introduction of oxygen caused rapid oxidation of both components. These data are interpreted in terms of the possible active site structure and mechanism of oxygen reduction to water.
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Affiliation(s)
- Amandine Maréchal
- Glynn Laboratory of Bioenergetics, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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48
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Fu A, Aluru M, Rodermel SR. Conserved active site sequences in Arabidopsis plastid terminal oxidase (PTOX): in vitro and in planta mutagenesis studies. J Biol Chem 2009; 284:22625-32. [PMID: 19542226 PMCID: PMC2755669 DOI: 10.1074/jbc.m109.017905] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/16/2009] [Indexed: 11/06/2022] Open
Abstract
The plastid terminal oxidase (PTOX) is distantly related to the mitochondrial alternative oxidase (AOX). Both are members of the diiron carboxylate quinol oxidase (DOX) class of proteins. PTOX and AOX contain 20 highly conserved amino acids, six of which are Fe-binding ligands. We have previously used in vitro and in planta activity assays to examine the functional importance of the Fe-binding sites. In this report, we conduct alanine-scanning mutagenesis on the 14 other conserved sites using our in vitro and in planta assay procedures. We found that the 14 sites fall into three classes: (i) Ala-139, Pro-142, Glu-171, Asn-174, Leu-179, Pro-216, Ala-230, Asp-287, and Arg-293 are dispensable for activity; (ii) Tyr-234 and Asp-295 are essential for activity; and (iii) Leu-135, His-151, and Tyr-212 are important but not essential for activity. Our data are consistent with the proposed role of some of these residues in active site conformation, substrate binding, and/or catalysis. Titration experiments showed that down-regulation of PTOX to approximately 3% of wild-type levels did not compromise plant growth, at least under ambient growth conditions. This suggests that PTOX is normally in excess, especially early in thylakoid membrane biogenesis.
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Affiliation(s)
- Aigen Fu
- From the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa 50011
| | - Maneesha Aluru
- From the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa 50011
| | - Steven R. Rodermel
- From the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa 50011
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49
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A novel functional element in the N-terminal region of Arum concinnatum alternative oxidase is indispensable for catalytic activity of the enzyme in HeLa cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1797:20-8. [PMID: 19643077 DOI: 10.1016/j.bbabio.2009.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 07/14/2009] [Accepted: 07/21/2009] [Indexed: 11/20/2022]
Abstract
Alternative oxidase (AOX) is a quinol-oxygen oxidoreductase, which is known to possess a dicarboxylate diiron reaction center held in structurally postulated alpha-helical bundle. However, little is known about the structural or functional features of its N-terminal region in any organism, with the exception of a regulatory cysteine residue (CysI) in angiosperm plants. Here, we show that transcripts of two AOX1 isozymes (AcoAOX1a and AcoAOX1b) are coexpressed in thermogenic appendices of Arum concinnatum, while their enzymatic activities seem to be distinct. Namely, AcoAOX1a, an abundantly expressed transcript in vivo, shows an apparent cyanide-insensitive and n-propyl gallate-sensitive respiration during ectopic expression of the protein in HeLa cells, whereas AcoAOX1b exhibits a lower transcript expression, and appears to be totally inactive as AOX at the protein level. Our functional analyses further reveal that an E83K substitution in AcoAOX1b, which is located far upstream of CysI in the N-terminal region, is the cause of this loss of function. These results suggest the presence of a naturally occurring inactive AOX homologue in thermogenic plants. Accordingly, our results further imply that the N-terminal region of the AOX protein functionally contributes to the dynamic activities of respiratory control within the mitochondria.
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50
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Grant N, Onda Y, Kakizaki Y, Ito K, Watling J, Robinson S. Two cys or not two cys? That is the question; alternative oxidase in the thermogenic plant sacred Lotus. PLANT PHYSIOLOGY 2009; 150:987-95. [PMID: 19386803 PMCID: PMC2689982 DOI: 10.1104/pp.109.139394] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 04/13/2009] [Indexed: 05/05/2023]
Abstract
Sacred lotus (Nelumbo nucifera) regulates temperature in its floral chamber to 32 degrees C to 35 degrees C across ambient temperatures of 8 degrees C to 40 degrees C with heating achieved through high alternative pathway fluxes. In most alternative oxidase (AOX) isoforms, two cysteine residues, Cys(1) and Cys(2), are highly conserved and play a role in posttranslational regulation of AOX. Further control occurs via interaction of reduced Cys(1) with alpha-keto acids, such as pyruvate. Here, we report on the in vitro regulation of AOX isolated from thermogenic receptacle tissues of sacred lotus. AOX protein was mostly present in the reduced form, and only a small fraction could be oxidized with diamide. Cyanide-resistant respiration in isolated mitochondria was stimulated 4-fold by succinate but not pyruvate or glyoxylate. Insensitivity of the alternative pathway of respiration to pyruvate and the inability of AOX protein to be oxidized by diamide suggested that AOX in these tissues may lack Cys(1). Subsequently, we isolated two novel cDNAs for AOX from thermogenic tissues of sacred lotus, designated as NnAOX1a and NnAOX1b. Deduced amino acid sequences of both confirmed that Cys(1) had been replaced by serine; however, Cys(2) was present. This contrasts with AOXs from thermogenic Aroids, which contain both Cys(1) and Cys(2). An additional cysteine was present at position 193 in NnAOX1b. The significance of the sequence data for regulation of the AOX protein in thermogenic sacred lotus is discussed and compared with AOXs from other thermogenic and nonthermogenic species.
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Affiliation(s)
- Nicole Grant
- Institute for Conservation Biology, University of Wollongong, Wollongong, New South Wales 2522, Australia.
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