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Chen Y, Zou H, Yan B, Wu X, Cao W, Qian Y, Zheng L, Yang G. Atomically Dispersed Cu Nanozyme with Intensive Ascorbate Peroxidase Mimic Activity Capable of Alleviating ROS-Mediated Oxidation Damage. Adv Sci (Weinh) 2022; 9:e2103977. [PMID: 34951150 PMCID: PMC8844488 DOI: 10.1002/advs.202103977] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 11/08/2021] [Indexed: 05/03/2023]
Abstract
Ascorbate peroxidase (APX) as a crucial antioxidant enzyme has drawn attentions for its utilization in preventing cells from oxidative stress responses by efficiently scavenging H2 O2 in plants. For eliminating the specific inactivation of natural APXs and regulating the catalytic activity, single-atom nanozymes are considered as promising classes of alternatives with similar active sites and maximal atomic utilization efficiency to natural APXs. Herein, graphitic carbon nitride (g-C3 N4 ) anchored with isolated single copper atoms (Cu SAs/CN) is designed as an efficient nanozyme with intrinsic APX mimetic behavior. The engineered Cu SAs/CN exhibits comparable specific activity and kinetics to the natural APXs. Based on the density functional theory (DFT), Cu-N4 moieties in the active center of Cu SAs/CN are determined to exert such favorable APX catalytic performance, in which the electron transfer between Cu and coordinated N atoms facilitates the activation and cleavage of the adsorbed H2 O2 molecules and results in fast kinetics. The constructed Cu SAs/CN nanozyme with superior APX-like performance and high biocompatibility can be applied for effectively protecting the H2 O2 -treated cells against oxidative injury in vitro. These findings report the single-atom nanozymes as a successful paradigm for guiding nanozymes to implement APX mimetic performance for reactive oxygen species-related biotherapeutic.
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Affiliation(s)
- Yuan Chen
- State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science and EngineeringSchool of PhysicsSun Yat‐sen UniversityGuangzhouGuangdong510275P. R. China
| | - Hang Zou
- Department of Laboratory MedicineNanfang Hospital, Southern Medical University/The First School of Clinical MedicineSouthern Medical UniversityGuangzhouGuangdong510515P. R. China
| | - Bo Yan
- State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science and EngineeringSchool of PhysicsSun Yat‐sen UniversityGuangzhouGuangdong510275P. R. China
| | - Xiaoju Wu
- State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science and EngineeringSchool of PhysicsSun Yat‐sen UniversityGuangzhouGuangdong510275P. R. China
| | - Weiwei Cao
- State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science and EngineeringSchool of PhysicsSun Yat‐sen UniversityGuangzhouGuangdong510275P. R. China
| | - Yihang Qian
- State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science and EngineeringSchool of PhysicsSun Yat‐sen UniversityGuangzhouGuangdong510275P. R. China
| | - Lei Zheng
- Department of Laboratory MedicineNanfang Hospital, Southern Medical University/The First School of Clinical MedicineSouthern Medical UniversityGuangzhouGuangdong510515P. R. China
| | - Guowei Yang
- State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science and EngineeringSchool of PhysicsSun Yat‐sen UniversityGuangzhouGuangdong510275P. R. China
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Abstract
Ascorbate peroxidase (APEX)-catalyzed proximity labeling has been recently established as a robust approach to uncover localized protein environments and transient protein-protein interactions occurring across mammalian cells. This molecular tool enables improved identification of individual proteins localized to and involved in specific cellular and subcellular pathways and functions. Engineering of an APEX2 fusion protein into the endogenous loci of proteins of interest enables directed biotinylation of neighboring polypeptides and mRNAs. This results in identification of subcellular and context-dependent proteomes or transcriptomes via quantitative mass spectrometry or RNA sequencing, respectively. Here, we describe the utility of APEX-mediated proximity labeling to recover components of stress granules (SGs) by endogenous tagging of well-established SG-associated proteins.
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Affiliation(s)
- Sara Elmsaouri
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Sebastian Markmiller
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA.
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Singer-Krüger B, Jansen RP. Proteomic Mapping by APEX2-Catalyzed Proximity Labeling in Saccharomyces cerevisiae Semipermeabilized Cells. Methods Mol Biol 2022; 2477:261-274. [PMID: 35524122 DOI: 10.1007/978-1-0716-2257-5_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Enzyme-catalyzed proximity labeling (PL) has proven to be a valuable resource for proteomic mapping of subcellular compartments and protein networks in living cells. We have used engineered ascorbate peroxidase (APEX2) to develop a PL approach for budding yeast. It is based on semipermeabilized cells to overcome poor cellular permeability of the APEX2 substrate biotin-phenol and difficulties in its delivery into the cell. The use of semipermeabilized cells has several advantages, in particular the avoidance of generating fragile spheroplasts and the opportunity of employing cells from a glucose-containing medium for APEX2 tagging. In this protocol we describe how to perform a ratiometric three-state stable isotope labeling by amino acids in cell culture (SILAC) approach that allows to map an open cellular compartment like the yeast nucleus. In particular, we focus on the proteomic sample preparation and provide instructions to achieve high-resolution mapping of a subcellular yeast proteome.
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Affiliation(s)
- Birgit Singer-Krüger
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany.
| | - Ralf-Peter Jansen
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
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Ledray AP, Mittra K, Green MT. NRVS investigation of ascorbate peroxidase compound II: Observation of Iron(IV)oxo stretching. J Inorg Biochem 2021; 224:111548. [PMID: 34481347 DOI: 10.1016/j.jinorgbio.2021.111548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/07/2021] [Accepted: 07/13/2021] [Indexed: 11/18/2022]
Abstract
The protonation state of ascorbate peroxidase compound II (APX-II) has been a subject of debate. A combined X-ray/neutron crystallographic study reported that APX-II is best described as an iron(IV)hydroxide species with an FeO distance of 1.88 Å (Kwon, et al. Nat Commun2016, 7, 13,445), while X-ray absorption spectroscopy (XAS) experiments (utilizing extended X-ray absorption fine structure (EXAFS) and pre-edge analyses) indicate APX-II is an authentic iron(IV)oxo species with an FeO distance 1.68 Å (Ledray, et al. Journal of the American Chemical Society2020,142, 20,419). Previous debates concerning ferryl protonation states have been resolved through the application of Badger's rule, which correlates FeO bond distances with FeO vibrational frequencies. To obtain the required vibrational data, we have collected Nuclear Resonance Vibrational Spectroscopy (NRVS) data for APX-II. We observe a broad vibrational feature in the range associated with iron(IV)oxo stretching (700-800 cm-1). This feature appears to have two peaks at 732 cm-1 and 770 cm-1, corresponding to FeO distances of 1.69 and 1.67 Å, respectively. The broad vibrational envelope and the presence of multiple resonances could reflect a distribution of hydrogen bonding interactions within the active-site pocket.
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Affiliation(s)
- Aaron P Ledray
- Department of Chemistry, University of California, Irvine, CA 92697, USA; Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA
| | - Kaustuv Mittra
- Department of Chemistry, University of California, Irvine, CA 92697, USA; Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA
| | - Michael T Green
- Department of Chemistry, University of California, Irvine, CA 92697, USA; Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.
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Ali S, Anjum MA, Ejaz S, Hussain S, Ercisli S, Saleem MS, Sardar H. Carboxymethyl cellulose coating delays chilling injury development and maintains eating quality of 'Kinnow' mandarin fruits during low temperature storage. Int J Biol Macromol 2020; 168:77-85. [PMID: 33301851 DOI: 10.1016/j.ijbiomac.2020.12.028] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/23/2020] [Accepted: 12/04/2020] [Indexed: 02/07/2023]
Abstract
The application of edible coatings is an efficient way to reduce mass loss and to conserve the quality of a coated fresh produce during postharvest storage. In the present research, the impact of carboxymethyl cellulose [CMC (1%] coating was studied on 'Kinnow' mandarins during cold storage at 5 ± 1 °C for 30 days. Results showed that CMC treatment substantially suppressed chilling injury symptoms, disease incidence, fresh weight loss, malondialdehyde content, hydrogen peroxide and electrolyte leakage compared with control. The CMC coated 'Kinnow' mandarins showed markedly higher ascorbate peroxidase, peroxidase, superoxide dismutase and catalase enzyme activities compared to control. The treatment of 'Kinnow' mandarins with CMC also suppressed the increase in total soluble solids, ripening index and showed substantially higher titratable acidity, ascorbic acid, total phenolics content, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity along with better sensory quality in contrast with uncoated fruits. In conclusion, CMC coating could be an effective approach for the chilling injury reduction and quality maintenance of harvested 'Kinnow' mandarin fruits during cold storage.
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Affiliation(s)
- Sajid Ali
- Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan.
| | - Muhammad Akbar Anjum
- Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
| | - Shaghef Ejaz
- Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
| | - Sajjad Hussain
- Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
| | - Sezai Ercisli
- Department of Horticulture, Agricultural Faculty, Ataturk University, Erzurum, Turkey
| | - Muhammad Shahzad Saleem
- Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
| | - Hasan Sardar
- Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
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Kwon H, Basran J, Devos JM, Suardíaz R, van der Kamp MW, Mulholland AJ, Schrader TE, Ostermann A, Blakeley MP, Moody PCE, Raven EL. Visualizing the protons in a metalloenzyme electron proton transfer pathway. Proc Natl Acad Sci U S A 2020; 117:6484-6490. [PMID: 32152099 PMCID: PMC7104402 DOI: 10.1073/pnas.1918936117] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In redox metalloenzymes, the process of electron transfer often involves the concerted movement of a proton. These processes are referred to as proton-coupled electron transfer, and they underpin a wide variety of biological processes, including respiration, energy conversion, photosynthesis, and metalloenzyme catalysis. The mechanisms of proton delivery are incompletely understood, in part due to an absence of information on exact proton locations and hydrogen bonding structures in a bona fide metalloenzyme proton pathway. Here, we present a 2.1-Å neutron crystal structure of the complex formed between a redox metalloenzyme (ascorbate peroxidase) and its reducing substrate (ascorbate). In the neutron structure of the complex, the protonation states of the electron/proton donor (ascorbate) and all of the residues involved in the electron/proton transfer pathway are directly observed. This information sheds light on possible proton movements during heme-catalyzed oxygen activation, as well as on ascorbate oxidation.
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Affiliation(s)
- Hanna Kwon
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Jaswir Basran
- Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, United Kingdom
- Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, United Kingdom
| | - Juliette M Devos
- Life Sciences Group, Institut Laue-Langevin, 38000 Grenoble, France
| | - Reynier Suardíaz
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Marc W van der Kamp
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
| | | | - Tobias E Schrader
- Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum, Forschungszentrum Jülich GmbH, 85748 Garching, Germany
| | - Andreas Ostermann
- Heinz Maier-Leibnitz Zentrum, Technische Universität München, D-85748 Garching, Germany
| | - Matthew P Blakeley
- Large-Scale Structures Group, Institut Laue-Langevin, 38000 Grenoble, France
| | - Peter C E Moody
- Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, United Kingdom;
- Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, United Kingdom
| | - Emma L Raven
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom;
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Benhalevy D, Hafner M. Proximity-CLIP Provides a Snapshot of Protein-Occupied RNA Elements at Subcellular Resolution and Transcriptome-Wide Scale. Methods Mol Biol 2020; 2166:283-305. [PMID: 32710416 DOI: 10.1007/978-1-0716-0712-1_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The distribution of messenger RNAs (mRNAs) to specific subcellular locations has been studied for the past two decades. Technically, studies of RNA localization are lagging those related to protein localization. Here we provide a detailed protocol for Proximity-CLIP, a method recently developed by our group, that combines proximity biotinylation of proteins with photoactivatable ribonucleoside-enhanced protein-RNA cross-linking to simultaneously profile the proteome including RNA-binding proteins (RBPs) and the RBP-bound transcriptome in any given subcellular compartment. The approach is fractionation independent and also enables studying localized RNA-processing intermediates, as well as the identification of regulatory cis-acting elements on RNAs occupied by proteins in a cellular compartment-specific manner.
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Affiliation(s)
- Daniel Benhalevy
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Markus Hafner
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
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Wu B, Wang B. Comparative analysis of ascorbate peroxidases (APXs) from selected plants with a special focus on Oryza sativa employing public databases. PLoS One 2019; 14:e0226543. [PMID: 31856232 PMCID: PMC6922425 DOI: 10.1371/journal.pone.0226543] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 11/29/2019] [Indexed: 12/28/2022] Open
Abstract
Reactive oxygen species (ROS) are produced by plants. Hydrogen peroxide (H2O2) is one important component of ROS and able to modulate plant growth and development at low level and damage plant cells at high concentrations. Ascorbate peroxidase (APX) shows high affinity towards H2O2 and plays vital roles in H2O2-scavenging. In order to explore the differences of APXs from selected plant species, bioinformatics methods and public databases were used to evaluate the physicochemical properties, conserved motifs, potential modifications and cis-elements in all the APXs, and protein-protein network and expression profiles of rice APXs. The results suggested that APXs in the selected plant species showed high evolutionary conservation and were able to divide into seven groups, group I to VII. Members in the groups contained abundant phosphorylation sites. Interestingly, group I and VII had only PKC site. Additionally, promoters of the APXs contained abundant stress-related cis-elements. APXs in rice plant were able to interact with dehydroascorbate reductase 2. The eight APXs expressed differently in root, leaf, panicle, anther, pistil and seed. Drought, Pi-free, Cd and Xanthomonas oryzae pv. oryzicola B8-12 treatments were able to significantly alter the expression profiles of rice APXs. This study increases our knowledge to further explore functions and mechanisms of APXs and also guides their applications.
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Affiliation(s)
- Baomei Wu
- International Center for Plant Molecular Genetics, School of Life Science, Shanxi Normal University, Linfen, PR China
- * E-mail:
| | - Binbin Wang
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China
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Liu JX, Feng K, Duan AQ, Li H, Yang QQ, Xu ZS, Xiong AS. Isolation, purification and characterization of an ascorbate peroxidase from celery and overexpression of the AgAPX1 gene enhanced ascorbate content and drought tolerance in Arabidopsis. BMC Plant Biol 2019; 19:488. [PMID: 31711410 PMCID: PMC6849298 DOI: 10.1186/s12870-019-2095-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 10/23/2019] [Indexed: 05/16/2023]
Abstract
BACKGROUND Celery is a widely cultivated vegetable abundant in ascorbate (AsA), a natural plant antioxidant capable of scavenging free radicals generated by abiotic stress in plants. Ascorbate peroxidase (APX) is a plant antioxidant enzyme that is important in the synthesis of AsA and scavenging of excess hydrogen peroxide. However, the characteristics and functions of APX in celery remain unclear to date. RESULTS In this study, a gene encoding APX was cloned from celery and named AgAPX1. The transcription level of the AgAPX1 gene was significantly upregulated under drought stress. AgAPX1 was expressed in Escherichia coli BL21 (DE3) and purified. The predicted molecular mass of rAgAPX1 was 33.16 kDa, which was verified by SDS-PAGE assay. The optimum pH and temperature for rAgAPX1 were 7.0 and 55 °C, respectively. Transgenic Arabidopsis hosting the AgAPX1 gene showed elevated AsA content, antioxidant capacity and drought resistance. Less decrease in net photosynthetic rate, chlorophyll content, and relative water content contributed to the high survival rate of transgenic Arabidopsis lines after drought. CONCLUSIONS The characteristics of APX in celery were different from that in other species. The enhanced drought resistance of overexpressing AgAPX1 in Arabidopsis may be achieved by increasing the accumulation of AsA, enhancing the activities of various antioxidant enzymes, and promoting stomatal closure. Our work provides new evidence to understand APX and its response mechanisms to drought stress in celery.
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Affiliation(s)
- Jie-Xia Liu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
| | - Kai Feng
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
| | - Ao-Qi Duan
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
| | - Hui Li
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
| | - Qing-Qing Yang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
| | - Zhi-Sheng Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
| | - Ai-Sheng Xiong
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095 China
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Sharma M, Mahajan P, Singh HP, Batish DR, Kohli RK. 24-Epibrassinolide pre-treatment reduces alkaline-induced oxidative stress in red rice seedlings. Environ Sci Pollut Res Int 2019; 26:23192-23197. [PMID: 31187379 DOI: 10.1007/s11356-019-05474-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 05/14/2019] [Indexed: 06/09/2023]
Abstract
Soil alkalinity caused by salts, such as sodium bicarbonate (NaHCO3), and the frequently associated waterlogging problems are pervasive in agriculture and have a deleterious impact on crop production. However, various plant growth regulators, including brassinosteroids, are considered to be important against different abiotic stresses experienced by plants due to drought, salinity, and heavy metal stress. We investigated the putative role of 24-epibrassinolide (EBL), an active brassinosteroid, on red rice plants experiencing alkaline stress. Seedlings were pre-treated with 0.01 μM EBL for 30 min and later, exposed to NaHCO3 (25 mM) and were sampled, 5 days after treatments. Results showed that the pre-treatment of seedlings with EBL under non-stress conditions could promote rice plant growth. Growth parameters including dry weight (DW), root and coleoptile lengths were reduced under alkaline stress, whereas EBL application reduced the level of inhibition, as compared with NaHCO3 treatment. Enhanced levels of malondialdehyde content, hydrogen peroxide, and superoxide radicals were significantly diminished by EBL pre-treatment. Moreover, pre-treatment of EBL to alkaline-treated rice seedlings largely stimulated the enzymatic activities of ascorbate peroxidase, catalase, and superoxide dismutase. Thus, the results suggest that pre-application of EBL significantly ameliorates alkaline stress in rice.
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Affiliation(s)
- Mansi Sharma
- Department of Environment Studies, Panjab University, Chandigarh, 160 014, India
| | - Priyanka Mahajan
- Department of Botany, Panjab University, Chandigarh, 160 014, India
| | - Harminder Pal Singh
- Department of Environment Studies, Panjab University, Chandigarh, 160 014, India.
| | | | - Ravinder Kumar Kohli
- Department of Botany, Panjab University, Chandigarh, 160 014, India
- Central University of Punjab, Mansa Road, Bathinda, 151 001, India
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Kabir AH, Rahman MM, Das U, Sarkar U, Roy NC, Reza MA, Talukder MR, Uddin MA. Reduction of cadmium toxicity in wheat through plasma technology. PLoS One 2019; 14:e0214509. [PMID: 30933989 PMCID: PMC6443147 DOI: 10.1371/journal.pone.0214509] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 03/14/2019] [Indexed: 01/10/2023] Open
Abstract
Cadmium (Cd) contamination in plant-derived food is a big concern. This study examines whether and how Ar/O2 and Ar/Air plasma techniques lead to Cd detoxification in wheat. Treatment with Ar/O2 and Ar/Air changed the seed surface and decreased the pH of seeds as well as the cultivation media. Generally, plants subjected to Cd treatment from seeds treated with Ar/O2and Ar/Air plasma showed considerable progress in morphology and total chlorophyll synthesis compared to Cd-treated wheat, suggesting that plasma technology is effective for Cd detoxification. Furthermore, Ar/O2 and Ar/Air plasma treated plants showed a significant decrease in root and shoot Cd concentration, which is consistent with the reduced expression of Cd transporters in the root (TaLCT1 and TaHMA2) compared with the plants not treated with plasma in response to Cd stress. This Cd inhibition is possibly accomplished by the decrease of pH reducing the bioavailability of Cd in the rhizosphere. These observations are in line with maintenance of total soluble protein along with reduced electrolyte leakage and cell death (%) in root and shoot due to Ar/O2 and Ar/Air treatments. Further, Cd-induced elevated H2O2 or oxidative damage in tissues was mainly diminished through the upregulation of antioxidant enzymes (SOD and CAT) and their corresponding genes (TaSOD and TaCAT) induced by Ar/O2 and Ar/Air plasma. Grafting results suggest that root originating nitric oxide signal possibly drives the mechanisms of Cd detoxification due to plasma treatment in wheat. These findings provide a novel and eco-friendly use of plasma technology for the mitigation of Cd toxicity in wheat plants.
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Affiliation(s)
- Ahmad Humayan Kabir
- Molecular Plant Physiology Laboratory, Department of Botany, University of Rajshahi, Rajshahi, Bangladesh
- * E-mail:
| | - Md Mosiur Rahman
- Molecular Plant Physiology Laboratory, Department of Botany, University of Rajshahi, Rajshahi, Bangladesh
| | - Urmi Das
- Molecular Plant Physiology Laboratory, Department of Botany, University of Rajshahi, Rajshahi, Bangladesh
| | - Urmi Sarkar
- Molecular Plant Physiology Laboratory, Department of Botany, University of Rajshahi, Rajshahi, Bangladesh
| | - Nepal Chandra Roy
- Plasma Science and Technology Laboratory, Department of Applied Physics and Electronic Engineering, University of Rajshahi, Rajshahi, Bangladesh
| | - Md Abu Reza
- Molecular Biology and Protein Science Laboratory, Department of Genetic Engineering and Biotechnology, University of Rajshahi, Rajshahi, Bangladesh
| | - Mamunur Rashid Talukder
- Plasma Science and Technology Laboratory, Department of Applied Physics and Electronic Engineering, University of Rajshahi, Rajshahi, Bangladesh
| | - Md Alfaz Uddin
- Department of Physics, University of Rajshahi, Rajshahi, Bangladesh
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12
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Chao WC, Lin LJ, Lu JF, Wang JS, Lin TC, Chen YH, Chen YT, Yang HC, Chou PT. Unveiling the water-associated conformational mobility in the active site of ascorbate peroxidase. Biochim Biophys Acta Gen Subj 2018; 1862:451-459. [PMID: 29104043 DOI: 10.1016/j.bbagen.2017.10.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 10/27/2017] [Accepted: 10/30/2017] [Indexed: 11/25/2022]
Abstract
We carried out comprehensive spectroscopic studies of wild type and mutants of ascorbate peroxidase (APX) to gain understanding of the conformational mobility of the active site. In this approach, three unnatural tryptophans were applied to replace the distal tryptophan (W41) in an aim to probe polarity/water environment near the edge of the heme-containing active site. 7-azatryptophan ((7-aza)Trp) is sensitive to environment polarity, while 2,7-azatryptophan ((2,7-aza)Trp) and 2,6-diazatryptophan ((2,6-aza)Trp) undergo excited-state water-catalyzed double and triple proton transfer, respectively, and are sensitive to the water network. The combination of their absorption, emission bands and the associated relaxation dynamics of these fluorescence probes, together with the Soret-band difference absorption and resonance Raman spectroscopy, lead us to unveil the water associated conformational mobility in the active site of APX. The results are suggestive of the existence of equilibrium between two different environments surrounding W41 in APX, i.e., the water-rich and water-scant forms with distinct fluorescence relaxation. Our results thus demonstrate for the first time the power of integrating multiple sensors (7-aza)Trp, (2,7-aza)Trp and (2,6-aza)Trp in probing the water environment of a specifically targeted Trp in proteins.
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Affiliation(s)
- Wei-Chih Chao
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan; School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Li-Ju Lin
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Jyh-Feng Lu
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan.
| | - Jinn-Shyan Wang
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan.
| | - Tzu-Chieh Lin
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Yi-Han Chen
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Yi-Ting Chen
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Hsiao-Ching Yang
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Pi-Tai Chou
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
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13
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Chu Q, Rathore A, Diedrich JK, Donaldson CJ, Yates JR, Saghatelian A. Identification of Microprotein-Protein Interactions via APEX Tagging. Biochemistry 2017; 56:3299-3306. [PMID: 28589727 PMCID: PMC5499098 DOI: 10.1021/acs.biochem.7b00265] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 05/17/2017] [Indexed: 02/08/2023]
Abstract
Microproteins are peptides and small proteins encoded by small open reading frames (smORFs). Newer technologies have led to the recent discovery of hundreds to thousands of new microproteins. The biological functions of a few microproteins have been elucidated, and these microproteins have fundamental roles in biology ranging from limb development to muscle function, highlighting the value of characterizing these molecules. The identification of microprotein-protein interactions (MPIs) has proven to be a successful approach to the functional characterization of these genes; however, traditional immunoprecipitation methods result in the enrichment of nonspecific interactions for microproteins. Here, we test and apply an in situ proximity tagging method that relies on an engineered ascorbate peroxidase 2 (APEX) to elucidate MPIs. The results demonstrate that APEX tagging is superior to traditional immunoprecipitation methods for microproteins. Furthermore, the application of APEX tagging to an uncharacterized microprotein called C11orf98 revealed that this microprotein interacts with nucleolar proteins nucleophosmin and nucleolin, demonstrating the ability of this approach to identify novel hypothesis-generating MPIs.
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Affiliation(s)
- Qian Chu
- Clayton
Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Annie Rathore
- Clayton
Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, United States
- Division
of Biological Sciences, University of California,
San Diego, 9500 Gilman
Drive, La Jolla, California 92093, United States
| | - Jolene K. Diedrich
- Clayton
Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, United States
- Department
of Chemical Physiology, The Scripps Research
Institute, 10550 North
Torrey Pines Road, La Jolla, California 92037, United States
| | - Cynthia J. Donaldson
- Clayton
Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, United States
| | - John R. Yates
- Department
of Chemical Physiology, The Scripps Research
Institute, 10550 North
Torrey Pines Road, La Jolla, California 92037, United States
| | - Alan Saghatelian
- Clayton
Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, United States
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14
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Chung CY, Khurana V, Yi S, Sahni N, Loh KH, Auluck PK, Baru V, Udeshi ND, Freyzon Y, Carr SA, Hill DE, Vidal M, Ting AY, Lindquist S. In Situ Peroxidase Labeling and Mass-Spectrometry Connects Alpha-Synuclein Directly to Endocytic Trafficking and mRNA Metabolism in Neurons. Cell Syst 2017; 4:242-250.e4. [PMID: 28131823 PMCID: PMC5578869 DOI: 10.1016/j.cels.2017.01.002] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 08/05/2016] [Accepted: 12/15/2016] [Indexed: 12/21/2022]
Abstract
Synucleinopathies, including Parkinson's disease (PD), are associated with the misfolding and mistrafficking of alpha-synuclein (α-syn). Here, using an ascorbate peroxidase (APEX)-based labeling method combined with mass spectrometry, we defined a network of proteins in the immediate vicinity of α-syn in living neurons to shed light on α-syn function. This approach identified 225 proteins, including synaptic proteins, proteins involved in endocytic vesicle trafficking, the retromer complex, phosphatases and mRNA binding proteins. Many were in complexes with α-syn, and some were encoded by genes known to be risk factors for PD and other neurodegenerative diseases. Endocytic trafficking and mRNA translation proteins within this spatial α-syn map overlapped with genetic modifiers of α-syn toxicity, developed in an accompanying study (Khurana et al., this issue of Cell Systems). Our data suggest that perturbation of these particular pathways is directly related to the spatial localization of α-syn within the cell. These approaches provide new avenues to systematically examine protein function and pathology in living cells.
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Affiliation(s)
- Chee Yeun Chung
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
| | - Vikram Khurana
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Ann Romney Center for Neurologic Disease, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA.
| | - Song Yi
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Nidhi Sahni
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Ken H Loh
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Pavan K Auluck
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Valeriya Baru
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Namrata D Udeshi
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Yelena Freyzon
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Steven A Carr
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - David E Hill
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Marc Vidal
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Alice Y Ting
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Susan Lindquist
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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15
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Siqueira-Silva AI, Pereira EG, Modolo LV, Lemos-Filho JP, Paiva EAS. Impact of cement dust pollution on Cedrela fissilis Vell. (Meliaceae): A potential bioindicator species. Chemosphere 2016; 158:56-65. [PMID: 27243585 DOI: 10.1016/j.chemosphere.2016.05.047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 04/07/2016] [Accepted: 05/17/2016] [Indexed: 06/05/2023]
Abstract
Considering the impacts caused to vegetation in the vicinity of cement factories, the aim of this study was to evaluate the impacts of cement dust on the structural organization and physiological/biochemical traits of Cedrela fissilis leaflets, a woody species native to tropical America. Plants were exposed to 2.5 or 5 mg cm-2 cement dust applied to the leaf surface, to the soil or simultaneously to the leaf surface and the soil.. Leaves of shoot-treated plants exhibited chlorosis, marginal and inter veins necrosis, diminished thickness, epidermal cells less turgid, cellular collapse, obstructed stomata, senescence, rolling and some abscission. In few cases, individual death was recorded. Cement dust-treated plants also presented decreased amount of photosynthetic pigments and iron (Fe) and increase in calcium (Ca) levels. The cement crust formed in leaves surface blocked from 30 to 50% of the incoming light and reduced the stomatal conductance and the potential quantum yield of photosystem II. Control or soil-treated plants did not exhibit morphophysiological changes throughout the experiment. The activity of superoxide dismutase, catalase and ascorbate peroxidase increased in leaves of plants upon treatment with 2.5 mg cm(-2) cement dust, independent of the site application. Overall, these results indicate that C. fissilis is highly sensitive to cement dust at the initial stage of development.
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Affiliation(s)
- Advanio Inácio Siqueira-Silva
- Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil
| | - Eduardo Gusmão Pereira
- Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Viçosa, Campus Florestal, 35690-000, Florestal, MG, Brazil
| | - Luzia Valentina Modolo
- Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil
| | - José Pires Lemos-Filho
- Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil
| | - Elder Antonio Sousa Paiva
- Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil.
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16
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Li Z, Zhang J, Li J, Li H, Zhang G. The Functional and Regulatory Mechanisms of the Thellungiella salsuginea Ascorbate Peroxidase 6 (TsAPX6) in Response to Salinity and Water Deficit Stresses. PLoS One 2016; 11:e0154042. [PMID: 27097028 PMCID: PMC4838305 DOI: 10.1371/journal.pone.0154042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 04/07/2016] [Indexed: 02/07/2023] Open
Abstract
Soil salinization is a resource and ecological problem in the world. Thellungiella salsuginea is becoming a new model plant because it resembles its relative species, Arabidopsis thaliana, in small genome and short life cycle. It is highly tolerant to salinity and drought stresses. Ascorbate peroxidase (APX) is an enzyme that clears H2O2 in plants. The function and molecular and regulation mechanisms of APX in T. salsuginea have rarely been reported. In this study, an APX gene, TsApx6, was cloned from T. salsuginea and its responses to abiotic stresses in transgenic Arabidopsis were studied. Under high salinity treatment, the expression of TsApx6 was significantly induced. Under drought treatment, overexpression of TsApx6 increased the survival rate and reduced leaf water loss rate in Arabidopsis. Compared to the wild type plants, high salinity treatment reduced the concentrations of MDA, H2O2 and proline but elevated the activities of APX, GPX, CAT and SOD in the TsApx6-overexpressing plants. Meanwhile, germination rate, cotyledon greening, and root length were improved in the transgenic plants compared to the wild type plants under salt and water deficit conditions. Based on these findings, TsApx6 has an important function in the resistance of plants to certain abiotic stresses. The TsApx6 promoter sequence was obtained using Genome Walking technology. Bioinformatics analysis indicated that it contains some cis-acting elements related to stress response. The treatments of salt, dehydration, and ABA induced the expression of Gus gene under the regulation of the TsApx6 promoter. Mutation analysis showed that the MBS motif present in the TsApx6 promoter might be a key negative regulatory element which has an important effect on the growth and developmental process of plants.
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Affiliation(s)
- Zeqin Li
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Jilong Zhang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Jingxiao Li
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Hongjie Li
- The National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China
- * E-mail: (GZ); (HL)
| | - Genfa Zhang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- * E-mail: (GZ); (HL)
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17
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Chen J, Liu X, Wang C, Yin SS, Li XL, Hu WJ, Simon M, Shen ZJ, Xiao Q, Chu CC, Peng XX, Zheng HL. Nitric oxide ameliorates zinc oxide nanoparticles-induced phytotoxicity in rice seedlings. J Hazard Mater 2015; 297:173-82. [PMID: 25958266 DOI: 10.1016/j.jhazmat.2015.04.077] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 04/26/2015] [Accepted: 04/27/2015] [Indexed: 05/07/2023]
Abstract
Nitric oxide (NO) has been found to function in enhancing plant tolerance to various environmental stresses. However, role of NO in relieving zinc oxide nanoparticles (ZnO NPs)-induced phytotoxicity remains unknown. Here, sodium nitroprusside (SNP, a NO donor) was used to investigate the possible roles and the regulatory mechanisms of NO in counteracting ZnO NPs toxicity in rice seedlings. Our results showed that 10 μM SNP significantly inhibited the appearance of ZnO NP toxicity symptoms. SNP addition significantly reduced Zn accumulation, reactive oxygen species production and lipid peroxidation caused by ZnO NPs. The protective role of SNP in reducing ZnO NPs-induced oxidative damage is closely related to NO-mediated antioxidant system. A decrease in superoxide dismutase activity, as well as an increase in reduced glutathione content and peroxidase, catalase and ascorbate peroxidase activity was observed under SNP and ZnO NPs combined treatments, compared to ZnO NPs treatment alone. The relative transcript abundance of corresponding antioxidant genes exhibited a similar change. The role of NO in enhancing ZnO NPs tolerance was further confirmed by genetic analysis using a NO excess mutant (noe1) and an OsNOA1-silenced plant (noa1) of rice. Together, this study provides the first evidence indicating that NO functions in ameliorating ZnO NPs-induced phytotoxicity.
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Affiliation(s)
- Juan Chen
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China; State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xiang Liu
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China
| | - Chao Wang
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Shan-Shan Yin
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China
| | - Xiu-Ling Li
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China
| | - Wen-Jun Hu
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China; Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang Province 310021, China
| | - Martin Simon
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China
| | - Zhi-Jun Shen
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China
| | - Qiang Xiao
- Laboratory of Biological Resources Protection and Utilization of Hubei Province, Hubei Institutes for Nationalities, Enshi, Hubei 445000, China
| | - Cheng-Cai Chu
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xin-Xiang Peng
- College of Life Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Hai-Lei Zheng
- Key Laboratory for Subtropical Wetland Ecosystem Research of MOE, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, China.
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18
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Zhao Y, Yang KJ, Li ZT, Zhao CJ, Xu JY, Hu XW, Shi XX, Ma LF. [Alleviation of salt stress during maize seed germination by presoaking with exogenous sugar]. Ying Yong Sheng Tai Xue Bao 2015; 26:2735-2742. [PMID: 26785556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The maize variety Kenyu 6 was used to study the effects of exogenous glucose (Glc) and sucrose (Suc) on salt tolerance of maize seeds at germination stage under 150 mmol · L(-1) NaCl treatment. Results showed that under salt stress condition, 0.5 mmol · L(-1) exogenous Glc and Suc presoaking could promote seed germination and early seedling growth. Compared with the salt treatment, Glc presoaking increased the shoot length, radicle length and corresponding dry mass up to 1.5, 1.3, 2.1 and 1.8 times, and those of the Suc presoaking treatment increased up to 1.7, 1.3. 2.7 and 1.9 times, respectively. Exogenous Glc and Suc presoaking resulted in decreased levels of thiobarbituric acid reactive substances (TBARS) and hydrogen peroxide (H2O2) content of maize shoot under salt stress, which were lowered by 24.9% and 20.6% respectively. Exogenous Glc and Suc presoaking could increase the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR) and induce glucose-6-phosphate dehydrogenase (G6PDH) activity of maize shoot under salt stress. Compared with the salt treatment. Glc presoaking increased the activity of SOD, APX, GPX, GR and G6PDH by 66.2%, 62.9%, 32.0%, 38.5% and 50.5%, and those of the Suc presoaking increased by 67.5%, 59.8%, 30.0%, 38.5% and 50.4%, respectively. Glc and Suc presoaking also significantly increased the contents of ascorbic acid (ASA) and glutathione (GSH), ASA/DHA and GSH/GSSG. The G6PDH activity was found closely related with the strong antioxidation capacity induced by exogenous sugars. In addition, Glc and Suc presoaking enhanced K+/Na+ in maize shoot by 1.3 and 1.4 times of water soaking salt treatment, respectively. These results indicated that exogenous Glc and Suc presoaking could improve antioxidation capacity of maize seeds and maintain the in vivo K+/Na+ ion balance to alleviate the inhibitory effect of salt stress on maize seed germination.
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19
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Kwak MK, Song SH, Ku M, Kang SO. Candida albicans erythroascorbate peroxidase regulates intracellular methylglyoxal and reactive oxygen species independently of D-erythroascorbic acid. FEBS Lett 2015; 589:1863-71. [PMID: 25957768 DOI: 10.1016/j.febslet.2015.04.050] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 04/12/2015] [Accepted: 04/22/2015] [Indexed: 11/18/2022]
Abstract
Candida albicans D-erythroascorbate peroxidase (EAPX1), which can catalyze the oxidation of D-erythroascorbic acid (EASC) to water, was observed to be inducible in EAPX1-deficient and EAPX1-overexpressing cells via activity staining. EAPX1-deficient cells have remarkably increased intracellular reactive oxygen species and methylglyoxal independent of the intracellular EASC content. The increased methylglyoxal caused EAPX1-deficient cells to activate catalase-peroxidase and cytochrome c peroxidase, which led to defects in cell growth, viability, mitochondrial respiration, filamentation and virulence. These findings indicate that EAPX1 mediates cell differentiation and virulence by regulating intracellular methylglyoxal along with oxidative stresses, regardless of endogenous EASC biosynthesis or alternative oxidase expression.
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Affiliation(s)
- Min-Kyu Kwak
- Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea
| | - Sung-Hyun Song
- Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea
| | - MyungHee Ku
- Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea
| | - Sa-Ouk Kang
- Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea.
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20
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Aroca Á, Serna A, Gotor C, Romero LC. S-sulfhydration: a cysteine posttranslational modification in plant systems. Plant Physiol 2015; 168:334-42. [PMID: 25810097 PMCID: PMC4424021 DOI: 10.1104/pp.15.00009] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 03/24/2015] [Indexed: 05/20/2023]
Abstract
Hydrogen sulfide is a highly reactive molecule that is currently accepted as a signaling compound. This molecule is as important as carbon monoxide in mammals and hydrogen peroxide in plants, as well as nitric oxide in both eukaryotic systems. Although many studies have been conducted on the physiological effects of hydrogen sulfide, the underlying mechanisms are poorly understood. One of the proposed mechanisms involves the posttranslational modification of protein cysteine residues, a process called S-sulfhydration. In this work, a modified biotin switch method was used for the detection of Arabidopsis (Arabidopsis thaliana) proteins modified by S-sulfhydration under physiological conditions. The presence of an S-sulfhydration-modified cysteine residue on cytosolic ascorbate peroxidase was demonstrated using liquid chromatography-tandem mass spectrometry analysis, and a total of 106 S-sulfhydrated proteins were identified. Immunoblot and enzyme activity analyses of some of these proteins showed that the sulfide added through S-sulfhydration reversibly regulates the functions of plant proteins in a manner similar to that described in mammalian systems.
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Affiliation(s)
- Ángeles Aroca
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla, 41092 Seville, Spain (A.A., C.G., L.C.R.); andAB Sciex, 28108 Alcobendas, Madrid, Spain (A.S.)
| | - Antonio Serna
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla, 41092 Seville, Spain (A.A., C.G., L.C.R.); andAB Sciex, 28108 Alcobendas, Madrid, Spain (A.S.)
| | - Cecilia Gotor
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla, 41092 Seville, Spain (A.A., C.G., L.C.R.); andAB Sciex, 28108 Alcobendas, Madrid, Spain (A.S.)
| | - Luis C Romero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla, 41092 Seville, Spain (A.A., C.G., L.C.R.); andAB Sciex, 28108 Alcobendas, Madrid, Spain (A.S.)
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21
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Pasqualetti CB, Sandrin CZ, Pedroso ANV, Domingos M, Figueiredo-Ribeiro RCL. Fructans, ascorbate peroxidase, and hydrogen peroxide in ryegrass exposed to ozone under contrasting meteorological conditions. Environ Sci Pollut Res Int 2015; 22:4771-4779. [PMID: 25583262 DOI: 10.1007/s11356-014-3965-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 12/08/2014] [Indexed: 06/04/2023]
Abstract
Ozone (O3) is the most abundant tropospheric oxidant as well as an important component of photochemical pollution. Once inside the plant, ozone can produce reactive oxygen species that change the antioxidative pool and the carbohydrate metabolism. The current study aimed to analyze whether the contents and the composition of the fructan, the ascorbate peroxidase activity, and the H2O2 accumulation were changed in Lolium multiflorum ssp. italicum cv. Lema plants as response to short-term exposure to ozone and/or to different meteorological conditions, in two contrasting seasons (winter and summer). Results showed that higher solar radiation tends to decrease fructose content and, along with temperature, increases the ascorbate peroxidase (APX) activity. Such activity and levels of fructans practically did not vary during the time the experiment was being done, but APX daylight variation was modified by the ozone. Thus, the higher levels of this pollutant decreased the APX activity and increased fructose content, as well as changed the size of the fructan chains. Hydrogen peroxide (H2O2) accumulation was higher in plants that were fumigated with ozone when compared to the control, and it decreased throughout the day. As a conclusion, fructan contents increased when the APX activity decreased. It suggested that fructans could also help the defense system when there is a reduction on the APX activity in the plant.
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Affiliation(s)
- C B Pasqualetti
- Núcleo de Pesquisa em Ecologia, Instituto de Botânica, Caixa Postal 68041, 04045-972, São Paulo, SP, Brazil
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22
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Siddiqui MH, Al-Whaibi MH, Faisal M, Al Sahli AA. Nano-silicon dioxide mitigates the adverse effects of salt stress on Cucurbita pepo L. Environ Toxicol Chem 2014; 33:2429-37. [PMID: 25066835 DOI: 10.1002/etc.2697] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 04/28/2014] [Accepted: 07/22/2014] [Indexed: 05/18/2023]
Abstract
Research into nanotechnology, an emerging science, has advanced in almost all fields of technology. The aim of the present study was to evaluate the role of nano-silicon dioxide (nano-SiO2 ) in plant resistance to salt stress through improvement of the antioxidant system of squash (Cucurbita pepo L. cv. white bush marrow). Seeds treated with NaCl showed reduced germination percentage, vigor, length, and fresh and dry weights of the roots and shoots. However, nano-SiO2 improved seed germination and growth characteristics by reducing malondialdehyde and hydrogen peroxide levels as well as electrolyte leakage. In addition, application of nano-SiO2 reduced chlorophyll degradation and enhanced the net photosynthetic rate (Pn ), stomatal conductance (gs ), transpiration rate, and water use efficiency. The increase in plant germination and growth characteristics through application of nano-SiO2 might reflect a reduction in oxidative damage as a result of the expression of antioxidant enzymes, such as catalase, peroxidase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase. These results indicate that nano-SiO2 may improve defense mechanisms of plants against salt stress toxicity by augmenting the Pn , gs , transpiration rate, water use efficiency, total chlorophyll, proline, and carbonic anhydrase activity in the leaves of plants.
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Affiliation(s)
- Manzer H Siddiqui
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
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23
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Xi JF, Tang L, Zhang JH, Zhang HJ, Chen XS, Mao ZG. [Characterization of structural change of ascorbate peroxidase from Chinese kale during denaturation by circular dichroism]. Guang Pu Xue Yu Guang Pu Fen Xi 2014; 34:3062-3065. [PMID: 25752058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Circular dichroism (CD) is a special absorption spectrum. The secondary structure of protein such as α-helix, β-sheet and β-turn in the far ultraviolet region (190-250 nm) has a characteristic CD spectrum. In order to understand the activity and structural changes of ascorbate peroxidase from Chinese kale (BaAPX) during denaturation, specific activity and percentage of secondary structure of BaAPX under different time, temperature and concentration were analyzed by CD dynamically. In addition, the percentage of four secondary structures in BaAPX was calculated by CD analysis software Dichroweb. The results show that BaAPX is a full α-type enzyme whose specific activity is positively related to the percentage of α-helix. During denaturation of BaAPX, three kinds of structural changes were proposed: the one-step structural change from initial state (N state) to minimum state of α-helix (R state) under low concentration and low temperature; the one-step structural change from N state to equilibrium state (T state) under high concentration and low temperature; the two-step structural changes from N state through R state to final T state under heat treatment and low temperature renaturation.
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24
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Liu HC, Tian DQ, Liu JX, Ma GY, Zou QC, Zhu ZJ. Cloning and functional analysis of a novel ascorbate peroxidase (APX) gene from Anthurium andraeanum. J Zhejiang Univ Sci B 2013; 14:1110-20. [PMID: 24302711 PMCID: PMC3863369 DOI: 10.1631/jzus.b1300105] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 08/09/2013] [Indexed: 11/11/2022]
Abstract
An 888-bp full-length ascorbate peroxidase (APX) complementary DNA (cDNA) gene was cloned from Anthurium andraeanum, and designated as AnAPX. It contains a 110-bp 5'-noncoding region, a 28-bp 3'-noncoding region, and a 750-bp open reading frame (ORF). This protein is hydrophilic with an aliphatic index of 81.64 and its structure consisting of α-helixes, β-turns, and random coils. The AnAPX protein showed 93%, 87%, 87%, 87%, and 86% similarities to the APX homologs from Zantedeschia aethiopica, Vitis pseudoreticulata, Gossypium hirsutum, Elaeis guineensis, and Zea mays, respectively. AnAPX gene transcript was measured non-significantly in roots, stems, leaves, spathes, and spadices by real-time polymerase chain reaction (RT-PCR) analysis. Interestingly, this gene expression was remarkably up-regulated in response to a cold stress under 6 °C, implying that AnAPX might play an important role in A. andraeanum tolerance to cold stress. To confirm this function we overexpressed AnAPX in tobacco plants by transformation with an AnAPX expression construct driven by CaMV 35S promoter. The transformed tobacco seedlings under 4 °C showed less electrolyte leakage (EL) and malondialdehyde (MDA) content than the control. The content of MDA was correlated with chilling tolerance in these transgenic plants. These results show that AnAPX can prevent the chilling challenged plant from cell membrane damage and ultimately enhance the plant cold tolerance.
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Affiliation(s)
- Hui-chun Liu
- College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
- Research & Development Center of Flower, Zhejiang Academy of Agricultural Sciences, Hangzhou 311202, China
| | - Dan-qing Tian
- Research & Development Center of Flower, Zhejiang Academy of Agricultural Sciences, Hangzhou 311202, China
| | - Jian-xin Liu
- Research & Development Center of Flower, Zhejiang Academy of Agricultural Sciences, Hangzhou 311202, China
| | - Guang-ying Ma
- Research & Development Center of Flower, Zhejiang Academy of Agricultural Sciences, Hangzhou 311202, China
| | - Qing-cheng Zou
- Research & Development Center of Flower, Zhejiang Academy of Agricultural Sciences, Hangzhou 311202, China
| | - Zhu-jun Zhu
- College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
- School of Agricultural and Food Science, Zhejiang A&F University, Lin’an 311300, China
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25
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Camillo LR, Filadelfo CR, Monzani PS, Corrêa RX, Gramacho KP, Micheli F, Pirovani CP. Tc-cAPX, a cytosolic ascorbate peroxidase of Theobroma cacao L. engaged in the interaction with Moniliophthora perniciosa, the causing agent of witches' broom disease. Plant Physiol Biochem 2013; 73:254-265. [PMID: 24161755 DOI: 10.1016/j.plaphy.2013.10.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 10/04/2013] [Indexed: 06/02/2023]
Abstract
The level of hydrogen peroxide (H2O2) in plants signalizes the induction of several genes, including that of ascorbate peroxidase (APX-EC 1.11.1.11). APX isoenzymes play a central role in the elimination of intracellular H2O2 and contribute to plant responses to diverse stresses. During the infection process in Theobroma cacao by Moniliophthora perniciosa oxidative stress is generated and the APX action recruited from the plant. The present work aimed to characterize the T. cacao APX involved in the molecular interaction of T. cacao-M. perniciosa. The peroxidase activity was analyzed in protein extracts from cocoa plants infected by M. perniciosa and showed the induction of peroxidases like APX in resistant cocoa plants. The cytosolic protein of T. cacao (GenBank: ABR68691.2) was phylogenetically analyzed in relation to other peroxidases from the cocoa genome and eight genes encoding APX proteins with conserved domains were also analyzed. The cDNA from cytosolic APX was cloned in pET28a and the recombinant protein expressed and purified (rTc-cAPX). The secondary structure of the protein was analyzed by Circular Dichroism (CD) displaying high proportion of α-helices when folded. The enzymatic assay shows stable activity using ascorbate and guaiacol as an electron donor for H2O2 reduction. The pH 7.5 is the optimum for enzyme activity. Chromatographic analysis suggests that rTc-cAPX is a homodimer in solution. Results indicate that the rTc-cAPX is correctly folded, stable and biochemically active. The purified rTc-cAPX presented biotechnological potential and is adequate for future structural and functional studies.
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Affiliation(s)
- Luciana Rodrigues Camillo
- Centro de Biotecnologia e Genética, Universidade Estadual de Santa Cruz - UESC, Rodovia Jorge Amado Km 16, 45662-900 Ilhéus, BA, Brazil
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26
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Abstract
We have previously demonstrated (Badyal et al., J. Biol. Chem., 2006, 281, 24512) that removal of the active site tryptophan (Trp41) in ascorbate peroxidase increases the conformational mobility of the distal histidine residue (His42) and that His42 coordinates to the iron in the oxidised W41A enzyme to give a 6-coordinate, low-spin peroxidase. In this work, we probe the conformational flexibility of the active site in more detail. We examine whether other residues (Cys, Tyr, Met) can also ligate to the heme at position 42; we find that introduction of other ligating amino acids created a cavity in the heme pocket, but that formation of 6-coordinate heme is not observed. In addition, we examine the role of Asn-71, which hydrogen bonds to His42 and tethers the distal histidine in the active site pocket; we find that removal of this hydrogen bond increases the proportion of low-spin heme. We suggest that, in addition to its well-known role in facilitating the reaction with peroxide, His42 also plays a role in defining the shape and folding of the active site pocket.
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Affiliation(s)
| | - Andrea Guimero
- Department of Chemistry, University of Leicester, University Road, Leicester, LE1 9HN, England, UK
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Hoque MA, Uraji M, Torii A, Banu MNA, Mori IC, Nakamura Y, Murata Y. Methylglyoxal inhibition of cytosolic ascorbate peroxidase from Nicotiana tabacum. J Biochem Mol Toxicol 2012; 26:315-21. [PMID: 22696433 DOI: 10.1002/jbt.21423] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 05/02/2012] [Accepted: 05/15/2012] [Indexed: 01/29/2023]
Abstract
Methylglyoxal (MG) is one of the aldehydes accumulated in plants under environmental stress. Cytosolic ascorbate peroxidase (cAPX) plays a key role in the protection of cells from oxidative damage by scavenging reactive oxygen species in higher plants. A cDNA encoding cAPX, named NtcAPX, was isolated from Nicotiana tabacum. We characterized recombinant NtcAPX (rNtcAPX) as a fusion protein with glutathione S-transferase to investigate the effects of MG on APX. NtcAPX consists of 250 amino acids and has a deduced molecular mass of 27.5 kDa. The rNtcAPX showed a higher APX activity. MG treatments resulted in a reduction of APX activity and modifications of amino groups in rNtcAPX with increasing K(m) for ascorbate. On the contrary, neither NaCl nor cadmium reduced the activity of APX. The present study suggests that inhibition of APX is in part due to the modification of amino acids by MG.
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Affiliation(s)
- Md Anamul Hoque
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
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Efimov I, Badyal SK, Metcalfe CL, Macdonald I, Gumiero A, Raven EL, Moody PCE. Proton delivery to ferryl heme in a heme peroxidase: enzymatic use of the Grotthuss mechanism. J Am Chem Soc 2011; 133:15376-83. [PMID: 21819069 DOI: 10.1021/ja2007017] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We test the hypothesized pathway by which protons are passed from the substrate, ascorbate, to the ferryl oxygen in the heme enzyme ascorbate peroxidase (APX). The role of amino acid side chains and bound solvent is demonstrated. We investigated solvent kinetic isotope effects (SKIE) for the wild-type enzyme and several site-directed replacements of the key residues which form the proposed proton path. Kinetic constants for H(2)O(2)-dependent enzyme oxidation to Compound I, k(1), and subsequent reduction of Compound II, k(3), were determined in steady-state assays by variation of both H(2)O(2) and ascorbate concentrations. A high value of the SKIE for wild type APX ((D)k(3) = 4.9) as well as a clear nonlinear dependence on the deuterium composition of the solvent in proton inventory experiments suggest the simultaneous participation of several protons in the transition state for proton transfer. The full SKIE and the proton inventory data were modeled by applying Gross-Butler-Swain-Kresge theory to a proton path inferred from the known structure of APX. The model has been tested by constructing and determining the X-ray structures of the R38K and R38A variants and accounts for their observed SKIEs. This work confirms APX uses two arginine residues in the proton path. Thus, Arg38 and Arg172 have dual roles, both in the formation of the ferryl species and binding of ascorbate respectively and to facilitate proton transfer between the two.
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Affiliation(s)
- Igor Efimov
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, England
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