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Iglesias R, Citores L, Gay CC, Ferreras JM. Antifungal Activity of Ribosome-Inactivating Proteins. Toxins (Basel) 2024; 16:192. [PMID: 38668617 PMCID: PMC11054410 DOI: 10.3390/toxins16040192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/04/2024] [Accepted: 04/12/2024] [Indexed: 04/29/2024] Open
Abstract
The control of crop diseases caused by fungi remains a major problem and there is a need to find effective fungicides that are environmentally friendly. Plants are an excellent source for this purpose because they have developed defense mechanisms to cope with fungal infections. Among the plant proteins that play a role in defense are ribosome-inactivating proteins (RIPs), enzymes obtained mainly from angiosperms that, in addition to inactivating ribosomes, have been studied as antiviral, fungicidal, and insecticidal proteins. In this review, we summarize and discuss the potential use of RIPs (and other proteins with similar activity) as antifungal agents, with special emphasis on RIP/fungus specificity, possible mechanisms of antifungal action, and the use of RIP genes to obtain fungus-resistant transgenic plants. It also highlights the fact that these proteins also have antiviral and insecticidal activity, which makes them very versatile tools for crop protection.
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Affiliation(s)
- Rosario Iglesias
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain; (R.I.); (L.C.)
| | - Lucía Citores
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain; (R.I.); (L.C.)
| | - Claudia C. Gay
- Laboratory of Protein Research, Institute of Basic and Applied Chemistry of Northeast Argentina (UNNE-CONICET), Faculty of Exact and Natural Sciences and Surveying, Av. Libertad 5470, Corrientes 3400, Argentina;
| | - José M. Ferreras
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain; (R.I.); (L.C.)
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2
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Patra A, Kandasamy T, Ghosh SS, Saini GK. In vitro anticancer effects of recombinant anisoplin through activation of SAPK/JNK and downregulation of NFκB. Toxicol In Vitro 2024; 94:105737. [PMID: 37984481 DOI: 10.1016/j.tiv.2023.105737] [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: 03/25/2023] [Revised: 10/31/2023] [Accepted: 11/15/2023] [Indexed: 11/22/2023]
Abstract
Emerging chemotherapeutic resistance is considered as one of the major obstacles in breast cancer therapy. Fungal ribotoxins possess promising therapeutic potential against cancer owing to their ribosome-targeted protein synthesis inhibitory action. Though the entomopathogenic ribotoxin anisoplin was characterized in the earlier study, its therapeutic efficacy against cancer cells remained unexplored. In the current study, recombinant anisoplin has been successfully produced in Escherichia coli BL21(DE3) expression system and further purified and validated by in silico, biophysical and functional characterizations. Recombinant anisoplin significantly reduced the viability of MCF-7 breast cancer cells in a dose-dependent manner. It exhibited an IC50 value of 4 μM with concurrent 3.5 fold elevation in the intracellular reactive oxygen species. Anisoplin also resulted in depolarization of the mitochondrial membrane and subsequently induced apoptosis, as evident from flow cytometric analyses. In addition, MCF-7 cells significantly lost their self-renewal capability for clonal expansion and regeneration upon treatment. Immunoblotting experiments further confirmed activation of downstream JNK-dependent MAP kinase signaling pathway due to ribotoxic stress response generated by anisoplin through upregulation of phospho-SAPK/JNK expression. This upregulation was further correlated with the NFκB expression profile, leading to cell death, highlighting therapeutic potential of the recombinant anisoplin.
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Affiliation(s)
- Arupam Patra
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, North Guwahati, Assam, India
| | - Thirukumaran Kandasamy
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, North Guwahati, Assam, India
| | - Siddhartha Sankar Ghosh
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, North Guwahati, Assam, India
| | - Gurvinder Kaur Saini
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, North Guwahati, Assam, India.
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3
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García-Montoya C, García-Linares S, Heras-Márquez D, Majnik M, Laxalde-Fernández D, Amigot-Sánchez R, Martínez-Del-Pozo Á, Palacios-Ortega J. The interaction of the ribotoxin α-sarcin with complex model lipid vesicles. Arch Biochem Biophys 2024; 751:109836. [PMID: 38000493 DOI: 10.1016/j.abb.2023.109836] [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: 10/10/2023] [Revised: 11/06/2023] [Accepted: 11/20/2023] [Indexed: 11/26/2023]
Abstract
Fungal ribotoxins are extracellular RNases that inactivate ribosomes by cleaving a single phosphodiester bond at the universally conserved sarcin-ricin loop of the large rRNA. However, to reach the ribosomes, they need to cross the plasma membrane. It is there where these toxins show their cellular specificity, being especially active against tumoral or virus-infected cells. Previous studies have shown that fungal ribotoxins interact with negatively charged membranes, typically containing phosphatidylserine or phosphatidylglycerol. This ability is rooted on their long, non-structured, positively charged loops, and its N-terminal β-hairpin. However, its effect on complex lipid mixtures, including sphingophospholipids or cholesterol, remains poorly studied. Here, wild-type α-sarcin was used to evaluate its interaction with a variety of membranes not assayed before, which resemble much more closely mammalian cell membranes. The results confirm that α-sarcin is particularly sensitive to charge density on the vesicle surface. Its ability to induce vesicle aggregation is strongly influenced by both the lipid headgroup and the degree of saturation of the fatty acid chains. Acyl chain length is indeed particularly important for lipid mixing. Finally, cholesterol plays an important role in diluting the concentration of available negative charges and modulates the ability of α-sarcin to cross the membrane.
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Affiliation(s)
- Carmen García-Montoya
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | - Diego Heras-Márquez
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | - Manca Majnik
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | | | - Rafael Amigot-Sánchez
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | | | - Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
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4
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Jia W, Yuan J, Li S, Cheng B. The role of dysregulated mRNA translation machinery in cancer pathogenesis and therapeutic value of ribosome-inactivating proteins. Biochim Biophys Acta Rev Cancer 2023; 1878:189018. [PMID: 37944831 DOI: 10.1016/j.bbcan.2023.189018] [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: 09/14/2023] [Revised: 10/17/2023] [Accepted: 11/02/2023] [Indexed: 11/12/2023]
Abstract
Dysregulated protein synthesis is a hallmark of tumors. mRNA translation reprogramming contributes to tumorigenesis, which is fueled by abnormalities in ribosome formation, tRNA abundance and modification, and translation factors. Not only malignant cells but also stromal cells within tumor microenvironment can undergo transformation toward tumorigenic phenotypes during translational reprogramming. Ribosome-inactivating proteins (RIPs) have garnered interests for their ability to selectively inhibit protein synthesis and suppress tumor growth. This review summarizes the role of dysregulated translation machinery in tumor development and explores the potential of RIPs in cancer treatment.
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Affiliation(s)
- Wentao Jia
- Oncology Department of Traditional Chinese Medicine, the First Affiliated Hospital of Naval Medical University, Shanghai 200433, China; Faculty of Traditional Chinese Medicine, Naval Medical University, Shanghai 200043, China
| | - Jiaying Yuan
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, Shanghai 200065, China
| | - Shu Li
- Department of Gastroenterology, Baoshan Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201900, China.
| | - Binbin Cheng
- Oncology Department of Traditional Chinese Medicine, the First Affiliated Hospital of Naval Medical University, Shanghai 200433, China; Faculty of Traditional Chinese Medicine, Naval Medical University, Shanghai 200043, China.
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5
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Ran G, Feng XL, Xie YL, Zheng QY, Guo PP, Yang M, Feng YL, Ling C, Zhu LQ, Zhong C. The use of miR122 and its target sequence in adeno-associated virus-mediated trichosanthin gene therapy. JOURNAL OF INTEGRATIVE MEDICINE-JIM 2021; 19:515-525. [PMID: 34538767 DOI: 10.1016/j.joim.2021.09.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Accepted: 05/10/2021] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Plant-derived cytotoxic transgene expression, such as trichosanthin (tcs), regulated by recombinant adeno-associated virus (rAAV) vector is a promising cancer gene therapy. However, the cytotoxic transgene can hamper the vector production in the rAAV producer cell line, human embryonic kidney (HEK293) cells. Here, we explored microRNA-122 (miR122) and its target sequence to limit the expression of the cytotoxic gene in the rAAV producer cells. METHODS A miR122 target (122T) sequence was incorporated into the 3' untranslated region of the tcs cDNA sequence. The firefly luciferase (fluc) transgene was used as an appropriate control. Cell line HEK293-mir122 was generated by the lentiviral vector-mediated genome integration of the mir122 gene in parental HEK293 cells. The effects of miR122 overexpression on cell growth, transgene expression, and rAAV production were determined. RESULTS The presence of 122T sequence significantly reduced transgene expression in the miR122-enriched Huh7 cell line (in vitro), fresh human hepatocytes (ex vivo), and mouse liver (in vivo). Also, the normal liver physiology was unaffected by delivery of 122T sequence by rAAV vectors. Compared with the parental cells, the miR122-overexpressing HEK293-mir122 cell line showed similar cell growth rate and expression of transgene without 122T, as well as the ability to produce liver-targeting rAAV vectors. Fascinatingly, the yield of rAAV vectors carrying the tcs-122T gene was increased by 77.7-fold in HEK293-mir122 cells. Moreover, the tcs-122T-containing rAAV vectors significantly reduced the proliferation of hepatocellular carcinoma cells without affecting the normal liver cells. CONCLUSION HEK293-mir122 cells along with the 122T sequence provide a potential tool to attenuate the cytotoxic transgene expression, such as tcs, during rAAV vector production.
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Affiliation(s)
- Gai Ran
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China; Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL 32611, USA
| | - Xi-Lin Feng
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China
| | - Yi-Lin Xie
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China
| | - Qing-Yun Zheng
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China
| | - Peng-Peng Guo
- Department of Traditional Chinese Medicine, Chinese People's Liberation Army 971 Hospital, Qingdao 266071, Shandong Province, China
| | - Ming Yang
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China
| | - Ying-Lu Feng
- Department of Traditional Chinese Medicine, Chinese People's Liberation Army 971 Hospital, Qingdao 266071, Shandong Province, China
| | - Chen Ling
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China; Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL 32611, USA
| | - Li-Qing Zhu
- Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, Zhejiang Province, China
| | - Chen Zhong
- State Key Laboratory of Genetic Engineering and Engineering Research Center of Gene Technology (Ministry of Education), School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China.
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6
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Islam S, Rahaman MM, Zhang S. RNAMotifContrast: a method to discover and visualize RNA structural motif subfamilies. Nucleic Acids Res 2021; 49:e61. [PMID: 33693841 PMCID: PMC8216276 DOI: 10.1093/nar/gkab131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 02/16/2021] [Accepted: 02/18/2021] [Indexed: 01/17/2023] Open
Abstract
Understanding the 3D structural properties of RNAs will play a critical role in identifying their functional characteristics and designing new RNAs for RNA-based therapeutics and nanotechnology. While several existing computational methods can help in the analysis of RNA properties by recognizing structural motifs, they do not provide the means to compare and contrast those motifs extensively. We have developed a new method, RNAMotifContrast, which focuses on analyzing the similarities and variations of RNA structural motif characteristics. In this method, a graph is formed to represent the similarities among motifs, and a new traversal algorithm is applied to generate visualizations of their structural properties. Analyzing the structural features among motifs, we have recognized and generalized the concept of motif subfamilies. To asses its effectiveness, we have applied RNAMotifContrast on a dataset of known RNA structural motif families. From the results, we observed that the derived subfamilies possess unique structural variations while holding standard features of the families. Overall, the visualization approach of this method presents a new perspective to observe the relation among motifs more closely, and the discovered subfamilies provide opportunities to achieve valuable insights into RNA’s diverse roles.
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Affiliation(s)
- Shahidul Islam
- Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA
| | - Md Mahfuzur Rahaman
- Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA
| | - Shaojie Zhang
- Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA
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7
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Kim C, Holm M, Mandava CS, Sanyal S. Optimization of a fluorescent-mRNA based real-time assay for precise kinetic measurements of ribosomal translocation. RNA Biol 2021; 18:2363-2375. [PMID: 33938388 PMCID: PMC8632105 DOI: 10.1080/15476286.2021.1913312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Kinetic characterization of ribosomal translocation is important for understanding the mechanism of elongation in protein synthesis. Here we have optimized a popular fluorescent-mRNA based translocation assay conducted in stopped-flow, by calibrating it with the functional tripeptide formation assay in quench-flow. We found that a fluorescently labelled mRNA, ten bases long from position +1 (mRNA+10), is best suited for both assays as it forms tripeptide at a fast rate equivalent to the longer mRNAs, and yet produces a large fluorescence change upon mRNA movement. Next, we compared the commonly used peptidyl tRNA analog, N-acetyl-Phe-tRNAPhe, with the natural dipeptidyl fMet-Phe-tRNAPhe in the stopped-flow assay. This analog translocates about two times slower than the natural dipeptidyl tRNA and produces biphasic kinetics. The rates reduce further at lower temperatures and with higher Mg2+ concentration, but improve with higher elongation factor G (EF-G) concentration, which increase both rate and amplitude of the fast phase significantly. In summary, we present here an improved real time assay for monitoring mRNA-translocation with the natural- and an N-Ac-analog of dipeptidyl tRNA.
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Affiliation(s)
- Changil Kim
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Mikael Holm
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | | | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
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8
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Landi N, Ragucci S, Culurciello R, Russo R, Valletta M, Pedone PV, Pizzo E, Di Maro A. Ribotoxin-like proteins from Boletus edulis: structural properties, cytotoxicity and in vitro digestibility. Food Chem 2021; 359:129931. [PMID: 33940474 DOI: 10.1016/j.foodchem.2021.129931] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/19/2021] [Accepted: 04/19/2021] [Indexed: 01/17/2023]
Abstract
Porcini are edible mushrooms widely used in cooking due to their extraordinary taste. Despite this, cases of food poisoning have been reported in the recent literature also for ingestion of porcini. Here, we report the isolation from Boletus edulis fruiting bodies of two novel ribotoxin-like proteins (RL-Ps), enzymes already studied in other organisms for their toxicity. These RL-Ps, named Edulitin 1 (16-kDa) and Edulitin 2 (14-kDa), show peculiar structural and enzymatic differences, which probably reflect their different bio-activities and a dose/time dependent toxicity (Edulitin 2) on normal and tumoral human cells. Particularly interesting is the resistance to proteolysis of Edulitin 2, for which it was observed that its toxicity was abolished only after heat treatment (90 °C) followed by proteolysis. As mushroom poisoning is a serious food safety issue, data here presented confirm the existence of toxins also in porcini and the importance of a proper cooking before their consumption.
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Affiliation(s)
- Nicola Landi
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), University of Campania 'Luigi Vanvitelli', Via Vivaldi 43, 81100 Caserta, Italy
| | - Sara Ragucci
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), University of Campania 'Luigi Vanvitelli', Via Vivaldi 43, 81100 Caserta, Italy
| | - Rosanna Culurciello
- Department of Biology, University of Naples 'Federico II', Via Cinthia 26, 80126 Naples, Italy
| | - Rosita Russo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), University of Campania 'Luigi Vanvitelli', Via Vivaldi 43, 81100 Caserta, Italy
| | - Mariangela Valletta
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), University of Campania 'Luigi Vanvitelli', Via Vivaldi 43, 81100 Caserta, Italy
| | - Paolo V Pedone
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), University of Campania 'Luigi Vanvitelli', Via Vivaldi 43, 81100 Caserta, Italy
| | - Elio Pizzo
- Department of Biology, University of Naples 'Federico II', Via Cinthia 26, 80126 Naples, Italy
| | - Antimo Di Maro
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), University of Campania 'Luigi Vanvitelli', Via Vivaldi 43, 81100 Caserta, Italy.
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9
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Gene Organization, Expression, and Localization of Ribotoxin-Like Protein Ageritin in Fruiting Body and Mycelium of Agrocybe aegerita. Int J Mol Sci 2020; 21:ijms21197158. [PMID: 32998313 PMCID: PMC7582721 DOI: 10.3390/ijms21197158] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 09/24/2020] [Accepted: 09/25/2020] [Indexed: 12/16/2022] Open
Abstract
The edible mushroom Agrocybe aegerita produces a ribotoxin-like protein known as Ageritin. In this work, the gene encoding Ageritin was characterized by sequence analysis. It contains several typical features of fungal genes such as three short introns (60, 55 and 69 bp) located at the 5' region of the coding sequence and typical splice junctions. This sequence codes for a precursor of 156 amino acids (~17-kDa) containing an additional N-terminal peptide of 21 amino acid residues, absent in the purified toxin (135 amino acid residues; ~15-kDa). The presence of 17-kDa and 15-kDa forms was investigated by Western blot in specific parts of fruiting body and in mycelia of A. aegerita. Data show that the 15-kDa Ageritin is the only form retrieved in the fruiting body and the principal form in mycelium. The immunolocalization by confocal laser scanning microscopy and transmission electron microscopy proves that Ageritin has vacuolar localization in hyphae. Coupling these data with a bioinformatics approach, we suggest that the N-terminal peptide of Ageritin (not found in the purified toxin) is a new signal peptide in fungi involved in intracellular routing from endoplasmic reticulum to vacuole, necessary for self-defense of A. aegerita ribosomes from Ageritin toxicity.
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10
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Olombrada M, Peña C, Rodríguez-Galán O, Klingauf-Nerurkar P, Portugal-Calisto D, Oborská-Oplová M, Altvater M, Gavilanes JG, Martínez-Del-Pozo Á, de la Cruz J, García-Ortega L, Panse VG. The ribotoxin α-sarcin can cleave the sarcin/ricin loop on late 60S pre-ribosomes. Nucleic Acids Res 2020; 48:6210-6222. [PMID: 32365182 PMCID: PMC7293039 DOI: 10.1093/nar/gkaa315] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 03/27/2020] [Accepted: 04/20/2020] [Indexed: 12/11/2022] Open
Abstract
The ribotoxin α-sarcin belongs to a family of ribonucleases that cleave the sarcin/ricin loop (SRL), a critical functional rRNA element within the large ribosomal subunit (60S), thereby abolishing translation. Whether α-sarcin targets the SRL only in mature 60S subunits remains unresolved. Here, we show that, in yeast, α-sarcin can cleave SRLs within late 60S pre-ribosomes containing mature 25S rRNA but not nucleolar/nuclear 60S pre-ribosomes containing 27S pre-rRNA in vivo. Conditional expression of α-sarcin is lethal, but does not impede early pre-rRNA processing, nuclear export and the cytoplasmic maturation of 60S pre-ribosomes. Thus, SRL-cleaved containing late 60S pre-ribosomes seem to escape cytoplasmic proofreading steps. Polysome analyses revealed that SRL-cleaved 60S ribosomal subunits form 80S initiation complexes, but fail to progress to the step of translation elongation. We suggest that the functional integrity of a α-sarcin cleaved SRL might be assessed only during translation.
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Affiliation(s)
- Miriam Olombrada
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense de Madrid, Spain.,Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, CH-8093 Zürich, Switzerland
| | - Cohue Peña
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, CH-8093 Zürich, Switzerland.,Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30, CH-8006 Zürich, Switzerland
| | - Olga Rodríguez-Galán
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Purnima Klingauf-Nerurkar
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, CH-8093 Zürich, Switzerland.,Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30, CH-8006 Zürich, Switzerland
| | - Daniela Portugal-Calisto
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30, CH-8006 Zürich, Switzerland
| | - Michaela Oborská-Oplová
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, CH-8093 Zürich, Switzerland.,Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30, CH-8006 Zürich, Switzerland
| | - Martin Altvater
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, CH-8093 Zürich, Switzerland
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense de Madrid, Spain
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense de Madrid, Spain
| | - Jesús de la Cruz
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Lucía García-Ortega
- Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense de Madrid, Spain
| | - Vikram Govind Panse
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30, CH-8006 Zürich, Switzerland
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11
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Bruni F, Proctor-Kent Y, Lightowlers RN, Chrzanowska-Lightowlers ZM. Messenger RNA delivery to mitoribosomes - hints from a bacterial toxin. FEBS J 2020; 288:437-451. [PMID: 32329962 PMCID: PMC7891357 DOI: 10.1111/febs.15342] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 04/06/2020] [Accepted: 04/21/2020] [Indexed: 11/28/2022]
Abstract
In mammalian mitochondria, messenger RNA is processed and matured from large primary transcripts in structures known as RNA granules. The identity of the factors and process transferring the matured mRNA to the mitoribosome for translation is unclear. Nascent mature transcripts are believed to associate initially with the small mitoribosomal subunit prior to recruitment of the large subunit to form the translationally active monosome. When the small subunit fails to assemble, however, the stability of mt‐mRNA is only marginally affected, and under these conditions, the LRPPRC/SLIRP RNA‐binding complex has been implicated in maintaining mt‐mRNA stability. Here, we exploit the activity of a bacterial ribotoxin, VapC20, to show that in the absence of the large mitoribosomal subunit, mt‐mRNA species are selectively lost. Further, if the small subunit is also depleted, the mt‐mRNA levels are recovered. As a consequence of these data, we suggest a natural pathway for loading processed mt‐mRNA onto the mitoribosome.
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Affiliation(s)
- Francesco Bruni
- The Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, UK.,Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Italy
| | - Yasmin Proctor-Kent
- The Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, UK
| | - Robert N Lightowlers
- The Wellcome Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, UK
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12
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Abstract
The ribosome and RNase P are cellular ribonucleoprotein complexes that perform peptide bond synthesis and phosphodiester bond cleavage, respectively. Both are ancient biological assemblies that were already present in the last universal common ancestor of all life. The large subunit rRNA in the ribosome and the RNA subunit of RNase P are the ribozyme components required for catalysis. Here, we explore the idea that these two large ribozymes may have begun their evolutionary odyssey as an assemblage of RNA "fragments" smaller than the contemporary full-length versions and that they transitioned through distinct stages along a pathway that may also be relevant for the evolution of other non-coding RNAs.
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Affiliation(s)
- Michael W Gray
- Department of Biochemistry and Molecular Biology and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
| | - Venkat Gopalan
- Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210.
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13
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Kudrin P, Dzhygyr I, Ishiguro K, Beljantseva J, Maksimova E, Oliveira SRA, Varik V, Payoe R, Konevega AL, Tenson T, Suzuki T, Hauryliuk V. The ribosomal A-site finger is crucial for binding and activation of the stringent factor RelA. Nucleic Acids Res 2019; 46:1973-1983. [PMID: 29390134 PMCID: PMC5829649 DOI: 10.1093/nar/gky023] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 01/24/2018] [Indexed: 01/18/2023] Open
Abstract
During amino acid starvation the Escherichia coli stringent response factor RelA recognizes deacylated tRNA in the ribosomal A-site. This interaction activates RelA-mediated synthesis of alarmone nucleotides pppGpp and ppGpp, collectively referred to as (p)ppGpp. These two alarmones are synthesized by addition of a pyrophosphate moiety to the 3' position of the abundant cellular nucleotide GTP and less abundant nucleotide GDP, respectively. Using untagged native RelA we show that allosteric activation of RelA by pppGpp increases the efficiency of GDP conversion to achieve the maximum rate of (p)ppGpp production. Using a panel of ribosomal RNA mutants, we show that the A-site finger structural element of 23S rRNA helix 38 is crucial for RelA binding to the ribosome and consequent activation, and deletion of the element severely compromises (p)ppGpp accumulation in E. coli upon amino acid starvation. Through binding assays and enzymology, we show that E. coli RelA does not form a stable complex with, and is not activated by, deacylated tRNA off the ribosome. This indicates that in the cell, RelA first binds the empty A-site and then recruits tRNA rather than first binding tRNA and then binding the ribosome.
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Affiliation(s)
- Pavel Kudrin
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Ievgen Dzhygyr
- Department of Molecular Biology, Umeå University, Building 6K, 6L, SE-901 87 Umeå, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Building 6K and 6L, SE-901 87 Umeå, Sweden
| | - Kensuke Ishiguro
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Jelena Beljantseva
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Elena Maksimova
- Petersburg Nuclear Physics Institute named by B.P. Konstantinov of National Research Centre "Kurchatov Institute", Gatchina 188300, Russia.,Peter the Great St. Petersburg Polytechnic University, Saint Petersburg 195251, Russia
| | | | - Vallo Varik
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Roshani Payoe
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Andrey L Konevega
- Petersburg Nuclear Physics Institute named by B.P. Konstantinov of National Research Centre "Kurchatov Institute", Gatchina 188300, Russia.,Peter the Great St. Petersburg Polytechnic University, Saint Petersburg 195251, Russia.,National Research Centre "Kurchatov Institute", Moscow 123182, Russia
| | - Tanel Tenson
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Tsutomu Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Vasili Hauryliuk
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia.,Department of Molecular Biology, Umeå University, Building 6K, 6L, SE-901 87 Umeå, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Building 6K and 6L, SE-901 87 Umeå, Sweden
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14
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Citores L, Ragucci S, Ferreras JM, Di Maro A, Iglesias R. Ageritin, a Ribotoxin from Poplar Mushroom ( Agrocybe aegerita) with Defensive and Antiproliferative Activities. ACS Chem Biol 2019; 14:1319-1327. [PMID: 31136705 DOI: 10.1021/acschembio.9b00291] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ribotoxins make up a group of extracellular rRNA endoribonucleases produced by ascomycetes that display cytotoxicity toward animal cells, having been proposed as insecticidal agents. Recently, the ribotoxin Ageritin has been isolated from the basidiomycetes Agrocybe aegerita (poplar mushroom), suggesting that ribotoxins are widely distributed among fungi. To gain insights into the protective properties of Ageritin against pathogens and its putative biotechnological applications, we have tested several biological activities of Ageritin, comparing them with those of the well-known ribotoxin α-sarcin, and we found that Ageritin displayed, in addition to the already reported activities, (i) antibacterial activity against Micrococcus lysodeikticus, (ii) activity against the tobacco mosaic virus RNA, (iii) endonuclease activity against a supercoiled plasmid, (iv) nuclease activity against genomic DNA, (v) cytotoxicity to COLO 320, HeLa, and Raji cells by promoting apoptosis, and (vi) antifungal activity against the green mold Penicillium digitatum. Therefore, Ageritin and α-sarcin can induce resistance not only to insects but also to viruses, bacteria, and fungi. The multiple biological activities of Ageritin could be exploited to improve resistance to different pathogens by engineering transgenic plants. Furthermore, the induction of cell death by different mechanisms turns these ribotoxins into useful tools for cancer therapy.
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Affiliation(s)
- Lucía Citores
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E−47011 Valladolid, Spain
| | - Sara Ragucci
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, I-81100 Caserta, Italy
| | - José M. Ferreras
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E−47011 Valladolid, Spain
| | - Antimo Di Maro
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, I-81100 Caserta, Italy
| | - Rosario Iglesias
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E−47011 Valladolid, Spain
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15
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Abstract
INTRODUCTION The success of binding site comparisons in drug discovery is based on the recognized fact that many different proteins have similar binding sites. Indeed, binding site comparisons have found many uses in drug development and have the potential to dramatically cut the cost and shorten the time necessary for the development of new drugs. Areas covered: The authors review recent methods for comparing protein binding sites and their use in drug repurposing and polypharmacology. They examine emerging fields including the use of binding site comparisons in precision medicine, the prediction of structured water molecules, the search for targets of natural compounds, and their application in the development of protein-based drugs by loop modeling and for comparison of RNA binding sites. Expert opinion: Binding site comparisons have produced many interesting results in drug development, but relatively little work has been done on protein-protein interaction sites, which are particularly relevant in view of the success of biological drugs. Growth of protein loop modeling for modulating biological drugs is anticipated. The fusion of currently distinct methods for the comparison of RNA and protein binding sites into a single comprehensive approach could allow the search for new selective ribosomal antibiotics and initiate pharmaceutical research into other nucleoproteins.
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Affiliation(s)
- Janez Konc
- a Theory Department , National Institute of Chemistry , Ljubljana , Slovenia.,b Faculty of Pharmacy , University of Ljubljana , Ljubljana , Slovenia.,c Faculty of Mathematics , Natural Sciences and Information Technologies, University of Primorska , Koper , Slovenia.,d Faculty of Chemistry and Chemical Technology , University of Maribor , Maribor , Slovenia
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16
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Citores L, Iglesias R, Ragucci S, Di Maro A, Ferreras JM. Antifungal Activity of α-Sarcin against Penicillium digitatum: Proposal of a New Role for Fungal Ribotoxins. ACS Chem Biol 2018; 13:1978-1982. [PMID: 29952541 DOI: 10.1021/acschembio.8b00410] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Among the putative defense proteins that occur in fungi, one of the best studied is α-sarcin, produced by the mold Aspergillus giganteus. This protein is the most significant member of the ribotoxin family, which consists of extracellular rRNA ribonucleases that display cytotoxic activity toward animal cells. Ribotoxins are rRNA endonucleases that catalyze the hydrolysis of the phosphodiester bond between G4325 and A4326 from the rat 28S rRNA. The results of several experimental approaches have led to propose ribotoxins as insecticidal agents. In this work, we report that α-sarcin displays a strong antifungal activity against Penicillium digitatum, being able to enter into the cytosol where it inactivates the ribosomes, thus killing the cells and arresting the growth of the fungus. This is the first time that a ribotoxin has been found to display antifungal activity. Therefore, this protein could play, besides the already proposed insecticidal function, a role in nature as an antifungal agent.
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Affiliation(s)
- Lucía Citores
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain
| | - Rosario Iglesias
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain
| | - Sara Ragucci
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, I-81100 Caserta, Italy
| | - Antimo Di Maro
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, I-81100 Caserta, Italy
| | - José M. Ferreras
- Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain
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17
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Ge P, Islam S, Zhong C, Zhang S. De novo discovery of structural motifs in RNA 3D structures through clustering. Nucleic Acids Res 2018; 46:4783-4793. [PMID: 29534235 PMCID: PMC5961109 DOI: 10.1093/nar/gky139] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 02/09/2018] [Accepted: 02/16/2018] [Indexed: 11/16/2022] Open
Abstract
As functional components in three-dimensional (3D) conformation of an RNA, the RNA structural motifs provide an easy way to associate the molecular architectures with their biological mechanisms. In the past years, many computational tools have been developed to search motif instances by using the existing knowledge of well-studied families. Recently, with the rapidly increasing number of resolved RNA 3D structures, there is an urgent need to discover novel motifs with the newly presented information. In this work, we classify all the loops in non-redundant RNA 3D structures to detect plausible RNA structural motif families by using a clustering pipeline. Compared with other clustering approaches, our method has two benefits: first, the underlying alignment algorithm is tolerant to the variations in 3D structures. Second, sophisticated downstream analysis has been performed to ensure the clusters are valid and easily applied to further research. The final clustering results contain many interesting new variants of known motif families, such as GNAA tetraloop, kink-turn, sarcin-ricin and T-loop. We have also discovered potential novel functional motifs conserved in ribosomal RNA, sgRNA, SRP RNA, riboswitch and ribozyme.
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Affiliation(s)
- Ping Ge
- Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA
| | - Shahidul Islam
- Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA
| | - Cuncong Zhong
- Department of Electrical Engineering and Computer Science, University of Kansas, Lawrence, KS 66045, USA
| | - Shaojie Zhang
- Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA
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18
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Minimized natural versions of fungal ribotoxins show improved active site plasticity. Arch Biochem Biophys 2017; 619:45-53. [DOI: 10.1016/j.abb.2017.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/03/2017] [Accepted: 03/05/2017] [Indexed: 01/29/2023]
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19
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Fungal Ribotoxins: A Review of Potential Biotechnological Applications. Toxins (Basel) 2017; 9:toxins9020071. [PMID: 28230789 PMCID: PMC5331450 DOI: 10.3390/toxins9020071] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 02/14/2017] [Accepted: 02/16/2017] [Indexed: 12/20/2022] Open
Abstract
Fungi establish a complex network of biological interactions with other organisms in nature. In many cases, these involve the production of toxins for survival or colonization purposes. Among these toxins, ribotoxins stand out as promising candidates for their use in biotechnological applications. They constitute a group of highly specific extracellular ribonucleases that target a universally conserved sequence of RNA in the ribosome, the sarcin-ricin loop. The detailed molecular study of this family of toxic proteins over the past decades has highlighted their potential in applied research. Remarkable examples would be the recent studies in the field of cancer research with promising results involving ribotoxin-based immunotoxins. On the other hand, some ribotoxin-producer fungi have already been studied in the control of insect pests. The recent role of ribotoxins as insecticides could allow their employment in formulas and even as baculovirus-based biopesticides. Moreover, considering the important role of their target in the ribosome, they can be used as tools to study how ribosome biogenesis is regulated and, eventually, may contribute to a better understanding of some ribosomopathies.
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20
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Olombrada M, Medina P, Budia F, Gavilanes JG, Martínez-del-Pozo Á, García-Ortega L. Characterization of a new toxin from the entomopathogenic fungus Metarhizium anisopliae: the ribotoxin anisoplin. Biol Chem 2017; 398:135-142. [DOI: 10.1515/hsz-2016-0119] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 07/21/2016] [Indexed: 12/15/2022]
Abstract
Abstract
Metarhizium anisopliae is an entomopathogenic fungus relevant in biotechnology with applications like malaria vector control. Studies of its virulence factors are therefore of great interest. Fungal ribotoxins are toxic ribonucleases with extraordinary efficiency against ribosomes and suggested as potential insecticides. Here we describe this ribotoxin characteristic activity in M. anisopliae cultures. Anisoplin has been obtained as a recombinant protein and further characterized. It is structurally similar to hirsutellin A, the ribotoxin from the entomopathogen Hirsutella thompsonii. Moreover, anisoplin shows the ribonucleolytic activity typical of ribotoxins and cytotoxicity against insect cells. How Metarhizium uses this toxin and possible applications are of interest.
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21
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Determination of nucleoside triphosphatase activities from measurement of true inorganic phosphate in the presence of labile phosphate compounds. Anal Biochem 2016; 520:62-67. [PMID: 28017740 DOI: 10.1016/j.ab.2016.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 12/10/2016] [Accepted: 12/14/2016] [Indexed: 11/24/2022]
Abstract
One of the most common assays for nucleoside triphosphatase (NTPase) activity entails the quantification of inorganic phosphate (Pi) as a colored phosphomolybdate complex at low pH. While this assay is very sensitive, it is not selective for Pi in the presence of labile organic phosphate compounds (OPCs). Since NTPase activity assays typically require a large excess of OPCs, such as nucleotides, selectivity for Pi in the presence of OPCs is often critical in evaluating enzyme activity. Here we present an improved method for the measurement of enzymatic nucleotide hydrolysis as Pi released, which achieves selectivity for Pi in the presence of OPCs while also avoiding the costs and hazards inherent in other methods for measuring nucleotide hydrolysis. We apply this method to the measurement of ATP hydrolysis by nitrogenase and GTP hydrolysis by elongation factor G (EF-G) in order to demonstrate the broad applicability of our method for the determination of nucleotide hydrolysis in the presence of interfering OPCs.
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22
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Structure and assembly model for the Trypanosoma cruzi 60S ribosomal subunit. Proc Natl Acad Sci U S A 2016; 113:12174-12179. [PMID: 27791004 DOI: 10.1073/pnas.1614594113] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ribosomes of trypanosomatids, a family of protozoan parasites causing debilitating human diseases, possess multiply fragmented rRNAs that together are analogous to 28S rRNA, unusually large rRNA expansion segments, and r-protein variations compared with other eukaryotic ribosomes. To investigate the architecture of the trypanosomatid ribosomes, we determined the 2.5-Å structure of the Trypanosoma cruzi ribosome large subunit by single-particle cryo-EM. Examination of this structure and comparative analysis of the yeast ribosomal assembly pathway allowed us to develop a stepwise assembly model for the eight pieces of the large subunit rRNAs and a number of ancillary "glue" proteins. This model can be applied to the characterization of Trypanosoma brucei and Leishmania spp. ribosomes as well. Together with other details, our atomic-level structure may provide a foundation for structure-based design of antitrypanosome drugs.
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23
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Jones TD, Hearn AR, Holgate RGE, Kozub D, Fogg MH, Carr FJ, Baker MP, Lacadena J, Gehlsen KR. A deimmunised form of the ribotoxin, α-sarcin, lacking CD4+ T cell epitopes and its use as an immunotoxin warhead. Protein Eng Des Sel 2016; 29:531-540. [PMID: 27578884 PMCID: PMC5081043 DOI: 10.1093/protein/gzw045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 06/30/2016] [Accepted: 07/25/2016] [Indexed: 12/30/2022] Open
Abstract
Fungal ribotoxins that block protein synthesis can be useful warheads in the context of a targeted immunotoxin. α-Sarcin is a small (17 kDa) fungal ribonuclease produced by Aspergillus giganteus that functions by catalytically cleaving a single phosphodiester bond in the sarcin–ricin loop of the large ribosomal subunit, thus making the ribosome unrecognisable to elongation factors and leading to inhibition of protein synthesis. Peptide mapping using an ex vivo human T cell assay determined that α-sarcin contained two T cell epitopes; one in the N-terminal 20 amino acids and the other in the C-terminal 20 amino acids. Various mutations were tested individually within each epitope and then in combination to isolate deimmunised α-sarcin variants that had the desired properties of silencing T cell epitopes and retention of the ability to inhibit protein synthesis (equivalent to wild-type, WT α-sarcin). A deimmunised variant (D9T/Q142T) demonstrated a complete lack of T cell activation in in vitro whole protein human T cell assays using peripheral blood mononuclear cells from donors with diverse HLA allotypes. Generation of an immunotoxin by fusion of the D9T/Q142T variant to a single-chain Fv targeting Her2 demonstrated potent cell killing equivalent to a fusion protein comprising the WT α-sarcin. These results represent the first fungal ribotoxin to be deimmunised with the potential to construct a new generation of deimmunised immunotoxin therapeutics.
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Affiliation(s)
- Tim D Jones
- Abzena plc., Babraham Research Campus, Babraham, CambridgeCB22 3AT, UK
| | - Arron R Hearn
- Abzena plc., Babraham Research Campus, Babraham, CambridgeCB22 3AT, UK
| | | | - Dorota Kozub
- Abzena plc., Babraham Research Campus, Babraham, CambridgeCB22 3AT, UK
| | - Mark H Fogg
- Abzena plc., Babraham Research Campus, Babraham, CambridgeCB22 3AT, UK
| | - Francis J Carr
- Abtelum Biomedical, Inc. 175 Briar Lane, Westwood, MA 02090, USA
| | - Matthew P Baker
- Abzena plc., Babraham Research Campus, Babraham, CambridgeCB22 3AT, UK
| | - Javier Lacadena
- Departamento de Bioquimica y Biologia Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid 28040, Spain
| | - Kurt R Gehlsen
- Research Corporation Technologies Inc., 5210 E. Williams Circle #240, Tucson, AZ 85711, USA
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24
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Olombrada M, García-Ortega L, Lacadena J, Oñaderra M, Gavilanes JG, Martínez-del-Pozo Á. Involvement of loop 5 lysine residues and the N-terminal β-hairpin of the ribotoxin hirsutellin A on its insecticidal activity. Biol Chem 2016; 397:135-45. [DOI: 10.1515/hsz-2015-0261] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 11/17/2015] [Indexed: 11/15/2022]
Abstract
Abstract
Ribotoxins are cytotoxic members of the family of fungal extracellular ribonucleases best represented by RNase T1. They share a high degree of sequence identity and a common structural fold, including the geometric arrangement of their active sites. However, ribotoxins are larger, with a well-defined N-terminal β-hairpin, and display longer and positively charged unstructured loops. These structural differences account for their cytotoxic properties. Unexpectedly, the discovery of hirsutellin A (HtA), a ribotoxin produced by the invertebrate pathogen Hirsutella thompsonii, showed how it was possible to accommodate these features into a shorter amino acid sequence. Examination of HtA N-terminal β-hairpin reveals differences in terms of length, charge, and spatial distribution. Consequently, four different HtA mutants were prepared and characterized. One of them was the result of deleting this hairpin [Δ(8-15)] while the other three affected single Lys residues in its close spatial proximity (K115E, K118E, and K123E). The results obtained support the general conclusion that HtA active site would show a high degree of plasticity, being able to accommodate electrostatic and structural changes not suitable for the other previously known larger ribotoxins, as the variants described here only presented small differences in terms of ribonucleolytic activity and cytotoxicity against cultured insect cells.
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Role of a ribosomal RNA phosphate oxygen during the EF-G-triggered GTP hydrolysis. Proc Natl Acad Sci U S A 2015; 112:E2561-8. [PMID: 25941362 DOI: 10.1073/pnas.1505231112] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Elongation factor-catalyzed GTP hydrolysis is a key reaction during the ribosomal elongation cycle. Recent crystal structures of G proteins, such as elongation factor G (EF-G) bound to the ribosome, as well as many biochemical studies, provide evidence that the direct interaction of translational GTPases (trGTPases) with the sarcin-ricin loop (SRL) of ribosomal RNA (rRNA) is pivotal for hydrolysis. However, the precise mechanism remains elusive and is intensively debated. Based on the close proximity of the phosphate oxygen of A2662 of the SRL to the supposedly catalytic histidine of EF-G (His87), we probed this interaction by an atomic mutagenesis approach. We individually replaced either of the two nonbridging phosphate oxygens at A2662 with a methyl group by the introduction of a methylphosphonate instead of the natural phosphate in fully functional, reconstituted bacterial ribosomes. Our major finding was that only one of the two resulting diastereomers, the SP methylphosphonate, was compatible with efficient GTPase activation on EF-G. The same trend was observed for a second trGTPase, namely EF4 (LepA). In addition, we provide evidence that the negative charge of the A2662 phosphate group must be retained for uncompromised activity in GTP hydrolysis. In summary, our data strongly corroborate that the nonbridging proSP phosphate oxygen at the A2662 of the SRL is critically involved in the activation of GTP hydrolysis. A mechanistic scenario is supported in which positioning of the catalytically active, protonated His87 through electrostatic interactions with the A2662 phosphate group and H-bond networks are key features of ribosome-triggered activation of trGTPases.
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Tomé-Amat J, Olombrada M, Ruiz-de-la-Herrán J, Pérez-Gómez E, Andradas C, Sánchez C, Martínez L, Martínez-Del-Pozo Á, Gavilanes JG, Lacadena J. Efficient in vivo antitumor effect of an immunotoxin based on ribotoxin α-sarcin in nude mice bearing human colorectal cancer xenografts. SPRINGERPLUS 2015; 4:168. [PMID: 25883890 PMCID: PMC4393403 DOI: 10.1186/s40064-015-0943-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 02/12/2015] [Accepted: 03/24/2015] [Indexed: 11/17/2022]
Abstract
Tagging of RNases, such as the ribotoxin α-sarcin, with the variable domains of antibodies directed to surface antigens that are selectively expressed on tumor cells endows cellular specificity to their cytotoxic action. A recombinant single-chain immunotoxin based on the ribotoxin α-sarcin (IMTXA33αS), produced in the generally regarded as safe (GRAS) yeast Pichia pastoris, has been recently described as a promising candidate for the treatment of colorectal cancer cells expressing the glycoprotein A33 (GPA33) antigen, due to its high specific and effective cytotoxic effect on in vitro assays against targeted cells. Here we report the in vivo antitumor effectiveness of this immunotoxin on nude mice bearing GPA33-positive human colon cancer xenografts. Two sets of independent assays were performed, including three experimental groups: control (PBS) and treatment with two different doses of immunotoxin (50 or 100 μg/ injection) (n = 8). Intraperitoneal administration of IMTXA33αS resulted in significant dose-dependent tumor growth inhibition. In addition, the remaining tumors excised from immunotoxin-treated mice showed absence of the GPA33 antigen and a clear inhibition of angiogenesis and proliferative capacity. No signs of immunotoxin-induced pathological changes were observed from specimens tissues. Overall these results show efficient and selective cytotoxic action on tumor xenografts, combined with the lack of severe side effects, suggesting that IMTXA33αS is a potential therapeutic agent against colorectal cancer.
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Affiliation(s)
- Jaime Tomé-Amat
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain ; Present address: Department of Microbiology, Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Miriam Olombrada
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain
| | - Javier Ruiz-de-la-Herrán
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain
| | - Eduardo Pérez-Gómez
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain ; Instituto de Investigación Hospital 12 de Octubre, Madrid, 28041 Spain
| | - Clara Andradas
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain ; Instituto de Investigación Hospital 12 de Octubre, Madrid, 28041 Spain
| | - Cristina Sánchez
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain ; Instituto de Investigación Hospital 12 de Octubre, Madrid, 28041 Spain
| | | | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain
| | - Javier Lacadena
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense s/n, Madrid, 28040 Spain
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Castaño-Rodríguez C, Olombrada M, Partida-Hanon A, Lacadena J, Oñaderra M, Gavilanes JG, García-Ortega L, Martínez-Del-Pozo Á. Involvement of loops 2 and 3 of α-sarcin on its ribotoxic activity. Toxicon 2015; 96:1-9. [PMID: 25598497 DOI: 10.1016/j.toxicon.2015.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 12/21/2014] [Accepted: 01/14/2015] [Indexed: 01/07/2023]
Abstract
Ribotoxins are a family of fungal ribosome-inactivating proteins displaying highly specific ribonucleolytic activity against the sarcin/ricin loop (SRL) of the larger rRNA, with α-sarcin as its best-characterized member. Their toxicity arises from the combination of this activity with their ability to cross cell membranes. The involvement of α-sarcin's loops 2 and 3 in SRL and ribosomal proteins recognition, as well as in the ribotoxin-lipid interactions involving cell penetration, has been suggested some time ago. In the work presented now different mutants have been prepared in order to study the role of these loops in their ribonucleolytic and lipid-interacting properties. The results obtained confirm that loop 3 residues Lys 111, 112, and 114 are key actors of the specific recognition of the SRL. In addition, it is also shown that Lys 114 and Tyr 48 conform a network of interactions which is essential for the catalysis. Lipid-interaction studies show that this Lys-rich region is indeed involved in the phospholipids recognition needed to cross cell membranes. Loop 2 is shown to be responsible for the conformational change which exposes the region establishing hydrophobic interactions with the membrane inner leaflets and eases penetration of ribotoxins target cells.
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Affiliation(s)
- Carlos Castaño-Rodríguez
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Miriam Olombrada
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Angélica Partida-Hanon
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Javier Lacadena
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Mercedes Oñaderra
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
| | - Lucía García-Ortega
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
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28
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Ishida H, Matsumoto A. Free-energy landscape of reverse tRNA translocation through the ribosome analyzed by electron microscopy density maps and molecular dynamics simulations. PLoS One 2014; 9:e101951. [PMID: 24999999 PMCID: PMC4084982 DOI: 10.1371/journal.pone.0101951] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 06/12/2014] [Indexed: 01/11/2023] Open
Abstract
To understand the mechanism of reverse tRNA translocation in the ribosome, all-atom molecular dynamics simulations of the ribosome-tRNAs-mRNA-EFG complex were performed. The complex at the post-translocational state was directed towards the translocational and pre-translocational states by fitting the complex into cryo-EM density maps. Between a series of the fitting simulations, umbrella sampling simulations were performed to obtain the free-energy landscape. Multistep structural changes, such as a ratchet-like motion and rotation of the head of the small subunit were observed. The free-energy landscape showed that there were two main free-energy barriers: one between the post-translocational and intermediate states, and the other between the pre-translocational and intermediate states. The former corresponded to a clockwise rotation, which was coupled to the movement of P-tRNA over the P/E-gate made of G1338, A1339 and A790 in the small subunit. The latter corresponded to an anticlockwise rotation of the head, which was coupled to the location of the two tRNAs in the hybrid state. This indicates that the coupled motion of the head rotation and tRNA translocation plays an important role in opening and closing of the P/E-gate during the ratchet-like movement in the ribosome. Conformational change of EF-G was interpreted to be the result of the combination of the external motion by L12 around an axis passing near the sarcin-ricin loop, and internal hinge-bending motion. These motions contributed to the movement of domain IV of EF-G to maintain its interaction with A/P-tRNA.
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Affiliation(s)
- Hisashi Ishida
- Quantum Beam Science Directorate and Center for Computational Science and e-Systems, Japan Atomic Energy Agency, Kyoto, Japan
- * E-mail:
| | - Atsushi Matsumoto
- Quantum Beam Science Directorate and Center for Computational Science and e-Systems, Japan Atomic Energy Agency, Kyoto, Japan
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29
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Olombrada M, Martínez-del-Pozo Á, Medina P, Budia F, Gavilanes JG, García-Ortega L. Fungal ribotoxins: Natural protein-based weapons against insects. Toxicon 2014; 83:69-74. [DOI: 10.1016/j.toxicon.2014.02.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 02/25/2014] [Indexed: 10/25/2022]
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30
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Olombrada M, Rodríguez-Mateos M, Prieto D, Pla J, Remacha M, Martínez-del-Pozo Á, Gavilanes JG, Ballesta JPG, García-Ortega L. The Acidic Ribosomal Stalk Proteins Are Not Required for the Highly Specific Inactivation Exerted by α-Sarcin of the Eukaryotic Ribosome. Biochemistry 2014; 53:1545-7. [DOI: 10.1021/bi401470u] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Miriam Olombrada
- Departamento
de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - María Rodríguez-Mateos
- Centro
de Biología Molecular Severo Ochoa, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Daniel Prieto
- Departamento
de Microbiología II, Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain
| | - Jesús Pla
- Departamento
de Microbiología II, Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain
| | - Miguel Remacha
- Centro
de Biología Molecular Severo Ochoa, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Álvaro Martínez-del-Pozo
- Departamento
de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - José G. Gavilanes
- Departamento
de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - Juan P. G. Ballesta
- Centro
de Biología Molecular Severo Ochoa, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Lucía García-Ortega
- Departamento
de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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31
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Yamamoto H, Qin Y, Achenbach J, Li C, Kijek J, Spahn CMT, Nierhaus KH. EF-G and EF4: translocation and back-translocation on the bacterial ribosome. Nat Rev Microbiol 2013; 12:89-100. [PMID: 24362468 DOI: 10.1038/nrmicro3176] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ribosomes translate the codon sequence of an mRNA into the amino acid sequence of the corresponding protein. One of the most crucial events is the translocation reaction, which involves movement of both the mRNA and the attached tRNAs by one codon length and is catalysed by the GTPase elongation factor G (EF-G). Interestingly, recent studies have identified a structurally related GTPase, EF4, that catalyses movement of the tRNA2-mRNA complex in the opposite direction when the ribosome stalls, which is known as back-translocation. In this Review, we describe recent insights into the mechanistic basis of both translocation and back-translocation.
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Affiliation(s)
- Hiroshi Yamamoto
- 1] Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany. [2]
| | - Yan Qin
- 1] Laboratory of noncoding RNA, Institute of Biophysics, Chinese Academy of Science; 15 Datun Road, Beijing 100101, China. [2]
| | - John Achenbach
- 1] NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany. [2]
| | - Chengmin Li
- Laboratory of noncoding RNA, Institute of Biophysics, Chinese Academy of Science; 15 Datun Road, Beijing 100101, China
| | - Jaroslaw Kijek
- Max Planck Institut für molekulare Genetik, Ihnestrasse 73, D-14195 Berlin, Germany
| | - Christian M T Spahn
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Knud H Nierhaus
- 1] Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany. [2] Max Planck Institut für molekulare Genetik, Ihnestrasse 73, D-14195 Berlin, Germany
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32
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Hirsutellin A: A Paradigmatic Example of the Insecticidal Function of Fungal Ribotoxins. INSECTS 2013; 4:339-56. [PMID: 26462423 PMCID: PMC4553468 DOI: 10.3390/insects4030339] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 11/17/2022]
Abstract
The fungal pathogen Hirsutella thompsonii produces an insecticidal protein named hirsutellin A (HtA), which has been described to be toxic to several species of mites, insect larvae, and cells. On the other hand, on the basis of an extensive biochemical and structural characterization, HtA has been considered to be a member of the ribotoxins family. Ribotoxins are fungal extracellular ribonucleases, which inactivate ribosomes by specifically cleaving a single phosphodiester bond located at the large rRNA. Although ribotoxins were brought to light in the 1960s as antitumor agents, their biological function has remained elusive. Thus, the consideration of hirsutellin A, an insecticidal protein, as a singular ribotoxin recalled the idea of the biological activity of these toxins as insecticidal agents. Further studies have demonstrated that the most representative member of the ribotoxin family, α-sarcin, also shows strong toxic action against insect cells. The determination of high resolution structures, the characterization of a large number of mutants, and the toxicity assays against different cell lines have been the tools used for the study of the mechanism of action of ribotoxins at the molecular level. The aim of this review is to serve as a compilation of the facts that allow identification of HtA as a paradigmatic example of the insecticidal function of fungal ribotoxins.
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Olombrada M, Herrero-Galán E, Tello D, Oñaderra M, Gavilanes JG, Martínez-del-Pozo Á, García-Ortega L. Fungal extracellular ribotoxins as insecticidal agents. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:39-46. [PMID: 23153726 DOI: 10.1016/j.ibmb.2012.10.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 10/24/2012] [Accepted: 10/25/2012] [Indexed: 06/01/2023]
Abstract
Fungal ribotoxins were discovered almost 50 years ago as extracellular ribonucleases (RNases) with antitumoral properties. However, the biological function of these toxic proteins has remained elusive. The discovery of the ribotoxin HtA, produced by the invertebrates pathogen Hirsutella thompsonii, revived the old proposal that insecticidal activity would be their long searched function. Unfortunately, HtA is rather singular among all ribotoxins known in terms of sequence and structure similarities. Thus, it was intriguing to answer the question of whether HtA is just an exception or, on the contrary, the paradigmatic example of the ribotoxins function. The work presented uses HtA and α-sarcin, the most representative member of the ribotoxins family, to show their strong toxic action against insect larvae and cells.
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Affiliation(s)
- Miriam Olombrada
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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34
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Mitkevich VA, Shyp V, Petrushanko IY, Soosaar A, Atkinson GC, Tenson T, Makarov AA, Hauryliuk V. GTPases IF2 and EF-G bind GDP and the SRL RNA in a mutually exclusive manner. Sci Rep 2012; 2:843. [PMID: 23150791 PMCID: PMC3496166 DOI: 10.1038/srep00843] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 10/17/2012] [Indexed: 01/05/2023] Open
Abstract
Translational GTPases (trGTPases) are involved in all four stages of protein biosynthesis: initiation, elongation, termination and ribosome recycling. The trGTPases Initiation Factor 2 (IF2) and Elongation Factor G (EF-G) respectively orchestrate initiation complex formation and translocation of the peptidyl-tRNA:mRNA complex through the bacterial ribosome. The ribosome regulates the GTPase cycle and efficiently discriminates between the GDP- and GTP-bound forms of these proteins. Using Isothermal Titration Calorimetry, we have investigated interactions of IF2 and EF-G with the sarcin-ricin loop of the 23S rRNA, a crucial element of the GTPase-associated center of the ribosome. We show that binding of IF2 and EF-G to a 27 nucleotide RNA fragment mimicking the sarcin-ricin loop is mutually exclusive with that of GDP, but not of GTP, providing a mechanism for destabilization of the ribosome-bound GDP forms of translational GTPases.
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Affiliation(s)
- Vladimir A Mitkevich
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia
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35
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Carreras-Sangrà N, Tomé-Amat J, García-Ortega L, Batt CA, Oñaderra M, Martínez-del-Pozo A, Gavilanes JG, Lacadena J. Production and characterization of a colon cancer-specific immunotoxin based on the fungal ribotoxin α-sarcin. Protein Eng Des Sel 2012; 25:425-35. [PMID: 22718791 DOI: 10.1093/protein/gzs032] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A single-chain fusion protein that directed the cytolytic activity of α-sarcin to A33 tumor antigen expressing cells was constructed and shown to effectively kill targeted cells. Glycoprotein A33 (GPA33) is a well-known colon cancer marker and a humanized antibody against it was used to target the α-sarcin. The fungal ribotoxin α-sarcin is one of the most potent and specific toxins known. It is small, protease resistant, thermostable and highly efficient towards the inactivation of ribosomes. This work describes the production and characterization of an immunotoxin resulting from fusing the single-chain variable fragment (scFv) of the monoclonal antibody that targets GPA33 to fungal α-sarcin. This chimeric protein (scFvA33αsarcin), produced in Pichia pastoris and purified in high yield was proven to be properly folded, active, specific and stable. It showed high specific toxicity against GPA33-positive tumoral cell lines providing scientific evidence to sustain that scFvA33αsarcin is a good immunotherapeutic candidate against GPA33-positive colon carcinomas.
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Affiliation(s)
- Nelson Carreras-Sangrà
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, 28040 Madrid, Spain
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36
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Shi X, Khade PK, Sanbonmatsu KY, Joseph S. Functional role of the sarcin-ricin loop of the 23S rRNA in the elongation cycle of protein synthesis. J Mol Biol 2012; 419:125-38. [PMID: 22459262 DOI: 10.1016/j.jmb.2012.03.016] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 03/10/2012] [Accepted: 03/17/2012] [Indexed: 11/19/2022]
Abstract
The sarcin-ricin loop (SRL) is one of the longest conserved sequences in the 23S ribosomal RNA. The SRL has been accepted as crucial for the activity of the ribosome because it is targeted by cytotoxins such as α-sarcin and ricin that completely abolish translation. Nevertheless, the precise functional role of the SRL in translation is not known. Recent biochemical and structural studies indicate that the SRL is critical for triggering GTP hydrolysis on elongation factor Tu (EF-Tu) and elongation factor G (EF-G). To determine the functional role of the SRL in the elongation stage of protein synthesis, we analyzed mutations in the SRL that are known to abolish protein synthesis and are lethal to cells. Here, we show that the SRL is not critical for GTP hydrolysis on EF-Tu and EF-G. The SRL also is not essential for peptide bond formation. Our results, instead, suggest that the SRL is crucial for anchoring EF-G on the ribosome during mRNA-tRNA translocation.
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MESH Headings
- Binding Sites
- Conserved Sequence
- Endoribonucleases/metabolism
- Escherichia coli/genetics
- Fungal Proteins/metabolism
- Guanosine Triphosphate/metabolism
- Mutation
- Nucleic Acid Conformation
- Peptide Chain Elongation, Translational
- Peptide Elongation Factor G/chemistry
- Peptide Elongation Factor G/genetics
- Peptide Elongation Factor G/metabolism
- Peptide Elongation Factor Tu/chemistry
- Peptide Elongation Factor Tu/genetics
- Peptide Elongation Factor Tu/metabolism
- Protein Binding
- Protein Biosynthesis
- Protein Structure, Secondary
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/metabolism
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Ribosomal, 23S/chemistry
- RNA, Ribosomal, 23S/genetics
- RNA, Ribosomal, 23S/metabolism
- RNA, Transfer/metabolism
- Ribosomes/genetics
- Ribosomes/metabolism
- Ricin/metabolism
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Affiliation(s)
- Xinying Shi
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0314, USA
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37
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Abstract
Ricin and Shiga toxins designated as ribosome inactivating proteins (RIPs) are RNA N-glycosidases that depurinate a specific adenine (A₄₃₂₄ in rat 28S rRNA) in the conserved α-sarcin/ricin loop of the large rRNA, inhibiting protein synthesis. Evidence obtained from a number of studies suggests that interaction with ribosomal proteins plays an important role in the catalytic activity and ribosome specificity of RIPs. This review summarizes the recent developments in identification of the ribosomal proteins that interact with ricin and Shiga toxins and the principles governing these interactions.
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Affiliation(s)
- Nilgun E Tumer
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520, USA.
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38
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Álvarez-García E, Diago-Navarro E, Herrero-Galán E, García-Ortega L, López-Villarejo J, Olmo N, Díaz-Orejas R, Gavilanes JG, Martínez-del-Pozo Á. The ribonucleolytic activity of the ribotoxin α-sarcin is not essential for in vitro protein biosynthesis inhibition. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1377-82. [DOI: 10.1016/j.bbapap.2011.06.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 06/21/2011] [Accepted: 06/29/2011] [Indexed: 11/16/2022]
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39
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Herrero-Galán E, García-Ortega L, Lacadena J, Martínez-Del-Pozo A, Olmo N, Gavilanes JG, Oñaderra M. Implication of an Asp residue in the ribonucleolytic activity of hirsutellin A reveals new electrostatic interactions at the active site of ribotoxins. Biochimie 2011; 94:427-33. [PMID: 21871524 DOI: 10.1016/j.biochi.2011.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 08/15/2011] [Indexed: 10/17/2022]
Abstract
Ribotoxins are fungal extracellular ribonucleases that specifically cleave ribosomes leading to cell-death via apoptosis. α-Sarcin is the ribotoxin studied in deepest detail, and therefore constitutes the referential protein for the whole family. It has been demonstrated that ribotoxin activity depends on a very precise structural microenvironment in which electrostatic interactions among residues in the active site are of the highest importance. Hirsutellin A (HtA) has been recently described as the smallest ribotoxin known to date, encompassing all the abilities of previously characterized members of this family into a shorter sequence. Comparison of HtA and α-sarcin three-dimensional structures suggested that residues presumably forming the catalytic triad of HtA would be His 42, Glu 66, and His 113. Within this same idea, the presence of an Asp residue (Asp 40) in a position equivalent to α-sarcin Tyr 48 is highlighted as a novelty in this field. In this work, substitution mutants H42Q, E66Q and H113Q, as well as double and triple mutants in all possible combinations, are studied regarding their ribonucleolytic activity and cytotoxicity. Implication of these three residues in the ribotoxin activity of HtA is confirmed, though none of them is strictly essential for ribosomal cleavage. Studies with mutants D40N and D40N/E66Q demonstrate an important role for Asp 40 in the activity of HtA and establish a new set of electrostatic interactions different from the one described for already known ribotoxins.
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Affiliation(s)
- Elías Herrero-Galán
- Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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40
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Zhabokritsky A, Kutky M, Burns LA, Karran RA, Hudak KA. RNA toxins: mediators of stress adaptation and pathogen defense. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:890-903. [PMID: 21809449 DOI: 10.1002/wrna.99] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
RNA toxins are a group of enzymes primarily synthesized by bacteria, fungi, and plants that either cleave or depurinate RNA molecules. These proteins may be divided according to their RNA substrates: ribotoxins are nucleases that cleave ribosomal RNA (rRNA), ribosome inactivating proteins are glycosidases that remove a base from rRNA, messenger RNA (mRNA) interferases are nucleases that cleave mRNAs, and anticodon nucleases cleave transfer RNAs (tRNAs). These modifications to the RNAs may substantially alter gene expression and translation rates. Given that some of these enzymes cause cell death, it has been suggested that they function mainly in defense, either to kill competing cells or to elicit suicide and thereby limit pathogen spread from infected cells. Although good correlations have been drawn between their enzymatic functions and toxicity, recent work has shown that some RNA toxins cause apoptosis in the absence of damage to RNA and that defense against pathogens can be achieved without host cell death. Moreover, a decrease in cellular translation rate, insufficient to cause cell death, allows some organisms to adapt to stress and environmental change. Although ascribing effects observed in vitro to the roles of these toxins in nature has been challenging, recent results have expanded our understanding of their modes of action, and emphasized the importance of these toxins in development, adaptation to stress and defense against pathogens.
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41
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Atkinson GC, Baldauf SL. Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms. Mol Biol Evol 2010; 28:1281-92. [PMID: 21097998 DOI: 10.1093/molbev/msq316] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Protein synthesis elongation factor G (EF-G) is an essential protein with central roles in both the elongation and ribosome recycling phases of protein synthesis. Although EF-G evolution is predicted to be conservative, recent reports suggest otherwise. We have characterized EF-G in terms of its molecular phylogeny, genomic context, and patterns of amino acid substitution. We find that most bacteria carry a single "canonical" EF-G, which is phylogenetically conservative and encoded in an str operon. However, we also find a number of EF-G paralogs. These include a pair of EF-Gs that are mostly found together and in an eclectic subset of bacteria, specifically δ-proteobacteria, spirochaetes, and planctomycetes (the "spd" bacteria). These spdEFGs have also given rise to the mitochondrial factors mtEFG1 and mtEFG2, which probably arrived in eukaryotes before the eukaryotic last common ancestor. Meanwhile, chloroplasts apparently use an α-proteobacterial-derived EF-G rather than the expected cyanobacterial form. The long-term comaintenance of the spd/mtEFGs may be related to their subfunctionalization for translocation and ribosome recycling. Consistent with this, patterns of sequence conservation and site-specific evolutionary rate shifts suggest that the faster evolving spd/mtEFG2 has lost translocation function, but surprisingly, the protein also shows little conservation of sites related to recycling activity. On the other hand, spd/mtEFG1, although more slowly evolving, shows signs of substantial remodeling. This is particularly extensive in the GTPase domain, including a highly conserved three amino acid insertion in switch I. We suggest that subfunctionalization of the spd/mtEFGs is not a simple case of specialization for subsets of original activities. Rather, the duplication allows the release of one paralog from the selective constraints imposed by dual functionality, thus allowing it to become more highly specialized. Thus, the potential for fine tuning afforded by subfunctionalization may explain the maintenance of EF-G paralogs.
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Affiliation(s)
- Gemma C Atkinson
- Department of Systematic Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
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