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Khan MA, Malik A, Domashevskiy AV, San A, Khan JM. Interaction of ferritin iron responsive element (IRE) mRNA with translation initiation factor eIF4F. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020; 243:118776. [PMID: 32829157 DOI: 10.1016/j.saa.2020.118776] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 07/26/2020] [Accepted: 07/26/2020] [Indexed: 06/11/2023]
Abstract
The interaction of ferritin iron responsive element (IRE) mRNA with eIF4F was examined by fluorescence and circular dichroism spectroscopy. Fluorescence quenching data indicated that eIF4F contains one high affinity binding site for ferritin IRE RNA. The Scatchard analysis revealed strong binding affinity (Ka = 11.1 × 107 M-1) and binding capacity (n = 1.0) between IRE RNA and eIF4F. The binding affinity of IRE RNA for eIF4F decreased (~4-fold) as temperature increased (from 5 °C to 30 °C). The van't Hoff analysis revealed that IRE RNA binding to eIF4F is enthalpy-driven (ΔH = -47.1 ± 3.4 kJ/mol) and entropy-opposed (ΔS = -30.1 ± 1.5 J/mol/K). The addition of iron increased the enthalpic, while decreasing the entropic contribution towards the eIF4F•IRE RNA complex, resulting in favorable free energy (ΔG = -49.8 ± 2.8 kJ/mol). Thermodynamic values and ionic strength data suggest that the presence of iron increases hydrogen bonding and decreases hydrophobic interactions, leading to formation of a more stable complex. The interaction of IRE RNA with eIF4F at higher concentrations produced significant changes in the secondary structure of the protein, as revealed from the far-UV CD results, clearly illustrating the structural alterations resulted from formation of the eIF4F•IRE RNA complex. A Lineweaver-Burk plot showed an uncompetitive binding behavior between IRE RNA and m7G cap for the eIF4F, indicating that there are different binding sites on the eIF4F for the IRE RNA and the cap analog; molecular docking analysis further supports this notion. Our findings suggest that the eIF4F•IRE RNA complex formation is accompanied by an elevated hydrogen bonding and weakened hydrophobic interactions, leading to an overall conformational change, favored in terms of its free energy. The conformational change in the eIF4F structure, caused by the IRE RNA binding, provides a more stable platform for effective IRE translation in iron homeostasis.
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Affiliation(s)
- Mateen A Khan
- Department of Life Sciences, College of Science & General Studies, Alfaisal University, Riyadh, Saudi Arabia.
| | - Ajamaluddin Malik
- Department of Biochemistry, Protein Research Laboratory, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Artem V Domashevskiy
- Department of Sciences, John Jay College of Criminal Justice, The City University of New York, New York, NY 10019, USA
| | - Avdar San
- Department of Chemistry, Brooklyn College of the City University of New York, NY, New York, USA
| | - Javed M Khan
- Department of Food Science and Nutrition, Faculty of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
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Aitbakieva VR, Ahmad R, Singh S, Domashevskiy AV. Inhibition of ricin A-chain (RTA) catalytic activity by a viral genome-linked protein (VPg). BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:645-653. [PMID: 30822539 DOI: 10.1016/j.bbapap.2019.02.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 02/04/2019] [Accepted: 02/13/2019] [Indexed: 12/01/2022]
Abstract
Ricin is a plant derived protein toxin produced by the castor bean plant (Ricinus communis). The Centers for Disease Control (CDC) classifies ricin as a Category B biological agent. Currently, there is neither an effective vaccine that can be used to protect against ricin exposure nor a therapeutic to reverse the effects once exposed. Here we quantitatively characterize interactions between catalytic ricin A-chain (RTA) and a viral genome-linked protein (VPg) from turnip mosaic virus (TuMV). VPg and its N-terminal truncated variant, VPg1-110, bind to RTA and abolish ricin's catalytic depurination of 28S rRNA in vitro and in a cell-free rabbit reticulocyte translational system. RTA and VPg bind in a 1 to 1 stoichiometric ratio, and their binding affinity increases ten-fold as temperature elevates (5 °C to 37 °C). RTA-VPg binary complex formation is enthalpically driven and favored by entropy, resulting in an overall favorable energy, ΔG = -136.8 kJ/mol. Molecular modeling supports our experimental observations and predicts a major contribution of electrostatic interactions, suggesting an allosteric mechanism of downregulation of RTA activity through conformational changes in RTA structure, and/or disruption of binding with the ribosomal stalk. Fluorescence anisotropy studies show that heat affects the rate constant and the activation energy for the RTA-VPg complex, Ea = -62.1 kJ/mol. The thermodynamic and kinetic findings presented here are an initial lead study with promising results and provides a rational approach for synthesis of therapeutic peptides that successfully eliminate toxicity of ricin, and other cytotoxic RIPs.
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Affiliation(s)
- Valentina R Aitbakieva
- Department of Sciences, John Jay College of Criminal Justice, the City University of New York, New York 10019, NY, United States of America
| | - Rahimah Ahmad
- Department of Biology, Brooklyn College, The City University of New York, Brooklyn, New York 11210, United States of America
| | - Shaneen Singh
- Department of Biology, Brooklyn College, The City University of New York, Brooklyn, New York 11210, United States of America
| | - Artem V Domashevskiy
- Department of Sciences, John Jay College of Criminal Justice, the City University of New York, New York 10019, NY, United States of America.
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Domashevskiy AV, Rodriguez DJ, Gunawardana D, Goss DJ. Preparation of Functional, Fluorescently Labeled mRNA Capped with Anthraniloyl-m(7)GpppG. Methods Mol Biol 2017; 1428:61-75. [PMID: 27236792 DOI: 10.1007/978-1-4939-3625-0_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Fluorescent mRNA molecules offer a wide range of applications for studying capping/decapping reactions, translation, and other biophysical studies. Furthermore, fluorescent tags prove invaluable for tracking RNA molecules in cells. Here, we describe an efficient synthesis of a fluorescent cap analog, anthranioyl-GTP, its purification, and in vitro cap labeling of transcribed mRNA catalyzed by the recombinant vaccinia capping enzyme to produce anthranioyl-m(7)GpppG-capped RNA.
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Affiliation(s)
- Artem V Domashevskiy
- Department of Sciences, John Jay College of Criminal Justice, City University of New York, New York, NY, USA.
| | - David J Rodriguez
- Department of Sciences, John Jay College of Criminal Justice, City University of New York, New York, NY, USA
| | - Dilantha Gunawardana
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia.,Department of Botany, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Dixie J Goss
- Department of Chemistry, Hunter College, City University of New York, New York, NY, USA
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Domashevskiy AV, Williams S, Kluge C, Cheng SY. Plant Translation Initiation Complex eIFiso4F Directs Pokeweed Antiviral Protein to Selectively Depurinate Uncapped Tobacco Etch Virus RNA. Biochemistry 2017; 56:5980-5990. [PMID: 29064680 DOI: 10.1021/acs.biochem.7b00598] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Pokeweed antiviral protein (PAP) is a ribosome inactivating protein (RIP) that depurinates the sarcin/ricin loop (SRL) of rRNA, inhibiting protein synthesis. PAP depurinates viral RNA, and in doing so, lowers the infectivity of many plant viruses. The mechanism by which PAP accesses uncapped viral RNA is not known, impeding scientists from developing effective antiviral agents for the prevention of the diseases caused by uncapped RNA viruses. Kinetic rates of PAP interacting with tobacco etch virus (TEV) RNA, in the presence and absence of eIFiso4F, were examined, addressing how the eIF affects selective PAP targeting and depurination of the uncapped viral RNA. PAP-eIFs copurification assay and fluorescence resonance energy transfer demonstrate that PAP forms a ternary complex with the eIFiso4G and eIFiso4E, directing the depurination of uncapped viral RNA. eIFiso4F selectively targets PAP to depurinate TEV RNA by increasing PAP's specificity constant for uncapped viral RNA 12-fold, when compared to the depurination of an oligonucleotide RNA that mimics the SRL of large rRNA, and cellular capped luciferase mRNA. This explains how PAP is able to lower infectivity of pokeweed viruses, while preserving its own ribosomes and cellular RNA from depurination: PAP utilizes cellular eIFiso4F in a novel strategy to target uncapped viral RNA. It may be possible to modulate and utilize these PAP-eIFs interactions for their public health benefit; by repurposing them to selectively target PAP to depurinate uncapped viral RNA, many plant and animal diseases caused by these viruses could be alleviated.
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Affiliation(s)
- Artem V Domashevskiy
- Department of Sciences, John Jay College of Criminal Justice, the City University of New York , New York, New York 10019, United States
| | - Shawn Williams
- Department of Sciences, John Jay College of Criminal Justice, the City University of New York , New York, New York 10019, United States
| | - Christopher Kluge
- Department of Sciences, John Jay College of Criminal Justice, the City University of New York , New York, New York 10019, United States
| | - Shu-Yuan Cheng
- Department of Sciences, John Jay College of Criminal Justice, the City University of New York , New York, New York 10019, United States
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Di R, Tumer NE. Pokeweed antiviral protein: its cytotoxicity mechanism and applications in plant disease resistance. Toxins (Basel) 2015; 7:755-72. [PMID: 25756953 PMCID: PMC4379523 DOI: 10.3390/toxins7030755] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Revised: 02/11/2015] [Accepted: 03/02/2015] [Indexed: 11/16/2022] Open
Abstract
Pokeweed antiviral protein (PAP) is a 29 kDa type I ribosome inactivating protein (RIP) found in pokeweed plants. Pokeweed produces different forms of PAP. This review focuses on the spring form of PAP isolated from Phytolacca americana leaves. PAP exerts its cytotoxicity by removing a specific adenine from the α-sarcin/ricin loop of the large ribosomal RNA. Besides depurination of the rRNA, PAP has additional activities that contribute to its cytotoxicity. The mechanism of PAP cytotoxicity is summarized based on evidence from the analysis of transgenic plants and the yeast model system. PAP was initially found to be anti-viral when it was co-inoculated with plant viruses onto plants. Transgenic plants expressing PAP and non-toxic PAP mutants have displayed broad-spectrum resistance to both viral and fungal infection. The mechanism of PAP-induced disease resistance in transgenic plants is summarized.
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Affiliation(s)
- Rong Di
- Department of Plant Biology and Pathology, Rutgers, the State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, USA.
| | - Nilgun E Tumer
- Department of Plant Biology and Pathology, Rutgers, the State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, USA.
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Domashevskiy AV, Goss DJ. Pokeweed antiviral protein, a ribosome inactivating protein: activity, inhibition and prospects. Toxins (Basel) 2015; 7:274-98. [PMID: 25635465 PMCID: PMC4344624 DOI: 10.3390/toxins7020274] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/07/2015] [Accepted: 01/23/2015] [Indexed: 01/30/2023] Open
Abstract
Viruses employ an array of elaborate strategies to overcome plant defense mechanisms and must adapt to the requirements of the host translational systems. Pokeweed antiviral protein (PAP) from Phytolacca americana is a ribosome inactivating protein (RIP) and is an RNA N-glycosidase that removes specific purine residues from the sarcin/ricin (S/R) loop of large rRNA, arresting protein synthesis at the translocation step. PAP is thought to play an important role in the plant's defense mechanism against foreign pathogens. This review focuses on the structure, function, and the relationship of PAP to other RIPs, discusses molecular aspects of PAP antiviral activity, the novel inhibition of this plant toxin by a virus counteraction-a peptide linked to the viral genome (VPg), and possible applications of RIP-conjugated immunotoxins in cancer therapeutics.
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MESH Headings
- Animals
- Binding Sites
- Endoribonucleases/chemistry
- Fungal Proteins/chemistry
- Genome, Viral
- Humans
- Protein Isoforms
- RNA Caps/chemistry
- RNA Caps/genetics
- RNA Caps/metabolism
- RNA, Plant/chemistry
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Ribosome Inactivating Proteins, Type 1/chemistry
- Ribosome Inactivating Proteins, Type 1/genetics
- Ribosome Inactivating Proteins, Type 1/metabolism
- Ribosome Inactivating Proteins, Type 1/pharmacology
- Ribosomes/chemistry
- Ribosomes/metabolism
- Ricin/chemistry
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Affiliation(s)
- Artem V Domashevskiy
- John Jay College of Criminal Justice, Department of Sciences, City University of New York, 524 West 59th Street, New York, NY 10019, USA.
| | - Dixie J Goss
- Department of Chemistry, Hunter College, City University of New York and the Graduate Center, 695 Park Avenue, New York, NY 10065, USA.
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Kushwaha GS, Yamini S, Kumar M, Sinha M, Kaur P, Sharma S, Singh TP. First structural evidence of sequestration of mRNA cap structures by type 1 ribosome inactivating protein from Momordica balsamina. Proteins 2013; 81:896-905. [PMID: 23280611 DOI: 10.1002/prot.24248] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 12/06/2012] [Accepted: 12/17/2012] [Indexed: 12/17/2022]
Abstract
This is the first structural evidence of recognition of mRNA cap structures by a ribosome inactivating protein. It is well known that a unique cap structure is formed at the 5' end of mRNA for carrying out various processes including mRNA maturation, translation initiation, and RNA turnover. The binding studies and crystal structure determinations of type 1 ribosome inactivating protein (RIP-1) from Momordica balsamina (MbRIP-1) were carried out with mRNA cap structures including (i) N7-methyl guanine (m7G), (ii) N7-methyl guanosine diphosphate (m7GDP), and (iii) N7-methyl guanosine triphosphate (m7GTP). These compounds showed affinities to MbRIP-1 at nanomolar concentrations. The structure determinations of the complexes of MbRIP-1 with m7G, m7GDP, and m7GTP at 2.65, 1.77, and 1.75 Å resolutions revealed that all the three compounds bound to MbRIP-1 in the substrate binding site at the positions which are slightly shifted towards Glu85 as compared to those of rRNA substrates. In this position, Glu85 forms several hydrogen bonds with guanine moiety while N-7 methyl group forms van der Waals contacts. However, the guanine rings are poorly stacked in these complexes. Thus, the mode of binding by MbRIP-1 to mRNA cap structures is different which results in the inhibition of depurination. Since some viruses are known to exploit the capping property of the host, this action of MbRIP-1 may have implications for the antiviral activity of this protein in vivo. The understanding of the mode of binding of MbRIP-1 to cap structures may also assist in the design of anti-viral agents.
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Domashevskiy AV, Miyoshi H, Goss DJ. Inhibition of pokeweed antiviral protein (PAP) by turnip mosaic virus genome-linked protein (VPg). J Biol Chem 2012; 287:29729-38. [PMID: 22773840 DOI: 10.1074/jbc.m112.367581] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pokeweed antiviral protein (PAP) from Phytolacca americana is a ribosome-inactivating protein (RIP) and an RNA N-glycosidase that removes specific purine residues from the sarcin/ricin loop of large rRNA, arresting protein synthesis at the translocation step. PAP is also a cap-binding protein and is a potent antiviral agent against many plant, animal, and human viruses. To elucidate the mechanism of RNA depurination, and to understand how PAP recognizes and targets various RNAs, the interactions between PAP and turnip mosaic virus genome-linked protein (VPg) were investigated. VPg can function as a cap analog in cap-independent translation and potentially target PAP to uncapped IRES-containing RNA. In this work, fluorescence spectroscopy and HPLC techniques were used to quantitatively describe PAP depurination activity and PAP-VPg interactions. PAP binds to VPg with high affinity (29.5 nm); the reaction is enthalpically driven and entropically favored. Further, VPg is a potent inhibitor of PAP depurination of RNA in wheat germ lysate and competes with structured RNA derived from tobacco etch virus for PAP binding. VPg may confer an evolutionary advantage by suppressing one of the plant defense mechanisms and also suggests the possible use of this protein against the cytotoxic activity of ribosome-inactivating proteins.
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Affiliation(s)
- Artem V Domashevskiy
- Department of Chemistry, Hunter College and the Graduate Center of the City University of New York, New York, NY 10065, USA
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