1
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Smith PR, Loerch S, Kunder N, Stanowick AD, Lou TF, Campbell ZT. Functionally distinct roles for eEF2K in the control of ribosome availability and p-body abundance. Nat Commun 2021; 12:6789. [PMID: 34815424 PMCID: PMC8611098 DOI: 10.1038/s41467-021-27160-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 11/07/2021] [Indexed: 11/09/2022] Open
Abstract
Processing bodies (p-bodies) are a prototypical phase-separated RNA-containing granule. Their abundance is highly dynamic and has been linked to translation. Yet, the molecular mechanisms responsible for coordinate control of the two processes are unclear. Here, we uncover key roles for eEF2 kinase (eEF2K) in the control of ribosome availability and p-body abundance. eEF2K acts on a sole known substrate, eEF2, to inhibit translation. We find that the eEF2K agonist nelfinavir abolishes p-bodies in sensory neurons and impairs translation. To probe the latter, we used cryo-electron microscopy. Nelfinavir stabilizes vacant 80S ribosomes. They contain SERBP1 in place of mRNA and eEF2 in the acceptor site. Phosphorylated eEF2 associates with inactive ribosomes that resist splitting in vitro. Collectively, the data suggest that eEF2K defines a population of inactive ribosomes resistant to recycling and protected from degradation. Thus, eEF2K activity is central to both p-body abundance and ribosome availability in sensory neurons.
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Affiliation(s)
- Patrick R. Smith
- grid.267323.10000 0001 2151 7939The University of Texas at Dallas, Department of Biological Sciences, Richardson, TX USA
| | - Sarah Loerch
- grid.443970.dJanelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA USA ,grid.205975.c0000 0001 0740 6917University of California, Santa Cruz, Department of Chemistry and Biochemistry, Santa Cruz, CA USA
| | - Nikesh Kunder
- grid.267323.10000 0001 2151 7939The University of Texas at Dallas, Department of Biological Sciences, Richardson, TX USA
| | - Alexander D. Stanowick
- grid.267323.10000 0001 2151 7939The University of Texas at Dallas, Department of Biological Sciences, Richardson, TX USA
| | - Tzu-Fang Lou
- grid.267323.10000 0001 2151 7939The University of Texas at Dallas, Department of Biological Sciences, Richardson, TX USA
| | - Zachary T. Campbell
- grid.267323.10000 0001 2151 7939The University of Texas at Dallas, Department of Biological Sciences, Richardson, TX USA ,grid.267323.10000 0001 2151 7939The Center for Advanced Pain Studies (CAPS), University of Texas at Dallas, Richardson, TX USA
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2
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Ranjan N, Pochopien AA, Chih-Chien Wu C, Beckert B, Blanchet S, Green R, V Rodnina M, Wilson DN. Yeast translation elongation factor eEF3 promotes late stages of tRNA translocation. EMBO J 2021; 40:e106449. [PMID: 33555093 PMCID: PMC7957392 DOI: 10.15252/embj.2020106449] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 12/10/2020] [Accepted: 12/21/2020] [Indexed: 11/21/2022] Open
Abstract
In addition to the conserved translation elongation factors eEF1A and eEF2, fungi require a third essential elongation factor, eEF3. While eEF3 has been implicated in tRNA binding and release at the ribosomal A and E sites, its exact mechanism of action is unclear. Here, we show that eEF3 acts at the mRNA–tRNA translocation step by promoting the dissociation of the tRNA from the E site, but independent of aminoacyl‐tRNA recruitment to the A site. Depletion of eEF3 in vivo leads to a general slowdown in translation elongation due to accumulation of ribosomes with an occupied A site. Cryo‐EM analysis of native eEF3‐ribosome complexes shows that eEF3 facilitates late steps of translocation by favoring non‐rotated ribosomal states, as well as by opening the L1 stalk to release the E‐site tRNA. Additionally, our analysis provides structural insights into novel translation elongation states, enabling presentation of a revised yeast translation elongation cycle.
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Affiliation(s)
- Namit Ranjan
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Agnieszka A Pochopien
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Munich, Germany.,Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Colin Chih-Chien Wu
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Bertrand Beckert
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Sandra Blanchet
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel N Wilson
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Munich, Germany.,Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
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3
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Li W, Agrawal RK. Joachim Frank's Binding with the Ribosome. Structure 2019; 27:411-419. [PMID: 30595455 PMCID: PMC11062599 DOI: 10.1016/j.str.2018.11.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/09/2018] [Accepted: 11/15/2018] [Indexed: 01/03/2023]
Abstract
With recent technological advancements, single-particle cryogenic electron microscopy (cryo-EM) is now the technique of choice to study structure and function of biological macromolecules at near-atomic resolution. Many single-particle EM reconstruction methods necessary for these advances were pioneered by Joachim Frank, and were optimized using the ribosome as a benchmark specimen. In doing so, he made several landmark contributions to the understanding of the structure and function of ribosomes. These include the first 3D visualization of ribosome-bound transfer RNAs, the first experimentally derived structures of the primary complexes formed during the bacterial translation elongation cycle, and the critical ribosomal conformational transitions required for translation. Over the years, his laboratory studied many important functional complexes of the ribosome from both eubacterial and eukaryotic systems, including ribosomes from pathogenic organisms. This article presents a brief account of the contributions made by Joachim Frank to the ribosome field.
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Affiliation(s)
- Wen Li
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
| | - Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA; Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, NY, USA.
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4
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Pellegrino S, Demeshkina N, Mancera-Martinez E, Melnikov S, Simonetti A, Myasnikov A, Yusupov M, Yusupova G, Hashem Y. Structural Insights into the Role of Diphthamide on Elongation Factor 2 in mRNA Reading-Frame Maintenance. J Mol Biol 2018; 430:2677-2687. [PMID: 29886014 DOI: 10.1016/j.jmb.2018.06.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 05/11/2018] [Accepted: 06/04/2018] [Indexed: 01/27/2023]
Abstract
One of the most critical steps of protein biosynthesis is the coupled movement of mRNA, which encodes genetic information, with tRNAs on the ribosome. In eukaryotes, this process is catalyzed by a conserved G-protein, the elongation factor 2 (eEF2), which carries a unique post-translational modification, called diphthamide, found in all eukaryotic species. Here we present near-atomic resolution cryo-electron microscopy structures of yeast 80S ribosome complexes containing mRNA, tRNA and eEF2 trapped in different GTP-hydrolysis states which provide further structural insights into the role of diphthamide in the mechanism of translation fidelity in eukaryotes.
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Affiliation(s)
- Simone Pellegrino
- Department of Integrated Structural Biology, Institute of Genetics and Molecular and Cellular Biology, CNRS UMR710, INSERM U964, University of Strasbourg, Strasbourg 67000, France
| | - Natalia Demeshkina
- Department of Integrated Structural Biology, Institute of Genetics and Molecular and Cellular Biology, CNRS UMR710, INSERM U964, University of Strasbourg, Strasbourg 67000, France
| | - Eder Mancera-Martinez
- Architecture and Reactivity of RNA, University of Strasbourg, Institute of Molecular and Cellular Biology of the CNRS UPR9002, Strasbourg 67084, France
| | - Sergey Melnikov
- Department of Integrated Structural Biology, Institute of Genetics and Molecular and Cellular Biology, CNRS UMR710, INSERM U964, University of Strasbourg, Strasbourg 67000, France
| | - Angelita Simonetti
- Architecture and Reactivity of RNA, University of Strasbourg, Institute of Molecular and Cellular Biology of the CNRS UPR9002, Strasbourg 67084, France
| | - Alexander Myasnikov
- Department of Integrated Structural Biology, Institute of Genetics and Molecular and Cellular Biology, CNRS UMR710, INSERM U964, University of Strasbourg, Strasbourg 67000, France
| | - Marat Yusupov
- Department of Integrated Structural Biology, Institute of Genetics and Molecular and Cellular Biology, CNRS UMR710, INSERM U964, University of Strasbourg, Strasbourg 67000, France; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Russia.
| | - Gulnara Yusupova
- Department of Integrated Structural Biology, Institute of Genetics and Molecular and Cellular Biology, CNRS UMR710, INSERM U964, University of Strasbourg, Strasbourg 67000, France.
| | - Yaser Hashem
- ARNA, U1212 Université de Bordeaux, Institut Européen de Chimie et de Biologie (IECB) Inserm, Pessac 33600, France.
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5
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Abeyrathne PD, Koh CS, Grant T, Grigorieff N, Korostelev AA. Ensemble cryo-EM uncovers inchworm-like translocation of a viral IRES through the ribosome. eLife 2016; 5. [PMID: 27159452 PMCID: PMC4896748 DOI: 10.7554/elife.14874] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 05/08/2016] [Indexed: 12/17/2022] Open
Abstract
Internal ribosome entry sites (IRESs) mediate cap-independent translation of viral mRNAs. Using electron cryo-microscopy of a single specimen, we present five ribosome structures formed with the Taura syndrome virus IRES and translocase eEF2•GTP bound with sordarin. The structures suggest a trajectory of IRES translocation, required for translation initiation, and provide an unprecedented view of eEF2 dynamics. The IRES rearranges from extended to bent to extended conformations. This inchworm-like movement is coupled with ribosomal inter-subunit rotation and 40S head swivel. eEF2, attached to the 60S subunit, slides along the rotating 40S subunit to enter the A site. Its diphthamide-bearing tip at domain IV separates the tRNA-mRNA-like pseudoknot I (PKI) of the IRES from the decoding center. This unlocks 40S domains, facilitating head swivel and biasing IRES translocation via hitherto-elusive intermediates with PKI captured between the A and P sites. The structures suggest missing links in our understanding of tRNA translocation.
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Affiliation(s)
| | - Cha San Koh
- RNA Therapeutics Institute, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States
| | - Timothy Grant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Nikolaus Grigorieff
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Andrei A Korostelev
- RNA Therapeutics Institute, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States
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6
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Kostopoulou ON, Kouvela EC, Magoulas GE, Garnelis T, Panagoulias I, Rodi M, Papadopoulos G, Mouzaki A, Dinos GP, Papaioannou D, Kalpaxis DL. Conjugation with polyamines enhances the antibacterial and anticancer activity of chloramphenicol. Nucleic Acids Res 2014; 42:8621-34. [PMID: 24939899 PMCID: PMC4117768 DOI: 10.1093/nar/gku539] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chloramphenicol (CAM) is a broad-spectrum antibiotic, limited to occasional only use in developed countries because of its potential toxicity. To explore the influence of polyamines on the uptake and activity of CAM into cells, a series of polyamine–CAM conjugates were synthesized. Both polyamine architecture and the position of CAM-scaffold substitution were crucial in augmenting the antibacterial and anticancer potency of the synthesized conjugates. Compounds 4 and 5, prepared by replacement of dichloro-acetyl group of CAM with succinic acid attached to N4 and N1 positions of N8,N8-dibenzylspermidine, respectively, exhibited higher activity than CAM in inhibiting the puromycin reaction in a bacterial cell-free system. Kinetic and footprinting analysis revealed that whereas the CAM-scaffold preserved its role in competing with the binding of aminoacyl-tRNA 3′-terminus to ribosomal A-site, the polyamine-tail could interfere with the rotatory motion of aminoacyl-tRNA 3′-terminus toward the P-site. Compared to CAM, compounds 4 and 5 exhibited comparable or improved antibacterial activity, particularly against CAM-resistant strains. Compound 4 also possessed enhanced toxicity against human cancer cells, and lower toxicity against healthy human cells. Thus, the designed conjugates proved to be suitable tools in investigating the ribosomal catalytic center plasticity and some of them exhibited greater efficacy than CAM itself.
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Affiliation(s)
- Ourania N Kostopoulou
- Department of Biochemistry, School of Medicine, University of Patras, GR-26504 Patras, Greece
| | - Ekaterini C Kouvela
- Department of Biochemistry, School of Medicine, University of Patras, GR-26504 Patras, Greece
| | - George E Magoulas
- Division of Hematology, Department of Internal Medicine, School of Medicine, University of Patras, GR-26504 Patras, Greece
| | - Thomas Garnelis
- Division of Hematology, Department of Internal Medicine, School of Medicine, University of Patras, GR-26504 Patras, Greece
| | - Ioannis Panagoulias
- Laboratory of Synthetic Organic Chemistry, Department of Chemistry, University of Patras, GR-26504 Patras, Greece
| | - Maria Rodi
- Laboratory of Synthetic Organic Chemistry, Department of Chemistry, University of Patras, GR-26504 Patras, Greece
| | - Georgios Papadopoulos
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26, GR-41221 Larissa, Greece
| | - Athanasia Mouzaki
- Laboratory of Synthetic Organic Chemistry, Department of Chemistry, University of Patras, GR-26504 Patras, Greece
| | - George P Dinos
- Department of Biochemistry, School of Medicine, University of Patras, GR-26504 Patras, Greece
| | - Dionissios Papaioannou
- Division of Hematology, Department of Internal Medicine, School of Medicine, University of Patras, GR-26504 Patras, Greece
| | - Dimitrios L Kalpaxis
- Department of Biochemistry, School of Medicine, University of Patras, GR-26504 Patras, Greece
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7
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Structure of EF-G-ribosome complex in a pretranslocation state. Nat Struct Mol Biol 2013; 20:1077-84. [PMID: 23912278 DOI: 10.1038/nsmb.2645] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 07/09/2013] [Indexed: 11/08/2022]
Abstract
In protein synthesis, elongation factor G (EF-G) facilitates movement of tRNA-mRNA by one codon, which is coupled to the ratchet-like rotation of the ribosome complex and is triggered by EF-G-mediated GTP hydrolysis. Here we report the structure of a pretranslocational ribosome bound to Thermus thermophilus EF-G trapped with a GTP analog. The positioning of the catalytic His87 into the active site coupled to hydrophobic-gate opening involves the 23S rRNA sarcin-ricin loop and domain III of EF-G and provides a structural basis for the GTPase activation of EF-G. Interactions of the hybrid peptidyl-site-exit-site tRNA with ribosomal elements, including the entire L1 stalk and proteins S13 and S19, shed light on how formation and stabilization of the hybrid tRNA is coupled to head swiveling and body rotation of the 30S as well as to closure of the L1 stalk.
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8
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Affiliation(s)
| | - V. Ramakrishnan
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom; ,
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9
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Sahu B, Khade PK, Joseph S. Functional replacement of two highly conserved tetraloops in the bacterial ribosome. Biochemistry 2012; 51:7618-26. [PMID: 22938718 DOI: 10.1021/bi300930r] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ribosomes are RNA-protein complexes responsible for protein synthesis. A dominant structural motif in the rRNAs is an RNA helix capped with a four-nucleotide loop, called a tetraloop. The sequence of the tetraloop is invariant at some positions in the rRNAs but is highly variable at other positions. The biological reason for the conservation of the tetraloop sequence at specific positions in the rRNAs is not clear. In the 16S rRNA, the GAAA tetraloop in helix 8 and the UACG tetraloop in helix 14 are highly conserved and located near the binding site for EF-Tu and EF-G. To investigate whether the structural stability of the tetraloop or the precise sequence of the tetraloop is important for function, we separately changed the GAAA tetraloop in helix 8 to a UACG tetraloop and the UACG tetraloop in helix 14 to a GAAA tetraloop. The effects of the tetraloop replacements on protein synthesis were analyzed in vivo and in vitro. Replacement of the tetraloops in helices 8 and 14 did not significantly affect the growth rate of the Escherichia coli (Δ7rrn) strain. However, the mutant ribosomes showed a slightly reduced rate of protein synthesis in vitro. In addition, we observed a 2-fold increase in the error rate of translation with the mutant ribosomes, which is consistent with an earlier report. Our results suggest that the tetraloops in helices 8 and 14 are highly conserved mainly for their structural stability and the precise sequences of these tetraloops are not critical for protein synthesis.
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Affiliation(s)
- Bhubanananda Sahu
- Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0314, USA
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10
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Wilson DN, Doudna Cate JH. The structure and function of the eukaryotic ribosome. Cold Spring Harb Perspect Biol 2012; 4:4/5/a011536. [PMID: 22550233 DOI: 10.1101/cshperspect.a011536] [Citation(s) in RCA: 215] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Structures of the bacterial ribosome have provided a framework for understanding universal mechanisms of protein synthesis. However, the eukaryotic ribosome is much larger than it is in bacteria, and its activity is fundamentally different in many key ways. Recent cryo-electron microscopy reconstructions and X-ray crystal structures of eukaryotic ribosomes and ribosomal subunits now provide an unprecedented opportunity to explore mechanisms of eukaryotic translation and its regulation in atomic detail. This review describes the X-ray crystal structures of the Tetrahymena thermophila 40S and 60S subunits and the Saccharomyces cerevisiae 80S ribosome, as well as cryo-electron microscopy reconstructions of translating yeast and plant 80S ribosomes. Mechanistic questions about translation in eukaryotes that will require additional structural insights to be resolved are also presented.
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11
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Ahmed A, Whitford PC, Sanbonmatsu KY, Tama F. Consensus among flexible fitting approaches improves the interpretation of cryo-EM data. J Struct Biol 2011; 177:561-70. [PMID: 22019767 DOI: 10.1016/j.jsb.2011.10.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 10/05/2011] [Accepted: 10/06/2011] [Indexed: 12/31/2022]
Abstract
Cryo-elecron microscopy (cryo-EM) can provide important structural information of large macromolecular assemblies in different conformational states. Recent years have seen an increase in structures deposited in the Protein Data Bank (PDB) by fitting a high-resolution structure into its low-resolution cryo-EM map. A commonly used protocol for accommodating the conformational changes between the X-ray structure and the cryo-EM map is rigid body fitting of individual domains. With the emergence of different flexible fitting approaches, there is a need to compare and revise these different protocols for the fitting. We have applied three diverse automated flexible fitting approaches on a protein dataset for which rigid domain fitting (RDF) models have been deposited in the PDB. In general, a consensus is observed in the conformations, which indicates a convergence from these theoretically different approaches to the most probable solution corresponding to the cryo-EM map. However, the result shows that the convergence might not be observed for proteins with complex conformational changes or with missing densities in cryo-EM map. In contrast, RDF structures deposited in the PDB can represent conformations that not only differ from the consensus obtained by flexible fitting but also from X-ray crystallography. Thus, this study emphasizes that a "consensus" achieved by the use of several automated flexible fitting approaches can provide a higher level of confidence in the modeled configurations. Following this protocol not only increases the confidence level of fitting, but also highlights protein regions with uncertain fitting. Hence, this protocol can lead to better interpretation of cryo-EM data.
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Affiliation(s)
- Aqeel Ahmed
- Department of Chemistry and Biochemistry, The University of Arizona, 1041 E. Lowell Street, Tucson, AZ 85721, USA.
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12
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Valle M. Almost lost in translation. Cryo-EM of a dynamic macromolecular complex: the ribosome. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:589-97. [DOI: 10.1007/s00249-011-0683-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/31/2011] [Accepted: 02/03/2011] [Indexed: 10/18/2022]
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13
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Voorhees RM, Schmeing TM, Kelley AC, Ramakrishnan V. The mechanism for activation of GTP hydrolysis on the ribosome. Science 2010; 330:835-838. [PMID: 21051640 PMCID: PMC3763471 DOI: 10.1126/science.1194460] [Citation(s) in RCA: 294] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Protein synthesis requires several guanosine triphosphatase (GTPase) factors, including elongation factor Tu (EF-Tu), which delivers aminoacyl-transfer RNAs (tRNAs) to the ribosome. To understand how the ribosome triggers GTP hydrolysis in translational GTPases, we have determined the crystal structure of EF-Tu and aminoacyl-tRNA bound to the ribosome with a GTP analog, to 3.2 angstrom resolution. EF-Tu is in its active conformation, the switch I loop is ordered, and the catalytic histidine is coordinating the nucleophilic water in position for inline attack on the γ-phosphate of GTP. This activated conformation is due to a critical and conserved interaction of the histidine with A2662 of the sarcin-ricin loop of the 23S ribosomal RNA. The structure suggests a universal mechanism for GTPase activation and hydrolysis in translational GTPases on the ribosome.
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MESH Headings
- Bacterial Proteins/chemistry
- Bacterial Proteins/metabolism
- Catalytic Domain
- Crystallography, X-Ray
- Enzyme Activation
- Guanosine Triphosphate/analogs & derivatives
- Guanosine Triphosphate/metabolism
- Hydrolysis
- Hydrophobic and Hydrophilic Interactions
- Nucleic Acid Conformation
- Paromomycin/metabolism
- Peptide Elongation Factor Tu/chemistry
- Peptide Elongation Factor Tu/metabolism
- Phosphates/metabolism
- Protein Structure, Tertiary
- RNA, Bacterial/chemistry
- RNA, Bacterial/metabolism
- RNA, Ribosomal, 23S/chemistry
- RNA, Ribosomal, 23S/metabolism
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Amino Acyl/metabolism
- Ribosomes/metabolism
- Thermus thermophilus/chemistry
- Thermus thermophilus/metabolism
- Thermus thermophilus/ultrastructure
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Affiliation(s)
| | | | - Ann C. Kelley
- MRC Laboratory of Molecular Biology, Cambridge, UK, CB2 0QH
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14
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Agirrezabala X, Frank J. From DNA to proteins via the ribosome: structural insights into the workings of the translation machinery. Hum Genomics 2010; 4:226-37. [PMID: 20511136 PMCID: PMC2976604 DOI: 10.1186/1479-7364-4-4-226] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Understanding protein synthesis in bacteria and humans is important for understanding the origin of many human diseases and devising treatments for them. Over the past decade, the field of structural biology has made significant advances in the visualisation of the molecular machinery involved in protein synthesis. It is now possible to discern, at least in outline, the way that interlocking ribosomal components and factors adapt their conformations throughout this process. The determination of structures in various functional contexts, along with the application of kinetic and fluorescent resonance energy transfer approaches to the problem, has given researchers the frame of reference for what remains as the greatest challenge: the complete dynamic portrait of protein synthesis in the cell.
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Abstract
Protein biosynthesis, or translation, occurs on the ribosome, a large RNA-protein assembly universally conserved in all forms of life. Over the last decade, structures of the small and large ribosomal subunits and of the intact ribosome have begun to reveal the molecular details of how the ribosome works. Both cryo-electron microscopy and X-ray crystallography continue to provide fresh insights into the mechanism of translation. In this review, we describe the most recent structural models of the bacterial ribosome that shed light on the movement of messenger RNA and transfer RNA on the ribosome after each peptide bond is formed, a process termed translocation. We also discuss recent structures that reveal the molecular basis for stop codon recognition during translation termination. Finally, we review recent advances in understanding how bacteria handle errors in both translocation and termination.
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Affiliation(s)
- Jack A Dunkle
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
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16
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Abstract
This essay gives the autho's personal account on the development of concepts underlying single-particle reconstruction, a technique in electron microscopy of macromolecular assemblies with a remarkable record of achievements as of late. The ribosome proved to be an ideal testing ground for the development of specimen preparation methods, cryo-EM techniques, and algorithms, with discoveries along the way as a rich reward. Increasingly, cryo-EM and single-particle reconstruction, in combination with classification techniques, is revealing dynamic information on functional molecular machines uninhibited by molecular contacts.
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Affiliation(s)
- Joachim Frank
- The Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
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17
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Ticu C, Nechifor R, Nguyen B, Desrosiers M, Wilson KS. Conformational changes in switch I of EF-G drive its directional cycling on and off the ribosome. EMBO J 2009; 28:2053-65. [PMID: 19536129 DOI: 10.1038/emboj.2009.169] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 05/26/2009] [Indexed: 11/09/2022] Open
Abstract
We have trapped elongation factor G (EF-G) from Escherichia coli in six, functionally defined states, representing intermediates in its unidirectional catalytic cycle, which couples GTP hydrolysis to tRNA-mRNA translocation in the ribosome. By probing EF-G with trypsin in each state, we identified a substantial conformational change involving its conserved switch I (sw1) element, which contacts the GTP substrate. By attaching FeBABE (a hydroxyl radical generating probe) to sw1, we could monitor sw1 movement (by approximately 20 A), relative to the 70S ribosome, during the EF-G cycle. In free EF-G, sw1 is disordered, particularly in GDP-bound and nucleotide-free states. On EF-G*GTP binding to the ribosome, sw1 becomes structured and tucked inside the ribosome, thereby locking GTP onto EF-G. After hydrolysis and translocation, sw1 flips out from the ribosome, greatly accelerating release of GDP and EF-G from the ribosome. Collectively, our results support a central role of sw1 in driving the EF-G cycle during protein synthesis.
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Affiliation(s)
- Cristina Ticu
- Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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Ribosome-induced changes in elongation factor Tu conformation control GTP hydrolysis. Proc Natl Acad Sci U S A 2009; 106:1063-8. [PMID: 19122150 DOI: 10.1073/pnas.0811370106] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In translation, elongation factor Tu (EF-Tu) molecules deliver aminoacyl-tRNAs to the mRNA-programmed ribosome. The GTPase activity of EF-Tu is triggered by ribosome-induced conformational changes of the factor that play a pivotal role in the selection of the cognate aminoacyl-tRNAs. We present a 6.7-A cryo-electron microscopy map of the aminoacyl-tRNA x EF-Tu x GDP x kirromycin-bound Escherichia coli ribosome, together with an atomic model of the complex obtained through molecular dynamics flexible fitting. The model reveals the conformational changes in the conserved GTPase switch regions of EF-Tu that trigger hydrolysis of GTP, along with key interactions, including those between the sarcin-ricin loop and the P loop of EF-Tu, and between the effector loop of EF-Tu and a conserved region of the 16S rRNA. Our data suggest that GTP hydrolysis on EF-Tu is controlled through a hydrophobic gate mechanism.
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