1
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Wang Y, Wang A, Mohanty U, Whitford PC. Precise Steric Features Control Aminoacyl-tRNA Accommodation on the Ribosome. J Phys Chem B 2022; 126:8447-8459. [PMID: 36251478 DOI: 10.1021/acs.jpcb.2c05513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Protein synthesis involves a complex series of large-scale conformational changes in the ribosome. While long-lived intermediate states of these processes can be characterized by experiments, computational methods can be used to identify the interactions that contribute to the rate-limiting free-energy barriers. To this end, we use a simplified energetic model to perform molecular dynamics (MD) simulations of aminoacyl-tRNA (aa-tRNA) accommodation on the ribosome. While numerous studies have probed the energetics of the early stages of accommodation, we focus on the final stage of accommodation, where the 3'-CCA tail of aa-tRNA enters the peptidyl transferase center (PTC). These simulations show how a distinct intermediate is induced by steric confinement of the tail, immediately before it completes accommodation. Multiple pathways for 3'-CCA tail accommodation can be quantitatively distinguished, where the tail enters the PTC by moving past a pocket enclosed by Helix 89, 90, and 92, or through an alternate route formed by Helix 93 and the P-site tRNA. C2573, located within Helix 90, is shown to provide the largest contribution to this late-accommodation steric barrier, such that sub-Å perturbations to this residue can alter the time scale of tail accommodation by nearly an order of magnitude. In terms of biological function, these calculations suggest how this late-stage sterically induced barrier may contribute to tRNA proofreading by the ribosome.
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Affiliation(s)
- Yang Wang
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts02467, United States
| | - Ailun Wang
- Center for Theoretical Biological Physics, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts02115, United States
| | - Udayan Mohanty
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts02467, United States
| | - Paul C Whitford
- Center for Theoretical Biological Physics, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts02115, United States.,Department of Physics, Northeastern University, Dana Research Center 111, 360 Huntington Avenue, Boston, Massachusetts02115, United States
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2
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Bowman JC, Petrov AS, Frenkel-Pinter M, Penev PI, Williams LD. Root of the Tree: The Significance, Evolution, and Origins of the Ribosome. Chem Rev 2020; 120:4848-4878. [PMID: 32374986 DOI: 10.1021/acs.chemrev.9b00742] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ribosome is an ancient molecular fossil that provides a telescope to the origins of life. Made from RNA and protein, the ribosome translates mRNA to coded protein in all living systems. Universality, economy, centrality and antiquity are ingrained in translation. The translation machinery dominates the set of genes that are shared as orthologues across the tree of life. The lineage of the translation system defines the universal tree of life. The function of a ribosome is to build ribosomes; to accomplish this task, ribosomes make ribosomal proteins, polymerases, enzymes, and signaling proteins. Every coded protein ever produced by life on Earth has passed through the exit tunnel, which is the birth canal of biology. During the root phase of the tree of life, before the last common ancestor of life (LUCA), exit tunnel evolution is dominant and unremitting. Protein folding coevolved with evolution of the exit tunnel. The ribosome shows that protein folding initiated with intrinsic disorder, supported through a short, primitive exit tunnel. Folding progressed to thermodynamically stable β-structures and then to kinetically trapped α-structures. The latter were enabled by a long, mature exit tunnel that partially offset the general thermodynamic tendency of all polypeptides to form β-sheets. RNA chaperoned the evolution of protein folding from the very beginning. The universal common core of the ribosome, with a mass of nearly 2 million Daltons, was finalized by LUCA. The ribosome entered stasis after LUCA and remained in that state for billions of years. Bacterial ribosomes never left stasis. Archaeal ribosomes have remained near stasis, except for the superphylum Asgard, which has accreted rRNA post LUCA. Eukaryotic ribosomes in some lineages appear to be logarithmically accreting rRNA over the last billion years. Ribosomal expansion in Asgard and Eukarya has been incremental and iterative, without substantial remodeling of pre-existing basal structures. The ribosome preserves information on its history.
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Affiliation(s)
- Jessica C Bowman
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Anton S Petrov
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Moran Frenkel-Pinter
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Petar I Penev
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Loren Dean Williams
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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3
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Yang H, Bandarkar P, Horne R, Leite VBP, Chahine J, Whitford PC. Diffusion of tRNA inside the ribosome is position-dependent. J Chem Phys 2019; 151:085102. [PMID: 31470725 DOI: 10.1063/1.5113814] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In recent years, there has been a growing interest to quantify the energy landscape that governs ribosome dynamics. However, in order to quantitatively integrate theoretical predictions and experimental measurements, it is essential that one has a detailed understanding of the associated diffusive properties. Here, all-atom explicit-solvent simulations (50 μs of aggregate sampling) predict that the diffusion coefficient of a tRNA molecule will depend on its position within the ribosome. Specifically, during aa-tRNA accommodation (i.e., the process by which tRNA enters the ribosome), the apparent diffusion coefficient decreases by approximately an order of magnitude. By comparing these to values obtained with an energetically "smooth" model, we show that the observed nonuniform behavior likely arises from electrostatic and solvation interactions between the tRNA and ribosome. These calculations also reveal the hierarchical character of ribosomal energetics, where steric interactions induce a large-scale free-energy barrier, and short-scale roughness determines the rate of diffusive movement across the landscape.
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Affiliation(s)
- Huan Yang
- Department of Physics, Northeastern University, Dana Research Center 111, 360 Huntington Ave., Boston, Massachusetts 02115, USA
| | - Prasad Bandarkar
- Department of Physics, Northeastern University, Dana Research Center 111, 360 Huntington Ave., Boston, Massachusetts 02115, USA
| | - Ransom Horne
- Department of Physics, Northeastern University, Dana Research Center 111, 360 Huntington Ave., Boston, Massachusetts 02115, USA
| | - Vitor B P Leite
- São Paulo State University (UNESP), IBILCE, São José do Rio Preto, Brazil
| | - Jorge Chahine
- São Paulo State University (UNESP), IBILCE, São José do Rio Preto, Brazil
| | - Paul C Whitford
- Department of Physics, Northeastern University, Dana Research Center 111, 360 Huntington Ave., Boston, Massachusetts 02115, USA
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4
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Binding and enzymatic properties of Ageritin, a fungal ribotoxin with novel zinc-dependent function. Int J Biol Macromol 2019; 136:625-631. [DOI: 10.1016/j.ijbiomac.2019.06.125] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 06/04/2019] [Accepted: 06/17/2019] [Indexed: 12/18/2022]
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5
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Levi M, Whitford PC. Dissecting the Energetics of Subunit Rotation in the Ribosome. J Phys Chem B 2019; 123:2812-2823. [PMID: 30844276 DOI: 10.1021/acs.jpcb.9b00178] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The accurate expression of proteins requires the ribosome to efficiently undergo elaborate conformational rearrangements. The most dramatic of these motions is subunit rotation, which is necessary for tRNA molecules to transition between ribosomal binding sites. While rigid-body descriptions provide a qualitative picture of the process, obtaining quantitative mechanistic insights requires one to account for the relationship between molecular flexibility and collective dynamics. Using simulated rotation events, we assess the quality of experimentally accessible measures for describing the collective displacement of the ∼4000-residue small subunit. For this, we ask whether each coordinate is able to identify the underlying free-energy barrier and transition state ensemble (TSE). We find that intuitive structurally motivated coordinates (e.g., rotation angle, interprotein distances) can distinguish between the endpoints, though they are poor indicators of barrier-crossing events, and they underestimate the free-energy barrier. In contrast, coordinates based on intersubunit bridges can identify the TSE. We additionally verify that the committor probability for the putative TSE configurations is 0.5, a hallmark feature of any transition state. In terms of structural properties, these calculations implicate a transition state in which flexibility allows for asynchronous rearrangements of the bridges, as the ribosome adopts a partially rotated orientation. This provides a theoretical foundation, upon which experimental techniques may precisely quantify the energy landscape of the ribosome.
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Affiliation(s)
- Mariana Levi
- Department of Physics , Northeastern University , Dana Research Center 111, 360 Huntington Avenue , Boston , Massachusetts 02115 , United States
| | - Paul C Whitford
- Department of Physics , Northeastern University , Dana Research Center 111, 360 Huntington Avenue , Boston , Massachusetts 02115 , United States
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6
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Rogers SO. Evolution of the genetic code based on conservative changes of codons, amino acids, and aminoacyl tRNA synthetases. J Theor Biol 2019; 466:1-10. [PMID: 30658052 DOI: 10.1016/j.jtbi.2019.01.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 01/10/2019] [Accepted: 01/14/2019] [Indexed: 11/30/2022]
Abstract
The genetic code, as arranged in the standard tabular form, displays a non-random structure relating to the characteristics of the amino acids. An alternative arrangement can be made by organizing the code according to aminoacyl-tRNA synthetases (aaRSs), codons, and reverse complement codons, which illuminates a coevolutionary process that led to the contemporary genetic code. As amino acids were added to the genetic code, they were recognized by aaRSs that interact with stereochemically similar amino acids. Single nucleotide changes in the codons and anticodons were favored over more extensive changes, such that there was a logical stepwise progression in the evolution of the genetic code. The model presented traces the evolution of the genetic code accounting for these steps. Amino acid frequencies in ancient proteins and the preponderance of GNN codons in mRNAs for ancient proteins indicate that the genetic code began with alanine, aspartate, glutamate, glycine, and valine, with alanine being in the highest proportions. In addition to being consistent in terms of conservative changes in codon nucleotides, the model also is consistent with respect to aaRS classes, aaRS attachment to the tRNA, amino acid stereochemistry, and to a large extent with amino acid physicochemistry, and biochemical pathways.
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Affiliation(s)
- Scott O Rogers
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States.
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7
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Rogers SO. Integrated evolution of ribosomal RNAs, introns, and intron nurseries. Genetica 2018; 147:103-119. [PMID: 30578455 DOI: 10.1007/s10709-018-0050-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Accepted: 12/13/2018] [Indexed: 12/21/2022]
Abstract
The initial components of ribosomes first appeared more than 3.8 billion years ago during a time when many types of RNAs were evolving. While modern ribosomes are complex molecular machines consisting of rRNAs and proteins, they were assembled during early evolution by the association and joining of small functional RNA units. Introns may have provided the means to ligate many of these pieces together. All four classes of introns (group I, group II, spliceosomal, and archaeal) are present in many rRNA gene loci over a broad phylogenetic range. A survey of rRNA intron sequences across the three major life domains suggests that some of the classes of introns may have diverged from one another within rRNA gene loci. Analyses of rRNA sequences revealed self-splicing group I and group II introns are present in ancestral regions of the SSU (small subunit) and LSU (large subunit), whereas spliceosomal and archaeal introns appeared in sections of the rRNA that evolved later. Most classes of introns increased in number for approximately 1 billion years. However, their frequencies are low in the most recently evolved regions added to the SSU and LSU rRNAs. Furthermore, many of the introns appear to have been in the same locations for billions of years, suggesting an ancient origin for these sequences. In this Perspectives paper, I reviewed and analyzed rRNA intron sequences, locations, structural characteristics, and splicing mechanisms; and suggest that rRNA gene loci may have served as evolutionary nurseries for intron formation and diversification.
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Affiliation(s)
- Scott O Rogers
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, 43403, USA.
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8
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Fritch B, Kosolapov A, Hudson P, Nissley DA, Woodcock HL, Deutsch C, O'Brien EP. Origins of the Mechanochemical Coupling of Peptide Bond Formation to Protein Synthesis. J Am Chem Soc 2018; 140:5077-5087. [PMID: 29577725 DOI: 10.1021/jacs.7b11044] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mechanical forces acting on the ribosome can alter the speed of protein synthesis, indicating that mechanochemistry can contribute to translation control of gene expression. The naturally occurring sources of these mechanical forces, the mechanism by which they are transmitted 10 nm to the ribosome's catalytic core, and how they influence peptide bond formation rates are largely unknown. Here, we identify a new source of mechanical force acting on the ribosome by using in situ experimental measurements of changes in nascent-chain extension in the exit tunnel in conjunction with all-atom and coarse-grained computer simulations. We demonstrate that when the number of residues composing a nascent chain increases, its unstructured segments outside the ribosome exit tunnel generate piconewtons of force that are fully transmitted to the ribosome's P-site. The route of force transmission is shown to be through the nascent polypetide's backbone, not through the wall of the ribosome's exit tunnel. Utilizing quantum mechanical calculations we find that a consequence of such a pulling force is to decrease the transition state free energy barrier to peptide bond formation, indicating that the elongation of a nascent chain can accelerate translation. Since nascent protein segments can start out as largely unfolded structural ensembles, these results suggest a pulling force is present during protein synthesis that can modulate translation speed. The mechanism of force transmission we have identified and its consequences for peptide bond formation should be relevant regardless of the source of the pulling force.
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Affiliation(s)
- Benjamin Fritch
- Department of Chemistry , Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Andrey Kosolapov
- Department of Physiology , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Phillip Hudson
- Department of Chemistry , University of South Florida , Tampa , Florida 33620 , United States.,Laboratory of Computational Biology , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Daniel A Nissley
- Department of Chemistry , Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - H Lee Woodcock
- Department of Chemistry , University of South Florida , Tampa , Florida 33620 , United States
| | - Carol Deutsch
- Department of Physiology , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Edward P O'Brien
- Department of Chemistry , Pennsylvania State University , University Park , Pennsylvania 16802 , United States.,Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences , Pennsylvania State University , University Park , Pennsylvania 16802 , United States
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9
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Levi M, Nguyen K, Dukaye L, Whitford PC. Quantifying the Relationship between Single-Molecule Probes and Subunit Rotation in the Ribosome. Biophys J 2018; 113:2777-2786. [PMID: 29262370 DOI: 10.1016/j.bpj.2017.10.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 10/12/2017] [Accepted: 10/16/2017] [Indexed: 11/18/2022] Open
Abstract
A major challenge in the study of biomolecular assemblies is to identify reaction coordinates that precisely monitor conformational rearrangements. This is central to the interpretation of single-molecule fluorescence resonance energy transfer measurements, where the observed dynamics depends on the labeling strategy. As an example, different probes of subunit rotation in the ribosome have provided qualitatively distinct descriptions. In one study, changes in fluorescence suggested that the 30S body undergoes a single rotation/back-rotation cycle during the process of mRNA-tRNA translocation. In contrast, an alternate assay implicated the presence of reversible rotation events before completing translocation. For future single-molecule experiments to unambiguously measure the relationship between subunit rotation and translocation, it is necessary to rationalize these conflicting descriptions. To this end, we have simulated hundreds of spontaneous subunit rotation events (≈8°) using a residue-level coarse-grained model of the ribosome. We analyzed nine different reaction coordinates and found that the apparently inconsistent measurements are likely a consequence of ribosomal flexibility. Further, we propose a metric for quantifying the degree of energetic coupling between experimentally measured degrees of freedom and subunit rotation. This analysis provides a physically grounded framework that can guide the development of more precise single-molecule techniques.
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Affiliation(s)
- Mariana Levi
- Department of Physics, Northeastern University, Boston, Massachusetts
| | - Kien Nguyen
- Department of Physics, Northeastern University, Boston, Massachusetts
| | - Liah Dukaye
- Department of Physics, Northeastern University, Boston, Massachusetts
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10
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Jeon Y, Ahn HK, Kang YW, Pai HS. Functional characterization of chloroplast-targeted RbgA GTPase in higher plants. PLANT MOLECULAR BIOLOGY 2017; 95:463-479. [PMID: 29038916 DOI: 10.1007/s11103-017-0664-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 10/01/2017] [Indexed: 06/07/2023]
Abstract
KEY MESSAGE Plant RbgA GTPase is targeted to chloroplasts and co-fractionated with chloroplast ribosomes, and plays a role in chloroplast rRNA processing and/or ribosome biogenesis. Ribosome Biogenesis GTPase A (RbgA) homologs are evolutionarily conserved GTPases that are widely distributed in both prokaryotes and eukaryotes. In this study, we investigated functions of chloroplast-targeted RbgA. Nicotiana benthamiana RbgA (NbRbgA) and Arabidopsis thaliana RbgA (AtRbgA) contained a conserved GTP-binding domain and a plant-specific C-terminal domain. NbRbgA and AtRbgA were mainly localized in chloroplasts, and possessed GTPase activity. Since Arabidopsis rbgA null mutants exhibited an embryonic lethal phenotype, virus-induced gene silencing (VIGS) of NbRbgA was performed in N. benthamiana. NbRbgA VIGS resulted in a leaf-yellowing phenotype caused by disrupted chloroplast development. NbRbgA was mainly co-fractionated with 50S/70S ribosomes and interacted with the chloroplast ribosomal proteins cpRPL6 and cpRPL35. NbRbgA deficiency lowered the levels of mature 23S and 16S rRNAs in chloroplasts and caused processing defects. Sucrose density gradient sedimentation revealed that NbRbgA-deficient chloroplasts contained reduced levels of mature 23S and 16S rRNAs and diverse plastid-encoded mRNAs in the polysomal fractions, suggesting decreased protein translation activity in the chloroplasts. Interestingly, NbRbgA protein was highly unstable under high light stress, suggesting its possible involvement in the control of chloroplast ribosome biogenesis under environmental stresses. Collectively, these results suggest a role for RbgA GTPase in chloroplast rRNA processing/ribosome biogenesis, affecting chloroplast protein translation in higher plants.
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Affiliation(s)
- Young Jeon
- Department of Systems Biology, Yonsei University, Seoul, 03722, South Korea
| | - Hee-Kyung Ahn
- Department of Systems Biology, Yonsei University, Seoul, 03722, South Korea
| | - Yong Won Kang
- R&D Center, Morechem Co., Ltd., Yongin, Gyeonggi-do, 16954, South Korea
| | - Hyun-Sook Pai
- Department of Systems Biology, Yonsei University, Seoul, 03722, South Korea.
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11
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Yang H, Noel JK, Whitford PC. Anisotropic Fluctuations in the Ribosome Determine tRNA Kinetics. J Phys Chem B 2017; 121:10593-10601. [PMID: 28910101 DOI: 10.1021/acs.jpcb.7b06828] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ribosome is a large ribonucleoprotein complex that is responsible for the production of proteins in all organisms. Accommodation is the process by which an incoming aminoacyl-tRNA (aa-tRNA) molecule binds the ribosomal A site, and its kinetics has been implicated in the accuracy of tRNA selection. In addition to rearrangements in the aa-tRNA molecule, the L11 stalk can undergo large-scale anisotropic motions during translation. To explore the potential impact of this protruding region on the rate of aa-tRNA accommodation, we used molecular dynamics simulations with a simplified model to evaluate the free energy as a function of aa-tRNA position. Specifically, these calculations describe the transition between A/T and elbow-accommodated (EA) configurations (∼20 Å displacement). We find that the free-energy barrier associated with elbow accommodation is proportional to the degree of mobility exhibited by the L11 stalk. That is, when L11 is more rigid, the free-energy barrier height is decreased. This effect arises from the ability of L11 to confine, and thereby destabilize, the A/T ensemble. In addition, when elongation factor Tu (EF-Tu) is present, the A/T ensemble is further destabilized in an L11-dependent manner. These results provide a framework that suggests how next-generation experiments may precisely control the dynamics of the ribosome.
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Affiliation(s)
- Huan Yang
- Department of Physics, Northeastern University , Dana Research Center 111, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Jeffrey K Noel
- Max Delbrück Center for Molecular Medicine , Berlin, Germany.,Fritz Haber Institute of the Max Planck Society , Berlin, Germany
| | - Paul C Whitford
- Department of Physics, Northeastern University , Dana Research Center 111, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
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12
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Noel JK, Whitford PC. How EF-Tu can contribute to efficient proofreading of aa-tRNA by the ribosome. Nat Commun 2016; 7:13314. [PMID: 27796304 PMCID: PMC5095583 DOI: 10.1038/ncomms13314] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 09/21/2016] [Indexed: 11/18/2022] Open
Abstract
It has long been recognized that the thermodynamics of mRNA–tRNA base pairing is insufficient to explain the high fidelity and efficiency of aminoacyl-tRNA (aa-tRNA) selection by the ribosome. To rationalize this apparent inconsistency, Hopfield proposed that the ribosome may improve accuracy by utilizing a multi-step kinetic proofreading mechanism. While biochemical, structural and single-molecule studies have provided a detailed characterization of aa-tRNA selection, there is a limited understanding of how the physical–chemical properties of the ribosome enable proofreading. To this end, we probe the role of EF-Tu during aa-tRNA accommodation (the proofreading step) through the use of energy landscape principles, molecular dynamics simulations and kinetic models. We find that the steric composition of EF-Tu can reduce the free-energy barrier associated with the first step of accommodation: elbow accommodation. We interpret this effect within an extended kinetic model of accommodation and show how EF-Tu can contribute to efficient and accurate proofreading.
The translation of mRNA by the ribosome is governed by a series of large-scale conformational transitions. Here the authors use MD simulations to demonstrate how the rate of dissociation of elongation factor Tu affects the dynamics of tRNA accommodation and proofreading.
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Affiliation(s)
- Jeffrey K Noel
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77030, USA.,Max Delbrück Center for Molecular Medicine, Kristallographie, Robert-Rössle-Strasse 10, Berlin 13125, Germany.,Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Berlin 14195, Germany
| | - Paul C Whitford
- Department of Physics, Northeastern University, Dana Research Center 111, 360 Huntington Avenue, Boston, Massachusetts 02115, USA
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13
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Amino acid sequence repertoire of the bacterial proteome and the occurrence of untranslatable sequences. Proc Natl Acad Sci U S A 2016; 113:7166-70. [PMID: 27307442 DOI: 10.1073/pnas.1606518113] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bioinformatic analysis of Escherichia coli proteomes revealed that all possible amino acid triplet sequences occur at their expected frequencies, with four exceptions. Two of the four underrepresented sequences (URSs) were shown to interfere with translation in vivo and in vitro. Enlarging the URS by a single amino acid resulted in increased translational inhibition. Single-molecule methods revealed stalling of translation at the entrance of the peptide exit tunnel of the ribosome, adjacent to ribosomal nucleotides A2062 and U2585. Interaction with these same ribosomal residues is involved in regulation of translation by longer, naturally occurring protein sequences. The E. coli exit tunnel has evidently evolved to minimize interaction with the exit tunnel and maximize the sequence diversity of the proteome, although allowing some interactions for regulatory purposes. Bioinformatic analysis of the human proteome revealed no underrepresented triplet sequences, possibly reflecting an absence of regulation by interaction with the exit tunnel.
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14
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Gulati M, Jain N, Davis JH, Williamson JR, Britton RA. Functional interaction between ribosomal protein L6 and RbgA during ribosome assembly. PLoS Genet 2014; 10:e1004694. [PMID: 25330043 PMCID: PMC4199504 DOI: 10.1371/journal.pgen.1004694] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 08/21/2014] [Indexed: 01/06/2023] Open
Abstract
RbgA is an essential GTPase that participates in the assembly of the large ribosomal subunit in Bacillus subtilis and its homologs are implicated in mitochondrial and eukaryotic large subunit assembly. How RbgA functions in this process is still poorly understood. To gain insight into the function of RbgA we isolated suppressor mutations that partially restored the growth of an RbgA mutation (RbgA-F6A) that caused a severe growth defect. Analysis of these suppressors identified mutations in rplF, encoding ribosomal protein L6. The suppressor strains all accumulated a novel ribosome intermediate that migrates at 44S in sucrose gradients. All of the mutations cluster in a region of L6 that is in close contact with helix 97 of the 23S rRNA. In vitro maturation assays indicate that the L6 substitutions allow the defective RbgA-F6A protein to function more effectively in ribosome maturation. Our results suggest that RbgA functions to properly position L6 on the ribosome, prior to the incorporation of L16 and other late assembly proteins. Ribosomes are complex macromolecular machines that carry out the essential function of protein synthesis in the cell. The assembly of ribosomal subunits is a multistep process that involves the accurate and timely assembly of 3 rRNA molecules and>50 ribosomal-proteins. In recent years many ribosome assembly factors have been identified in bacterial and eukaryotic cells; however, their precise functions in ribosome biogenesis are poorly understood. We have previously shown that the GTPase RbgA, a protein conserved from bacteria to humans, is essential for ribosome assembly in Bacillus subtilis. Here, we show that growth defect caused by a mutation in RbgA is partially suppressed by mutations in ribosomal protein L6. The suppressor strains accumulate novel ribosomal intermediates that appear to suppress the RbgA defect by weakening the interaction of L6 for the ribosome and facilitating RbgA dependent assembly. Our work provides evidence for a functional interaction between ribosome assembly factor RbgA and ribosomal protein L6 during assembly, a function that is likely important for mitochondrial, chloroplast, and eukaryotic ribosome assembly as well.
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Affiliation(s)
- Megha Gulati
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Nikhil Jain
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Joseph H. Davis
- Department of Integrative Structural and Computational Biology, Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - James R. Williamson
- Department of Integrative Structural and Computational Biology, Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Robert A. Britton
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail: .
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15
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Liu Y, Zhao C, Zhang F, Chen H, Chen M, Wang H. High prevalence and molecular analysis of macrolide-nonsusceptible Moraxella catarrhalis isolated from nasopharynx of healthy children in China. Microb Drug Resist 2012; 18:417-26. [PMID: 22394083 DOI: 10.1089/mdr.2011.0175] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Three hundred eighty-three isolates of Moraxella catarrhalis were collected from healthy children aged less than 2 years in China and assessed for antimicrobial resistance. We found that 92.2% (n=353) produced a β-lactamase. Nonsusceptibility rates to erythromycin and azithromycin, determined using Clinical Laboratory Standards Institute (CLSI) breakpoints, were 40.3% and 22.5%, respectively; nonsusceptibility rates determined using pharmacokinetics/pharmacodynamics breakpoints, however, were 59% and 60.1%. The minimal inhibitory concentration (MIC)(90) values were >256 μg/ml. Nonsusceptibility rates varied by region from 9.7% in Dongguan to 75.9% in Jinan. Further, concomitant resistance to β-lactam antibiotics was also observed. Pulsed-field gel electrophoresis analysis of 27/37 high-level macrolide-resistant M. catarrhalis isolates showed that closely related pulsotypes dominated, with a total of 11 different pulsotypes being observed. The closely related pulsotypes were observed in isolates originating from all six Chinese cities investigated, possibly as a consequence of the mobility of the Chinese population. Sixteen patterns of 23S rRNA mutations were found among 97 selected isolates using polymerase chain reaction and sequencing, but no known ermA, ermB, mefA, or mefE genes could be detected. Mutations A2982T and A2796T in 23S rRNA were related to high-level macrolide resistance (MICs ranging from 24 to >256 μg/ml), while an A2983T mutation was associated with low-level macrolide resistance (MICs ranging from 0.19 to 16 μg/ml).
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Affiliation(s)
- Yali Liu
- Department of Clinical Laboratory, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
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McCoy LS, Xie Y, Tor Y. Antibiotics that target protein synthesis. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 2:209-32. [DOI: 10.1002/wrna.60] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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17
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O'Brien EP, Hsu STD, Christodoulou J, Vendruscolo M, Dobson CM. Transient tertiary structure formation within the ribosome exit port. J Am Chem Soc 2010; 132:16928-37. [PMID: 21062068 DOI: 10.1021/ja106530y] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The exit tunnel of the ribosome is commonly considered to be sufficiently narrow that co-translational folding can begin only when specific segments of nascent chains are fully extruded from the tunnel. Here we show, on the basis of molecular simulations and comparison with experiment, that the long-range contacts essential for initiating protein folding can form within a nascent chain when it reaches the last 20 Å of the exit tunnel. We further show that, in this "exit port", a significant proportion of native and non-native tertiary structure can form without steric overlap with the ribosome itself, and provide a library of structural elements that our simulations predict can form in the exit tunnel and is amenable to experimental testing. Our results show that these elements of folded tertiary structure form only transiently and are at their midpoints of stability at the boundary region between the inside and the outside of the tunnel. These findings provide a framework for interpreting a range of recent experimental studies of ribosome nascent chain complexes and for understanding key aspects of the nature of co-translational folding.
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Affiliation(s)
- Edward P O'Brien
- Department of Chemistry, Lensfield Road, University of Cambridge, UK
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18
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Rangelov MA, Petrova GP, Yomtova VM, Vayssilov GN. Hierarchical approach to conformational search and selection of computational method in modeling the mechanism of ester ammonolysis. J Mol Graph Model 2010; 29:246-55. [DOI: 10.1016/j.jmgm.2010.07.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Revised: 07/17/2010] [Accepted: 07/20/2010] [Indexed: 02/02/2023]
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19
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Bibi E. Early targeting events during membrane protein biogenesis in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:841-50. [PMID: 20682283 DOI: 10.1016/j.bbamem.2010.07.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 07/21/2010] [Accepted: 07/22/2010] [Indexed: 10/19/2022]
Abstract
All living cells have co-translational pathways for targeting membrane proteins. Co-translation pathways for secretory proteins also exist but mostly in eukaryotes. Unlike secretory proteins, the biosynthetic pathway of most membrane proteins is conserved through evolution and these proteins are usually synthesized by membrane-bound ribosomes. Translation on the membrane requires that both the ribosomes and the mRNAs be properly localized. Theoretically, this can be achieved by several means. (i) The current view is that the targeting of cytosolic mRNA-ribosome-nascent chain complexes (RNCs) to the membrane is initiated by information in the emerging hydrophobic nascent polypeptides. (ii) The alternative model suggests that ribosomes may be targeted to the membrane also constitutively, whereas the appropriate mRNAs may be carried on small ribosomal subunits or targeted by other cellular factors to the membrane-bound ribosomes. Importantly, the available experimental data do not rule out the possibility that cells may also utilize both pathways in parallel. In any case, it is well documented that a major player in the targeting pathway is the signal recognition particle (SRP) system composed of the SRP and its receptor (SR). Although the functional core of the SRP system is evolutionarily conserved, its composition and biological practice come with different flavors in various organisms. This review is dedicated mainly to the Escherichia (E.) coli SRP, where the biochemical and structural properties of components of the SRP system have been relatively characterized, yielding essential information about various aspects of the pathway. In addition, several cellular interactions of the SRP and its receptor have been described in E. coli, providing insights into their spatial function. Collectively, these in vitro studies have led to the current view of the targeting pathway [see (i) above]. Interestingly, however, in vivo studies of the role of the SRP and its receptor, with emphasis on the temporal progress of the pathway, elicited an alternative hypothesis [see (ii) above]. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- Eitan Bibi
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
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20
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Cabrita L, Dobson CM, Christodoulou J. Early Nascent Chain Folding Events on the Ribosome. Isr J Chem 2010. [DOI: 10.1002/ijch.201000015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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21
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Yonath A. Winterschlafende Bären, Antibiotika und die Evolution des Ribosoms (Nobel-Aufsatz). Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201001297] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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22
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Yonath A. Hibernating Bears, Antibiotics, and the Evolving Ribosome (Nobel Lecture). Angew Chem Int Ed Engl 2010; 49:4341-54. [DOI: 10.1002/anie.201001297] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Kirst HA. 11th International Conference on the Chemistry of Antibiotics and other Bioactive Compounds (ICCA-11) Donostia—San Sebastian, Spain 29 September–2 October 2009. J Antibiot (Tokyo) 2009. [DOI: 10.1038/ja.2009.115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Nobelpreise 2009. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200905679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Nobel Prizes 2009. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/anie.200905679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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Yonath A. Large facilities and the evolving ribosome, the cellular machine for genetic-code translation. J R Soc Interface 2009; 6 Suppl 5:S575-85. [PMID: 19656820 DOI: 10.1098/rsif.2009.0167.focus] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Well-focused X-ray beams, generated by advanced synchrotron radiation facilities, yielded high-resolution diffraction data from crystals of ribosomes, the cellular nano-machines that translate the genetic code into proteins. These structures revealed the decoding mechanism, localized the mRNA path and the positions of the tRNA molecules in the ribosome and illuminated the interactions of the ribosome with initiation, release and recycling factors. They also showed that the ribosome is a ribozyme whose active site is situated within a universal symmetrical region that is embedded in the otherwise asymmetric ribosome structure. As this highly conserved region provides the machinery required for peptide bond formation and for ribosome polymerase activity, it may be the remnant of the proto-ribosome, a dimeric pre-biotic machine that formed peptide bonds and non-coded polypeptide chains. Synchrotron radiation also enabled the determination of structures of complexes of ribosomes with antibiotics targeting them, which revealed the principles allowing for their clinical use, revealed resistance mechanisms and showed the bases for discriminating pathogens from hosts, hence providing valuable structural information for antibiotics improvement.
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Affiliation(s)
- Ada Yonath
- Department of Structural Biology, Weizmann Institute, 76100 Rehovot, Israel.
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Ribosome: an Ancient Cellular Nano-Machine for Genetic Code Translation. NATO SCIENCE FOR PEACE AND SECURITY SERIES B: PHYSICS AND BIOPHYSICS 2009. [DOI: 10.1007/978-90-481-2368-1_8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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