1
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Lahry K, Datta M, Varshney U. Genetic analysis of translation initiation in bacteria: An initiator tRNA-centric view. Mol Microbiol 2024. [PMID: 38410838 DOI: 10.1111/mmi.15243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/03/2024] [Accepted: 02/09/2024] [Indexed: 02/28/2024]
Abstract
Translation of messenger RNA (mRNA) in bacteria occurs in the steps of initiation, elongation, termination, and ribosome recycling. The initiation step comprises multiple stages and uses a special transfer RNA (tRNA) called initiator tRNA (i-tRNA), which is first aminoacylated and then formylated using methionine and N10 -formyl-tetrahydrofolate (N10 -fTHF), respectively. Both methionine and N10 -fTHF are produced via one-carbon metabolism, linking translation initiation with active cellular metabolism. The fidelity of i-tRNA binding to the ribosomal peptidyl-site (P-site) is attributed to the structural features in its acceptor stem, and the highly conserved three consecutive G-C base pairs (3GC pairs) in the anticodon stem. The acceptor stem region is important in formylation of the amino acid attached to i-tRNA and in its initial binding to the P-site. And, the 3GC pairs are crucial in transiting the i-tRNA through various stages of initiation. We utilized the feature of 3GC pairs to investigate the nuanced layers of scrutiny that ensure fidelity of translation initiation through i-tRNA abundance and its interactions with the components of the translation apparatus. We discuss the importance of i-tRNA in the final stages of ribosome maturation, as also the roles of the Shine-Dalgarno sequence, ribosome heterogeneity, initiation factors, ribosome recycling factor, and coevolution of the translation apparatus in orchestrating a delicate balance between the fidelity of initiation and/or its leakiness to generate proteome plasticity in cells to confer growth fitness advantages in response to the dynamic nutritional states.
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Affiliation(s)
- Kuldeep Lahry
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
| | - Madhurima Datta
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
| | - Umesh Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India
- Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru, India
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2
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Prabhakar A, Pavlov MY, Zhang J, Indrisiunaite G, Wang J, Lawson M, Ehrenberg M, Puglisi JD. Dynamics of release factor recycling during translation termination in bacteria. Nucleic Acids Res 2023; 51:5774-5790. [PMID: 37102635 PMCID: PMC10287982 DOI: 10.1093/nar/gkad286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 04/05/2023] [Accepted: 04/09/2023] [Indexed: 04/28/2023] Open
Abstract
In bacteria, release of newly synthesized proteins from ribosomes during translation termination is catalyzed by class-I release factors (RFs) RF1 or RF2, reading UAA and UAG or UAA and UGA codons, respectively. Class-I RFs are recycled from the post-termination ribosome by a class-II RF, the GTPase RF3, which accelerates ribosome intersubunit rotation and class-I RF dissociation. How conformational states of the ribosome are coupled to the binding and dissociation of the RFs remains unclear and the importance of ribosome-catalyzed guanine nucleotide exchange on RF3 for RF3 recycling in vivo has been disputed. Here, we profile these molecular events using a single-molecule fluorescence assay to clarify the timings of RF3 binding and ribosome intersubunit rotation that trigger class-I RF dissociation, GTP hydrolysis, and RF3 dissociation. These findings in conjunction with quantitative modeling of intracellular termination flows reveal rapid ribosome-dependent guanine nucleotide exchange to be crucial for RF3 action in vivo.
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Affiliation(s)
- Arjun Prabhakar
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA
- Program in Biophysics, Stanford University, Stanford, CA 94305-5126, USA
| | - Michael Y Pavlov
- Department of Cell and Molecular Biology, Biomedical Center, Box 596, Uppsala University, Uppsala, Sweden
| | - Jingji Zhang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA
| | - Gabriele Indrisiunaite
- Department of Cell and Molecular Biology, Biomedical Center, Box 596, Uppsala University, Uppsala, Sweden
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA
| | - Michael R Lawson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA
| | - Måns Ehrenberg
- Department of Cell and Molecular Biology, Biomedical Center, Box 596, Uppsala University, Uppsala, Sweden
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA
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3
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Nagao A, Nakanishi Y, Yamaguchi Y, Mishina Y, Karoji M, Toya T, Fujita T, Iwasaki S, Miyauchi K, Sakaguchi Y, Suzuki T. Quality control of protein synthesis in the early elongation stage. Nat Commun 2023; 14:2704. [PMID: 37198183 PMCID: PMC10192219 DOI: 10.1038/s41467-023-38077-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 04/14/2023] [Indexed: 05/19/2023] Open
Abstract
In the early stage of bacterial translation, peptidyl-tRNAs frequently dissociate from the ribosome (pep-tRNA drop-off) and are recycled by peptidyl-tRNA hydrolase. Here, we establish a highly sensitive method for profiling of pep-tRNAs using mass spectrometry, and successfully detect a large number of nascent peptides from pep-tRNAs accumulated in Escherichia coli pthts strain. Based on molecular mass analysis, we found about 20% of the peptides bear single amino-acid substitutions of the N-terminal sequences of E. coli ORFs. Detailed analysis of individual pep-tRNAs and reporter assay revealed that most of the substitutions take place at the C-terminal drop-off site and that the miscoded pep-tRNAs rarely participate in the next round of elongation but dissociate from the ribosome. These findings suggest that pep-tRNA drop-off is an active mechanism by which the ribosome rejects miscoded pep-tRNAs in the early elongation, thereby contributing to quality control of protein synthesis after peptide bond formation.
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Affiliation(s)
- Asuteka Nagao
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Yui Nakanishi
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yutaro Yamaguchi
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yoshifumi Mishina
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Minami Karoji
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Takafumi Toya
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Tomoya Fujita
- RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama, 351-0198, Japan
| | - Shintaro Iwasaki
- RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama, 351-0198, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, 277-8561, Japan
| | - Kenjyo Miyauchi
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yuriko Sakaguchi
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Tsutomu Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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4
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McDonnell JM, Dhaliwal B, Sutton BJ, Gould HJ. IgE, IgE Receptors and Anti-IgE Biologics: Protein Structures and Mechanisms of Action. Annu Rev Immunol 2023; 41:255-275. [PMID: 36737596 DOI: 10.1146/annurev-immunol-061020-053712] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The evolution of IgE in mammals added an extra layer of immune protection at body surfaces to provide a rapid and local response against antigens from the environment. The IgE immune response employs potent expulsive and inflammatory forces against local antigen provocation, at the risk of damaging host tissues and causing allergic disease. Two well-known IgE receptors, the high-affinity FcεRI and low-affinity CD23, mediate the activities of IgE. Unlike other known antibody receptors, CD23 also regulates IgE expression, maintaining IgE homeostasis. This mechanism evolved by adapting the function of the complement receptor CD21. Recent insights into the dynamic character of IgE structure, its resultant capacity for allosteric modulation, and the potential for ligand-induced dissociation have revealed previously unappreciated mechanisms for regulation of IgE and IgE complexes. We describe recent research, highlighting structural studies of the IgE network of proteins to analyze the uniquely versatile activities of IgE and anti-IgE biologics.
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Affiliation(s)
- J M McDonnell
- Randall Centre for Cell and Molecular Biophysics and School of Basic and Medical Biosciences, King's College London, London, UK; , ,
| | | | - B J Sutton
- Randall Centre for Cell and Molecular Biophysics and School of Basic and Medical Biosciences, King's College London, London, UK; , ,
| | - H J Gould
- Randall Centre for Cell and Molecular Biophysics and School of Basic and Medical Biosciences, King's College London, London, UK; , ,
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5
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Bao L, Karpenko VV, Forster AC. Rate-limiting hydrolysis in ribosomal release reactions revealed by ester activation. J Biol Chem 2022; 298:102509. [PMID: 36300356 PMCID: PMC9589212 DOI: 10.1016/j.jbc.2022.102509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 09/12/2022] [Accepted: 09/14/2022] [Indexed: 11/27/2022] Open
Abstract
Translation terminates by releasing the polypeptide chain in one of two chemical reactions catalyzed by the ribosome. Release is also a target for engineering, as readthrough of a stop codon enables incorporation of unnatural amino acids and treatment of genetic diseases. Hydrolysis of the ester bond of peptidyl-tRNA requires conformational changes of both a class I release factor (RF) protein and the peptidyl transferase center of a large subunit rRNA. The rate-limiting step was proposed to be hydrolysis at physiological pH and an RF conformational change at higher pH, but evidence was indirect. Here, we tested this by activating the ester electrophile at the Escherichia coli ribosomal P site using a trifluorine-substituted amino acid. Quench-flow kinetics revealed that RF1-catalyzed release could be accelerated, but only at pH 6.2-7.7 and not higher pH. This provided direct evidence for rate-limiting hydrolysis at physiological or lower pH and a different rate limitation at higher pH. Additionally, we optimized RF-free release catalyzed by unacylated tRNA or the CCA trinucleotide (in 30% acetone). We determined that these two model release reactions, although very slow, were surprisingly accelerated by the trifluorine analog but to a different extent from each other and from RF-catalyzed release. Hence, hydrolysis was rate limiting in all three reactions. Furthermore, in 20% ethanol, we found that there was significant competition between fMet-ethyl ester formation and release in all three release reactions. We thus favor proposed mechanisms for translation termination that do not require a fully-negatively-charged OH− nucleophile.
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6
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Balasanyants SM, Aleksandrova EV, Polikanov YS. The Role of Release Factors in the Hydrolysis of Ester Bond in Peptidyl-tRNA. BIOCHEMISTRY (MOSCOW) 2021; 86:1122-1127. [PMID: 34565315 DOI: 10.1134/s0006297921090078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Class I release factors (RFs) recognize stop codons in the sequences of mRNAs and are required for the hydrolysis of peptidyl-tRNA in the ribosomal P site during the final step of protein synthesis in bacteria, resulting in the release of a complete polypeptide chain from the ribosome. A key role in this process belongs to the highly conserved GGQ motif in RFs. Mutations in this motif can reduce the hydrolysis rate or even completely inhibit the reaction. Previously, it was hypothesized that the amino acid residues of GGQ (especially glutamine) are essential for the proper coordination of the water molecule for subsequent hydrolysis of the ester bond. However, available structures of the 70S ribosome termination complex do not allow unambiguous identification of the exact orientation of the carbonyl group in peptidyl-tRNA relative to the GGQ, as well as of the position of the catalytic water molecule in the peptidyl transferase center (PTC). This mini-review summarizes key facts and hypotheses on the role of GGQ in the catalysis of peptide release, as well as suggests and discusses future experiments aimed to produce high-quality structural data for deciphering the precise mechanism of RF-mediated catalysis.
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Affiliation(s)
- Samson M Balasanyants
- Department of Biological Sciences, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Elena V Aleksandrova
- Department of Biological Sciences, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yury S Polikanov
- Department of Biological Sciences, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA.
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7
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Korostelev AA. Diversity and Similarity of Termination and Ribosome Rescue in Bacterial, Mitochondrial, and Cytoplasmic Translation. BIOCHEMISTRY (MOSCOW) 2021; 86:1107-1121. [PMID: 34565314 DOI: 10.1134/s0006297921090066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
When a ribosome encounters the stop codon of an mRNA, it terminates translation, releases the newly made protein, and is recycled to initiate translation on a new mRNA. Termination is a highly dynamic process in which release factors (RF1 and RF2 in bacteria; eRF1•eRF3•GTP in eukaryotes) coordinate peptide release with large-scale molecular rearrangements of the ribosome. Ribosomes stalled on aberrant mRNAs are rescued and recycled by diverse bacterial, mitochondrial, or cytoplasmic quality control mechanisms. These are catalyzed by rescue factors with peptidyl-tRNA hydrolase activity (bacterial ArfA•RF2 and ArfB, mitochondrial ICT1 and mtRF-R, and cytoplasmic Vms1), that are distinct from each other and from release factors. Nevertheless, recent structural studies demonstrate a remarkable similarity between translation termination and ribosome rescue mechanisms. This review describes how these pathways rely on inherent ribosome dynamics, emphasizing the active role of the ribosome in all translation steps.
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Affiliation(s)
- Andrei A Korostelev
- RNA Therapeutics Institute, Department of Biochemistry and Molecular Pharmacology, UMass Medical School, Worcester, MA, USA.
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8
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Lawson MR, Lessen LN, Wang J, Prabhakar A, Corsepius NC, Green R, Puglisi JD. Mechanisms that ensure speed and fidelity in eukaryotic translation termination. Science 2021; 373:876-882. [PMID: 34413231 PMCID: PMC9017434 DOI: 10.1126/science.abi7801] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 07/07/2021] [Indexed: 11/02/2022]
Abstract
Translation termination, which liberates a nascent polypeptide from the ribosome specifically at stop codons, must occur accurately and rapidly. We established single-molecule fluorescence assays to track the dynamics of ribosomes and two requisite release factors (eRF1 and eRF3) throughout termination using an in vitro-reconstituted yeast translation system. We found that the two eukaryotic release factors bound together to recognize stop codons rapidly and elicit termination through a tightly regulated, multistep process that resembles transfer RNA selection during translation elongation. Because the release factors are conserved from yeast to humans, the molecular events that underlie yeast translation termination are likely broadly fundamental to eukaryotic protein synthesis.
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Affiliation(s)
- Michael R Lawson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Laura N Lessen
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
- Program in Molecular Biophysics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Arjun Prabhakar
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Nicholas C Corsepius
- Program in Molecular Biophysics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Rachel Green
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- 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
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
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9
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Kumar N, Sharma S, Kaushal PS. Protein synthesis in Mycobacterium tuberculosis as a potential target for therapeutic interventions. Mol Aspects Med 2021; 81:101002. [PMID: 34344520 DOI: 10.1016/j.mam.2021.101002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 07/11/2021] [Accepted: 07/16/2021] [Indexed: 12/18/2022]
Abstract
Mycobacterium tuberculosis (Mtb) causes one of humankind's deadliest diseases, tuberculosis. Mtb protein synthesis machinery possesses several unique species-specific features, including its ribosome that carries two mycobacterial specific ribosomal proteins, bL37 and bS22, and ribosomal RNA segments. Since the protein synthesis is a vital cellular process that occurs on the ribosome, a detailed knowledge of the structure and function of mycobacterial ribosomes is essential to understand the cell's proteome by translation regulation. Like in many bacterial species such as Bacillus subtilis and Streptomyces coelicolor, two distinct populations of ribosomes have been identified in Mtb. Under low-zinc conditions, Mtb ribosomal proteins S14, S18, L28, and L33 are replaced with their non-zinc binding paralogues. Depending upon the nature of physiological stress, species-specific modulation of translation by stress factors and toxins that interact with the ribosome have been reported. In addition, about one-fourth of messenger RNAs in mycobacteria have been reported to be leaderless, i.e., without 5' UTR regions. However, the mechanism by which they are recruited to the Mtb ribosome is not understood. In this review, we highlight the mycobacteria-specific features of the translation apparatus and propose exploiting these features to improve the efficacy and specificity of existing antibiotics used to treat tuberculosis.
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Affiliation(s)
- Niraj Kumar
- Structural Biology & Translation Regulation Laboratory, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, 121 001, India
| | - Shivani Sharma
- Structural Biology & Translation Regulation Laboratory, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, 121 001, India
| | - Prem S Kaushal
- Structural Biology & Translation Regulation Laboratory, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, 121 001, India.
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10
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Koripella RK, Deep A, Agrawal EK, Keshavan P, Banavali NK, Agrawal RK. Distinct mechanisms of the human mitoribosome recycling and antibiotic resistance. Nat Commun 2021; 12:3607. [PMID: 34127662 PMCID: PMC8203779 DOI: 10.1038/s41467-021-23726-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 05/14/2021] [Indexed: 11/16/2022] Open
Abstract
Ribosomes are recycled for a new round of translation initiation by dissociation of ribosomal subunits, messenger RNA and transfer RNA from their translational post-termination complex. Here we present cryo-EM structures of the human 55S mitochondrial ribosome (mitoribosome) and the mitoribosomal large 39S subunit in complex with mitoribosome recycling factor (RRFmt) and a recycling-specific homolog of elongation factor G (EF-G2mt). These structures clarify an unusual role of a mitochondria-specific segment of RRFmt, identify the structural distinctions that confer functional specificity to EF-G2mt, and show that the deacylated tRNA remains with the dissociated 39S subunit, suggesting a distinct sequence of events in mitoribosome recycling. Furthermore, biochemical and structural analyses reveal that the molecular mechanism of antibiotic fusidic acid resistance for EF-G2mt is markedly different from that of mitochondrial elongation factor EF-G1mt, suggesting that the two human EF-Gmts have evolved diversely to negate the effect of a bacterial antibiotic. High-resolution cryo-EM structures and biochemical analyses of the human mitoribosome, in complex with mitochondria-specific factors mediating mitoribosome recycling, RRFmt and EF-G2mt, offer insight into mechanisms of mitoribosome recycling and resistance to antibiotic fusidic acid.
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Affiliation(s)
- Ravi Kiran Koripella
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Ayush Deep
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Ekansh K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Pooja Keshavan
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Nilesh K Banavali
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA.,Department of Biomedical Sciences, University at Albany, Albany, NY, USA
| | - Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA. .,Department of Biomedical Sciences, University at Albany, Albany, NY, USA.
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11
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Zhao L, Castanié-Cornet MP, Kumar S, Genevaux P, Hayer-Hartl M, Hartl FU. Bacterial RF3 senses chaperone function in co-translational folding. Mol Cell 2021; 81:2914-2928.e7. [PMID: 34107307 DOI: 10.1016/j.molcel.2021.05.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 04/05/2021] [Accepted: 05/13/2021] [Indexed: 10/21/2022]
Abstract
Molecular chaperones assist with protein folding by interacting with nascent polypeptide chains (NCs) during translation. Whether the ribosome can sense chaperone defects and, in response, abort translation of misfolding NCs has not yet been explored. Here we used quantitative proteomics to investigate the ribosome-associated chaperone network in E. coli and the consequences of its dysfunction. Trigger factor and the DnaK (Hsp70) system are the major NC-binding chaperones. HtpG (Hsp90), GroEL, and ClpB contribute increasingly when DnaK is deficient. Surprisingly, misfolding because of defects in co-translational chaperone function or amino acid analog incorporation results in recruitment of the non-canonical release factor RF3. RF3 recognizes aberrant NCs and then moves to the peptidyltransferase site to cooperate with RF2 in mediating chain termination, facilitating clearance by degradation. This function of RF3 reduces the accumulation of misfolded proteins and is critical for proteostasis maintenance and cell survival under conditions of limited chaperone availability.
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Affiliation(s)
- Liang Zhao
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Marie-Pierre Castanié-Cornet
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Sneha Kumar
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Pierre Genevaux
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Manajit Hayer-Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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12
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Pundir S, Ge X, Sanyal S. GGQ methylation enhances both speed and accuracy of stop codon recognition by bacterial class-I release factors. J Biol Chem 2021; 296:100681. [PMID: 33887323 PMCID: PMC8131318 DOI: 10.1016/j.jbc.2021.100681] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 10/28/2022] Open
Abstract
Accurate translation termination in bacteria requires correct recognition of the stop codons by the class-I release factors (RFs) RF1 and RF2, which release the nascent peptide from the peptidyl tRNA after undergoing a "compact to open" conformational transition. These RFs possess a conserved Gly-Gly-Gln (GGQ) peptide release motif, of which the Q residue is posttranslationally methylated. GGQ-methylated RFs have been shown to be faster in peptide release than the unmethylated ones, but it was unknown whether this modification had additional roles. Using a fluorescence-based real-time in vitro translation termination assay in a stopped-flow instrument, we demonstrate that methylated RF1 and RF2 are two- to four-fold more accurate in the cognate stop codon recognition than their unmethylated variants. Using pH titration, we show that the lack of GGQ methylation facilitates the "compact to open" transition, which results in compromised accuracy of the unmethylated RFs. Furthermore, thermal melting studies using circular dichroism and SYPRO-orange fluorescence demonstrate that GGQ methylation increases overall stability of the RF proteins. This increased stability, we suspect, is the basis for the more controlled conformational change of the methylated RFs upon codon recognition, which enhances both their speed and accuracy. This GGQ methylation-based modulation of the accuracy of RFs can be a tool for regulating translational termination in vivo.
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Affiliation(s)
- Shreya Pundir
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden
| | - Xueliang Ge
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden.
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13
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Abdalaal H, Pundir S, Ge X, Sanyal S, Näsvall J. Collateral Toxicity Limits the Evolution of Bacterial Release Factor 2 toward Total Omnipotence. Mol Biol Evol 2020; 37:2918-2930. [PMID: 32437534 PMCID: PMC7530605 DOI: 10.1093/molbev/msaa129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
When new genes evolve through modification of existing genes, there are often tradeoffs between the new and original functions, making gene duplication and amplification necessary to buffer deleterious effects on the original function. We have used experimental evolution of a bacterial strain lacking peptide release factor 1 (RF1) in order to study how peptide release factor 2 (RF2) evolves to compensate the loss of RF1. As expected, amplification of the RF2-encoding gene prfB to high copy number was a rapid initial response, followed by the appearance of mutations in RF2 and other components of the translation machinery. Characterization of the evolved RF2 variants by their effects on bacterial growth rate, reporter gene expression, and in vitro translation termination reveals a complex picture of reduced discrimination between the cognate and near-cognate stop codons and highlights a functional tradeoff that we term "collateral toxicity." We suggest that this type of tradeoff may be a more serious obstacle in new gene evolution than the more commonly discussed evolutionary tradeoffs between "old" and "new" functions of a gene, as it cannot be overcome by gene copy number changes. Further, we suggest a model for how RF2 autoregulation responds to alterations in the demand not only for RF2 activity but also for RF1 activity.
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Affiliation(s)
- Hind Abdalaal
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Shreya Pundir
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Xueliang Ge
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Joakim Näsvall
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
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14
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Saito K, Green R, Buskirk AR. Ribosome recycling is not critical for translational coupling in Escherichia coli. eLife 2020; 9:59974. [PMID: 32965213 PMCID: PMC7538156 DOI: 10.7554/elife.59974] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 09/22/2020] [Indexed: 12/23/2022] Open
Abstract
We used ribosome profiling to characterize the biological role of ribosome recycling factor (RRF) in Escherichia coli. As expected, RRF depletion leads to enrichment of post-termination 70S complexes in 3′-UTRs. We also observe that elongating ribosomes are unable to complete translation because they are blocked by non-recycled ribosomes at stop codons. Previous studies have suggested a role for recycling in translational coupling within operons; if a ribosome remains bound to an mRNA after termination, it may re-initiate downstream. We found, however, that RRF depletion did not significantly affect coupling efficiency in reporter assays or in ribosome density genome-wide. These findings argue that re-initiation is not a major mechanism of translational coupling in E. coli. Finally, RRF depletion has dramatic effects on the activity of ribosome rescue factors tmRNA and ArfA. Our results provide a global view of the effects of the loss of ribosome recycling on protein synthesis in E. coli.
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Affiliation(s)
- Kazuki Saito
- Department of Molecular Biology and Genetics, Baltimore, United States
| | - Rachel Green
- Department of Molecular Biology and Genetics, Baltimore, United States.,Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Allen R Buskirk
- Department of Molecular Biology and Genetics, Baltimore, United States
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15
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Kurita D, Abo T, Himeno H. Molecular determinants of release factor 2 for ArfA-mediated ribosome rescue. J Biol Chem 2020; 295:13326-13337. [PMID: 32727848 DOI: 10.1074/jbc.ra120.014664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/27/2020] [Indexed: 02/01/2023] Open
Abstract
Translation termination in bacteria requires that the stop codon be recognized by release factor RF1 or RF2, leading to hydrolysis of the ester bond between the peptide and tRNA on the ribosome. As a consequence, normal termination cannot proceed if the translated mRNA lacks a stop codon. In Escherichia coli, the ribosome rescue factor ArfA releases the nascent polypeptide from the stalled ribosome with the help of RF2 in a stop codon-independent manner. Interestingly, the reaction does not proceed if RF1 is instead provided, even though the structures of RF1 and RF2 are very similar. Here, we identified the regions of RF2 required for the ArfA-dependent ribosome rescue system. Introduction of hydrophobic residues from RF2 found at the interface between RF2 and ArfA into RF1 allowed RF1 to associate with the ArfA-ribosome complex to a certain extent but failed to promote peptidyl-tRNA hydrolysis, whereas WT RF1 did not associate with the complex. We also identified the key residues required for the process after ribosome binding. Our findings provide a basis for understanding how the ArfA-ribosome complex is specifically recognized by RF2 and how RF2 undergoes a conformational change upon binding to the ArfA-ribosome complex.
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Affiliation(s)
- Daisuke Kurita
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan.
| | - Tatsuhiko Abo
- Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Hyouta Himeno
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan.
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16
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Abstract
Many organisms, including bacteria, code for multiple paralogues of some ribosomal protein subunits. The relative contribution of these alternative subunits to ribosome function and protein synthesis is unknown and controversial. Many studies on alternative ribosomes have been confounded by isolation of alternative and canonical ribosomes from different strains or growth conditions, potentially confounding results. Here, we show that one form of alternative ribosome from Mycobacterium smegmatis has a distinct translational profile compared with canonical ribosomes purified from an identical cellular context. We also identify a role for alternative ribosomes in iron homeostasis. Given the prevalence of alternative ribosomal genes in diverse organisms, our study suggests that alternative ribosomes may represent a further layer of regulation of gene translation. Alternative ribosome subunit proteins are prevalent in the genomes of diverse bacterial species, but their functional significance is controversial. Attempts to study microbial ribosomal heterogeneity have mostly relied on comparing wild-type strains with mutants in which subunits have been deleted, but this approach does not allow direct comparison of alternate ribosome isoforms isolated from identical cellular contexts. Here, by simultaneously purifying canonical and alternative RpsR ribosomes from Mycobacterium smegmatis, we show that alternative ribosomes have distinct translational features compared with their canonical counterparts. Both alternative and canonical ribosomes actively take part in protein synthesis, although they translate a subset of genes with differential efficiency as measured by ribosome profiling. We also show that alternative ribosomes have a relative defect in initiation complex formation. Furthermore, a strain of M. smegmatis in which the alternative ribosome protein operon is deleted grows poorly in iron-depleted medium, uncovering a role for alternative ribosomes in iron homeostasis. Our work confirms the distinct and nonredundant contribution of alternative bacterial ribosomes for adaptation to hostile environments.
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17
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Morais P, Adachi H, Yu YT. Suppression of Nonsense Mutations by New Emerging Technologies. Int J Mol Sci 2020; 21:ijms21124394. [PMID: 32575694 PMCID: PMC7352488 DOI: 10.3390/ijms21124394] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 12/18/2022] Open
Abstract
Nonsense mutations often result from single nucleotide substitutions that change a sense codon (coding for an amino acid) to a nonsense or premature termination codon (PTC) within the coding region of a gene. The impact of nonsense mutations is two-fold: (1) the PTC-containing mRNA is degraded by a surveillance pathway called nonsense-mediated mRNA decay (NMD) and (2) protein translation stops prematurely at the PTC codon, and thus no functional full-length protein is produced. As such, nonsense mutations result in a large number of human diseases. Nonsense suppression is a strategy that aims to correct the defects of hundreds of genetic disorders and reverse disease phenotypes and conditions. While most clinical trials have been performed with small molecules, there is an increasing need for sequence-specific repair approaches that are safer and adaptable to personalized medicine. Here, we discuss recent advances in both conventional strategies as well as new technologies. Several of these will soon be tested in clinical trials as nonsense therapies, even if they still have some limitations and challenges to overcome.
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Affiliation(s)
- Pedro Morais
- ProQR Therapeutics, Zernikedreef 9, 2333 CK Leiden, The Netherlands;
| | - Hironori Adachi
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA;
| | - Yi-Tao Yu
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA;
- Correspondence: ; Tel.: +1-(585)-275-1271; Fax: +1-(585)-275-6007
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18
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Weber M, Burgos R, Yus E, Yang J, Lluch‐Senar M, Serrano L. Impact of C-terminal amino acid composition on protein expression in bacteria. Mol Syst Biol 2020; 16:e9208. [PMID: 32449593 PMCID: PMC7246954 DOI: 10.15252/msb.20199208] [Citation(s) in RCA: 17] [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: 08/28/2019] [Revised: 04/07/2020] [Accepted: 04/09/2020] [Indexed: 11/30/2022] Open
Abstract
The C-terminal sequence of a protein is involved in processes such as efficiency of translation termination and protein degradation. However, the general relationship between features of this C-terminal sequence and levels of protein expression remains unknown. Here, we identified C-terminal amino acid biases that are ubiquitous across the bacterial taxonomy (1,582 genomes). We showed that the frequency is higher for positively charged amino acids (lysine, arginine), while hydrophobic amino acids and threonine are lower. We then studied the impact of C-terminal composition on protein levels in a library of Mycoplasma pneumoniae mutants, covering all possible combinations of the two last codons. We found that charged and polar residues, in particular lysine, led to higher expression, while hydrophobic and aromatic residues led to lower expression, with a difference in protein levels up to fourfold. We further showed that modulation of protein degradation rate could be one of the main mechanisms driving these differences. Our results demonstrate that the identity of the last amino acids has a strong influence on protein expression levels.
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Affiliation(s)
- Marc Weber
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Raul Burgos
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Eva Yus
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Jae‐Seong Yang
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Maria Lluch‐Senar
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Luis Serrano
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
- Universitat Pompeu Fabra (UPF)BarcelonaSpain
- ICREABarcelonaSpain
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19
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Ayyub SA, Gao F, Lightowlers RN, Chrzanowska-Lightowlers ZM. Rescuing stalled mammalian mitoribosomes - what can we learn from bacteria? J Cell Sci 2020; 133:133/1/jcs231811. [PMID: 31896602 DOI: 10.1242/jcs.231811] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In the canonical process of translation, newly completed proteins escape from the ribosome following cleavage of the ester bond that anchors the polypeptide to the P-site tRNA, after which the ribosome can be recycled to initiate a new round of translation. Not all protein synthesis runs to completion as various factors can impede the progression of ribosomes. Rescuing of stalled ribosomes in mammalian mitochondria, however, does not share the same mechanisms that many bacteria use. The classic method for rescuing bacterial ribosomes is trans-translation. The key components of this system are absent from mammalian mitochondria; however, four members of a translation termination factor family are present, with some evidence of homology to members of a bacterial back-up rescue system. To date, there is no definitive demonstration of any other member of this family functioning in mitoribosome rescue. Here, we provide an overview of the processes and key players of canonical translation termination in both bacteria and mammalian mitochondria, followed by a perspective of the bacterial systems used to rescue stalled ribosomes. We highlight any similarities or differences with the mitochondrial translation release factors, and suggest potential roles for these proteins in ribosome rescue in mammalian mitochondria.
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Affiliation(s)
- Shreya Ahana Ayyub
- The Wellcome Centre for Mitochondrial Research, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Fei Gao
- The Wellcome Centre for Mitochondrial Research, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert N Lightowlers
- The Wellcome Centre for Mitochondrial Research, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Zofia M Chrzanowska-Lightowlers
- The Wellcome Centre for Mitochondrial Research, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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20
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Ho AT, Hurst LD. In eubacteria, unlike eukaryotes, there is no evidence for selection favouring fail-safe 3' additional stop codons. PLoS Genet 2019; 15:e1008386. [PMID: 31527909 PMCID: PMC6764699 DOI: 10.1371/journal.pgen.1008386] [Citation(s) in RCA: 10] [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: 06/11/2019] [Revised: 09/27/2019] [Accepted: 08/27/2019] [Indexed: 12/23/2022] Open
Abstract
Errors throughout gene expression are likely deleterious, hence genomes are under selection to ameliorate their consequences. Additional stop codons (ASCs) are in-frame nonsense ‘codons’ downstream of the primary stop which may be read by translational machinery should the primary stop have been accidentally read through. Prior evidence in several eukaryotes suggests that ASCs are selected to prevent potentially-deleterious consequences of read-through. We extend this evidence showing that enrichment of ASCs is common but not universal for single cell eukaryotes. By contrast, there is limited evidence as to whether the same is true in other taxa. Here, we provide the first systematic test of the hypothesis that ASCs act as a fail-safe mechanism in eubacteria, a group with high read-through rates. Contra to the predictions of the hypothesis we find: there is paucity, not enrichment, of ASCs downstream; substitutions that degrade stops are more frequent in-frame than out-of-frame in 3’ sequence; highly expressed genes are no more likely to have ASCs than lowly expressed genes; usage of the leakiest primary stop (TGA) in highly expressed genes does not predict ASC enrichment even compared to usage of non-leaky stops (TAA) in lowly expressed genes, beyond downstream codon +1. Any effect at the codon immediately proximal to the primary stop can be accounted for by a preference for a T/U residue immediately following the stop, although if anything, TT- and TC- starting codons are preferred. We conclude that there is no compelling evidence for ASC selection in eubacteria. This presents an unusual case in which the same error could be solved by the same mechanism in eukaryotes and prokaryotes but is not. We discuss two possible explanations: that, owing to the absence of nonsense mediated decay, bacteria may solve read-through via gene truncation and in eukaryotes certain prion states cause raised read-through rates. In all organisms, gene expression is error-prone. One such error, translational read-through, occurs where the primary stop codon of an expressed gene is missed by the translational machinery. Failure to terminate is likely to be costly, hence genomes are under selection to prevent this from happening. One proposed error-proofing strategy involves in-frame proximal additional stop codons (ASCs) which may act as a ‘fail-safe’ mechanism by providing another opportunity for translation to terminate. There is evidence for ASC enrichment in several eukaryotes. We extend this evidence showing it to be common but not universal in single celled eukaryotes. However, the situation in bacteria is poorly understood, despite bacteria having high read-through rates. Here, we test the fail-safe hypothesis within a broad range of bacteria. To our surprise, we find that not only are ASCs not enriched, but they may even be selected against. This provides evidence for an unusual circumstance where eukaryotes and prokaryotes could solve the same problem the same way but don’t. What are we to make of this? We suggest that if read-through is the problem, ASCs are not necessarily the expected solution. Owing to the absence of nonsense-mediated decay, a process that makes gene truncation in eukaryotes less viable, we propose bacteria may rescue a leaky stop by mutation that creates a new stop upstream. Alternatively, raised read-through rates in some particular conditions in eukaryotes might explain the difference.
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Affiliation(s)
- Alexander T. Ho
- Milner Centre for Evolution, University of Bath, Bath, United Kingdom
- * E-mail:
| | - Laurence D. Hurst
- Milner Centre for Evolution, University of Bath, Bath, United Kingdom
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21
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Svidritskiy E, Demo G, Loveland AB, Xu C, Korostelev AA. Extensive ribosome and RF2 rearrangements during translation termination. eLife 2019; 8:46850. [PMID: 31513010 PMCID: PMC6742477 DOI: 10.7554/elife.46850] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 08/28/2019] [Indexed: 12/31/2022] Open
Abstract
Protein synthesis ends when a ribosome reaches an mRNA stop codon. Release factors (RFs) decode the stop codon, hydrolyze peptidyl-tRNA to release the nascent protein, and then dissociate to allow ribosome recycling. To visualize termination by RF2, we resolved a cryo-EM ensemble of E. coli 70S•RF2 structures at up to 3.3 Å in a single sample. Five structures suggest a highly dynamic termination pathway. Upon peptidyl-tRNA hydrolysis, the CCA end of deacyl-tRNA departs from the peptidyl transferase center. The catalytic GGQ loop of RF2 is rearranged into a long β-hairpin that plugs the peptide tunnel, biasing a nascent protein toward the ribosome exit. Ribosomal intersubunit rotation destabilizes the catalytic RF2 domain on the 50S subunit and disassembles the central intersubunit bridge B2a, resulting in RF2 departure. Our structures visualize how local rearrangements and spontaneous inter-subunit rotation poise the newly-made protein and RF2 to dissociate in preparation for ribosome recycling.
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Affiliation(s)
- Egor Svidritskiy
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| | - Gabriel Demo
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| | - Anna B Loveland
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| | - Chen Xu
- Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States
| | - Andrei A Korostelev
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States.,Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States
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22
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Prabhakar A, Puglisi EV, Puglisi JD. Single-Molecule Fluorescence Applied to Translation. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a032714. [PMID: 29891562 DOI: 10.1101/cshperspect.a032714] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Single-molecule fluorescence methods have illuminated the dynamics of the translational machinery. Structural and bulk biochemical experiments have provided detailed atomic and global mechanistic views of translation, respectively. Single-molecule studies of translation have bridged these views by temporally connecting the conformational and compositional states defined from structural data within the mechanistic framework of translation produced from biochemical studies. Here, we discuss the context for applying different single-molecule fluorescence experiments, and present recent applications to studying prokaryotic and eukaryotic translation. We underscore the power of observing single translating ribosomes to delineate and sort complex mechanistic pathways during initiation and elongation, and discuss future applications of current and improved technologies.
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Affiliation(s)
- Arjun Prabhakar
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305.,Program in Biophysics, Stanford University, Stanford, California 94305
| | - Elisabetta Viani Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305
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23
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Narrowe AB, Spang A, Stairs CW, Caceres EF, Baker BJ, Miller CS, Ettema TJG. Complex Evolutionary History of Translation Elongation Factor 2 and Diphthamide Biosynthesis in Archaea and Parabasalids. Genome Biol Evol 2018; 10:2380-2393. [PMID: 30060184 PMCID: PMC6143161 DOI: 10.1093/gbe/evy154] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2018] [Indexed: 12/22/2022] Open
Abstract
Diphthamide is a modified histidine residue which is uniquely present in archaeal and eukaryotic elongation factor 2 (EF-2), an essential GTPase responsible for catalyzing the coordinated translocation of tRNA and mRNA through the ribosome. In part due to the role of diphthamide in maintaining translational fidelity, it was previously assumed that diphthamide biosynthesis genes (dph) are conserved across all eukaryotes and archaea. Here, comparative analysis of new and existing genomes reveals that some archaea (i.e., members of the Asgard superphylum, Geoarchaea, and Korarchaeota) and eukaryotes (i.e., parabasalids) lack dph. In addition, while EF-2 was thought to exist as a single copy in archaea, many of these dph-lacking archaeal genomes encode a second EF-2 paralog missing key residues required for diphthamide modification and for normal translocase function, perhaps suggesting functional divergence linked to loss of diphthamide biosynthesis. Interestingly, some Heimdallarchaeota previously suggested to be most closely related to the eukaryotic ancestor maintain dph genes and a single gene encoding canonical EF-2. Our findings reveal that the ability to produce diphthamide, once thought to be a universal feature in archaea and eukaryotes, has been lost multiple times during evolution, and suggest that anticipated compensatory mechanisms evolved independently.
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Affiliation(s)
- Adrienne B Narrowe
- Department of Integrative Biology, University of Colorado Denver, Denver
| | - Anja Spang
- Department of Marine Microbiology and Biogeochemistry, NIOZ, Royal Netherlands Institute for Sea Research, Utrecht University, AB Den Burg, The Netherlands
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Sweden
| | - Courtney W Stairs
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Sweden
| | - Eva F Caceres
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Sweden
| | - Brett J Baker
- Department of Marine Science, Marine Science Institute, University of Texas Austin, Port Aransas
| | | | - Thijs J G Ettema
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Sweden
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24
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Graf M, Huter P, Maracci C, Peterek M, Rodnina MV, Wilson DN. Visualization of translation termination intermediates trapped by the Apidaecin 137 peptide during RF3-mediated recycling of RF1. Nat Commun 2018; 9:3053. [PMID: 30076302 PMCID: PMC6076264 DOI: 10.1038/s41467-018-05465-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/06/2018] [Indexed: 12/20/2022] Open
Abstract
During translation termination in bacteria, the release factors RF1 and RF2 are recycled from the ribosome by RF3. While high-resolution structures of the individual termination factors on the ribosome exist, direct structural insight into how RF3 mediates dissociation of the decoding RFs has been lacking. Here we have used the Apidaecin 137 peptide to trap RF1 together with RF3 on the ribosome and visualize an ensemble of termination intermediates using cryo-electron microscopy. Binding of RF3 to the ribosome induces small subunit (SSU) rotation and swivelling of the head, yielding intermediate states with shifted P-site tRNAs and RF1 conformations. RF3 does not directly eject RF1 from the ribosome, but rather induces full rotation of the SSU that indirectly dislodges RF1 from its binding site. SSU rotation is coupled to the accommodation of the GTPase domain of RF3 on the large subunit (LSU), thereby promoting GTP hydrolysis and dissociation of RF3 from the ribosome. In bacteria, the process of translation termination is performed by three termination release factors RF1, RF2 and RF3. Here the authors provide detailed structural insights into the mechanism by which RF1 is dissociated from the ribosome by RF3 during termination.
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Affiliation(s)
- Michael Graf
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany
| | - Paul Huter
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany
| | - Cristina Maracci
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, 37077, Germany
| | - Miroslav Peterek
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, 37077, Germany
| | - Daniel N Wilson
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany.
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25
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Purifying and positive selection in the evolution of stop codons. Sci Rep 2018; 8:9260. [PMID: 29915293 PMCID: PMC6006363 DOI: 10.1038/s41598-018-27570-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 05/18/2018] [Indexed: 12/13/2022] Open
Abstract
Modes of evolution of stop codons in protein-coding genes, especially the conservation of UAA, have been debated for many years. We reconstructed the evolution of stop codons in 40 groups of closely related prokaryotic and eukaryotic genomes. The results indicate that the UAA codons are maintained by purifying selection in all domains of life. In contrast, positive selection appears to drive switches from UAG to other stop codons in prokaryotes but not in eukaryotes. Changes in stop codons are significantly associated with increased substitution frequency immediately downstream of the stop. These positions are otherwise more strongly conserved in evolution compared to sites farther downstream, suggesting that such substitutions are compensatory. Although GC content has a major impact on stop codon frequencies, its contribution to the decreased frequency of UAA differs between bacteria and archaea, presumably, due to differences in their translation termination mechanisms.
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26
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Adio S, Sharma H, Senyushkina T, Karki P, Maracci C, Wohlgemuth I, Holtkamp W, Peske F, Rodnina MV. Dynamics of ribosomes and release factors during translation termination in E. coli. eLife 2018; 7:34252. [PMID: 29889659 PMCID: PMC5995542 DOI: 10.7554/elife.34252] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 05/11/2018] [Indexed: 12/28/2022] Open
Abstract
Release factors RF1 and RF2 promote hydrolysis of peptidyl-tRNA during translation termination. The GTPase RF3 promotes recycling of RF1 and RF2. Using single molecule FRET and biochemical assays, we show that ribosome termination complexes that carry two factors, RF1–RF3 or RF2–RF3, are dynamic and fluctuate between non-rotated and rotated states, whereas each factor alone has its distinct signature on ribosome dynamics and conformation. Dissociation of RF1 depends on peptide release and the presence of RF3, whereas RF2 can dissociate spontaneously. RF3 binds in the GTP-bound state and can rapidly dissociate without GTP hydrolysis from termination complex carrying RF1. In the absence of RF1, RF3 is stalled on ribosomes if GTP hydrolysis is blocked. Our data suggest how the assembly of the ribosome–RF1–RF3–GTP complex, peptide release, and ribosome fluctuations promote termination of protein synthesis and recycling of the release factors. Inside cells, molecular machines called ribosomes make proteins using messenger RNA as a template. However, the template contains more than just the information needed to create the protein. A ‘stop codon’ in the mRNA marks where the ribosome should stop. When this is reached a group of proteins called release factors removes the newly made protein from the ribosome. Bacteria typically have three types of release factors. RF1 and RF2 recognize the stop codon, and RF3 helps to release RF1 or RF2 from the ribosome so that it can be recycled to produce another protein. It was not fully understood how the release factors interact with the ribosome and how this terminates protein synthesis. Adio et al. used TIRF microscopy to study individual ribosomes from the commonly studied bacteria species Escherichia coli. This technique allows researchers to monitor movements of the ribosome and record how release factors bind to it. The results of the experiments performed by Adio et al. show that although RF1 and RF2 are very similar to each other, they interact with the ribosome in different ways. In addition, only RF1 relies upon RF3 to release it from the ribosome; RF2 can release itself. RF3 releases RF1 by forcing the ribosome to change shape. RF3 then uses energy produced by the breakdown of a molecule called GTP to help release itself from the ribosome. Most importantly, the findings presented by Adio et al. highlight that the movements of ribosomes and release factors during termination are only loosely coupled rather than occur in a set order. Other molecular machines are likely to work in a similar way. The results could also help us to understand the molecular basis of several human diseases, such as Duchenne muscular dystrophy and cystic fibrosis, that result from ribosomes not recognizing stop codons in the mRNA.
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Affiliation(s)
- Sarah Adio
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Heena Sharma
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Tamara Senyushkina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Prajwal Karki
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Cristina Maracci
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Ingo Wohlgemuth
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Wolf Holtkamp
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Frank Peske
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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27
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Casy W, Prater AR, Cornish PV. Operative Binding of Class I Release Factors and YaeJ Stabilizes the Ribosome in the Nonrotated State. Biochemistry 2018; 57:1954-1966. [PMID: 29499110 DOI: 10.1021/acs.biochem.7b00824] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
During translation, the small subunit of the ribosome rotates with respect to the large subunit primarily between two states as mRNA is being translated into a protein. At the termination of bacterial translation, class I release factors (RFs) bind to a stop codon in the A-site and catalyze the release of the peptide chain from the ribosome. Periodically, mRNA is truncated prematurely, and the translating ribosome stalls at the end of the mRNA forming a nonstop complex requiring one of several ribosome rescue factors to intervene. One factor, YaeJ, is structurally homologous with the catalytic region of RFs but differs by binding to the ribosome directly through its C-terminal tail. Structures of the ribosome show that the ribosome adopts the nonrotated state conformation when these factors are bound. However, these studies do not elucidate the influence of binding to cognate or noncognate codons on the dynamics of intersubunit rotation. Here, we investigate the effects of wild-type and mutant forms of RF1, RF2, and YaeJ binding on ribosome intersubunit rotation using single-molecule Förster resonance energy transfer. We show that both RF1 binding and RF2 binding are sufficient to shift the population of posthydrolysis ribosome complexes from primarily the rotated to the nonrotated state only when a cognate stop codon is present in the A-site. Similarly, YaeJ binding stabilizes nonstop ribosomal complexes in the nonrotated state. Along with previous studies, these results are consistent with the idea that directed conformational changes and binding of subsequent factors to the ribosome are requisite for efficient termination and ribosome recycling.
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Affiliation(s)
- Widler Casy
- Department of Biochemistry , University of Missouri , Columbia , Missouri 65211 , United States
| | - Austin R Prater
- Department of Biochemistry , University of Missouri , Columbia , Missouri 65211 , United States
| | - Peter V Cornish
- Department of Biochemistry , University of Missouri , Columbia , Missouri 65211 , United States
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28
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Post-termination Ribosome Intermediate Acts as the Gateway to Ribosome Recycling. Cell Rep 2018; 20:161-172. [PMID: 28683310 DOI: 10.1016/j.celrep.2017.06.028] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/06/2017] [Accepted: 06/09/2017] [Indexed: 01/24/2023] Open
Abstract
During termination of translation, the nascent peptide is first released from the ribosome, which must be subsequently disassembled into subunits in a process known as ribosome recycling. In bacteria, termination and recycling are mediated by the translation factors RF, RRF, EF-G, and IF3, but their precise roles have remained unclear. Here, we use single-molecule fluorescence to track the conformation and composition of the ribosome in real time during termination and recycling. Our results show that peptide release by RF induces a rotated ribosomal conformation. RRF binds to this rotated intermediate to form the substrate for EF-G that, in turn, catalyzes GTP-dependent subunit disassembly. After the 50S subunit departs, IF3 releases the deacylated tRNA from the 30S subunit, thus preventing reassembly of the 70S ribosome. Our findings reveal the post-termination rotated state as the crucial intermediate in the transition from termination to recycling.
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29
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Marchisio MA. Computational Gene Circuit Design. INTRODUCTION IN SYNTHETIC BIOLOGY 2018:109-129. [DOI: 10.1007/978-981-10-8752-3_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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30
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Gibbs MR, Fredrick K. Roles of elusive translational GTPases come to light and inform on the process of ribosome biogenesis in bacteria. Mol Microbiol 2017; 107:445-454. [PMID: 29235176 DOI: 10.1111/mmi.13895] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 12/07/2017] [Accepted: 12/08/2017] [Indexed: 12/25/2022]
Abstract
Protein synthesis relies on several translational GTPases (trGTPases), related proteins that couple the hydrolysis of GTP to specific molecular events on the ribosome. Most bacterial trGTPases, including IF2, EF-Tu, EF-G and RF3, play well-known roles in translation. The cellular functions of LepA (also termed EF4) and BipA (also termed TypA), conversely, have remained enigmatic. Recent studies provide compelling in vivo evidence that LepA and BipA function in biogenesis of the 30S and 50S subunit respectively. These findings have important implications for ribosome biogenesis in bacteria. Because the GTPase activity of each of these proteins depends on interactions with both ribosomal subunits, some portion of 30S and 50S assembly must occur in the context of the 70S ribosome. In this review, we introduce the trGTPases of bacteria, describe the new functional data on LepA and BipA, and discuss the how these findings shape our current view of ribosome biogenesis in bacteria.
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Affiliation(s)
- Michelle R Gibbs
- Department of Microbiology and Center for RNA Biology, The Ohio State University, 484 W. 12th Ave, Columbus, OH 43210, USA
| | - Kurt Fredrick
- Department of Microbiology and Center for RNA Biology, The Ohio State University, 484 W. 12th Ave, Columbus, OH 43210, USA
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31
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Buskirk AR, Green R. Ribosome pausing, arrest and rescue in bacteria and eukaryotes. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0183. [PMID: 28138069 DOI: 10.1098/rstb.2016.0183] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 12/17/2022] Open
Abstract
Ribosomes translate genetic information into polypeptides in several basic steps: initiation, elongation, termination and recycling. When ribosomes are arrested during elongation or termination, the cell's capacity for protein synthesis is reduced. There are numerous quality control systems in place to distinguish between paused ribosomes that need some extra input to proceed and terminally stalled ribosomes that need to be rescued. Here, we discuss similarities and differences in the systems for resolution of pauses and rescue of arrested ribosomes in bacteria and eukaryotes, and how ribosome profiling has transformed our ability to decipher these molecular events.This article is part of the themed issue 'Perspectives on the ribosome'.
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Affiliation(s)
- Allen R Buskirk
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Howard Hughes Medical Institute, Baltimore, MD, USA
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Howard Hughes Medical Institute, Baltimore, MD, USA
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32
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Korkmaz G, Sanyal S. R213I mutation in release factor 2 (RF2) is one step forward for engineering an omnipotent release factor in bacteria Escherichia coli. J Biol Chem 2017; 292:15134-15142. [PMID: 28743745 DOI: 10.1074/jbc.m117.785238] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 07/23/2017] [Indexed: 11/06/2022] Open
Abstract
The current understanding of the specificity of the bacterial class I release factors (RFs) in decoding stop codons has evolved beyond a simple tripeptide anticodon model. A recent molecular dynamics study for deciphering the principles for specific stop codon recognition by RFs identified Arg-213 as a crucial residue on Escherichia coli RF2 for discriminating guanine in the third position (G3). Interestingly, Arg-213 is highly conserved in RF2 and substituted by Ile-196 in the corresponding position in RF1. Another similar pair is Leu-126 in RF1 and Asp-143 in RF2, which are also conserved within their respective groups. With the hypothesis that replacement of Arg-213 and Asp-143 with the corresponding RF1 residues will reduce G3 discrimination by RF2, we swapped these residues between E. coli RF1 and RF2 by site-directed mutagenesis and characterized their preference for different codons using a competitive peptide release assay. Among these, the R213I mutant of RF2 showed 5-fold improved reading of the RF1-specific UAG codon relative to UAA, the universal stop codon, compared with the wild type (WT). In-depth fast kinetic studies revealed that the gain in UAG reading by RF2 R213I is associated with a reduced efficiency of termination on the cognate UAA codon. Our work highlights the notion that stop codon recognition involves complex interactions with multiple residues beyond the PXT/SPF motifs. We propose that the R213I mutation in RF2 brings us one step forward toward engineering an omnipotent RF in bacteria, capable of reading all three stop codons.
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Affiliation(s)
- Gürkan Korkmaz
- From the Department of Cell and Molecular Biology, Uppsala University, Box-596, 75124 Uppsala, Sweden
| | - Suparna Sanyal
- From the Department of Cell and Molecular Biology, Uppsala University, Box-596, 75124 Uppsala, Sweden
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33
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Prabhakar A, Choi J, Wang J, Petrov A, Puglisi JD. Dynamic basis of fidelity and speed in translation: Coordinated multistep mechanisms of elongation and termination. Protein Sci 2017; 26:1352-1362. [PMID: 28480640 DOI: 10.1002/pro.3190] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 05/03/2017] [Indexed: 12/11/2022]
Abstract
As the universal machine that transfers genetic information from RNA to protein, the ribosome synthesizes proteins with remarkably high fidelity and speed. This is a result of the accurate and efficient decoding of mRNA codons via multistep mechanisms during elongation and termination stages of translation. These mechanisms control how the correct sense codon is recognized by a tRNA for peptide elongation, how the next codon is presented to the decoding center without change of frame during translocation, and how the stop codon is discriminated for timely release of the nascent peptide. These processes occur efficiently through coupling of chemical energy expenditure, ligand interactions, and conformational changes. Understanding this coupling in detail required integration of many techniques that were developed in the past two decades. This multidisciplinary approach has revealed the dynamic nature of translational control and uncovered how external cellular factors such as tRNA abundance and mRNA modifications affect the synthesis of the protein product. Insights from these studies will aid synthetic biology and therapeutic approaches to translation.
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Affiliation(s)
- Arjun Prabhakar
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California, 94305.,Program in Biophysics, Stanford University, Stanford, California, 94305
| | - Junhong Choi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California, 94305.,Department of Applied Physics, Stanford University, Stanford, California, 94305
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California, 94305
| | - Alexey Petrov
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California, 94305
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California, 94305
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Carlson MA, Haddad BG, Weis AJ, Blackwood CS, Shelton CD, Wuerth ME, Walter JD, Spiegel PC. Ribosomal protein L7/L12 is required for GTPase translation factors EF-G, RF3, and IF2 to bind in their GTP state to 70S ribosomes. FEBS J 2017; 284:1631-1643. [PMID: 28342293 DOI: 10.1111/febs.14067] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 03/06/2017] [Accepted: 03/22/2017] [Indexed: 12/01/2022]
Abstract
Ribosomal protein L7/L12 is associated with translation initiation, elongation, and termination by the 70S ribosome. The guanosine 5' triphosphate hydrolase (GTPase) activity of elongation factor G (EF-G) requires the presence of L7/L12, which is critical for ribosomal translocation. Here, we have developed new methods for the complete depletion of L7/L12 from Escherichia coli 70S ribosomes to analyze the effect of L7/L12 on the activities of the GTPase factors EF-G, RF3, IF2, and LepA. Upon removal of L7/L12 from ribosomes, the GTPase activities of EF-G, RF3, and IF2 decreased to basal levels, while the activity of LepA decreased marginally. Upon reconstitution of ribosomes with recombinant L12, the GTPase activities of all GTPases returned to full activity. Moreover, ribosome binding assays indicated that EF-G, RF3, and IF2 require L7/L12 for stable binding in the GTP state, and LepA retained > 50% binding. Lastly, an EF-G∆G' truncation mutant possessed ribosome-dependent GTPase activity, which was insensitive to L7/L12. Our results indicate that L7/L12 is required for stable binding of ribosome-dependent GTPases that harbor direct interactions to the L7/L12 C-terminal domains, either through a G' domain (EF-G, RF3) or a unique N-terminal domain (IF2). Furthermore, we hypothesize this interaction is concomitant with counterclockwise ribosomal intersubunit rotation, which is required for translocation, initiation, and post-termination.
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Affiliation(s)
- Markus A Carlson
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
| | - Bassam G Haddad
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
| | - Amanda J Weis
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
| | - Colby S Blackwood
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
| | | | - Michelle E Wuerth
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
| | - Justin D Walter
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
| | - Paul Clint Spiegel
- Department of Chemistry, Western Washington University, Bellingham, WA, USA
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35
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Baggett NE, Zhang Y, Gross CA. Global analysis of translation termination in E. coli. PLoS Genet 2017; 13:e1006676. [PMID: 28301469 PMCID: PMC5373646 DOI: 10.1371/journal.pgen.1006676] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 03/30/2017] [Accepted: 03/08/2017] [Indexed: 01/01/2023] Open
Abstract
Terminating protein translation accurately and efficiently is critical for both protein fidelity and ribosome recycling for continued translation. The three bacterial release factors (RFs) play key roles: RF1 and 2 recognize stop codons and terminate translation; and RF3 promotes disassociation of bound release factors. Probing release factors mutations with reporter constructs containing programmed frameshifting sequences or premature stop codons had revealed a propensity for readthrough or frameshifting at these specific sites, but their effects on translation genome-wide have not been examined. We performed ribosome profiling on a set of isogenic strains with well-characterized release factor mutations to determine how they alter translation globally. Consistent with their known defects, strains with increasingly severe release factor defects exhibit increasingly severe accumulation of ribosomes over stop codons, indicative of an increased duration of the termination/release phase of translation. Release factor mutant strains also exhibit increased occupancy in the region following the stop codon at a significant number of genes. Our global analysis revealed that, as expected, translation termination is generally efficient and accurate, but that at a significant number of genes (≥ 50) the ribosome signature after the stop codon is suggestive of translation past the stop codon. Even native E. coli K-12 exhibits the ribosome signature suggestive of protein extension, especially at UGA codons, which rely exclusively on the reduced function RF2 variant of the K-12 strain for termination. Deletion of RF3 increases the severity of the defect. We unambiguously demonstrate readthrough and frameshifting protein extensions and their further accumulation in mutant strains for a few select cases. In addition to enhancing recoding, ribosome accumulation over stop codons disrupts attenuation control of biosynthetic operons, and may alter expression of some overlapping genes. Together, these functional alterations may either augment the protein repertoire or produce deleterious proteins. Proteins are the cellular workhorses, performing essentially all of the functions required for cell and organismal survival. But, it takes a great deal of energy to make proteins, making it critical that proteins are made accurately and in the proper time frame. After a ribosome synthesizes a protein, release factors catalyze the accurate and timely release of the finished protein from the ribosome, a process called termination. Ribosomes are then recycled and start the next protein. We utilized ribosome profiling, a method that allows us to follow the position of every ribosome that is making a protein, to globally investigate and strengthen insights on termination fidelity for cells with and without mutant release factors. We find that as we decrease release factor function, the time to terminate/release a protein increases across the genome. We observe that the accuracy of terminating a protein at the correct place decreases on a global scale. Using this metric we identify genes with inherently low termination efficiency and confirm two novel events resulting in extended protein products. In addition we find that beyond disrupting accurate protein synthesis, release factor mutations can alter expression of genes involved in the production of key amino acids.
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Affiliation(s)
- Natalie E. Baggett
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Yan Zhang
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Carol A. Gross
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, California, United States of America
- California Institute of Quantitative Biology, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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36
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Conserved GTPase LepA (Elongation Factor 4) functions in biogenesis of the 30S subunit of the 70S ribosome. Proc Natl Acad Sci U S A 2017; 114:980-985. [PMID: 28096346 DOI: 10.1073/pnas.1613665114] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The physiological role of LepA, a paralog of EF-G found in all bacteria, has been a mystery for decades. Here, we show that LepA functions in ribosome biogenesis. In cells lacking LepA, immature 30S particles accumulate. Four proteins are specifically underrepresented in these particles-S3, S10, S14, and S21-all of which bind late in the assembly process and contribute to the folding of the 3' domain of 16S rRNA. Processing of 16S rRNA is also delayed in the mutant strain, as indicated by increased levels of precursor 17S rRNA in assembly intermediates. Mutation ΔlepA confers a synthetic growth phenotype in absence of RsgA, another GTPase, well known to act in 30S subunit assembly. Analysis of the ΔrsgA strain reveals accumulation of intermediates that resemble those seen in the absence of LepA. These data suggest that RsgA and LepA play partially redundant roles to ensure efficient 30S assembly.
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37
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Lyu Z, Whitman WB. Evolution of the archaeal and mammalian information processing systems: towards an archaeal model for human disease. Cell Mol Life Sci 2017; 74:183-212. [PMID: 27261368 PMCID: PMC11107668 DOI: 10.1007/s00018-016-2286-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 05/05/2016] [Accepted: 05/27/2016] [Indexed: 12/22/2022]
Abstract
Current evolutionary models suggest that Eukaryotes originated from within Archaea instead of being a sister lineage. To test this model of ancient evolution, we review recent studies and compare the three major information processing subsystems of replication, transcription and translation in the Archaea and Eukaryotes. Our hypothesis is that if the Eukaryotes arose within the archaeal radiation, their information processing systems will appear to be one of kind and not wholly original. Within the Eukaryotes, the mammalian or human systems are emphasized because of their importance in understanding health. Biochemical as well as genetic studies provide strong evidence for the functional similarity of archaeal homologs to the mammalian information processing system and their dissimilarity to the bacterial systems. In many independent instances, a simple archaeal system is functionally equivalent to more elaborate eukaryotic homologs, suggesting that evolution of complexity is likely an central feature of the eukaryotic information processing system. Because fewer components are often involved, biochemical characterizations of the archaeal systems are often easier to interpret. Similarly, the archaeal cell provides a genetically and metabolically simpler background, enabling convenient studies on the complex information processing system. Therefore, Archaea could serve as a parsimonious and tractable host for studying human diseases that arise in the information processing systems.
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Affiliation(s)
- Zhe Lyu
- Department of Microbiology, University of Georgia, Athens, GA, 30602, USA
| | - William B Whitman
- Department of Microbiology, University of Georgia, Athens, GA, 30602, USA.
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38
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Habib S, Vaishya S, Gupta K. Translation in Organelles of Apicomplexan Parasites. Trends Parasitol 2016; 32:939-952. [DOI: 10.1016/j.pt.2016.07.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/19/2016] [Accepted: 07/25/2016] [Indexed: 01/27/2023]
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39
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Shi X, Joseph S. Mechanism of Translation Termination: RF1 Dissociation Follows Dissociation of RF3 from the Ribosome. Biochemistry 2016; 55:6344-6354. [PMID: 27779391 DOI: 10.1021/acs.biochem.6b00921] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Release factors 1 and 2 (RF1 and RF2, respectively) bind to ribosomes that have a stop codon in the A site and catalyze the release of the newly synthesized protein. Following peptide release, the dissociation of RF1 and RF2 from the ribosome is accelerated by release factor 3 (RF3). The mechanism for RF3-promoted dissociation of RF1 and RF2 is unclear. It was previously proposed that RF3 hydrolyzes GTP and dissociates from the ribosome after RF1 dissociation. Here we monitored directly the dissociation kinetics of RF1 and RF3 using Förster resonance energy transfer-based assays. In contrast to the previous model, our data show that RF3 hydrolyzes GTP and dissociates from the ribosome before RF1 dissociation. We propose that RF3 stabilizes the ratcheted state of the ribosome, which consequently accelerates the dissociation of RF1 and RF2.
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Affiliation(s)
- Xinying Shi
- Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, La Jolla, California 92093-0314, United States
| | - Simpson Joseph
- Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, La Jolla, California 92093-0314, United States
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40
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Arenz S, Wilson DN. Bacterial Protein Synthesis as a Target for Antibiotic Inhibition. Cold Spring Harb Perspect Med 2016; 6:cshperspect.a025361. [PMID: 27481773 DOI: 10.1101/cshperspect.a025361] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Protein synthesis occurs on macromolecular machines, called ribosomes. Bacterial ribosomes and the translational machinery represent one of the major targets for antibiotics in the cell. Therefore, structural and biochemical investigations into ribosome-targeting antibiotics provide not only insight into the mechanism of action and resistance of antibiotics, but also insight into the fundamental process of protein synthesis. This review summarizes the recent advances in our understanding of protein synthesis, particularly with respect to X-ray and cryoelectron microscopy (cryo-EM) structures of ribosome complexes, and highlights the different steps of translation that are targeted by the diverse array of known antibiotics. Such findings will be important for the ongoing development of novel and improved antimicrobial agents to combat the rapid emergence of multidrug resistant pathogenic bacteria.
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Affiliation(s)
- Stefan Arenz
- Center for Integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany
| | - Daniel N Wilson
- Center for Integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany Gene Center and Department for Biochemistry, University of Munich, 81377 Munich, Germany
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41
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Degiacomi G, Personne Y, Mondésert G, Ge X, Mandava CS, Hartkoorn RC, Boldrin F, Goel P, Peisker K, Benjak A, Barrio MB, Ventura M, Brown AC, Leblanc V, Bauer A, Sanyal S, Cole ST, Lagrange S, Parish T, Manganelli R. Micrococcin P1 - A bactericidal thiopeptide active against Mycobacterium tuberculosis. Tuberculosis (Edinb) 2016; 100:95-101. [PMID: 27553416 DOI: 10.1016/j.tube.2016.07.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/13/2016] [Accepted: 07/20/2016] [Indexed: 10/21/2022]
Abstract
The lack of proper treatment for serious infectious diseases due to the emergence of multidrug resistance reinforces the need for the discovery of novel antibiotics. This is particularly true for tuberculosis (TB) for which 3.7% of new cases and 20% of previously treated cases are estimated to be caused by multi-drug resistant strains. In addition, in the case of TB, which claimed 1.5 million lives in 2014, the treatment of the least complicated, drug sensitive cases is lengthy and disagreeable. Therefore, new drugs with novel targets are urgently needed to control resistant Mycobacterium tuberculosis strains. In this manuscript we report the characterization of the thiopeptide micrococcin P1 as an anti-tubercular agent. Our biochemical experiments show that this antibiotic inhibits the elongation step of protein synthesis in mycobacteria. We have further identified micrococcin resistant mutations in the ribosomal protein L11 (RplK); the mutations were located in the proline loop at the N-terminus. Reintroduction of the mutations into a clean genetic background, confirmed that they conferred resistance, while introduction of the wild type RplK allele into resistant strains re-established sensitivity. We also identified a mutation in the 23S rRNA gene. These data, in good agreement with previous structural studies suggest that also in M. tuberculosis micrococcin P1 functions by binding to the cleft between the 23S rRNA and the L11 protein loop, thus interfering with the binding of elongation factors Tu and G (EF-Tu and EF-G) and inhibiting protein translocation.
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Affiliation(s)
- Giulia Degiacomi
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Yoann Personne
- Queen Mary University of London, London E1 2AD, United Kingdom
| | | | - Xueliang Ge
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | | | - Ruben C Hartkoorn
- Ecole Polytechnique Fédérale de Lausanne, Global Health Institute, Lausanne, Switzerland
| | - Francesca Boldrin
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Pavitra Goel
- Queen Mary University of London, London E1 2AD, United Kingdom
| | - Kristin Peisker
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Andrej Benjak
- Ecole Polytechnique Fédérale de Lausanne, Global Health Institute, Lausanne, Switzerland
| | | | - Marcello Ventura
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Amanda C Brown
- Queen Mary University of London, London E1 2AD, United Kingdom
| | | | - Armin Bauer
- Sanofi-Aventis R&D, Drug Disposition, 69367 Lyon, France
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Stewart T Cole
- Ecole Polytechnique Fédérale de Lausanne, Global Health Institute, Lausanne, Switzerland
| | | | - Tanya Parish
- Queen Mary University of London, London E1 2AD, United Kingdom
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42
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The molecular choreography of protein synthesis: translational control, regulation, and pathways. Q Rev Biophys 2016; 49:e11. [PMID: 27658712 DOI: 10.1017/s0033583516000056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Translation of proteins by the ribosome regulates gene expression, with recent results underscoring the importance of translational control. Misregulation of translation underlies many diseases, including cancer and many genetic diseases. Decades of biochemical and structural studies have delineated many of the mechanistic details in prokaryotic translation, and sketched the outlines of eukaryotic translation. However, translation may not proceed linearly through a single mechanistic pathway, but likely involves multiple pathways and branchpoints. The stochastic nature of biological processes would allow different pathways to occur during translation that are biased by the interaction of the ribosome with other translation factors, with many of the steps kinetically controlled. These multiple pathways and branchpoints are potential regulatory nexus, allowing gene expression to be tuned at the translational level. As research focus shifts toward eukaryotic translation, certain themes will be echoed from studies on prokaryotic translation. This review provides a general overview of the dynamic data related to prokaryotic and eukaryotic translation, in particular recent findings with single-molecule methods, complemented by biochemical, kinetic, and structural findings. We will underscore the importance of viewing the process through the viewpoints of regulation, translational control, and heterogeneous pathways.
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Steinchen W, Bange G. The magic dance of the alarmones (p)ppGpp. Mol Microbiol 2016; 101:531-44. [PMID: 27149325 DOI: 10.1111/mmi.13412] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2016] [Indexed: 11/26/2022]
Abstract
The alarmones (p)ppGpp are important second messengers that orchestrate pleiotropic adaptations of bacteria and plant chloroplasts in response to starvation and stress. Here, we review our structural and mechanistic knowledge on (p)ppGpp metabolism including their synthesis, degradation and interconversion by a highly diverse set of enzymes. Increasing structural information shows how (p)ppGpp interacts with an incredibly diverse set of different targets that are essential for replication, transcription, translation, ribosome assembly and metabolism. This raises the question how the chemically rather simple (p)ppGpp is able to interact with these different targets? Structural analysis shows that the diversity of (p)ppGpp interaction with cellular targets critically relies on the conformational flexibility of the 3' and 5' phosphate moieties allowing alarmones to efficiently modulate the activity of target structures in a broad concentration range. Current approaches in the design of (p)ppGpp-analogs as future antibiotics might be aided by the comprehension of conformational flexibility exhibited by the magic dancers (p)ppGpp.
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Affiliation(s)
- Wieland Steinchen
- Department of Chemistry, LOEWE Center for Synthetic Microbiology (Synmikro), Philipps University Marburg, Hans-Meerwein-Strasse, Marburg, 35043, Germany
| | - Gert Bange
- Department of Chemistry, LOEWE Center for Synthetic Microbiology (Synmikro), Philipps University Marburg, Hans-Meerwein-Strasse, Marburg, 35043, Germany
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Vaishya S, Kumar V, Gupta A, Siddiqi MI, Habib S. Polypeptide release factors and stop codon recognition in the apicoplast and mitochondrion of Plasmodium falciparum. Mol Microbiol 2016; 100:1080-95. [PMID: 26946524 DOI: 10.1111/mmi.13369] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2016] [Indexed: 11/30/2022]
Abstract
Correct termination of protein synthesis would be a critical step in translation of organellar open reading frames (ORFs) of the apicoplast and mitochondrion of the malaria parasite. We identify release factors (RFs) responsible for recognition of the UAA and UGA stop-codons of apicoplast ORFs and the sole UAA stop-codon that terminates translation from the three mitochondrial ORFs. A single nuclear-encoded canonical RF2, PfRF2Api , localizes to the apicoplast. It has a conserved tripeptide motif (SPF) for stop-codon recognition and is sufficient for peptidyl-tRNA hydrolysis (PTH) from both UAA and UGA. Two RF family proteins are targeted to the parasite mitochondrion; a canonical RF1, PfRF1Mit , with a variant codon-recognition motif (PxN instead of the conserved RF1 PxT) is the major peptidyl-hydrolase with specific recognition of the UAA codon relevant to mitochondrial ORFs. Mutation of the N residue of the PfRF1Mit PxN motif and two other conserved residues of the codon recognition domain lowers PTH activity from pre-termination ribosomes indicating their role in codon-recognition. The second RF imported by the mitochondrion is the non-canonical PfICT1 that functions as a dimer and mediates codon nonspecific peptide release. Our results help delineate a critical step in organellar translation in Plasmodium, which is an important target for anti-malarials.
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Affiliation(s)
- Suniti Vaishya
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Vikash Kumar
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Ankit Gupta
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Mohammad Imran Siddiqi
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Saman Habib
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
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Liu Q, Fredrick K. Intersubunit Bridges of the Bacterial Ribosome. J Mol Biol 2016; 428:2146-64. [PMID: 26880335 DOI: 10.1016/j.jmb.2016.02.009] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 01/29/2016] [Accepted: 02/05/2016] [Indexed: 02/02/2023]
Abstract
The ribosome is a large two-subunit ribonucleoprotein machine that translates the genetic code in all cells, synthesizing proteins according to the sequence of the mRNA template. During translation, the primary substrates, transfer RNAs, pass through binding sites formed between the two subunits. Multiple interactions between the ribosomal subunits, termed intersubunit bridges, keep the ribosome intact and at the same time govern dynamics that facilitate the various steps of translation such as transfer RNA-mRNA movement. Here, we review the molecular nature of these intersubunit bridges, how they change conformation during translation, and their functional roles in the process.
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Affiliation(s)
- Qi Liu
- Ohio State Biochemistry Program, Department of Microbiology, and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Kurt Fredrick
- Ohio State Biochemistry Program, Department of Microbiology, and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
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Borg A, Pavlov M, Ehrenberg M. Complete kinetic mechanism for recycling of the bacterial ribosome. RNA (NEW YORK, N.Y.) 2016; 22:10-21. [PMID: 26527791 PMCID: PMC4691825 DOI: 10.1261/rna.053157.115] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 09/03/2015] [Indexed: 05/05/2023]
Abstract
How EF-G and RRF act together to split a post-termination ribosomal complex into its subunits has remained obscure. Here, using stopped-flow experiments with Rayleigh light scattering detection and quench-flow experiments with radio-detection of GTP hydrolysis, we have clarified the kinetic mechanism of ribosome recycling and obtained precise estimates of its kinetic parameters. Ribosome splitting requires that EF-G binds to an already RRF-containing ribosome. EF-G binding to RRF-free ribosomes induces futile rounds of GTP hydrolysis and inhibits ribosome splitting, implying that while RRF is purely an activator of recycling, EF-G acts as both activator and competitive inhibitor of RRF in recycling of the post-termination ribosome. The ribosome splitting rate and the number of GTPs consumed per splitting event depend strongly on the free concentrations of EF-G and RRF. The maximal recycling rate, here estimated as 25 sec(-1), is approached at very high concentrations of EF-G and RRF with RRF in high excess over EF-G. The present in vitro results, suggesting an in vivo ribosome recycling rate of ∼5 sec(-1), are discussed in the perspective of rapidly growing bacterial cells.
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Affiliation(s)
- Anneli Borg
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, 751 24 Uppsala, Sweden
| | - Michael Pavlov
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, 751 24 Uppsala, Sweden
| | - Måns Ehrenberg
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, 751 24 Uppsala, Sweden
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Saito K, Ito K. Genetic analysis of L123 of the tRNA-mimicking eukaryote release factor eRF1, an amino acid residue critical for discrimination of stop codons. Nucleic Acids Res 2015; 43:4591-601. [PMID: 25897120 PMCID: PMC4482090 DOI: 10.1093/nar/gkv376] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/09/2015] [Indexed: 11/18/2022] Open
Abstract
In eukaryotes, the tRNA-mimicking polypeptide-chain release factor, eRF1, decodes stop codons on the ribosome in a complex with eRF3; this complex exhibits striking structural similarity to the tRNA–eEF1A–GTP complex. Although amino acid residues or motifs of eRF1 that are critical for stop codon discrimination have been identified, the details of the molecular mechanisms involved in the function of the ribosomal decoding site remain obscure. Here, we report analyses of the position-123 amino acid of eRF1 (L123 in Saccharomyces cerevisiae eRF1), a residue that is phylogenetically conserved among species with canonical and variant genetic codes. In vivo readthrough efficiency analysis and genetic growth complementation analysis of the residue-123 systematic mutants suggested that this amino acid functions in stop codon discrimination in a manner coupled with eRF3 binding, and distinctive from previously reported adjacent residues. Furthermore, aminoglycoside antibiotic sensitivity analysis and ribosomal docking modeling of eRF1 in a quasi-A/T state suggested a functional interaction between the side chain of L123 and ribosomal residues critical for codon recognition in the decoding site, as a molecular explanation for coupling with eRF3. Our results provide insights into the molecular mechanisms underlying stop codon discrimination by a tRNA-mimicking protein on the ribosome.
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Affiliation(s)
- Kazuki Saito
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa-city, Chiba 277-8562, Japan
| | - Koichi Ito
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa-city, Chiba 277-8562, Japan
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Carvalho ATP, Szeler K, Vavitsas K, Åqvist J, Kamerlin SCL. Modeling the mechanisms of biological GTP hydrolysis. Arch Biochem Biophys 2015; 582:80-90. [PMID: 25731854 DOI: 10.1016/j.abb.2015.02.027] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 02/19/2015] [Accepted: 02/21/2015] [Indexed: 01/11/2023]
Abstract
Enzymes that hydrolyze GTP are currently in the spotlight, due to their molecular switch mechanism that controls many cellular processes. One of the best-known classes of these enzymes are small GTPases such as members of the Ras superfamily, which catalyze the hydrolysis of the γ-phosphate bond in GTP. In addition, the availability of an increasing number of crystal structures of translational GTPases such as EF-Tu and EF-G have made it possible to probe the molecular details of GTP hydrolysis on the ribosome. However, despite a wealth of biochemical, structural and computational data, the way in which GTP hydrolysis is activated and regulated is still a controversial topic and well-designed simulations can play an important role in resolving and rationalizing the experimental data. In this review, we discuss the contributions of computational biology to our understanding of GTP hydrolysis on the ribosome and in small GTPases.
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Affiliation(s)
- Alexandra T P Carvalho
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden
| | - Klaudia Szeler
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden
| | - Konstantinos Vavitsas
- Copenhagen Plant Science Centre (CPSC), Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
| | - Johan Åqvist
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden
| | - Shina C L Kamerlin
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden.
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Atkinson GC. The evolutionary and functional diversity of classical and lesser-known cytoplasmic and organellar translational GTPases across the tree of life. BMC Genomics 2015; 16:78. [PMID: 25756599 PMCID: PMC4342817 DOI: 10.1186/s12864-015-1289-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 01/27/2015] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND The ribosome translates mRNA to protein with the aid of a number of accessory protein factors. Translational GTPases (trGTPases) are an integral part of the 'core set' of essential translational factors, and are some of the most conserved proteins across life. This study takes advantage of the wealth of available genomic data, along with novel functional information that has come to light for a number of trGTPases to address the full evolutionary and functional diversity of this superfamily across all domains of life. RESULTS Through sensitive sequence searching combined with phylogenetic analysis, 57 distinct subfamilies of trGTPases are identified: 14 bacterial, 7 archaeal and 35 eukaryotic (of which 21 are known or predicted to be organellar). The results uncover the functional evolution of trGTPases from before the last common ancestor of life on earth to the current day. CONCLUSIONS While some trGTPases are universal, others are limited to certain taxa, suggesting lineage-specific translational control mechanisms that exist on a base of core factors. These lineage-specific features may give organisms the ability to tune their translation machinery to respond to their environment. Only a fraction of the diversity of the trGTPase superfamily has been subjected to experimental analyses; this comprehensive classification brings to light novel and overlooked translation factors that are worthy of further investigation.
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O’Connor M. Interactions of release factor RF3 with the translation machinery. Mol Genet Genomics 2015; 290:1335-44. [DOI: 10.1007/s00438-015-0994-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/09/2015] [Indexed: 10/24/2022]
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