1
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Schuntermann DB, Jaskolowski M, Reynolds NM, Vargas-Rodriguez O. The central role of transfer RNAs in mistranslation. J Biol Chem 2024; 300:107679. [PMID: 39154912 DOI: 10.1016/j.jbc.2024.107679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 07/22/2024] [Accepted: 07/23/2024] [Indexed: 08/20/2024] Open
Abstract
Transfer RNAs (tRNA) are essential small non-coding RNAs that enable the translation of genomic information into proteins in all life forms. The principal function of tRNAs is to bring amino acid building blocks to the ribosomes for protein synthesis. In the ribosome, tRNAs interact with messenger RNA (mRNA) to mediate the incorporation of amino acids into a growing polypeptide chain following the rules of the genetic code. Accurate interpretation of the genetic code requires tRNAs to carry amino acids matching their anticodon identity and decode the correct codon on mRNAs. Errors in these steps cause the translation of codons with the wrong amino acids (mistranslation), compromising the accurate flow of information from DNA to proteins. Accumulation of mutant proteins due to mistranslation jeopardizes proteostasis and cellular viability. However, the concept of mistranslation is evolving, with increasing evidence indicating that mistranslation can be used as a mechanism for survival and acclimatization to environmental conditions. In this review, we discuss the central role of tRNAs in modulating translational fidelity through their dynamic and complex interplay with translation factors. We summarize recent discoveries of mistranslating tRNAs and describe the underlying molecular mechanisms and the specific conditions and environments that enable and promote mistranslation.
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Affiliation(s)
- Dominik B Schuntermann
- Department of Biology, Institute of Molecular Biology and Biophysics, Zurich, Switzerland
| | - Mateusz Jaskolowski
- Department of Biology, Institute of Molecular Biology and Biophysics, Zurich, Switzerland
| | - Noah M Reynolds
- School of Integrated Sciences, Sustainability, and Public Health, University of Illinois Springfield, Springfield, Illinois, USA
| | - Oscar Vargas-Rodriguez
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut, USA.
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2
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Cruz-Navarrete FA, Griffin WC, Chan YC, Martin MI, Alejo JL, Brady RA, Natchiar SK, Knudson IJ, Altman RB, Schepartz A, Miller SJ, Blanchard SC. β-Amino Acids Reduce Ternary Complex Stability and Alter the Translation Elongation Mechanism. ACS CENTRAL SCIENCE 2024; 10:1262-1275. [PMID: 38947208 PMCID: PMC11212133 DOI: 10.1021/acscentsci.4c00314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 05/20/2024] [Accepted: 05/21/2024] [Indexed: 07/02/2024]
Abstract
Templated synthesis of proteins containing non-natural amino acids (nnAAs) promises to expand the chemical space available to biological therapeutics and materials, but existing technologies are still limiting. Addressing these limitations requires a deeper understanding of the mechanism of protein synthesis and how it is perturbed by nnAAs. Here we examine the impact of nnAAs on the formation and ribosome utilization of the central elongation substrate: the ternary complex of native, aminoacylated tRNA, thermally unstable elongation factor, and GTP. By performing ensemble and single-molecule fluorescence resonance energy transfer measurements, we reveal that both the (R)- and (S)-β2 isomers of phenylalanine (Phe) disrupt ternary complex formation to levels below in vitro detection limits, while (R)- and (S)-β3-Phe reduce ternary complex stability by 1 order of magnitude. Consistent with these findings, (R)- and (S)-β2-Phe-charged tRNAs were not utilized by the ribosome, while (R)- and (S)-β3-Phe stereoisomers were utilized inefficiently. (R)-β3-Phe but not (S)-β3-Phe also exhibited order of magnitude defects in the rate of translocation after mRNA decoding. We conclude from these findings that non-natural amino acids can negatively impact the translation mechanism on multiple fronts and that the bottlenecks for improvement must include the consideration of the efficiency and stability of ternary complex formation.
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Affiliation(s)
- F. Aaron Cruz-Navarrete
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - Wezley C. Griffin
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - Yuk-Cheung Chan
- Department
of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Maxwell I. Martin
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - Jose L. Alejo
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - Ryan A. Brady
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - S. Kundhavai Natchiar
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - Isaac J. Knudson
- College
of Chemistry, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Roger B. Altman
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
| | - Alanna Schepartz
- College
of Chemistry, University of California,
Berkeley, Berkeley, California 94720, United States
- Molecular
and Cell Biology, University of California,
Berkeley, Berkeley, California 94720, United States
- California
Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, California 94720, United States
- Chan
Zuckerberg Biohub, San Francisco, California 94158, United States
- Innovation
Investigator, ARC Institute, Palo Alto, California 94304, United States
| | - Scott J. Miller
- Department
of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Scott C. Blanchard
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, Memphis, Tennessee 38105, United States
- Department
of Chemical Biology & Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
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3
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Weiss JL, Decker JC, Bolano A, Krahn N. Tuning tRNAs for improved translation. Front Genet 2024; 15:1436860. [PMID: 38983271 PMCID: PMC11231383 DOI: 10.3389/fgene.2024.1436860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Accepted: 06/06/2024] [Indexed: 07/11/2024] Open
Abstract
Transfer RNAs have been extensively explored as the molecules that translate the genetic code into proteins. At this interface of genetics and biochemistry, tRNAs direct the efficiency of every major step of translation by interacting with a multitude of binding partners. However, due to the variability of tRNA sequences and the abundance of diverse post-transcriptional modifications, a guidebook linking tRNA sequences to specific translational outcomes has yet to be elucidated. Here, we review substantial efforts that have collectively uncovered tRNA engineering principles that can be used as a guide for the tuning of translation fidelity. These principles have allowed for the development of basic research, expansion of the genetic code with non-canonical amino acids, and tRNA therapeutics.
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Affiliation(s)
- Joshua L Weiss
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - J C Decker
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Ariadna Bolano
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Natalie Krahn
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
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4
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Sigal M, Matsumoto S, Beattie A, Katoh T, Suga H. Engineering tRNAs for the Ribosomal Translation of Non-proteinogenic Monomers. Chem Rev 2024; 124:6444-6500. [PMID: 38688034 PMCID: PMC11122139 DOI: 10.1021/acs.chemrev.3c00894] [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: 12/01/2023] [Revised: 02/21/2024] [Accepted: 04/10/2024] [Indexed: 05/02/2024]
Abstract
Ribosome-dependent protein biosynthesis is an essential cellular process mediated by transfer RNAs (tRNAs). Generally, ribosomally synthesized proteins are limited to the 22 proteinogenic amino acids (pAAs: 20 l-α-amino acids present in the standard genetic code, selenocysteine, and pyrrolysine). However, engineering tRNAs for the ribosomal incorporation of non-proteinogenic monomers (npMs) as building blocks has led to the creation of unique polypeptides with broad applications in cellular biology, material science, spectroscopy, and pharmaceuticals. Ribosomal polymerization of these engineered polypeptides presents a variety of challenges for biochemists, as translation efficiency and fidelity is often insufficient when employing npMs. In this Review, we will focus on the methodologies for engineering tRNAs to overcome these issues and explore recent advances both in vitro and in vivo. These efforts include increasing orthogonality, recruiting essential translation factors, and creation of expanded genetic codes. After our review on the biochemical optimizations of tRNAs, we provide examples of their use in genetic code manipulation, with a focus on the in vitro discovery of bioactive macrocyclic peptides containing npMs. Finally, an analysis of the current state of tRNA engineering is presented, along with existing challenges and future perspectives for the field.
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Affiliation(s)
- Maxwell Sigal
- Department of Chemistry,
Graduate School of Science, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Satomi Matsumoto
- Department of Chemistry,
Graduate School of Science, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Adam Beattie
- Department of Chemistry,
Graduate School of Science, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takayuki Katoh
- Department of Chemistry,
Graduate School of Science, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hiroaki Suga
- Department of Chemistry,
Graduate School of Science, The University
of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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5
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Bondarchuk TV, Shalak VF, Lozhko DM, Fatalska A, Szczepanowski R, Liudkovska V, Tsuvariev O, Dadlez M, El'skaya A, Negrutskii B. Quaternary organization of the human eEF1B complex reveals unique multi-GEF domain assembly. Nucleic Acids Res 2022; 50:9490-9504. [PMID: 35971611 PMCID: PMC9458455 DOI: 10.1093/nar/gkac685] [Citation(s) in RCA: 4] [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: 02/25/2022] [Revised: 07/12/2022] [Accepted: 07/31/2022] [Indexed: 12/24/2022] Open
Abstract
Protein synthesis in eukaryotic cell is spatially and structurally compartmentalized that ensures high efficiency of this process. One of the distinctive features of higher eukaryotes is the existence of stable multi-protein complexes of aminoacyl-tRNA synthetases and translation elongation factors. Here, we report a quaternary organization of the human guanine-nucleotide exchange factor (GEF) complex, eEF1B, comprising α, β and γ subunits that specifically associate into a heterotrimeric form eEF1B(αβγ)3. As both the eEF1Bα and eEF1Bβ proteins have structurally conserved GEF domains, their total number within the complex is equal to six. Such, so far, unique structural assembly of the guanine-nucleotide exchange factors within a stable complex may be considered as a 'GEF hub' that ensures efficient maintenance of the translationally active GTP-bound conformation of eEF1A in higher eukaryotes.
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Affiliation(s)
- Tetiana V Bondarchuk
- Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo St., 03143 Kyiv, Ukraine
| | - Vyacheslav F Shalak
- Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo St., 03143 Kyiv, Ukraine
| | - Dmytro M Lozhko
- Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo St., 03143 Kyiv, Ukraine
| | - Agnieszka Fatalska
- Institute of Biochemistry and Biophysics, PAN, Pawinskiego 5a, 02-109 Warsaw, Poland
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Roman H Szczepanowski
- International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw, Poland
| | - Vladyslava Liudkovska
- Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo St., 03143 Kyiv, Ukraine
- International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw, Poland
| | - Oleksandr Yu Tsuvariev
- Institute of High Technologies, Taras Shevchenko National University of Kyiv, Akademik Glushkov Ave. 4-g, 03022 Kyiv, Ukraine
| | - Michal Dadlez
- Institute of Biochemistry and Biophysics, PAN, Pawinskiego 5a, 02-109 Warsaw, Poland
| | - Anna V El'skaya
- Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo St., 03143 Kyiv, Ukraine
| | - Boris S Negrutskii
- Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo St., 03143 Kyiv, Ukraine
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6
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Ayan GB, Park HJ, Gallie J. The birth of a bacterial tRNA gene by large-scale, tandem duplication events. eLife 2020; 9:57947. [PMID: 33124983 PMCID: PMC7661048 DOI: 10.7554/elife.57947] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 10/29/2020] [Indexed: 12/20/2022] Open
Abstract
Organisms differ in the types and numbers of tRNA genes that they carry. While the evolutionary mechanisms behind tRNA gene set evolution have been investigated theoretically and computationally, direct observations of tRNA gene set evolution remain rare. Here, we report the evolution of a tRNA gene set in laboratory populations of the bacterium Pseudomonas fluorescens SBW25. The growth defect caused by deleting the single-copy tRNA gene, serCGA, is rapidly compensated by large-scale (45–290 kb) duplications in the chromosome. Each duplication encompasses a second, compensatory tRNA gene (serTGA) and is associated with a rise in tRNA-Ser(UGA) in the mature tRNA pool. We postulate that tRNA-Ser(CGA) elimination increases the translational demand for tRNA-Ser(UGA), a pressure relieved by increasing serTGA copy number. This work demonstrates that tRNA gene sets can evolve through duplication of existing tRNA genes, a phenomenon that may contribute to the presence of multiple, identical tRNA gene copies within genomes.
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Affiliation(s)
- Gökçe B Ayan
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Hye Jin Park
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany.,Asia Pacific Center for Theoretical Physics, Pohang, Republic of Korea
| | - Jenna Gallie
- Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany
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7
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Disruption of evolutionarily correlated tRNA elements impairs accurate decoding. Proc Natl Acad Sci U S A 2020; 117:16333-16338. [PMID: 32601241 DOI: 10.1073/pnas.2004170117] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Bacterial transfer RNAs (tRNAs) contain evolutionarily conserved sequences and modifications that ensure uniform binding to the ribosome and optimal translational accuracy despite differences in their aminoacyl attachments and anticodon nucleotide sequences. In the tRNA anticodon stem-loop, the anticodon sequence is correlated with a base pair in the anticodon loop (nucleotides 32 and 38) to tune the binding of each tRNA to the decoding center in the ribosome. Disruption of this correlation renders the ribosome unable to distinguish correct from incorrect tRNAs. The molecular basis for how these two tRNA features combine to ensure accurate decoding is unclear. Here, we solved structures of the bacterial ribosome containing either wild-type [Formula: see text] or [Formula: see text] containing a reversed 32-38 pair on cognate and near-cognate codons. Structures of wild-type [Formula: see text] bound to the ribosome reveal 23S ribosomal RNA (rRNA) nucleotide A1913 positional changes that are dependent on whether the codon-anticodon interaction is cognate or near cognate. Further, the 32-38 pair is destabilized in the context of a near-cognate codon-anticodon pair. Reversal of the pairing in [Formula: see text] ablates A1913 movement regardless of whether the interaction is cognate or near cognate. These results demonstrate that disrupting 32-38 and anticodon sequences alters interactions with the ribosome that directly contribute to misreading.
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8
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Hammerling MJ, Krüger A, Jewett MC. Strategies for in vitro engineering of the translation machinery. Nucleic Acids Res 2020; 48:1068-1083. [PMID: 31777928 PMCID: PMC7026604 DOI: 10.1093/nar/gkz1011] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 10/07/2019] [Accepted: 10/17/2019] [Indexed: 01/06/2023] Open
Abstract
Engineering the process of molecular translation, or protein biosynthesis, has emerged as a major opportunity in synthetic and chemical biology to generate novel biological insights and enable new applications (e.g. designer protein therapeutics). Here, we review methods for engineering the process of translation in vitro. We discuss the advantages and drawbacks of the two major strategies-purified and extract-based systems-and how they may be used to manipulate and study translation. Techniques to engineer each component of the translation machinery are covered in turn, including transfer RNAs, translation factors, and the ribosome. Finally, future directions and enabling technological advances for the field are discussed.
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Affiliation(s)
- Michael J Hammerling
- Department of Chemical and Biological Engineering, Center for Synthetic Biology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Antje Krüger
- Department of Chemical and Biological Engineering, Center for Synthetic Biology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Michael C Jewett
- Department of Chemical and Biological Engineering, Center for Synthetic Biology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
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9
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Characterization of glutamyl-tRNA-dependent dehydratases using nonreactive substrate mimics. Proc Natl Acad Sci U S A 2019; 116:17245-17250. [PMID: 31409709 DOI: 10.1073/pnas.1905240116] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The peptide natural product nisin has been used as a food preservative for 6 decades with minimal development of resistance. Nisin contains the unusual amino acids dehydroalanine and dehydrobutyrine, which are posttranslationally installed by class I lanthipeptide dehydratases (LanBs) on a linear peptide substrate through an unusual glutamyl-tRNA-dependent dehydration of Ser and Thr. To date, little is known about how LanBs catalyze the transfer of glutamate from charged tRNAGlu to the peptide substrate, or how they carry out the subsequent elimination of the peptide-glutamyl adducts to afford dehydro amino acids. Here, we describe the synthesis of inert analogs that mimic substrate glutamyl-tRNAGlu and the glutamylated peptide intermediate, and determine the crystal structures of 2 LanBs in complex with each of these compounds. Mutational studies were used to characterize the function of the glutamylation and glutamate elimination active-site residues identified through the structural analysis. These combined studies provide insights into the mechanisms of substrate recognition, glutamylation, and glutamate elimination by LanBs to effect a net dehydration reaction of Ser and Thr.
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10
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Uhlenbeck OC, Schrader JM. Evolutionary tuning impacts the design of bacterial tRNAs for the incorporation of unnatural amino acids by ribosomes. Curr Opin Chem Biol 2018; 46:138-145. [PMID: 30059836 DOI: 10.1016/j.cbpa.2018.07.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 04/27/2018] [Accepted: 07/13/2018] [Indexed: 01/23/2023]
Abstract
In order to function on the ribosome with uniform rate and adequate accuracy, each bacterial tRNA has evolved to have a characteristic sequence and set of modifications that compensate for the differing physical properties of its esterified amino acid and its codon-anticodon interaction. The sequence of the T-stem of each tRNA compensates for the differential effect of the esterified amino acid on the binding and release of EF-Tu during decoding. The sequence and modifications in the anticodon loop and core of tRNA impact the codon-anticodon strength and the ability of the tRNA to bend during codon recognition. These discoveries impact the design of tRNAs for the efficient and accurate incorporation of unnatural amino acids into proteins using bacterial translation systems.
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Affiliation(s)
- Olke C Uhlenbeck
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
| | - Jared M Schrader
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
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11
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Abstract
Pyrrolysine is the 22nd proteinogenic amino acid encoded into proteins in response to amber (TAG) codons in a small number of archaea and bacteria. The incorporation of pyrrolysine is facilitated by a specialized aminoacyl-tRNA synthetase (PylRS) and its cognate tRNA (tRNAPyl). The secondary structure of tRNAPyl contains several unique features not found in canonical tRNAs. Numerous studies have demonstrated that the PylRS/tRNAPyl pair from archaea is orthogonal in E. coli and eukaryotic hosts, which has led to the widespread use of this pair for the genetic incorporation of non-canonical amino acids. In this brief review we examine the work that has been done to elucidate the structure of tRNAPyl, its interaction with PylRS, and survey recent progress on the use of tRNAPyl as a tool for genetic code expansion.
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Affiliation(s)
- Jeffery M Tharp
- a Department of Chemistry , Texas A&M University , College Station , TX , USA
| | - Andreas Ehnbom
- a Department of Chemistry , Texas A&M University , College Station , TX , USA
| | - Wenshe R Liu
- a Department of Chemistry , Texas A&M University , College Station , TX , USA
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12
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Masuda I, Igarashi T, Sakaguchi R, Nitharwal RG, Takase R, Han KY, Leslie BJ, Liu C, Gamper H, Ha T, Sanyal S, Hou YM. A genetically encoded fluorescent tRNA is active in live-cell protein synthesis. Nucleic Acids Res 2017; 45:4081-4093. [PMID: 27956502 PMCID: PMC5397188 DOI: 10.1093/nar/gkw1229] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 12/06/2016] [Indexed: 11/14/2022] Open
Abstract
Transfer RNAs (tRNAs) perform essential tasks for all living cells. They are major components of the ribosomal machinery for protein synthesis and they also serve in non-ribosomal pathways for regulation and signaling metabolism. We describe the development of a genetically encoded fluorescent tRNA fusion with the potential for imaging in live Escherichia coli cells. This tRNA fusion carries a Spinach aptamer that becomes fluorescent upon binding of a cell-permeable and non-toxic fluorophore. We show that, despite having a structural framework significantly larger than any natural tRNA species, this fusion is a viable probe for monitoring tRNA stability in a cellular quality control mechanism that degrades structurally damaged tRNA. Importantly, this fusion is active in E. coli live-cell protein synthesis allowing peptidyl transfer at a rate sufficient to support cell growth, indicating that it is accommodated by translating ribosomes. Imaging analysis shows that this fusion and ribosomes are both excluded from the nucleoid, indicating that the fusion and ribosomes are in the cytosol together possibly engaged in protein synthesis. This fusion methodology has the potential for developing new tools for live-cell imaging of tRNA with the unique advantage of both stoichiometric labeling and broader application to all cells amenable to genetic engineering.
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Affiliation(s)
- Isao Masuda
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Takao Igarashi
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Reiko Sakaguchi
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Ram G Nitharwal
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC 75124, Uppsala, Sweden
| | - Ryuichi Takase
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Kyu Young Han
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,CREOL, College of Optics & Photonics, University of Central Florida, 4304 Scorpius St., Orlando, FL 32816, USA
| | - Benjamin J Leslie
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,Howard Hughes Medical Institute, Baltimore, MD 21205, USA
| | - Cuiping Liu
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Howard Gamper
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Taekjip Ha
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,Howard Hughes Medical Institute, Baltimore, MD 21205, USA.,Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.,Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.,Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC 75124, Uppsala, Sweden
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
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13
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Maracci C, Rodnina MV. Review: Translational GTPases. Biopolymers 2017; 105:463-75. [PMID: 26971860 PMCID: PMC5084732 DOI: 10.1002/bip.22832] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/09/2016] [Accepted: 03/10/2016] [Indexed: 01/26/2023]
Abstract
Translational GTPases (trGTPases) play key roles in facilitating protein synthesis on the ribosome. Despite the high degree of evolutionary conservation in the sequences of their GTP-binding domains, the rates of GTP hydrolysis and nucleotide exchange vary broadly between different trGTPases. EF-Tu, one of the best-characterized model G proteins, evolved an exceptionally rapid and tightly regulated GTPase activity, which ensures rapid and accurate incorporation of amino acids into the nascent chain. Other trGTPases instead use the energy of GTP hydrolysis to promote movement or to ensure the forward commitment of translation reactions. Recent data suggest the GTPase mechanism of EF-Tu and provide an insight in the catalysis of GTP hydrolysis by its unusual activator, the ribosome. Here we summarize these advances in understanding the functional cycle and the regulation of trGTPases, stimulated by the elucidation of their structures on the ribosome and the progress in dissecting the reaction mechanism of GTPases. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 463-475, 2016.
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Affiliation(s)
- Cristina Maracci
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Goettingen, 37077, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Goettingen, 37077, Germany
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14
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Moutiez M, Belin P, Gondry M. Aminoacyl-tRNA-Utilizing Enzymes in Natural Product Biosynthesis. Chem Rev 2017; 117:5578-5618. [DOI: 10.1021/acs.chemrev.6b00523] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Mireille Moutiez
- Institute for Integrative Biology of the
Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France
| | - Pascal Belin
- Institute for Integrative Biology of the
Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France
| | - Muriel Gondry
- Institute for Integrative Biology of the
Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France
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15
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Achenbach J, Jahnz M, Bethge L, Paal K, Jung M, Schuster M, Albrecht R, Jarosch F, Nierhaus KH, Klussmann S. Outwitting EF-Tu and the ribosome: translation with d-amino acids. Nucleic Acids Res 2015; 43:5687-98. [PMID: 26026160 PMCID: PMC4499158 DOI: 10.1093/nar/gkv566] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/18/2015] [Indexed: 01/09/2023] Open
Abstract
Key components of the translational apparatus, i.e. ribosomes, elongation factor EF-Tu and most aminoacyl-tRNA synthetases, are stereoselective and prevent incorporation of d-amino acids (d-aa) into polypeptides. The rare appearance of d-aa in natural polypeptides arises from post-translational modifications or non-ribosomal synthesis. We introduce an in vitro translation system that enables single incorporation of 17 out of 18 tested d-aa into a polypeptide; incorporation of two or three successive d-aa was also observed in several cases. The system consists of wild-type components and d-aa are introduced via artificially charged, unmodified tRNAGly that was selected according to the rules of ‘thermodynamic compensation’. The results reveal an unexpected plasticity of the ribosomal peptidyltransferase center and thus shed new light on the mechanism of chiral discrimination during translation. Furthermore, ribosomal incorporation of d-aa into polypeptides may greatly expand the armamentarium of in vitro translation towards the identification of peptides and proteins with new properties and functions.
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Affiliation(s)
- John Achenbach
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Michael Jahnz
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Lucas Bethge
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Krisztina Paal
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Maria Jung
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Maja Schuster
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Renate Albrecht
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Florian Jarosch
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Knud H Nierhaus
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Sven Klussmann
- NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
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16
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Zhang J, Ferré-D'Amaré AR. Structure and mechanism of the T-box riboswitches. WILEY INTERDISCIPLINARY REVIEWS-RNA 2015; 6:419-33. [PMID: 25959893 DOI: 10.1002/wrna.1285] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/19/2015] [Accepted: 03/25/2015] [Indexed: 01/11/2023]
Abstract
In most Gram-positive bacteria, including many clinically devastating pathogens from genera such as Bacillus, Clostridium, Listeria, and Staphylococcus, T-box riboswitches sense and regulate intracellular availability of amino acids through a multipartite messenger RNA (mRNA)-transfer RNA (tRNA) interaction. The T-box mRNA leaders respond to nutrient starvation by specifically binding cognate tRNAs and sensing whether the bound tRNA is aminoacylated, as a proxy for amino acid availability. Based on this readout, T-boxes direct a transcriptional or translational switch to control the expression of downstream genes involved in various aspects of amino acid metabolism: biosynthesis, transport, aminoacylation, transamidation, and so forth. Two decades after its discovery, the structural and mechanistic underpinnings of the T-box riboswitch were recently elucidated, producing a wealth of insights into how two structured RNAs can recognize each other with robust affinity and exquisite selectivity. The T-box paradigm exemplifies how natural noncoding RNAs can interact not just through sequence complementarity but can add molecular specificity by precisely juxtaposing RNA structural motifs, exploiting inherently flexible elements and the biophysical properties of post-transcriptional modifications, ultimately achieving a high degree of shape complementarity through mutually induced fit. The T-box also provides a proof-of-principle that compact RNA domains can recognize minute chemical changes (such as tRNA aminoacylation) on another RNA. The unveiling of the structure and mechanism of the T-box system thus expands our appreciation of the range of capabilities and modes of action of structured noncoding RNAs, and hints at the existence of networks of noncoding RNAs that communicate through both, structural and sequence specificity.
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Affiliation(s)
- Jinwei Zhang
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, MD, USA
| | - Adrian R Ferré-D'Amaré
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, MD, USA
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17
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Yikilmaz E, Chapman SJ, Schrader JM, Uhlenbeck OC. The interface between Escherichia coli elongation factor Tu and aminoacyl-tRNA. Biochemistry 2014; 53:5710-20. [PMID: 25094027 PMCID: PMC4159200 DOI: 10.1021/bi500533x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Nineteen of the highly conserved
residues of Escherichia
coli (E. coli) Elongation factor Tu (EF-Tu)
that form the binding interface with aa-tRNA were mutated to alanine
to better understand how modifying the thermodynamic properties of
EF-Tu–tRNA interaction can affect the decoding properties of
the ribosome. Comparison of ΔΔGo values for binding EF-Tu to aa-tRNA show that the majority of the
interface residues stabilize the ternary complex and their thermodynamic
contribution can depend on the tRNA species that is used. Experiments
with a very tight binding mutation of tRNATyr indicate
that interface amino acids distant from the tRNA mutation can contribute
to the specificity. For nearly all of the mutations, the values of
ΔΔGo were identical to those
previously determined at the orthologous positions of Thermus
thermophilus (T. thermophilus) EF-Tu indicating
that the thermodynamic properties of the interface were conserved
between distantly related bacteria. Measurement of the rate of GTP
hydrolysis on programmed ribosomes revealed that nearly all of the
interface mutations were able to function in ribosomal decoding. The
only interface mutation with greatly impaired GTPase activity was
R223A which is the only one that also forms a direct contact with
the ribosome. Finally, the ability of the EF-Tu interface mutants
to destabilize the EF-Tu–aa-tRNA interaction on the ribosome
after GTP hydrolysis were evaluated by their ability to suppress the
hyperstable T1 tRNATyr variant where EF-Tu release is sufficiently
slow to limit the rate of peptide bond formation (kpep) . In general, interface mutations that destabilize
EF-Tu binding are also able to stimulate kpep of T1 tRNATyr, suggesting that the thermodynamic properties
of the EF-Tu–aa-tRNA interaction on the ribosome are quite
similar to those found in the free ternary complex.
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Affiliation(s)
- Emine Yikilmaz
- Department of Molecular Biosciences, Northwestern University , Evanston, Illinois 60208, United States
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18
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Fung AWS, Leung CCY, Fahlman RP. The determination of tRNALeu recognition nucleotides for Escherichia coli L/F transferase. RNA (NEW YORK, N.Y.) 2014; 20:1210-1222. [PMID: 24935875 PMCID: PMC4105747 DOI: 10.1261/rna.044529.114] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 04/28/2014] [Indexed: 06/03/2023]
Abstract
Escherichia coli leucyl/phenylalanyl-tRNA protein transferase catalyzes the tRNA-dependent post-translational addition of amino acids onto the N-terminus of a protein polypeptide substrate. Based on biochemical and structural studies, the current tRNA recognition model by L/F transferase involves the identity of the 3' aminoacyl adenosine and the sequence-independent docking of the D-stem of an aminoacyl-tRNA to the positively charged cluster on L/F transferase. However, this model does not explain the isoacceptor preference observed 40 yr ago. Using in vitro-transcribed tRNA and quantitative MALDI-ToF MS enzyme activity assays, we have confirmed that, indeed, there is a strong preference for the most abundant leucyl-tRNA, tRNA(Leu) (anticodon 5'-CAG-3') isoacceptor for L/F transferase activity. We further investigate the molecular mechanism for this preference using hybrid tRNA constructs. We identified two independent sequence elements in the acceptor stem of tRNA(Leu) (CAG)-a G₃:C₇₀ base pair and a set of 4 nt (C₇₂, A₄:U₆₉, C₆₈)-that are important for the optimal binding and catalysis by L/F transferase. This maps a more specific, sequence-dependent tRNA recognition model of L/F transferase than previously proposed.
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Affiliation(s)
- Angela Wai Shan Fung
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
| | | | - Richard Peter Fahlman
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7 Department of Oncology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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19
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Burnett BJ, Altman RB, Ferguson A, Wasserman MR, Zhou Z, Blanchard SC. Direct evidence of an elongation factor-Tu/Ts·GTP·Aminoacyl-tRNA quaternary complex. J Biol Chem 2014; 289:23917-27. [PMID: 24990941 DOI: 10.1074/jbc.m114.583385] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During protein synthesis, elongation factor-Tu (EF-Tu) bound to GTP chaperones the entry of aminoacyl-tRNA (aa-tRNA) into actively translating ribosomes. In so doing, EF-Tu increases the rate and fidelity of the translation mechanism. Recent evidence suggests that EF-Ts, the guanosine nucleotide exchange factor for EF-Tu, directly accelerates both the formation and dissociation of the EF-Tu-GTP-Phe-tRNA(Phe) ternary complex (Burnett, B. J., Altman, R. B., Ferrao, R., Alejo, J. L., Kaur, N., Kanji, J., and Blanchard, S. C. (2013) J. Biol. Chem. 288, 13917-13928). A central feature of this model is the existence of a quaternary complex of EF-Tu/Ts·GTP·aa-tRNA(aa). Here, through comparative investigations of phenylalanyl, methionyl, and arginyl ternary complexes, and the development of a strategy to monitor their formation and decay using fluorescence resonance energy transfer, we reveal the generality of this newly described EF-Ts function and the first direct evidence of the transient quaternary complex species. These findings suggest that EF-Ts may regulate ternary complex abundance in the cell through mechanisms that are distinct from its guanosine nucleotide exchange factor functions.
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Affiliation(s)
| | | | - Angelica Ferguson
- Tri-Institutional Program in Chemical Biology, Weill Cornell Medical College, New York, New York 10065
| | | | - Zhou Zhou
- From the Department of Physiology and Biophysics and
| | - Scott C Blanchard
- From the Department of Physiology and Biophysics and Tri-Institutional Program in Chemical Biology, Weill Cornell Medical College, New York, New York 10065
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20
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Zhang J, Ferré-D'Amaré AR. Direct evaluation of tRNA aminoacylation status by the T-box riboswitch using tRNA-mRNA stacking and steric readout. Mol Cell 2014; 55:148-55. [PMID: 24954903 DOI: 10.1016/j.molcel.2014.05.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 03/28/2014] [Accepted: 04/08/2014] [Indexed: 01/01/2023]
Abstract
T-boxes are gene-regulatory mRNA elements with which Gram-positive bacteria sense amino acid availability. T-boxes have two functional domains. Stem I recognizes the overall shape and anticodon of tRNA, while a 3' domain evaluates its aminoacylation status, overcoming an otherwise stable transcriptional terminator if the bound tRNA is uncharged. Although T-boxes are believed to evaluate tRNA charge status without using any proteins, this has not been demonstrated experimentally because of the instability of aminoacyl-tRNA. Using a simple method to prepare homogeneous aminoacyl-tRNA, we show that the Bacillus subtilis glyQS T-box functions independently of any tRNA-binding protein. Comparison of aminoacyl-tRNA analogs demonstrates that the T-box detects the molecular volume of tRNA 3'-substituents. Calorimetry and fluorescence lifetime analysis of labeled RNAs shows that the tRNA acceptor end coaxially stacks on a helix in the T-box 3' domain. This intimate intermolecular association, selective for uncharged tRNA, stabilizes the antiterminator conformation of the T-box.
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Affiliation(s)
- Jinwei Zhang
- National Heart, Lung and Blood Institute, 50 South Drive, MSC 8012, Bethesda, MD 20892-8012, USA
| | - Adrian R Ferré-D'Amaré
- National Heart, Lung and Blood Institute, 50 South Drive, MSC 8012, Bethesda, MD 20892-8012, USA.
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21
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Javahishvili T, Manibusan A, Srinagesh S, Lee D, Ensari S, Shimazu M, Schultz PG. Role of tRNA orthogonality in an expanded genetic code. ACS Chem Biol 2014; 9:874-9. [PMID: 24443971 PMCID: PMC4167058 DOI: 10.1021/cb4005172] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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We found that Methanocaldococcus
jannaschii DSM2661
tyrosyl-tRNA synthetase (Mj E9RS), specifically evolved
to charge its cognate tRNA with the unnatural amino acid p-acetylphenylalanine (pAcF) in E. coli, misaminoacylates the endogenous E. coli prolyl-tRNAs
with pAcF at a low level (0.5% per proline frequency)
in both the absence or presence of its co-evolved amber suppressor
tRNA (M. jannaschii tyrosyl-tRNA, tRNACUAMjTyr). In contrast to other E. coli tRNAs, the identity elements for recognition of the proly tRNAs
by the E. coli prolyl-tRNA synthetase (C1, G72, and
A73) are similar to those in tRNACUAMjTyr. Although
the unique acceptor stem identity elements of the prolyl-tRNAs likely
lower their recognition by the other endogenous aaRSs in E.
coli, resulting in enhanced fidelity in the wild type strain,
they lead to misaminoacylation by the archae-derived E9RS. Misincorporation
of pAcF for proline was resolved to below detectable levels by overexpression
of the endogenous E. coli prolyl-tRNA synthetase
(proS) gene in combination with additional genomic
manipulations to further increase the intracellular ratio of the ProS
over its cognate proline tRNAs. These experiments suggest another
mechanism by which the cell maintains the high fidelity of protein
biosynthesis.
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Affiliation(s)
| | | | | | - Darin Lee
- Ambrx, Inc., La Jolla, California 92037, United States
| | - Semsi Ensari
- Ambrx, Inc., La Jolla, California 92037, United States
| | - Mark Shimazu
- Ambrx, Inc., La Jolla, California 92037, United States
| | - Peter G. Schultz
- The Scripps Research Institute, La
Jolla, California 92037, United States
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22
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Cloning and characterization of EF-Tu and EF-Ts from Pseudomonas aeruginosa. BIOMED RESEARCH INTERNATIONAL 2013; 2013:585748. [PMID: 23984384 PMCID: PMC3747624 DOI: 10.1155/2013/585748] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/12/2013] [Indexed: 11/17/2022]
Abstract
We have cloned genes encoding elongation factors EF-Tu and EF-Ts from Pseudomonas aeruginosa and expressed and purified the proteins to greater than 95% homogeneity. Sequence analysis indicated that P. aeruginosa EF-Tu and EF-Ts are 84% and 55% identical to E. coli counterparts, respectively. P. aeruginosa EF-Tu was active when assayed in GDP exchange assays. Kinetic parameters for the interaction of EF-Tu with GDP in the absence of EF-Ts were observed to be K M = 33 μM, k cat (obs) = 0.003 s(-1), and the specificity constant k cat (obs)/K M was 0.1 × 10(-3) s(-1) μM(-1). In the presence of EF-Ts, these values were shifted to K M = 2 μM, k cat (obs) = 0.005 s(-1), and the specificity constant k(cat)(obs)/K M was 2.5 × 10(-3) s(-1) μM(-1). The equilibrium dissociation constants governing the binding of EF-Tu to GDP (K GDP) were 30-75 nM and to GTP (K GTP) were 125-200 nM. EF-Ts stimulated the exchange of GDP by EF-Tu 10-fold. P. aeruginosa EF-Tu was active in forming a ternary complex with GTP and aminoacylated tRNA and was functional in poly(U)-dependent binding of Phe-tRNA(Phe) at the A-site of P. aeruginosa ribosomes. P. aeruginosa EF-Tu was active in poly(U)-programmed polyphenylalanine protein synthesis system composed of all P. aeruginosa components.
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23
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Ieong KW, Pavlov MY, Kwiatkowski M, Forster AC, Ehrenberg M. Inefficient Delivery but Fast Peptide Bond Formation of Unnatural l-Aminoacyl-tRNAs in Translation. J Am Chem Soc 2012; 134:17955-62. [DOI: 10.1021/ja3063524] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ka-Weng Ieong
- Department of Cell and Molecular
Biology, Uppsala University, Husargatan
3, Box 596, Uppsala
75124, Sweden
| | - Michael Y. Pavlov
- Department of Cell and Molecular
Biology, Uppsala University, Husargatan
3, Box 596, Uppsala
75124, Sweden
| | - Marek Kwiatkowski
- Department of Cell and Molecular
Biology, Uppsala University, Husargatan
3, Box 596, Uppsala
75124, Sweden
| | - Anthony C. Forster
- Department of Cell and Molecular
Biology, Uppsala University, Husargatan
3, Box 596, Uppsala
75124, Sweden
| | - Måns Ehrenberg
- Department of Cell and Molecular
Biology, Uppsala University, Husargatan
3, Box 596, Uppsala
75124, Sweden
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24
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Tzivelekidis T, Jank T, Pohl C, Schlosser A, Rospert S, Knudsen CR, Rodnina MV, Belyi Y, Aktories K. Aminoacyl-tRNA-charged eukaryotic elongation factor 1A is the bona fide substrate for Legionella pneumophila effector glucosyltransferases. PLoS One 2011; 6:e29525. [PMID: 22216304 PMCID: PMC3245282 DOI: 10.1371/journal.pone.0029525] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 11/30/2011] [Indexed: 01/08/2023] Open
Abstract
Legionella pneumophila, which is the causative organism of Legionnaireś disease, translocates numerous effector proteins into the host cell cytosol by a type IV secretion system during infection. Among the most potent effector proteins of Legionella are glucosyltransferases (lgt's), which selectively modify eukaryotic elongation factor (eEF) 1A at Ser-53 in the GTP binding domain. Glucosylation results in inhibition of protein synthesis. Here we show that in vitro glucosylation of yeast and mouse eEF1A by Lgt3 in the presence of the factors Phe-tRNAPhe and GTP was enhanced 150 and 590-fold, respectively. The glucosylation of eEF1A catalyzed by Lgt1 and 2 was increased about 70-fold. By comparison of uncharged tRNA with two distinct aminoacyl-tRNAs (His-tRNAHis and Phe-tRNAPhe) we could show that aminoacylation is crucial for Lgt-catalyzed glucosylation. Aminoacyl-tRNA had no effect on the enzymatic properties of lgt's and did not enhance the glucosylation rate of eEF1A truncation mutants, consisting of the GTPase domain only or of a 5 kDa peptide covering Ser-53 of eEF1A. Furthermore, binding of aminoacyl-tRNA to eEF1A was not altered by glucosylation. Taken together, our data suggest that the ternary complex, consisting of eEF1A, aminoacyl-tRNA and GTP, is the bona fide substrate for lgt's.
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Affiliation(s)
- Tina Tzivelekidis
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität, Freiburg, Germany
- Fakultät für Biologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Thomas Jank
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität, Freiburg, Germany
| | - Corinna Pohl
- Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
| | - Andreas Schlosser
- Zentrum für Biosystemanalyse, Core Facility Proteomics, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Sabine Rospert
- Institut für Biochemie und Mikrobiologie, ZBMZ, Albert-Ludwigs-Universität, Freiburg, Germany
| | | | | | - Yury Belyi
- Gamaleya Research Institute, Moscow, Russia
| | - Klaus Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität, Freiburg, Germany
- * E-mail:
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25
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Chapman SJ, Schrader JM, Uhlenbeck OC. Histidine 66 in Escherichia coli elongation factor tu selectively stabilizes aminoacyl-tRNAs. J Biol Chem 2011; 287:1229-34. [PMID: 22105070 DOI: 10.1074/jbc.m111.294850] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The universally conserved His-66 of elongation factor Tu (EF-Tu) stacks on the side chain of the esterified Phe of Phe-tRNA(Phe). The affinities of eight aminoacyl-tRNAs were differentially destabilized by the introduction of the H66A mutation into Escherichia coli EF-Tu, whereas Ala-tRNA(Ala) and Gly-tRNA(Gly) were unaffected. The H66F and H66W proteins each show a different pattern of binding of 10 different aminoacyl-tRNAs, clearly showing that this position is critical in establishing the specificity of EF-Tu for different esterified amino acids. However, the H66A mutation does not greatly affect the ability of the ternary complex to bind ribosomes, hydrolyze GTP, or form dipeptide, suggesting that this residue does not directly participate in ribosomal decoding. Selective mutation of His-66 may improve the ability of certain unnatural amino acids to be incorporated by the ribosome.
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Affiliation(s)
- Stephen J Chapman
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA
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26
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Schrader JM, Uhlenbeck OC. Is the sequence-specific binding of aminoacyl-tRNAs by EF-Tu universal among bacteria? Nucleic Acids Res 2011; 39:9746-58. [PMID: 21893586 PMCID: PMC3239215 DOI: 10.1093/nar/gkr641] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Three base pairs in the T-stem are primarily responsible for the sequence-specific interaction of tRNA with Escherichia coli and Thermus thermophilus EF-Tu. While the amino acids on the surface of EF-Tu that contact aminoacyl-tRNA (aa-tRNA) are highly conserved among bacteria, the T-stem sequences of individual tRNA are variable, making it unclear whether or not this protein–nucleic acid interaction is also sequence specific in other bacteria. We propose and validate a thermodynamic model that predicts the ΔG° of any tRNA to EF-Tu using the sequence of its three T-stem base pairs. Despite dramatic differences in T-stem sequences, the predicted ΔG° values for the majority of tRNA classes are similar in all bacteria and closely match the ΔG° values determined for E. coli tRNAs. Each individual tRNA class has evolved to have a characteristic ΔG° value to EF-Tu, but different T-stem sequences are used to achieve this ΔG° value in different bacteria. Thus, the compensatory relationship between the affinity of the tRNA body and the affinity of the esterified amino acid is universal among bacteria. Additionally, we predict and validate a small number of aa-tRNAs that bind more weakly to EF-Tu than expected and thus are candidates for acting as activated amino acid donors in processes outside of translation.
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Affiliation(s)
- Jared M Schrader
- Department of Molecular Biosciences, Northwestern University, Hogan 2-100, Evanston, IL 60208, USA
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27
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Tuning the affinity of aminoacyl-tRNA to elongation factor Tu for optimal decoding. Proc Natl Acad Sci U S A 2011; 108:5215-20. [PMID: 21402928 DOI: 10.1073/pnas.1102128108] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To better understand why aminoacyl-tRNAs (aa-tRNAs) have evolved to bind bacterial elongation factor Tu (EF-Tu) with uniform affinities, mutant tRNAs with differing affinities for EF-Tu were assayed for decoding on Escherichia coli ribosomes. At saturating EF-Tu concentrations, weaker-binding aa-tRNAs decode their cognate codons similarly to wild-type tRNAs. However, tighter-binding aa-tRNAs show reduced rates of peptide bond formation due to slow release from EF-Tu•GDP. Thus, the affinities of aa-tRNAs for EF-Tu are constrained to be uniform by their need to bind tightly enough to form the ternary complex but weakly enough to release from EF-Tu during decoding. Consistent with available crystal structures, the identity of the esterified amino acid and three base pairs in the T stem of tRNA combine to define the affinity of each aa-tRNA for EF-Tu, both off and on the ribosome.
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28
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Cheung MY, Xue Y, Zhou L, Li MW, Sun SSM, Lam HM. An ancient P-loop GTPase in rice is regulated by a higher plant-specific regulatory protein. J Biol Chem 2010; 285:37359-69. [PMID: 20876569 DOI: 10.1074/jbc.m110.172080] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
YchF is a subfamily of the Obg family in the TRAFAC class of P-loop GTPases. The wide distribution of YchF homologues in both eukarya and bacteria suggests that they are descendents of an ancient protein, yet their physiological roles remain unclear. Using the OsYchF1-OsGAP1 pair from rice as the prototype, we provide evidence for the regulation of GTPase/ATPase activities and RNA binding capacity of a plant YchF (OsYchF1) by its regulatory protein (OsGAP1). The effects of OsGAP1 on the subcellular localization/cycling and physiological functions of OsYchF1 are also discussed. The finding that OsYchF1 and OsGAP1 are involved in plant defense response might shed light on the functional roles of YchF homologues in plants. This work suggests that during evolution, an ancestral P-loop GTPase/ATPase may acquire new regulation and function(s) by the evolution of a lineage-specific regulatory protein.
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Affiliation(s)
- Ming-Yan Cheung
- State Key Laboratory of Agrobiotechnology and School of Life Sciences, Chinese University of Hong Kong, Shatin, Hong Kong
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29
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Schrader JM, Chapman SJ, Uhlenbeck OC. Understanding the sequence specificity of tRNA binding to elongation factor Tu using tRNA mutagenesis. J Mol Biol 2009; 386:1255-64. [PMID: 19452597 DOI: 10.1016/j.jmb.2009.01.021] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Measuring the binding affinities of 42 single-base-pair mutants in the acceptor and T Psi C stems of Saccharomyces cerevisiae tRNA Phe to Thermus thermophilus elongation factor Tu (EF-Tu) revealed that much of the specificity for tRNA occurs at the 49-65, 50-64, and 51-63 base pairs. Introducing the same mutations at the three positions into Escherichia coli tRNA CAG Leu resulted in similar changes in binding affinity. Swapping the three pairs from several E. coli tRNAs into yeast tRNA Phe resulted in chimeras with EF-Tu binding affinities similar to those for the donor tRNA. Finally, analysis of double- and triple-base-pair mutants of tRNA Phe showed that the thermodynamic contributions at the three sites are additive, permitting reasonably accurate prediction of the EF-Tu binding affinity for all E. coli tRNAs. Thus, it appears that the thermodynamic contributions of three base pairs in the T Psi C stem primarily account for tRNA binding specificity to EF-Tu.
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Affiliation(s)
- Jared M Schrader
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, 2205 Tech Drive, Hogan 2-100, Evanston, IL 60208, USA
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30
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A sequence element that tunes Escherichia coli tRNA(Ala)(GGC) to ensure accurate decoding. Nat Struct Mol Biol 2009; 16:359-64. [PMID: 19305403 PMCID: PMC2769084 DOI: 10.1038/nsmb.1581] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 02/20/2009] [Indexed: 11/08/2022]
Abstract
Mutating the rare A32-U38 nucleotide pair at the top of the anticodon loop of Escherichia coli tRNA(Ala)(GGC) to a more common U32-A38 pair results in a tRNA that performs almost normally on cognate codons but is unusually efficient in reading near-cognate codons. Pre-steady state kinetic measurements on E. coli ribosomes show that, unlike the wild-type tRNA(Ala)(GGC), the misreading mutant tRNA(Ala)(GGC) shows rapid GTP hydrolysis and no detectable proofreading on near-cognate codons. Similarly, tRNA(Ala)(GGC) mutated to contain C32-G38, a pair that is found in some bacterial tRNA(Ala)(GGC) sequences, was able to decode only the cognate codons, whereas tRNA(Ala)(GGC) containing a more common C32-A38 pair was able to decode all cognate and near-cognate codons tested. We propose that many of the phylogenetically conserved sequence elements present in each tRNA have evolved to suppress translation of near-cognate codons.
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31
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Futernyk PV, Negrutskii BS, El'ska GV. Noncanonical complexes of mammalian eEF1A with various deacylated tRNAs. ACTA ACUST UNITED AC 2008. [DOI: 10.7124/bc.0007bd] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- P. V. Futernyk
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - B. S. Negrutskii
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - G. V. El'ska
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
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32
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Jones CN, Jones CI, Graham WD, Agris PF, Spremulli LL. A disease-causing point mutation in human mitochondrial tRNAMet rsults in tRNA misfolding leading to defects in translational initiation and elongation. J Biol Chem 2008; 283:34445-56. [PMID: 18835817 DOI: 10.1074/jbc.m806992200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial tRNA genes are hot spots for mutations that lead to human disease. A single point mutation (T4409C) in the gene for human mitochondrial tRNA(Met) (hmtRNA(Met)) has been found to cause mitochondrial myopathy. This mutation results in the replacement of U8 in hmtRNA(Met) with a C8. The hmtRNA(Met) serves both in translational initiation and elongation in human mitochondria making this tRNA of particular interest in mitochondrial protein synthesis. Here we show that the single 8U-->C mutation leads to a failure of the tRNA to respond conformationally to Mg(2+). This mutation results in a drastic disruption of the structure of the hmtRNA(Met), which significantly reduces its aminoacylation. The small fraction of hmtRNA(Met) that can be aminoacylated is not formylated by the mitochondrial Met-tRNA transformylase preventing its function in initiation, and it is unable to form a stable ternary complex with elongation factor EF-Tu preventing any participation in chain elongation. We have used structural probing and molecular reconstitution experiments to examine the structures formed by the normal and mutated tRNAs. In the presence of Mg(2+), the normal tRNA displays the structural features expected of a tRNA. However, even in the presence of Mg(2+), the mutated tRNA does not form the cloverleaf structure typical of tRNAs. Thus, we believe that this mutation has disrupted a critical Mg(2+)-binding site on the tRNA required for formation of the biologically active structure. This work establishes a foundation for understanding the physiological consequences of the numerous mitochondrial tRNA mutations that result in disease in humans.
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Affiliation(s)
- Christie N Jones
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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33
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Ledoux S, Uhlenbeck OC. Different aa-tRNAs are selected uniformly on the ribosome. Mol Cell 2008; 31:114-23. [PMID: 18614050 DOI: 10.1016/j.molcel.2008.04.026] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 01/16/2008] [Accepted: 04/25/2008] [Indexed: 10/21/2022]
Abstract
Ten E. coli aminoacyl-tRNAs (aa-tRNAs) were assessed for their ability to decode cognate codons on E. coli ribosomes by using three assays that evaluate the key steps in the decoding pathway. Despite a wide variety of structural features, each aa-tRNA exhibited similar kinetic and thermodynamic properties in each assay. This surprising kinetic and thermodynamic uniformity is likely to reflect the importance of ribosome conformational changes in defining the rates and affinities of the decoding process as well as the evolutionary "tuning" of each aa-tRNA sequence to modify their individual interactions with the ribosome at each step.
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Affiliation(s)
- Sarah Ledoux
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA
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34
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Lee T, Feig AL. The RNA binding protein Hfq interacts specifically with tRNAs. RNA (NEW YORK, N.Y.) 2008; 14:514-23. [PMID: 18230766 PMCID: PMC2248270 DOI: 10.1261/rna.531408] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 11/28/2007] [Indexed: 05/24/2023]
Abstract
Hfq is an RNA binding protein that has been studied extensively for its role in the biology of small noncoding RNAs (ncRNAs) in bacteria, where it facilitates post-transcriptional gene regulation during stress responses. We show that Hfq also binds with high specificity and nanomolar affinity to tRNAs despite their lack of a canonical A/U rich single-stranded sequence. This affinity is comparable to that of Hfq for its validated ncRNA targets. Two sites on tRNAs are protected by Hfq binding, one on the D-stem and the other on the T-stem. Mutational analysis and competitive binding experiments indicate that Hfq uses its proximal surface (also called the L4 face) to bind tRNAs, the same surface that interacts with ncRNAs but a site distinct from where poly(A) oligonucleotides bind. hfq knockout strains are known to have broad pleiotropic phenotypes, but none of them are easily explained by or imply a role for tRNA binding. We show that hfq deletion strains have a previously unrecognized phenotype associated with mistranslation and significantly reduced translational fidelity. We infer that tRNA binding and reduced fidelity are linked by a role for Hfq in tRNA modification.
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MESH Headings
- Base Sequence
- Binding Sites/genetics
- Escherichia coli K12/genetics
- Escherichia coli K12/metabolism
- Escherichia coli Proteins/chemistry
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/metabolism
- Genes, Bacterial
- Host Factor 1 Protein/chemistry
- Host Factor 1 Protein/genetics
- Host Factor 1 Protein/metabolism
- Kinetics
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Nucleic Acid Conformation
- Protein Binding
- Protein Structure, Quaternary
- RNA Processing, Post-Transcriptional
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
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Affiliation(s)
- Taewoo Lee
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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35
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Sanderson LE, Uhlenbeck OC. The 51-63 base pair of tRNA confers specificity for binding by EF-Tu. RNA (NEW YORK, N.Y.) 2007; 13:835-40. [PMID: 17449728 PMCID: PMC1869040 DOI: 10.1261/rna.485307] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Elongation factor Tu (EF-Tu) exhibits significant specificity for the different elongator tRNA bodies in order to offset its variable affinity to the esterified amino acid. Three X-ray cocrystal structures reveal that while most of the contacts with the protein involve the phosphodiester backbone of tRNA, a single hydrogen bond is observed between the Glu390 and the amino group of a guanine in the 51-63 base pair in the T-stem of tRNA. Here we show that the Glu390Ala mutation of Thermus thermophilus EF-Tu selectively destabilizes binding of those tRNAs containing a guanine at either position 51 or 63 and that mutagenesis of the 51-63 base pair in several tRNAs modulates their binding affinities to EF-Tu. A comparison of Escherichia coli tRNA sequences suggests that this specificity mechanism is conserved across the bacterial domain. While this contact is an important specificity determinant, it is clear that others remain to be identified.
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Affiliation(s)
- Lee E Sanderson
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208, USA
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36
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Sanderson LE, Uhlenbeck OC. Exploring the Specificity of Bacterial Elongation Factor Tu for Different tRNAs. Biochemistry 2007; 46:6194-200. [PMID: 17489561 DOI: 10.1021/bi602548v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to identify amino acids in Thermus thermophilus elongation factor Tu which contribute to its specificity for different tRNAs, the binding affinities of 20 point mutations were compared to that of wild type protein using four tRNAs of differing affinities. The observed specificity for tRNA is the result of the varying contributions of five amino acids which make contacts with the T-stem and the 3' terminus of tRNA. For three of the amino acids the test tRNAs differ in sequence at the site of contact, presumably explaining the specificity. However, the remaining two amino acids contact tRNA at conserved positions, suggesting that more global structural or dynamic properties of the free tRNA contribute to specificity.
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Affiliation(s)
- Lee E Sanderson
- Northwestern University, 2205 Tech Drive, Hogan 2-100, Evanston, Illinois 60208, USA
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37
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Sanderson LE, Uhlenbeck OC. Directed mutagenesis identifies amino acid residues involved in elongation factor Tu binding to yeast Phe-tRNAPhe. J Mol Biol 2007; 368:119-30. [PMID: 17328911 PMCID: PMC2246379 DOI: 10.1016/j.jmb.2007.01.075] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 01/25/2007] [Accepted: 01/28/2007] [Indexed: 11/24/2022]
Abstract
The co-crystal structure of Thermus aquaticus elongation factor Tu.guanosine 5'- [beta,gamma-imido]triphosphate (EF-Tu.GDPNP) bound to yeast Phe-tRNA(Phe) reveals that EF-Tu interacts with the tRNA body primarily through contacts with the phosphodiester backbone. Twenty amino acids in the tRNA binding cleft of Thermus Thermophilus EF-Tu were each mutated to structurally conservative alternatives and the affinities of the mutant proteins to yeast Phe-tRNA(Phe) determined. Eleven of the 20 mutations reduced the binding affinity from fourfold to >100-fold, while the remaining ten had no effect. The thermodynamically important residues were spread over the entire tRNA binding interface, but were concentrated in the region which contacts the tRNA T-stem. Most of the data could be reconciled by considering the crystal structures of both free EF-Tu.GTP and the ternary complex and allowing for small (1.0 A) movements in the amino acid side-chains. Thus, despite the non-physiological crystallization conditions and crystal lattice interactions, the crystal structures reflect the biochemically relevant interaction in solution.
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38
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Dale T, Uhlenbeck OC. Binding of misacylated tRNAs to the ribosomal A site. RNA (NEW YORK, N.Y.) 2005; 11:1610-5. [PMID: 16244128 PMCID: PMC1370846 DOI: 10.1261/rna.2130505] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Accepted: 08/15/2005] [Indexed: 05/05/2023]
Abstract
To test whether the ribosome displays specificity for the esterified amino acid and the tRNA body of an aminoacyl-tRNA (aa-tRNA), the stabilities of 4 correctly acylated and 12 misacylated tRNAs in the ribosomal A site were determined. By introducing the GAC (valine) anticodon into each tRNA, a constant anticodon.codon interaction was maintained, thus removing concern that different anticodon.codon strengths might affect the binding of the different aa-tRNAs to the A site. Surprisingly, all 16 aa-tRNAs displayed similar dissociation rate constants from the A site. These results suggest that either the ribosome is not specific for different amino acids and tRNA bodies when intact aa-tRNAs are used or the specificity for the amino acid side chain and tRNA body is masked by a conformational change upon aa-tRNA release.
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Affiliation(s)
- Taraka Dale
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA
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39
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Sakamoto K, Ishimaru S, Kobayashi T, Walker JR, Yokoyama S. The Escherichia coli argU10(Ts) phenotype is caused by a reduction in the cellular level of the argU tRNA for the rare codons AGA and AGG. J Bacteriol 2004; 186:5899-905. [PMID: 15317795 PMCID: PMC516816 DOI: 10.1128/jb.186.17.5899-5905.2004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Escherichia coli argU10(Ts) mutation in the argU gene, encoding the minor tRNA(Arg) species for the rare codons AGA and AGG, causes pleiotropic defects, including growth inhibition at high temperatures, as well as the Pin phenotype at 30 degrees C. In the present study, we first showed that the codon selectivity and the arginine-accepting activity of the argU tRNA are both essential for complementing the temperature-sensitive growth, indicating that this defect is caused at the level of translation. An in vitro analysis of the effects of the argU10(Ts) mutation on tRNA functions revealed that the affinity with elongation factor Tu-GTP of the argU10(Ts) mutant tRNA is impaired at 30 and 43 degrees C, and this defect is more serious at the higher temperature. The arginine acceptance is also impaired significantly but to similar extents at the two temperatures. An in vivo analysis of aminoacylation levels showed that 30% of the argU10(Ts) tRNA molecules in the mutant cells are actually deacylated at 30 degrees C, while most of the argU tRNA molecules in the wild-type cells are aminoacylated. Furthermore, the cellular level of this mutant tRNA is one-tenth that of the wild-type argU tRNA. At 43 degrees C, the cellular level of the argU10(Ts) tRNA is further reduced to a trace amount, while neither the cellular abundance nor the aminoacylation level of the wild-type argU tRNA changes. We concluded that the phenotypic properties of the argU10(Ts) mutant result from these reduced intracellular levels of the tRNA, which are probably caused by the defective interactions with elongation factor Tu and arginyl-tRNA synthetase.
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Affiliation(s)
- Kensaku Sakamoto
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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40
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Dale T, Sanderson LE, Uhlenbeck OC. The affinity of elongation factor Tu for an aminoacyl-tRNA is modulated by the esterified amino acid. Biochemistry 2004; 43:6159-66. [PMID: 15147200 DOI: 10.1021/bi036290o] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
When different mutations were introduced into the anticodon loop and at position 73 of YFA2, a derivative of yeast tRNA(Phe), a single tRNA body was misacylated with 13 different amino acids. The affinities of these misacylated tRNAs for Thermus thermophilus elongation factor Tu (EF-Tu).GTP were determined using a ribonuclease protection assay. A range of 2.5 kcal/mol in the binding energies was observed, clearly demonstrating that EF-Tu specifically recognizes the side chain of the esterified amino acid. Furthermore, this specificity can be altered by introducing a mutation in the amino acid binding pocket on the surface of EF-Tu. Also, when discussed in conjunction with the previously determined specificity of EF-Tu for the tRNA body, these experiments further demonstrate that EF-Tu uses thermodynamic compensation to bind cognate aminoacyl-tRNAs similarly.
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Affiliation(s)
- Taraka Dale
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208, USA
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41
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Hunter SE, Spremulli LL. Mutagenesis of glutamine 290 in Escherichia coli and mitochondrial elongation factor Tu affects interactions with mitochondrial aminoacyl-tRNAs and GTPase activity. Biochemistry 2004; 43:6917-27. [PMID: 15170329 DOI: 10.1021/bi036068j] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Elongation factor Tu (EF-Tu) is responsible for the delivery of the aminoacyl-tRNAs (aa-tRNA) to the ribosome during protein synthesis. The primary sequence of domain II of EF-Tu is highly conserved. However, several residues thought to be important for aa-tRNA binding in this domain are not conserved between the mammalian mitochondrial and bacterial factors. One of these residues is located at position 290 (Escherichia coli numbering). Residue 290 is Gln in most of the prokaryotic factors but is conserved as Leu (L338) in the mammalian mitochondrial factors. This residue is in a loop contacting the switch II region of domain I in the GTP-bound structure. It also helps to form the binding pocket for the 5' end of the aa-tRNA in the ternary complex. In the present work, Leu338 was mutated to Gln (L338Q) in EF-Tu(mt). The complementary mutation was created at the equivalent position in E. coli EF-Tu (Q290L). EF-Tu(mt) L338Q functions as effectively as wild-type EF-Tu(mt) in poly(U)-directed polymerization with both prokaryotic and mitochondrial substrates and in ternary complex formation assays with E. coli aa-tRNA. However, the L338Q mitochondrial variant has a reduced affinity for mitochondrial Phe-tRNA(Phe). E. coli EF-Tu Q290L is more active in poly(U)-directed polymerization with both mitochondrial and prokaryotic substrates and has a higher GTPase activity in both the absence and presence of ribosomes. Surprisingly, while E. coli EF-Tu Q290L is more active in polymerization with mitochondrial Phe-tRNA(Phe), this variant has low activity in the formation of a stable ternary complex with mitochondrial aa-tRNA.
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Affiliation(s)
- Senyene Eyo Hunter
- Department of Chemistry, University of North Carolina, Campus Box 3290, Chapel Hill, North Carolina 27599-3290, USA
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42
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Hunter SE, Spremulli LL. Effects of mutagenesis of residue 221 on the properties of bacterial and mitochondrial elongation factor EF-Tu. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1699:173-82. [PMID: 15158725 DOI: 10.1016/j.bbapap.2004.02.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Revised: 01/14/2004] [Accepted: 02/19/2004] [Indexed: 11/19/2022]
Abstract
During protein biosynthesis, elongation factor Tu (EF-Tu) delivers aminoacyl-tRNA (aa-tRNA) to the A-site of ribosomes. This factor is highly conserved throughout evolution. However, several key residues differ between bacterial and mammalian mitochondrial EF-Tu (EF-Tu(mt)). One such residue is Ser221 (Escherichia coli numbering). This residue is conserved as a Ser or Thr in the bacterial factors but is present as Pro269 in EF-Tu(mt). Pro269 reorients the loop containing this residue and shifts the adjoining beta-strand in EF-Tu(mt) compared to that of E. coli EF-Tu potentially altering the binding pocket for the acceptor stem of the aa-tRNA. Pro269 was mutated to a serine residue (P269S) in EF-Tu(mt). For comparison, the complementary mutation was created at Ser221 in E. coli EF-Tu (S221P). The E. coli EF-Tu S221P variant is poorly expressed in E. coli and the majority of the molecules fail to fold into an active conformation. In contrast, EF-Tu(mt) P269S is expressed to a high level in E. coli. When corrected for the percentage of active molecules, both variants function as effectively as their respective wild-type factors in ternary complex formation using E. coli Phe-tRNA(Phe) and Cys-tRNA(Cys). They are also active in A-site binding and in vitro translation assays with E. coli Phe-tRNA(Phe). In addition, both variants are as active as their respective wild-type factors in ternary complex formation, A-site binding and in vitro translation assays using mitochondrial Phe-tRNA(Phe).
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Affiliation(s)
- Senyene Eyo Hunter
- Department of Chemistry, Lineberger Cancer Research Center, University of North Carolina, Campus Box 3290, Chapel Hill, NC 27599-3290, USA
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43
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Navratil T, Spremulli LL. Effects of mutagenesis of Gln97 in the switch II region of Escherichia coli elongation factor Tu on its interaction with guanine nucleotides, elongation factor Ts, and aminoacyl-tRNA. Biochemistry 2004; 42:13587-95. [PMID: 14622005 DOI: 10.1021/bi034855a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Elongation factor Tu (EF-Tu) delivers aminoacyl-tRNA to the A-site of the ribosome. In a multiple-sequence alignment of prokaryotic EF-Tu's, Gln97 is nearly 100% conserved. In contrast, in mammalian mitochondrial EF-Tu's, the corresponding position is occupied by a conserved proline residue. Gln97 is located in the switch II region in the GDP/GTP binding domain of EF-Tu. This domain undergoes a significant structural rearrangement upon GDP/GTP exchange. To investigate the role of Gln97 in bacterial EF-Tu, the E. coli EF-Tu variant Q97P was prepared. The Q97P variant displayed no activity in the incorporation of [(14)C]Phe on poly(U)-programmed E. coli ribosomes. The Q97P variant bound GDP more tightly than the wild-type EF-Tu with K(d) values of 7.5 and 12 nM, respectively. The intrinsic rate of GDP exchange was 2-3-fold lower for the Q97P variant than for wild-type EF-Tu in the absence of elongation factor Ts (EF-Ts). Addition of EF-Ts equalized the GDP exchange rate between the variant and wild-type EF-Tu. The variant bound GTP at 3-fold lower levels than the wild-type EF-Tu. Strikingly, the Q97P variant was completely inactive in ternary complex formation, accounting for its inability to function in polymerization. The structural basis of these observations is discussed.
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Affiliation(s)
- Tomas Navratil
- Department of Chemistry, Campus Box 3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
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44
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Spremulli LL, Coursey A, Navratil T, Hunter SE. Initiation and elongation factors in mammalian mitochondrial protein biosynthesis. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2004; 77:211-61. [PMID: 15196894 DOI: 10.1016/s0079-6603(04)77006-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Linda L Spremulli
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
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45
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Dupuy LC, Kelly NJ, Elgavish TE, Harvey SC, Morrow CD. Probing the importance of tRNA anticodon: human immunodeficiency virus type 1 (HIV-1) RNA genome complementarity with an HIV-1 that selects tRNA(Glu) for replication. J Virol 2003; 77:8756-64. [PMID: 12885895 PMCID: PMC167254 DOI: 10.1128/jvi.77.16.8756-8764.2003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The initiation of human immunodeficiency virus type 1 (HIV-1) reverse transcription occurs at the primer binding site (PBS) that is complementary to the 3'-terminal nucleotides of tRNA(3)(Lys). Why all known strains of HIV-1 select tRNA(3)(Lys) for replication is unknown. Previous studies on the effect of altering the PBS of HIV-1 on replication identified an HIV-1 with a PBS complementary to tRNA(Glu). Since the virus was not initially designed to use tRNA(Glu), the virus had selected tRNA(Glu) from the intracellular pool of tRNA for use in replication. Further characterization of HIV-1 that uses tRNA(Glu) may provide new insights into the preference for tRNA(3)(Lys). HIV-1 constructed with the PBS complementary to tRNA(Glu) was more stable than HIV-1 with the PBS complementary to tRNA(Met) or tRNA(His); however, all of these viruses eventually reverted back to using tRNA(3)(Lys) following growth in SupT1 cells or peripheral blood mononuclear cells (PBMCs). New HIV-1 mutants with nucleotides in U5 complementary to the anticodon of tRNA(Glu) remained stable when grown in SupT1 cells or PBMCs, although the mutants grew more slowly than the wild-type virus. Sequence analysis of the U5 region and the PBS revealed additional mutations predicted to further promote tRNA-viral genome interaction. The results support the importance of the tRNA anticodon-genome interaction in the selection of the tRNA primer and highlight the fact that unique features of tRNA(3)(Lys) are exploited by HIV-1 for selection as the reverse transcription primer.
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Affiliation(s)
- Lesley C Dupuy
- Department of Cell Biology, University of Alabama at Birmingham, 35294, USA
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46
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Abstract
Translation elongation factors are the workhorses of protein synthesis on the ribosome. They assist in elongating the nascent polypeptide chain by one amino acid at a time. The general biochemical outline of the translation elongation cycle is well preserved in all biological kingdoms. Recently, there has been structural insight into the effects of antibiotics on elongation. These structures provide a scaffold for understanding the biological function of elongation factors before high-resolution structures of such factors in complex with ribosomes are obtained. Very recent structures of the yeast translocation factor and its complex with the antifungal drug sordarin reveal an unexpected conformational flexibility that might be crucial to the mechanism of translocation.
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Affiliation(s)
- Gregers R Andersen
- Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
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Stortchevoi A, Varshney U, RajBhandary UL. Common location of determinants in initiator transfer RNAs for initiator-elongator discrimination in bacteria and in eukaryotes. J Biol Chem 2003; 278:17672-9. [PMID: 12639964 DOI: 10.1074/jbc.m212890200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Initiator tRNAs are used exclusively for initiation of protein synthesis and not for elongation. We show that both Escherichia coli and eukaryotic initiator tRNAs have negative determinants, at the same positions, that block their activity in elongation. The primary negative determinant in E. coli initiator tRNA is the C1xA72 mismatch at the end of the acceptor stem. The primary negative determinant in eukaryotic initiator tRNAs is located in the TPsiC stem, whereas a secondary negative determinant is the A1:U72 base pair at the end of the acceptor stem. Here we show that E. coli initiator tRNA also has a secondary negative determinant for elongation and that it is the U50.G64 wobble base pair, located at the same position in the TPsiC stem as the primary negative determinant in eukaryotic initiator tRNAs. Mutation of the U50.G64 wobble base pair to C50:G64 or U50:A64 base pairs increases the in vivo amber suppressor activity of initiator tRNA mutants that have changes in the acceptor stem and in the anticodon sequence necessary for amber suppressor activity. Binding assays of the mutant aminoacyl-tRNAs carrying the C50 and A64 changes to the elongation factor EF-Tu.GTP show marginally higher affinity of the C50 and A64 mutant tRNAs and increased stability of the EF-Tu.GTP. aminoacyl-tRNA ternary complexes. Other results show a large effect of the amino acid attached to a tRNA, glutamine versus methionine, on the binding affinity toward EF-Tu.GTP and on the stability of the EF-Tu.GTP.aminoacyl-tRNA ternary complex.
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Affiliation(s)
- Alexei Stortchevoi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Murase K, Morrison KL, Tam PY, Stafford RL, Jurnak F, Weiss GA. EF-Tu binding peptides identified, dissected, and affinity optimized by phage display. CHEMISTRY & BIOLOGY 2003; 10:161-8. [PMID: 12618188 DOI: 10.1016/s1074-5521(03)00025-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The highly abundant GTP binding protein elongation factor Tu (EF-Tu) fulfills multiple roles in bacterial protein biosynthesis. Phage-displayed peptides with high affinity for EF-Tu were selected from a library of approximately 4.7 x 10(11) different peptides. The lack of sequence homology among the identified EF-Tu ligands demonstrates promiscuous peptide binding by EF-Tu. Homolog shotgun scanning of an EF-Tu ligand was used to dissect peptide molecular recognition by EF-Tu. All homolog shotgun scanning selectants bound to EF-Tu with higher affinity than the starting ligand. Thus, homolog shotgun scanning can simultaneously optimize binding affinity and rapidly provide detailed structure activity relationships for multiple side chains of a polypeptide ligand. The reported peptide ligands do not compete for binding to EF-Tu with various antibiotic EF-Tu inhibitors, and could identify an EF-Tu peptide binding site distinct from the antibiotic inhibitory sites.
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Affiliation(s)
- Katsuyuki Murase
- Department of Chemistry, 346-D Med Sci I, University of California, Irvine, Irvine, CA 92697, USA
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49
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Abstract
By introducing a GAC anticodon, 21 different Escherichia coli tRNAs were misacylated with either phenylalanine or valine and assayed for their affinity to Thermus thermophilus elongation factor Tu (EF-Tu)*GTP by using a ribonuclease protection assay. The presence of a common esterified amino acid permits the thermodynamic contribution of each tRNA body to the overall affinity to be evaluated. The E. coli elongator tRNAs exhibit a wide range of binding affinities that varied from -11.7 kcal/mol for Val-tRNA(Glu) to -8.1 kcal/mol for Val-tRNA(Tyr), clearly establishing EF-Tu*GTP as a sequence-specific RNA-binding protein. Because the ionic strength dependence of k(off) varied among tRNAs, some of the affinity differences are the results of a different number of phosphate contacts formed between tRNA and protein. Because EF-Tu is known to contact only the phosphodiester backbone of tRNA, the observed specificity must be a consequence of an indirect readout mechanism.
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MESH Headings
- Acylation
- Anticodon/genetics
- Base Sequence
- Binding Sites
- Escherichia coli/genetics
- Genetic Engineering
- Mutation/genetics
- Nuclease Protection Assays
- Osmolar Concentration
- Peptide Elongation Factor Tu/metabolism
- Protein Binding
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Substrate Specificity
- Thermodynamics
- Thermus thermophilus/enzymology
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Affiliation(s)
- Haruichi Asahara
- Department of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, CO 80309-0215, USA
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Hanada T, Suzuki T, Yokogawa T, Takemoto-Hori C, Sprinzl M, Watanabe K. Translation ability of mitochondrial tRNAsSer with unusual secondary structures in an in vitro translation system of bovine mitochondria. Genes Cells 2001; 6:1019-30. [PMID: 11737263 DOI: 10.1046/j.1365-2443.2001.00491.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Metazoan mitochondrial (mt) tRNAs are structurally quite different from the canonical cloverleaf secondary structure. The mammalian mt tRNASerGCU for AGY codons (Y = C or U) lacks the entire D arm, whereas tRNASerUGA for UCN codons (N = A, G, C or U) has an extended anti-codon stem. It has been a long-standing problem to prove experimentally how these tRNAsSer work in the mt translation system. RESULTS To solve the above-mentioned problem, we examined their translational abilities in an in vitro bovine mitochondrial translation system using transcripts of altered tRNASer analogues derived from bovine mitochondria. Both tRNASer analogues had almost the same ability to form ternary complexes with mt EF-Tu and GTP. The D-arm-lacking tRNASer GCU analogue had considerably lower translational activity than the tRNASerUGA analogue and produced mostly short oligopeptides, up to a tetramer. In addition, tRNASerGCU analogue was disfavoured by the ribosome when other tRNAs capable of decoding the cognate codon were available. CONCLUSION Both mt tRNASerGCU and tRNASerUGA analogues with unusual secondary structure were found to be capable of translation on the ribosome. However, the tRNASerGCU analogue has some molecular disadvantage on the ribosome, which probably derives from the lack of a D arm.
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Affiliation(s)
- T Hanada
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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