1
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Ishida S, Ngo PHT, Gundlach A, Ellington A. Engineering Ribosomal Machinery for Noncanonical Amino Acid Incorporation. Chem Rev 2024; 124:7712-7730. [PMID: 38829723 DOI: 10.1021/acs.chemrev.3c00912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
The introduction of noncanonical amino acids into proteins has enabled researchers to modify fundamental physicochemical and functional properties of proteins. While the alteration of the genetic code, via the introduction of orthogonal aminoacyl-tRNA synthetase:tRNA pairs, has driven many of these efforts, the various components involved in the process of translation are important for the development of new genetic codes. In this review, we will focus on recent advances in engineering ribosomal machinery for noncanonical amino acid incorporation and genetic code modification. The engineering of the ribosome itself will be considered, as well as the many factors that interact closely with the ribosome, including both tRNAs and accessory factors, such as the all-important EF-Tu. Given the success of genome re-engineering efforts, future paths for radical alterations of the genetic code will require more expansive alterations in the translation machinery.
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Affiliation(s)
- Satoshi Ishida
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712, United States
| | - Phuoc H T Ngo
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712, United States
| | - Arno Gundlach
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712, United States
| | - Andrew Ellington
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712, United States
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2
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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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3
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Thaenert A, Sevostyanova A, Chung CZ, Vargas-Rodriguez O, Melnikov SV, Söll D. Engineered mRNA-ribosome fusions for facile biosynthesis of selenoproteins. Proc Natl Acad Sci U S A 2024; 121:e2321700121. [PMID: 38442159 PMCID: PMC10945757 DOI: 10.1073/pnas.2321700121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2023] [Accepted: 01/31/2024] [Indexed: 03/07/2024] Open
Abstract
Ribosomes are often used in synthetic biology as a tool to produce desired proteins with enhanced properties or entirely new functions. However, repurposing ribosomes for producing designer proteins is challenging due to the limited number of engineering solutions available to alter the natural activity of these enzymes. In this study, we advance ribosome engineering by describing a novel strategy based on functional fusions of ribosomal RNA (rRNA) with messenger RNA (mRNA). Specifically, we create an mRNA-ribosome fusion called RiboU, where the 16S rRNA is covalently attached to selenocysteine insertion sequence (SECIS), a regulatory RNA element found in mRNAs encoding selenoproteins. When SECIS sequences are present in natural mRNAs, they instruct ribosomes to decode UGA codons as selenocysteine (Sec, U) codons instead of interpreting them as stop codons. This enables ribosomes to insert Sec into the growing polypeptide chain at the appropriate site. Our work demonstrates that the SECIS sequence maintains its functionality even when inserted into the ribosome structure. As a result, the engineered ribosomes RiboU interpret UAG codons as Sec codons, allowing easy and site-specific insertion of Sec in a protein of interest with no further modification to the natural machinery of protein synthesis. To validate this approach, we use RiboU ribosomes to produce three functional target selenoproteins in Escherichia coli by site-specifically inserting Sec into the proteins' active sites. Overall, our work demonstrates the feasibility of creating functional mRNA-rRNA fusions as a strategy for ribosome engineering, providing a novel tool for producing Sec-containing proteins in live bacterial cells.
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Affiliation(s)
- Anna Thaenert
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT06511
| | | | - Christina Z. Chung
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT06511
| | | | - Sergey V. Melnikov
- Biosciences Institute, Newcastle University, Newcastle upon TyneNE2 4HH, United Kingdom
- Biosciences Institute, Newcastle University Medical School, Newcastle upon TyneNE2 4HH, United Kingdom
| | - Dieter Söll
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT06511
- Department of Chemistry, Yale University, New Haven, CT06511
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4
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Kim Y, Cho S, Kim JC, Park HS. tRNA engineering strategies for genetic code expansion. Front Genet 2024; 15:1373250. [PMID: 38516376 PMCID: PMC10954879 DOI: 10.3389/fgene.2024.1373250] [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: 01/19/2024] [Accepted: 02/26/2024] [Indexed: 03/23/2024] Open
Abstract
The advancement of genetic code expansion (GCE) technology is attributed to the establishment of specific aminoacyl-tRNA synthetase/tRNA pairs. While earlier improvements mainly focused on aminoacyl-tRNA synthetases, recent studies have highlighted the importance of optimizing tRNA sequences to enhance both unnatural amino acid incorporation efficiency and orthogonality. Given the crucial role of tRNAs in the translation process and their substantial impact on overall GCE efficiency, ongoing efforts are dedicated to the development of tRNA engineering techniques. This review explores diverse tRNA engineering approaches and provides illustrative examples in the context of GCE, offering insights into the user-friendly implementation of GCE technology.
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Affiliation(s)
| | | | | | - Hee-Sung Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
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5
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Wright DE, O’Donoghue P. Biosynthesis, Engineering, and Delivery of Selenoproteins. Int J Mol Sci 2023; 25:223. [PMID: 38203392 PMCID: PMC10778597 DOI: 10.3390/ijms25010223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 12/14/2023] [Accepted: 12/18/2023] [Indexed: 01/12/2024] Open
Abstract
Selenocysteine (Sec) was discovered as the 21st genetically encoded amino acid. In nature, site-directed incorporation of Sec into proteins requires specialized biosynthesis and recoding machinery that evolved distinctly in bacteria compared to archaea and eukaryotes. Many organisms, including higher plants and most fungi, lack the Sec-decoding trait. We review the discovery of Sec and its role in redox enzymes that are essential to human health and important targets in disease. We highlight recent genetic code expansion efforts to engineer site-directed incorporation of Sec in bacteria and yeast. We also review methods to produce selenoproteins with 21 or more amino acids and approaches to delivering recombinant selenoproteins to mammalian cells as new applications for selenoproteins in synthetic biology.
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Affiliation(s)
- David E. Wright
- Department of Biochemistry, The University of Western Ontario, London, ON N6A 5C1, Canada;
| | - Patrick O’Donoghue
- Department of Biochemistry, The University of Western Ontario, London, ON N6A 5C1, Canada;
- Department of Chemistry, The University of Western Ontario, London, ON N6A 5C1, Canada
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6
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Hoffman KS, Chung CZ, Mukai T, Krahn N, Jiang HK, Balasuriya N, O'Donoghue P, Söll D. Recoding UAG to selenocysteine in Saccharomyces cerevisiae. RNA (NEW YORK, N.Y.) 2023; 29:1400-1410. [PMID: 37279998 PMCID: PMC10573291 DOI: 10.1261/rna.079658.123] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 05/16/2023] [Indexed: 06/08/2023]
Abstract
Unique chemical and physical properties are introduced by inserting selenocysteine (Sec) at specific sites within proteins. Recombinant and facile production of eukaryotic selenoproteins would benefit from a yeast expression system; however, the selenoprotein biosynthetic pathway was lost in the evolution of the kingdom Fungi as it diverged from its eukaryotic relatives. Based on our previous development of efficient selenoprotein production in bacteria, we designed a novel Sec biosynthesis pathway in Saccharomyces cerevisiae using Aeromonas salmonicida translation components. S. cerevisiae tRNASer was mutated to resemble A. salmonicida tRNASec to allow recognition by S. cerevisiae seryl-tRNA synthetase as well as A. salmonicida selenocysteine synthase (SelA) and selenophosphate synthetase (SelD). Expression of these Sec pathway components was then combined with metabolic engineering of yeast to enable the production of active methionine sulfate reductase enzyme containing genetically encoded Sec. Our report is the first demonstration that yeast is capable of selenoprotein production by site-specific incorporation of Sec.
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Affiliation(s)
- Kyle S Hoffman
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
| | - Christina Z Chung
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
| | - Takahito Mukai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
| | - Natalie Krahn
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
| | - Han-Kai Jiang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
| | - Nileeka Balasuriya
- Department of Biochemistry, The University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Patrick O'Donoghue
- Department of Biochemistry, The University of Western Ontario, London, Ontario N6A 3K7, Canada
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, USA
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7
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Chung CZ, Söll D, Krahn N. Creating Selenocysteine-Specific Reporters Using Inteins. Methods Mol Biol 2023; 2676:69-86. [PMID: 37277625 DOI: 10.1007/978-1-0716-3251-2_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The selenium moiety in selenocysteine (Sec) imparts enhanced chemical properties to this amino acid and ultimately the protein in which it is inserted. These characteristics are attractive for designing highly active enzymes or extremely stable proteins and studying protein folding or electron transfer, to name a few. There are also 25 human selenoproteins, of which many are essential for our survival. The ability to create or study these selenoproteins is significantly hindered by the inability to easily produce them. Engineering translation has yielded simpler systems to facilitate site-specific insertion of Sec; however, Ser misincorporation remains problematic. Therefore, we have designed two Sec-specific reporters which promote high-throughput screening of Sec translation systems to overcome this barrier. This protocol outlines the workflow to engineer these Sec-specific reporters, with the application to any gene of interest and the ability to transfer this strategy to any organism.
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Affiliation(s)
- Christina Z Chung
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Department of Chemistry, Yale University, New Haven, CT, USA
| | - Natalie Krahn
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
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8
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Chung CZ, Krahn N. The selenocysteine toolbox: A guide to studying the 21st amino acid. Arch Biochem Biophys 2022; 730:109421. [DOI: 10.1016/j.abb.2022.109421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/22/2022] [Accepted: 09/26/2022] [Indexed: 11/28/2022]
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9
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Prabhakar A, Krahn N, Zhang J, Vargas-Rodriguez O, Krupkin M, Fu Z, Acosta-Reyes FJ, Ge X, Choi J, Crnković A, Ehrenberg M, Puglisi EV, Söll D, Puglisi J. Uncovering translation roadblocks during the development of a synthetic tRNA. Nucleic Acids Res 2022; 50:10201-10211. [PMID: 35882385 PMCID: PMC9561287 DOI: 10.1093/nar/gkac576] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/14/2022] [Accepted: 07/22/2022] [Indexed: 11/24/2022] Open
Abstract
Ribosomes are remarkable in their malleability to accept diverse aminoacyl-tRNA substrates from both the same organism and other organisms or domains of life. This is a critical feature of the ribosome that allows the use of orthogonal translation systems for genetic code expansion. Optimization of these orthogonal translation systems generally involves focusing on the compatibility of the tRNA, aminoacyl-tRNA synthetase, and a non-canonical amino acid with each other. As we expand the diversity of tRNAs used to include non-canonical structures, the question arises as to the tRNA suitability on the ribosome. Specifically, we investigated the ribosomal translation of allo-tRNAUTu1, a uniquely shaped (9/3) tRNA exploited for site-specific selenocysteine insertion, using single-molecule fluorescence. With this technique we identified ribosomal disassembly occurring from translocation of allo-tRNAUTu1 from the A to the P site. Using cryo-EM to capture the tRNA on the ribosome, we pinpointed a distinct tertiary interaction preventing fluid translocation. Through a single nucleotide mutation, we disrupted this tertiary interaction and relieved the translation roadblock. With the continued diversification of genetic code expansion, our work highlights a targeted approach to optimize translation by distinct tRNAs as they move through the ribosome.
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Affiliation(s)
| | | | | | - Oscar Vargas-Rodriguez
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Miri Krupkin
- Department of Structural Biology, Stanford University, Stanford, CA 94305-5126, USA
| | - Ziao Fu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Francisco J Acosta-Reyes
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Xueliang Ge
- Department of Cell and Molecular Biology, Uppsala University, Uppsala 751 24, Sweden
| | - Junhong Choi
- Department of Structural Biology, Stanford University, Stanford, CA 94305-5126, USA
| | - Ana Crnković
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Måns Ehrenberg
- Department of Cell and Molecular Biology, Uppsala University, Uppsala 751 24, Sweden
| | | | - Dieter Söll
- Correspondence may also be addressed to Dieter Söll.
| | - Joseph Puglisi
- To whom correspondence should be addressed. Tel: +1 650 498 4397;
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10
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Reactive Human Plasma Glutathione Peroxidase Mutant with Diselenide Bond Succeeds in Tetramer Formation. Antioxidants (Basel) 2022; 11:antiox11061083. [PMID: 35739980 PMCID: PMC9220127 DOI: 10.3390/antiox11061083] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/25/2022] [Accepted: 05/27/2022] [Indexed: 12/05/2022] Open
Abstract
Plasma glutathione peroxidase (GPx3) belongs to the GPx superfamily, and it is the only known secreted selenocysteine (Sec)−containing GPx in humans. It exists as a glycosylated homotetramer and catalyzes the reduction of hydrogen peroxide and lipid peroxides, depending on the Sec in its active center. In this study, a previously reported chimeric tRNAUTuT6 was used for the incorporation of Sec at the UAG amber codon, and the mature form of human GPx3 (hGPx3) without the signal peptide was expressed in amber−less E. coli C321.ΔA.exp. Reactive Sec−hGPx3, able to reduce H2O2 and tert−butyl hydroperoxide (t−BuOOH), was produced with high purity and yield. Study of the quaternary structure suggested that the recombinant Sec−hGPx3 contained an intra−molecular disulfide bridge but failed to form tetramer. Mutational and structural analysis of the mutants with three Cys residues, individually or jointly replaced with Ser, indicated that the formation of intra−molecular disulfide bridges involved structure conformational changes. The secondary structure containing Cys77 and Cys132 was flexible and could form a disulfide bond, or form a sulfhydryl–selenyl bond with Sec49 in relative mutants. Mutation of Cys8 and Cys132 to Sec8 and Sec132 could fix the oligomerization loop through the formation of diselenide bond, which, in turn, facilitated tetramer formation and noticeably improved the GPx activity. This research provides an important foundation for the further catalysis and functional study of hGPx3.
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11
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Expressing recombinant selenoproteins using redefinition of a single UAG codon in an RF1-depleted E. coli host strain. Methods Enzymol 2022; 662:95-118. [PMID: 35101220 DOI: 10.1016/bs.mie.2021.10.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Selenoproteins containing the rare amino acid selenocysteine (Sec), typically being enzymes utilizing the selenium atom of Sec for promoted catalysis of redox reactions, are challenging to obtain at high amounts in pure form. The technical challenges limiting selenoprotein supply derive from intricacies in their translation, necessitating the recoding of a UGA stop codon to a sense codon for Sec. This, in turn, involves the interactions of a Sec-dedicated elongation factor, either directly or indirectly, with a structure in the selenoprotein-encoding mRNA called a SECIS element (Selenocysteine Insertion Sequence), a dedicated tRNA species for Sec with an anticodon for the UGA, and several accessory enzymes and proteins involved in the selenoprotein synthesis. Here, we describe an alternative method for recombinant selenoprotein production using UAG as the Sec codon in a specific strain of E. coli lacking other UAG codons and lacking the release factor RF1 that normally terminates translation at UAG. We also describe how such recombinant selenoproteins can be purified and further analyzed for final Sec contents. The methodology can be used for production of natural selenoproteins in recombinant form as well as for production of synthetic selenoproteins that may be designed to use the unique biophysical properties of Sec for diverse biotechnological applications.
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12
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Chung CZ, Söll D, Krahn N. Using selenocysteine-specific reporters to screen for efficient tRNA Sec variants. Methods Enzymol 2022; 662:63-93. [PMID: 35101219 DOI: 10.1016/bs.mie.2021.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The unique properties of selenocysteine (Sec) have generated an interest in the scientific community to site-specifically incorporate Sec into a protein of choice. Current technologies have rewired the natural Sec-specific translation factor-dependent selenoprotein biosynthesis pathway by harnessing the canonical elongation factor (EF-Tu) to simplify the requirements for Sec incorporation in Escherichia coli. This strategy is versatile and can be applied to Sec incorporation at any position in a protein of interest. However, selenoprotein production is still limited by yield and serine misincorporation. This protocol outlines a method in E. coli to design and optimize tRNA libraries which can be selected and screened for by the use of Sec-specific intein-based reporters. This provides a fast and simple way to engineer tRNAs with enhanced Sec-incorporation ability.
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Affiliation(s)
- Christina Z Chung
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, United States
| | - Dieter Söll
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, United States; Department of Chemistry, Yale University, New Haven, CT, United States.
| | - Natalie Krahn
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, United States
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13
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Patel A, Mulder DW, Söll D, Krahn N. Harnessing selenocysteine to enhance microbial cell factories for hydrogen production. FRONTIERS IN CATALYSIS 2022; 2. [PMID: 36844461 PMCID: PMC9961374 DOI: 10.3389/fctls.2022.1089176] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Hydrogen is a clean, renewable energy source, that when combined with oxygen, produces heat and electricity with only water vapor as a biproduct. Furthermore, it has the highest energy content by weight of all known fuels. As a result, various strategies have engineered methods to produce hydrogen efficiently and in quantities that are of interest to the economy. To approach the notion of producing hydrogen from a biological perspective, we take our attention to hydrogenases which are naturally produced in microbes. These organisms have the machinery to produce hydrogen, which when cleverly engineered, could be useful in cell factories resulting in large production of hydrogen. Not all hydrogenases are efficient at hydrogen production, and those that are, tend to be oxygen sensitive. Therefore, we provide a new perspective on introducing selenocysteine, a highly reactive proteinogenic amino acid, as a strategy towards engineering hydrogenases with enhanced hydrogen production, or increased oxygen tolerance.
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Affiliation(s)
- Armaan Patel
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
| | - David W Mulder
- National Renewable Energy Laboratory, Biosciences Center, Golden, CO, United States
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States.,Department of Chemistry, Yale University, New Haven, CT, United States
| | - Natalie Krahn
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
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14
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Chung CZ, Krahn N, Crnković A, Söll D. Intein-based Design Expands Diversity of Selenocysteine Reporters. J Mol Biol 2021; 434:167199. [PMID: 34411545 PMCID: PMC8847544 DOI: 10.1016/j.jmb.2021.167199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/28/2021] [Accepted: 08/04/2021] [Indexed: 12/27/2022]
Abstract
The presence of selenocysteine in a protein confers many unique properties that make the production of recombinant selenoproteins desirable. Targeted incorporation of Sec into a protein of choice is possible by exploiting elongation factor Tu-dependent reassignment of UAG codons, a strategy that has been continuously improved by a variety of means. Improving selenoprotein yield by directed evolution requires selection and screening markers that are titratable, have a high dynamic range, enable high-throughput screening, and can discriminate against nonspecific UAG decoding. Current screening techniques are limited to a handful of reporters where a cysteine (Cys) or Sec residue normally affords activity. Unfortunately, these existing Cys/Sec-dependent reporters lack the dynamic range of more ubiquitous reporters or suffer from other limitations. Here we present a versatile strategy to adapt established reporters for specific Sec incorporation. Inteins are intervening polypeptides that splice themselves from the precursor protein in an autocatalytic splicing reaction. Using an intein that relies exclusively on Sec for splicing, we show that this intein cassette can be placed in-frame within selection and screening markers, affording reporter activity only upon successful intein splicing. Furthermore, because functional splicing can only occur when a catalytic Sec is present, the amount of synthesized reporter directly measures UAG-directed Sec incorporation. Importantly, we show that results obtained with intein-containing reporters are comparable to the Sec incorporation levels determined by mass spectrometry of isolated recombinant selenoproteins. This result validates the use of these intein-containing reporters to screen for evolved components of a translation system yielding increased selenoprotein amounts.
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Affiliation(s)
- Christina Z Chung
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06511, USA.
| | - Natalie Krahn
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06511, USA.
| | - Ana Crnković
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06511, USA.
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06511, USA; Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511, USA.
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15
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Ho JML, Miller CA, Smith KA, Mattia JR, Bennett MR. Improved pyrrolysine biosynthesis through phage assisted non-continuous directed evolution of the complete pathway. Nat Commun 2021; 12:3914. [PMID: 34168131 PMCID: PMC8225853 DOI: 10.1038/s41467-021-24183-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 06/04/2021] [Indexed: 11/29/2022] Open
Abstract
Pyrrolysine (Pyl, O) exists in nature as the 22nd proteinogenic amino acid. Despite being a fundamental building block of proteins, studies of Pyl have been hindered by the difficulty and inefficiency of both its chemical and biological syntheses. Here, we improve Pyl biosynthesis via rational engineering and directed evolution of the entire biosynthetic pathway. To accommodate toxicity of Pyl biosynthetic genes in Escherichia coli, we also develop Alternating Phage Assisted Non-Continuous Evolution (Alt-PANCE) that alternates mutagenic and selective phage growths. The evolved pathway provides 32-fold improved yield of Pyl-containing reporter protein compared to the rationally engineered ancestor. Evolved PylB mutants are present at up to 4.5-fold elevated levels inside cells, and show up to 2.2-fold increased protease resistance. This study demonstrates that Alt-PANCE provides a general approach for evolving proteins exhibiting toxic side effects, and further provides an improved pathway capable of producing substantially greater quantities of Pyl-proteins in E. coli. Pyrrolysine (Pyl) exists in nature as the 22nd proteinogenic amino acid, but studies of Pyl have been hindered by the difficulty and inefficiency of both its chemical and biological syntheses. Here, the authors developed an improved PANCE approach to evolve the pylBCD pathway for increased production of Pyl proteins in E. coli.
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Affiliation(s)
- Joanne M L Ho
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Corwin A Miller
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Kathryn A Smith
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Jacob R Mattia
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Matthew R Bennett
- Department of Biosciences, Rice University, Houston, TX, USA. .,Department of Bioengineering, Rice University, Houston, TX, USA.
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16
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Chung CZ, Miller C, Söll D, Krahn N. Introducing Selenocysteine into Recombinant Proteins in Escherichia coli. Curr Protoc 2021; 1:e54. [PMID: 33566458 DOI: 10.1002/cpz1.54] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Selenoproteins contain the 21st amino acid, selenocysteine. Selenocysteine is the only amino acid that is synthesized on its cognate tRNA, and it is inserted at specific recoded UGA stop codons via a complex translation system. Although highly similar to cysteine, selenocysteine has unique properties, including a stronger nucleophilic ability and lower reduction potential. Efforts to site-specifically incorporate selenocysteine to create recombinant selenoproteins involve a recoded UAG stop codon and expression of the necessary selenocysteine translation machinery. This article presents a protocol for expressing and purifying selenoproteins in Escherichia coli. © 2021 Wiley Periodicals LLC. Basic Protocol: Recombinant selenoprotein production in E. coli using a rewired translation system.
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Affiliation(s)
- Christina Z Chung
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Corwin Miller
- Department of Biosciences, Rice University, Houston, Texas
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut.,Department of Chemistry, Yale University, New Haven, Connecticut
| | - Natalie Krahn
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
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17
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Wang Y, Liu P, Chang J, Xu Y, Wang J. Site-Specific Selenocysteine Incorporation into Proteins by Genetic Engineering. Chembiochem 2021; 22:2918-2924. [PMID: 33949764 DOI: 10.1002/cbic.202100124] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/03/2021] [Indexed: 01/23/2023]
Abstract
Selenocysteine (Sec), a rare naturally proteinogenic amino acid, is the major form of essential trace element selenium in living organisms. Selenoproteins, with one or several Sec residues, are found in all three domains of life. Many selenoproteins play a role in critical cellular functions such as maintaining cell redox homeostasis. Sec is usually encoded by an in-frame stop codon UGA in the selenoprotein mRNA, and its incorporation in vivo is highly species-dependent and requires the reprogramming of translation. This mechanistic complexity of selenoprotein synthesis poses a big challenge to produce synthetic selenoproteins. To understand the functions of natural as well as engineered selenoproteins, many strategies have recently been developed to overcome the inherent barrier for recombinant selenoprotein production. In this review, we will describe the progress in selenoprotein production methodology.
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Affiliation(s)
- Yuchuan Wang
- Shenzhen Institute of Transfusion Medicine Shenzhen Blood Center, Shenzhen, Futian District, 518052, P. R. China.,Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 1068 Xueyuan Avenue, Shenzhen, Nanshan District, 518055, P. R. China
| | - Pengcheng Liu
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, Chaoyang District, 100101, P. R. China
| | - Jiao Chang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, Chaoyang District, 100101, P. R. China
| | - Yunping Xu
- Shenzhen Institute of Transfusion Medicine Shenzhen Blood Center, Shenzhen, Futian District, 518052, P. R. China
| | - Jiangyun Wang
- Shenzhen Institute of Transfusion Medicine Shenzhen Blood Center, Shenzhen, Futian District, 518052, P. R. China.,Institute of Biophysics, Chinese Academy of Sciences, Beijing, Chaoyang District, 100101, P. R. China.,Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 1068 Xueyuan Avenue, Shenzhen, Nanshan District, 518055, P. R. China
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18
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Welegedara AP, Maleckis A, Bandara R, Mahawaththa MC, Dilhani Herath I, Jiun Tan Y, Giannoulis A, Goldfarb D, Otting G, Huber T. Cell-Free Synthesis of Selenoproteins in High Yield and Purity for Selective Protein Tagging. Chembiochem 2021; 22:1480-1486. [PMID: 33319405 DOI: 10.1002/cbic.202000785] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 12/10/2020] [Indexed: 01/10/2023]
Abstract
The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. GdIII -GdIII distances measured by double electron-electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-GdIII were indistinguishable from GdIII -GdIII distances measured of MBP containing cysteine reacted with 4Br-MDPA tags.
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Affiliation(s)
- Adarshi P Welegedara
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia.,Department of Chemistry, University of Peradeniya, Peradeniya, 20400, Sri Lanka
| | - Ansis Maleckis
- Latvian Institute of Organic Synthesis, 1006, Riga, Latvia
| | - Ruchira Bandara
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Mithun C Mahawaththa
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Iresha Dilhani Herath
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Yi Jiun Tan
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Angeliki Giannoulis
- Department of Chemical and Biological Physics Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Daniella Goldfarb
- Department of Chemical and Biological Physics Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Gottfried Otting
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Thomas Huber
- Australian National University, Research School of Chemistry, Canberra, ACT 2601, Australia
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19
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Cui Z, Johnston WA, Alexandrov K. Cell-Free Approach for Non-canonical Amino Acids Incorporation Into Polypeptides. Front Bioeng Biotechnol 2020; 8:1031. [PMID: 33117774 PMCID: PMC7550873 DOI: 10.3389/fbioe.2020.01031] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 08/07/2020] [Indexed: 12/12/2022] Open
Abstract
Synthetic biology holds promise to revolutionize the life sciences and biomedicine via expansion of macromolecular diversity outside the natural chemical space. Use of non-canonical amino acids (ncAAs) via codon reassignment has found diverse applications in protein structure and interaction analysis, introduction of post-translational modifications, production of constrained peptides, antibody-drug conjugates, and novel enzymes. However, simultaneously encoding multiple ncAAs in vivo requires complex engineering and is sometimes restricted by the cell's poor uptake of ncAAs. In contrast the open nature of cell-free protein synthesis systems offers much greater freedom for manipulation and repurposing of the biosynthetic machinery by controlling the level and identity of translational components and reagents, and allows simultaneous incorporation of multiple ncAAs with non-canonical side chains and even backbones (N-methyl, D-, β-amino acids, α-hydroxy acids etc.). This review focuses on the two most used Escherichia coli-based cell-free protein synthesis systems; cell extract- and PURE-based systems. The former is a biological mixture with >500 proteins, while the latter consists of 38 individually purified biomolecules. We delineate compositions of these two systems and discuss their respective advantages and applications. Also, we dissect the translational components required for ncAA incorporation and compile lists of ncAAs that can be incorporated into polypeptides via different acylation approaches. We highlight the recent progress in using unnatural nucleobase pairs to increase the repertoire of orthogonal codons, as well as using tRNA-specific ribozymes for in situ acylation. We summarize advances in engineering of translational machinery such as tRNAs, aminoacyl-tRNA synthetases, elongation factors, and ribosomes to achieve efficient incorporation of structurally challenging ncAAs. We note that, many engineered components of biosynthetic machinery are developed for the use in vivo but are equally applicable to the in vitro systems. These are included in the review to provide a comprehensive overview for ncAA incorporation and offer new insights for the future development in cell-free systems. Finally, we highlight the exciting progress in the genomic engineering, resulting in E. coli strains free of amber and some redundant sense codons. These strains can be used for preparation of cell extracts offering multiple reassignment options.
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Affiliation(s)
- Zhenling Cui
- Synthetic Biology Laboratory, School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Wayne A Johnston
- Synthetic Biology Laboratory, School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Kirill Alexandrov
- Synthetic Biology Laboratory, School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
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20
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Abstract
The aminoacyl-tRNA synthetases are an essential and universally distributed family of enzymes that plays a critical role in protein synthesis, pairing tRNAs with their cognate amino acids for decoding mRNAs according to the genetic code. Synthetases help to ensure accurate translation of the genetic code by using both highly accurate cognate substrate recognition and stringent proofreading of noncognate products. While alterations in the quality control mechanisms of synthetases are generally detrimental to cellular viability, recent studies suggest that in some instances such changes facilitate adaption to stress conditions. Beyond their central role in translation, synthetases are also emerging as key players in an increasing number of other cellular processes, with far-reaching consequences in health and disease. The biochemical versatility of the synthetases has also proven pivotal in efforts to expand the genetic code, further emphasizing the wide-ranging roles of the aminoacyl-tRNA synthetase family in synthetic and natural biology.
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Affiliation(s)
- Miguel Angel Rubio Gomez
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Michael Ibba
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, USA
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21
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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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22
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Serrão VHB, Scortecci JF. Why Selenocysteine Is Unique? Front Mol Biosci 2020; 7:2. [PMID: 32039236 PMCID: PMC6987413 DOI: 10.3389/fmolb.2020.00002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 01/03/2020] [Indexed: 11/18/2022] Open
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23
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Abstract
Selenoproteins are the family of proteins that contain the amino acid selenocysteine. Many selenoproteins, including glutathione peroxidases and thioredoxin reductases, play a role in maintaining cellular redox homeostasis. There are a number of examples of homologues of selenoproteins that utilize cysteine residues, raising the question of why selenocysteines are utilized. One hypothesis is that incorporation of selenocysteine protects against irreversible overoxidation, typical of cysteine-containing homologues under high oxidative stress. Studies of selenocysteine function are hampered by challenges both in detection and in recombinant expression of selenoproteins. In fact, about half of the 25 known human selenoproteins remain uncharacterized. Historically, selenoproteins were first detected via labeling with radioactive 75Se or by use of inductively coupled plasma-mass spectrometry to monitor nonradioactive selenium. More recently, tandem mass-spectrometry techniques have been developed to detect selenocysteine-containing peptides. For example, the isotopic distribution of selenium has been used as a unique signature to identify selenium-containing peptides from unenriched proteome samples. Additionally, selenocysteine-containing proteins and peptides were selectively enriched using thiol-reactive electrophiles by exploiting the increased reactivity of selenols relative to thiols, especially under low pH conditions. Importantly, the reactivity-based enrichment of selenoproteins can differentiate between oxidized and reduced selenoproteins, providing insight into the activity state. These mass spectrometry-based selenoprotein detection approaches have enabled (1) production of selenoproteome expression atlases, (2) identification of aging-associated changes in selenoprotein expression, (3) characterization of selenocysteine reactivity across the selenoprotein family, and (4) interrogation of selenoprotein targets of small-molecule drugs. Further investigations of selenoprotein function would benefit from recombinant expression of selenoproteins. However, the endogenous mechanism of selenoprotein production makes recombinant expression challenging. Primarily, selenocysteine is biosynthesized on its own tRNA, is dependent on multiple enzymatic steps, and is highly sensitive to selenium concentrations. Furthermore, selenocysteine is encoded by the stop codon UGA, and suppression of that stop codon requires a selenocysteine insertion sequence element in the selenoprotein mRNA. In order to circumvent the low efficiency of the endogenous machinery, selenoproteins have been produced in vitro through native chemical ligation and expressed protein ligation. Attempts have also been made to engineer the endogenous machinery for increased efficiency, including recoding the selenocysteine codon, and engineering the tRNA and the selenocysteine insertion sequence element. Alternatively, genetic code expansion can be used to generate selenoproteins. This approach allows for selenoprotein production directly within its native cellular environment, while bypassing the endogenous selenocysteine incorporation machinery. Furthermore, by incorporating a caged selenocysteine by genetic code expansion, selenoprotein activity can be spatially and temporally controlled. Genetic code expansion has allowed for the expression and uncaging of human selenoproteins in E. coli and more recently in mammalian cells. Together, advances in selenoprotein detection and expression should enable a better understanding of selenoprotein function and provide insight into the necessity for selenocysteine production.
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Affiliation(s)
- Jennifer C. Peeler
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Eranthie Weerapana
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
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24
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Aminoacyl-tRNA Synthetases and tRNAs for an Expanded Genetic Code: What Makes them Orthogonal? Int J Mol Sci 2019; 20:ijms20081929. [PMID: 31010123 PMCID: PMC6515474 DOI: 10.3390/ijms20081929] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/16/2019] [Accepted: 04/17/2019] [Indexed: 12/16/2022] Open
Abstract
In the past two decades, tRNA molecules and their corresponding aminoacyl-tRNA synthetases (aaRS) have been extensively used in synthetic biology to genetically encode post-translationally modified and unnatural amino acids. In this review, we briefly examine one fundamental requirement for the successful application of tRNA/aaRS pairs for expanding the genetic code. This requirement is known as “orthogonality”—the ability of a tRNA and its corresponding aaRS to interact exclusively with each other and avoid cross-reactions with additional types of tRNAs and aaRSs in a given organism.
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25
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Sakamoto K, Hayashi A. Synthetic Tyrosine tRNA Molecules with Noncanonical Secondary Structures. Int J Mol Sci 2018; 20:ijms20010092. [PMID: 30587834 PMCID: PMC6337575 DOI: 10.3390/ijms20010092] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/19/2018] [Accepted: 12/22/2018] [Indexed: 12/17/2022] Open
Abstract
The L-shape form of tRNA is maintained by tertiary interactions occurring in the core. Base changes in this domain can cause structural defects and impair tRNA activity. Here, we report on a method to safely engineer structural variations in this domain utilizing the noncanonical scaffold of tRNAPyl. First, we constructed a naïve hybrid between archaeal tRNAPyl and tRNATyr, which consisted of the acceptor and T stems of tRNATyr and the other parts of tRNAPyl. This hybrid tRNA efficiently translated the UAG codon to 3-iodotyrosine in Escherichia coli cells, when paired with a variant of the archaeal tyrosyl-tRNA synthetase. The amber suppression efficiency was slightly lower than that of the “bench-mark” archaeal tRNATyr suppressor assuming the canonical structure. After a series of modifications to this hybrid tRNA, we obtained two artificial types of tRNATyr: ZtRNA had an augmented D (auD) helix in a noncanonical form and the D and T loops bound by the standard tertiary base pairs, and YtRNA had a canonical auD helix and non-standard interloop interactions. It was then suggested that the ZtRNA scaffold could also support the glycylation and glutaminylation of tRNA. The synthetic diversity of tRNA would help create new tRNA–aminoacyl-tRNA synthetase pairs for reprogramming the genetic code.
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Affiliation(s)
- Kensaku Sakamoto
- Laboratory for Nonnatural Amino Acid Technology, RIKEN Center for Biosystems Dynamics Research (BDR), 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
| | - Akiko Hayashi
- Laboratory for Nonnatural Amino Acid Technology, RIKEN Center for Biosystems Dynamics Research (BDR), 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
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26
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Abstract
One of the most remarkable, but typically unremarked, aspects of the translation apparatus is the pleiotropic pliability of tRNA. This humble cloverleaf/L-shaped molecule must implement the first genetic code, via base pairing and wobble interactions, but is also largely responsible for the specificity of the second genetic code, the pairings between amino acids, tRNA synthetases, and tRNAs. Despite the overarching similarities between tRNAs, they must nonetheless be specifically recognized by cognate tRNA synthetases and largely rejected by noncognate synthetases. Conversely, despite the differences between tRNAs that allow such discrimination, they must be uniformly accepted by the ribosome, in part via the machinations of the translation elongation factors, which work with a diverse coterie of tRNA-amino acid conjugates to balance binding and loading. While it is easy to ascribe both discrimination and acceptance to the individual proteins (synthetases and EF-Tu/eEF-1) that recognize tRNAs, there is a large body of evidence that suggests that the sequences, structures, and dynamics of tRNAs are instrumental in the choices these proteins make.
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Affiliation(s)
- Ross Thyer
- Department of Molecular Biosciences , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Andrew D Ellington
- Department of Molecular Biosciences , The University of Texas at Austin , Austin , Texas 78712 , United States
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27
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Versatility of Synthetic tRNAs in Genetic Code Expansion. Genes (Basel) 2018; 9:genes9110537. [PMID: 30405060 PMCID: PMC6267555 DOI: 10.3390/genes9110537] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 10/31/2018] [Accepted: 11/05/2018] [Indexed: 12/16/2022] Open
Abstract
Transfer RNA (tRNA) is a dynamic molecule used by all forms of life as a key component of the translation apparatus. Each tRNA is highly processed, structured, and modified, to accurately deliver amino acids to the ribosome for protein synthesis. The tRNA molecule is a critical component in synthetic biology methods for the synthesis of proteins designed to contain non-canonical amino acids (ncAAs). The multiple interactions and maturation requirements of a tRNA pose engineering challenges, but also offer tunable features. Major advances in the field of genetic code expansion have repeatedly demonstrated the central importance of suppressor tRNAs for efficient incorporation of ncAAs. Here we review the current status of two fundamentally different translation systems (TSs), selenocysteine (Sec)- and pyrrolysine (Pyl)-TSs. Idiosyncratic requirements of each of these TSs mandate how their tRNAs are adapted and dictate the techniques used to select or identify the best synthetic variants.
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28
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Fu X, Crnković A, Sevostyanova A, Söll D. Designing seryl-tRNA synthetase for improved serylation of selenocysteine tRNAs. FEBS Lett 2018; 592:3759-3768. [PMID: 30317559 PMCID: PMC6263840 DOI: 10.1002/1873-3468.13271] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 09/28/2018] [Accepted: 10/03/2018] [Indexed: 12/28/2022]
Abstract
Selenocysteine (Sec) lacks a cognate aminoacyl-tRNA synthetase. Instead, seryl-tRNA synthetase (SerRS) produces Ser-tRNASec , which is subsequently converted by selenocysteine synthase to Sec-tRNASec . Escherichia coli SerRS serylates tRNASec poorly; this may hinder efficient production of designer selenoproteins in vivo. Guided by structural modelling and selection for chloramphenicol acetyltransferase activity, we evolved three SerRS variants capable of improved Ser-tRNASec synthesis. They display 10-, 8-, and 4-fold increased kcat /KM values compared to wild-type SerRS using synthetic tRNASec species as substrates. The enzyme variants also facilitate in vivo read-through of a UAG codon in the position of the critical serine146 of chloramphenicol acetyltransferase. These results indicate that the naturally evolved SerRS is capable of further evolution for increased recognition of a specific tRNA isoacceptor.
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MESH Headings
- Base Sequence
- Codon, Terminator/genetics
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Escherichia coli Proteins/chemistry
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/metabolism
- Kinetics
- Models, Molecular
- Mutation
- Nucleic Acid Conformation
- Protein Domains
- RNA, Transfer, Amino Acid-Specific/chemistry
- RNA, Transfer, Amino Acid-Specific/genetics
- RNA, Transfer, Amino Acid-Specific/metabolism
- RNA, Transfer, Ser/chemistry
- RNA, Transfer, Ser/genetics
- RNA, Transfer, Ser/metabolism
- Selenoproteins/genetics
- Selenoproteins/metabolism
- Serine/genetics
- Serine/metabolism
- Serine-tRNA Ligase/chemistry
- Serine-tRNA Ligase/genetics
- Serine-tRNA Ligase/metabolism
- Substrate Specificity
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Affiliation(s)
- Xian Fu
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Ana Crnković
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Anastasia Sevostyanova
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Dieter Söll
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06511, USA
- Department of Chemistry, Yale University, New Haven, CT 06520, USA
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29
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Whitford CM, Dymek S, Kerkhoff D, März C, Schmidt O, Edich M, Droste J, Pucker B, Rückert C, Kalinowski J. Auxotrophy to Xeno-DNA: an exploration of combinatorial mechanisms for a high-fidelity biosafety system for synthetic biology applications. J Biol Eng 2018; 12:13. [PMID: 30123321 PMCID: PMC6090650 DOI: 10.1186/s13036-018-0105-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 06/25/2018] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Biosafety is a key aspect in the international Genetically Engineered Machine (iGEM) competition, which offers student teams an amazing opportunity to pursue their own research projects in the field of Synthetic Biology. iGEM projects often involve the creation of genetically engineered bacterial strains. To minimize the risks associated with bacterial release, a variety of biosafety systems were constructed, either to prevent survival of bacteria outside the lab or to hinder horizontal or vertical gene transfer. MAIN BODY Physical containment methods such as bioreactors or microencapsulation are considered the first safety level. Additionally, various systems involving auxotrophies for both natural and synthetic compounds have been utilized by iGEM teams in recent years. Combinatorial systems comprising multiple auxotrophies have been shown to reduced escape frequencies below the detection limit. Furthermore, a number of natural toxin-antitoxin systems can be deployed to kill cells under certain conditions. Additionally, parts of naturally occurring toxin-antitoxin systems can be used for the construction of 'kill switches' controlled by synthetic regulatory modules, allowing control of cell survival. Kill switches prevent cell survival but do not completely degrade nucleic acids. To avoid horizontal gene transfer, multiple mechanisms to cleave nucleic acids can be employed, resulting in 'self-destruction' of cells. Changes in light or temperature conditions are powerful regulators of gene expression and could serve as triggers for kill switches or self-destruction systems. Xenobiology-based containment uses applications of Xeno-DNA, recoded codons and non-canonical amino acids to nullify the genetic information of constructed cells for wild type organisms. A 'minimal genome' approach brings the opportunity to reduce the genome of a cell to only genes necessary for survival under lab conditions. Such cells are unlikely to survive in the natural environment and are thus considered safe hosts. If suitable for the desired application, a shift to cell-free systems based on Xeno-DNA may represent the ultimate biosafety system. CONCLUSION Here we describe different containment approaches in synthetic biology, ranging from auxotrophies to minimal genomes, which can be combined to significantly improve reliability. Since the iGEM competition greatly increases the number of people involved in synthetic biology, we will focus especially on biosafety systems developed and applied in the context of the iGEM competition.
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Affiliation(s)
| | - Saskia Dymek
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Denise Kerkhoff
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Camilla März
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Olga Schmidt
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Maximilian Edich
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Julian Droste
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
| | - Boas Pucker
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
- Present address: Evolution and Diversity, Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Christian Rückert
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
| | - Jörn Kalinowski
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
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30
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Liu J, Zheng F, Cheng R, Li S, Rozovsky S, Wang Q, Wang L. Site-Specific Incorporation of Selenocysteine Using an Expanded Genetic Code and Palladium-Mediated Chemical Deprotection. J Am Chem Soc 2018; 140:8807-8816. [PMID: 29984990 PMCID: PMC6082430 DOI: 10.1021/jacs.8b04603] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Selenoproteins containing the 21st amino acid selenocysteine (Sec) exist in all three kingdoms of life and play essential roles in human health and development. The distinct low p Ka, high reactivity, and redox property of Sec also afford unique routes to protein modification and engineering. However, natural Sec incorporation requires idiosyncratic translational machineries that are dedicated to Sec and species-dependent, which makes it challenging to recombinantly prepare selenoproteins with high Sec specificity. As a consequence, the function of half of human selenoproteins remains unclear, and Sec-based protein manipulation has been greatly hampered. Here we report a new general method enabling the site-specific incorporation of Sec into proteins in E. coli. An orthogonal tRNAPyl-ASecRS was evolved to specifically incorporate Se-allyl selenocysteine (ASec) in response to the amber codon, and the incorporated ASec was converted to Sec in high efficiency through palladium-mediated cleavage under mild conditions compatible with proteins and cells. This approach completely obviates the natural Sec-dedicated factors, thus allowing various selenoproteins, regardless of Sec position and species source, to be prepared with high Sec specificity and enzyme activity, as shown by the preparation of human thioredoxin and glutathione peroxidase 1. Sec-selective labeling in the presence of Cys was also demonstrated on the surface of live E. coli cells. The tRNAPyl-ASecRS pair was further used in mammalian cells to incorporate ASec, which was converted into Sec by palladium catalyst in cellulo. This robust and versatile method should greatly facilitate the study of diverse natural selenoproteins and the engineering of proteins in general via site-specific introduction of Sec.
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Affiliation(s)
- Jun Liu
- University of California, San Francisco, Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, San Francisco, CA, 94158
| | - Feng Zheng
- Hangzhou Research Institute of Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China, 310018
| | - Rujin Cheng
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE, 19716
| | - Shanshan Li
- University of California, San Francisco, Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, San Francisco, CA, 94158
- Department of Chemistry and Center for Therapeutics and Diagnostics, Georgia State University, Atlanta, Georgia 30302, United States
| | - Sharon Rozovsky
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE, 19716
| | - Qian Wang
- Hangzhou Research Institute of Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China, 310018
| | - Lei Wang
- University of California, San Francisco, Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, San Francisco, CA, 94158
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Mukai T, Sevostyanova A, Suzuki T, Fu X, Söll D. [A facile method for producing selenocysteine-containing proteins]. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 130:7333-7337. [PMID: 30002564 PMCID: PMC6039127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Ein einfacher Ansatz nutzt einen erweiterten genetischen Code von Escherichia coli zur Biosynthese von Selenoproteinen mit zahlreichen Sec-Resten. Kürzlich wurden so genannte allo-tRNAs entdeckt. Diese verfügen über eine ungewöhnliche Struktur, sind genauso effiziente Serinakzeptoren wie die normale tRNASer aus E. coli und werden von der Aeromonas-salmonicida-Selenocysteinsynthase (SelA) von Ser-allo-tRNA zu Sec-allo-tRNA umgesetzt. Anschließend ermöglicht es Sec-allo-tRNA, fünf UAG-Stop-Codons auf der fdhF-mRNA für E.-coli-Formatdehydrogenase H als Sec zu translatieren und katalytisch aktive E.-coli-Formatdehydrogenase mit fünf Sec-Resten in E. coli zu produzieren. Weiterhin konnte gezeigt werden, dass sich in E. coli durch Kombination genetischer Varianten von allo-tRNA und SelA mit einem modifizierten Selenstoffwechsel das humane Selenoenzym GPx1 mit über 80% Sec-Einbaurate rekombinant produzieren lässt. Beide Beispiele belegen den Wert von allo-tRNAUTu als molekulare Plattform zur Entwicklung neuartiger Selenoproteine.
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Affiliation(s)
- Takahito Mukai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 (USA)
| | - Anastasia Sevostyanova
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 (USA)
| | - Tateki Suzuki
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 (USA)
| | - Xian Fu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 (USA)
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 (USA)
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32
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Welegedara AP, Adams LA, Huber T, Graham B, Otting G. Site-Specific Incorporation of Selenocysteine by Genetic Encoding as a Photocaged Unnatural Amino Acid. Bioconjug Chem 2018; 29:2257-2264. [DOI: 10.1021/acs.bioconjchem.8b00254] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Adarshi P. Welegedara
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Luke A. Adams
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Thomas Huber
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Gottfried Otting
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
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Mukai T, Sevostyanova A, Suzuki T, Fu X, Söll D. Eine einfache Methode zur Produktion von Selenoproteinen. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201713215] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Takahito Mukai
- Department of Molecular Biophysics and Biochemistry Yale University New Haven CT 06520 USA
| | - Anastasia Sevostyanova
- Department of Molecular Biophysics and Biochemistry Yale University New Haven CT 06520 USA
| | - Tateki Suzuki
- Department of Molecular Biophysics and Biochemistry Yale University New Haven CT 06520 USA
| | - Xian Fu
- Department of Molecular Biophysics and Biochemistry Yale University New Haven CT 06520 USA
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry Yale University New Haven CT 06520 USA
- Department of Chemistry Yale University New Haven CT 06520 USA
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34
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Mukai T, Sevostyanova A, Suzuki T, Fu X, Söll D. A Facile Method for Producing Selenocysteine-Containing Proteins. Angew Chem Int Ed Engl 2018; 57:7215-7219. [PMID: 29631320 DOI: 10.1002/anie.201713215] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/20/2018] [Indexed: 01/14/2023]
Abstract
Selenocysteine (Sec, U) confers new chemical properties on proteins. Improved tools are thus required that enable Sec insertion into any desired position of a protein. We report a facile method for synthesizing selenoproteins with multiple Sec residues by expanding the genetic code of Escherichia coli. We recently discovered allo-tRNAs, tRNA species with unusual structure, that are as efficient serine acceptors as E. coli tRNASer . Ser-allo-tRNA was converted into Sec-allo-tRNA by Aeromonas salmonicida selenocysteine synthase (SelA). Sec-allo-tRNA variants were able to read through five UAG codons in the fdhF mRNA coding for E. coli formate dehydrogenase H, and produced active FDHH with five Sec residues in E. coli. Engineering of the E. coli selenium metabolism along with mutational changes in allo-tRNA and SelA improved the yield and purity of recombinant human glutathione peroxidase 1 (to over 80 %). Thus, our allo-tRNAUTu system offers a new selenoprotein engineering platform.
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Affiliation(s)
- Takahito Mukai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Anastasia Sevostyanova
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Tateki Suzuki
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Xian Fu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA.,Department of Chemistry, Yale University, New Haven, CT, 06520, USA
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Liu J, Cheng R, Rozovsky S. Synthesis and semisynthesis of selenopeptides and selenoproteins. Curr Opin Chem Biol 2018; 46:41-47. [PMID: 29723718 DOI: 10.1016/j.cbpa.2018.04.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/09/2018] [Accepted: 04/16/2018] [Indexed: 11/19/2022]
Abstract
The versatile chemistry of the genetically encoded amino acid selenocysteine (Sec) is employed in Nature to expand the reactivity of enzymes. In addition to, its role in biology, Sec is used in protein engineering to modify folding, stability, and reactivity of proteins, to introduce conjugations and to facilitate reactions. However, due to limitations related to Sec's insertion mechanism in Nature, much of the production of Sec containing peptides and proteins relies on synthesis and semisynthesis. Here, we review recent advances that have enabled the assembly of complicated selenoproteins, including novel uses of protecting groups for solid phase peptide synthesis, rapid selenoester driven chemical ligations and versatile expressed protein ligations.
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Affiliation(s)
- Jun Liu
- University of California, San Francisco, Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, San Francisco, CA 94158, United States.
| | - Rujin Cheng
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE 19716, United States
| | - Sharon Rozovsky
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE 19716, United States.
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36
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Fu X, Söll D, Sevostyanova A. Challenges of site-specific selenocysteine incorporation into proteins by Escherichia coli. RNA Biol 2018; 15:461-470. [PMID: 29447106 DOI: 10.1080/15476286.2018.1440876] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Selenocysteine (Sec), a rare genetically encoded amino acid with unusual chemical properties, is of great interest for protein engineering. Sec is synthesized on its cognate tRNA (tRNASec) by the concerted action of several enzymes. While all other aminoacyl-tRNAs are delivered to the ribosome by the elongation factor Tu (EF-Tu), Sec-tRNASec requires a dedicated factor, SelB. Incorporation of Sec into protein requires recoding of the stop codon UGA aided by a specific mRNA structure, the SECIS element. This unusual biogenesis restricts the use of Sec in recombinant proteins, limiting our ability to study the properties of selenoproteins. Several methods are currently available for the synthesis selenoproteins. Here we focus on strategies for in vivo Sec insertion at any position(s) within a recombinant protein in a SECIS-independent manner: (i) engineering of tRNASec for use by EF-Tu without the SECIS requirement, and (ii) design of a SECIS-independent SelB route.
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Affiliation(s)
- Xian Fu
- a Department of Molecular Biophysics and Biochemistry , Yale University , New Haven , CT , USA
| | - Dieter Söll
- a Department of Molecular Biophysics and Biochemistry , Yale University , New Haven , CT , USA.,b Department of Chemistry , Yale University , New Haven , CT , USA
| | - Anastasia Sevostyanova
- a Department of Molecular Biophysics and Biochemistry , Yale University , New Haven , CT , USA
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37
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Fan Z, Song J, Guan T, Lv X, Wei J. Efficient Expression of Glutathione Peroxidase with Chimeric tRNA in Amber-less Escherichia coli. ACS Synth Biol 2018; 7:249-257. [PMID: 28866886 DOI: 10.1021/acssynbio.7b00290] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The active center of selenium-containing glutathione peroxidase (GPx) is selenocysteine (Sec), which is is biosynthesized on its tRNA in organisms. The decoding of Sec depends on a specific elongation factor and a Sec Insertion Sequence (SECIS) to suppress the UGA codon. The expression of mammalian GPx is extremely difficult with traditional recombinant DNA technology. Recently, a chimeric tRNA (tRNAUTu) that is compatible with elongation factor Tu (EF-Tu) has made selenoprotein expression easier. In this study, human glutathione peroxidase (hGPx) was expressed in amber-less Escherichia coli C321.ΔA.exp using tRNAUTu and seven chimeric tRNAs that were constructed on the basis of tRNAUTu. We found that chimeric tRNAUTu2, which substitutes the acceptor stem and T-stem of tRNAUTu with those from tRNASec, enabled the expression of reactive hGPx with high yields. We also found that chimeric tRNAUTuT6, which has a single base change (A59C) compared to tRNAUTu, mediated the highest reactive expression of hGPx1. The hGPx1 expressed exists as a tetramer and reacts with positive cooperativity. The SDS-PAGE analysis of hGPx2 produced by tRNAUTuT6 with or without sodium selenite supplementation showed that the incorporation of Sec is nearly 90%. Our approach enables efficient selenoprotein expression in amber-less Escherichia coli and should enable further characterization of selenoproteins in vitro.
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Affiliation(s)
- Zhenlin Fan
- College of Pharmaceutical Science, Jilin University, Changchun 130021, PR China
| | - Jian Song
- College of Electronic Science and Engineering, Jilin University, Changchun 130000, PR China
| | - Tuchen Guan
- College of Pharmaceutical Science, Jilin University, Changchun 130021, PR China
| | - Xiuxiu Lv
- College of Pharmaceutical Science, Jilin University, Changchun 130021, PR China
| | - Jingyan Wei
- College of Pharmaceutical Science, Jilin University, Changchun 130021, PR China
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38
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Abstract
Expression of selenoproteins necessitates a process of decoding of a UGA codon from termination of translation to insertion of selenocysteine. The mechanisms of this process pose major challenges with regards to recombinant selenoprotein production in E. coli, which however can be overcome especially if the Sec residue is located close to the C-terminal end, as is the case for several naturally found selenoproteins. This chapter summarizes a method to achieve such a production.
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39
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Abstract
The genetic code-the language used by cells to translate their genomes into proteins that perform many cellular functions-is highly conserved throughout natural life. Rewriting the genetic code could lead to new biological functions such as expanding protein chemistries with noncanonical amino acids (ncAAs) and genetically isolating synthetic organisms from natural organisms and viruses. It has long been possible to transiently produce proteins bearing ncAAs, but stabilizing an expanded genetic code for sustained function in vivo requires an integrated approach: creating recoded genomes and introducing new translation machinery that function together without compromising viability or clashing with endogenous pathways. In this review, we discuss design considerations and technologies for expanding the genetic code. The knowledge obtained by rewriting the genetic code will deepen our understanding of how genomes are designed and how the canonical genetic code evolved.
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Affiliation(s)
- Takahito Mukai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511;
| | - Marc J Lajoie
- Department of Biochemistry, University of Washington, Seattle, Washington 98195
| | - Markus Englert
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511;
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511; .,Department of Chemistry, Yale University, New Haven, Connecticut 06511
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40
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Liu J, Chen Q, Rozovsky S. Utilizing Selenocysteine for Expressed Protein Ligation and Bioconjugations. J Am Chem Soc 2017; 139:3430-3437. [PMID: 28186733 PMCID: PMC5824972 DOI: 10.1021/jacs.6b10991] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Employing selenocysteine-containing protein fragments to form the amide bond between respective protein fragments significantly extends the current capabilities of the widely used protein engineering method, expressed protein ligation. Selenocysteine-mediated ligation is noteworthy for its high yield and efficiency. However, it has so far been restricted to solid-phase synthesized seleno-peptides and thus constrained by where the selenocysteine can be positioned. Here we employ heterologously expressed seleno-fragments to overcome the placement and size restrictions in selenocysteine-mediated chemical ligation. Following ligation, the selenocysteine can be deselenized into an alanine or serine, resulting in nonselenoproteins. This greatly extends the flexibility in selecting the conjugation site in expressed protein ligations with no influence on native cysteines. Furthermore, the selenocysteine can be used to selectively introduce site-specific protein modifications. Therefore, selenocysteine-mediated expressed protein ligation simplifies incorporation of post-translational modifications into the protein scaffold.
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Affiliation(s)
| | | | - Sharon Rozovsky
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE, 19716
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41
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Future of the Genetic Code. Life (Basel) 2017; 7:life7010010. [PMID: 28264473 PMCID: PMC5370410 DOI: 10.3390/life7010010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 02/20/2017] [Accepted: 02/23/2017] [Indexed: 11/17/2022] Open
Abstract
The methods for establishing synthetic lifeforms with rewritten genetic codes comprising non-canonical amino acids (NCAA) in addition to canonical amino acids (CAA) include proteome-wide replacement of CAA, insertion through suppression of nonsense codon, and insertion via the pyrrolysine and selenocysteine pathways. Proteome-wide reassignments of nonsense codons and sense codons are also under development. These methods enable the application of NCAAs to enrich both fundamental and applied aspects of protein chemistry and biology. Sense codon reassignment to NCAA could incur problems arising from the usage of anticodons as identity elements on tRNA, and possible misreading of NNY codons by UNN anticodons. Evidence suggests that the problem of anticodons as identity elements can be diminished or resolved through removal from the tRNA of all identity elements besides the anticodon, and the problem of misreading of NNY codons by UNN anticodon can be resolved by the retirement of both the UNN anticodon and its complementary NNA codon from the proteome in the event that a restrictive post-transcriptional modification of the UNN anticodon by host enzymes to prevent the misreading cannot be obtained.
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42
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Cheng Q, Arnér ESJ. Selenocysteine Insertion at a Predefined UAG Codon in a Release Factor 1 (RF1)-depleted Escherichia coli Host Strain Bypasses Species Barriers in Recombinant Selenoprotein Translation. J Biol Chem 2017; 292:5476-5487. [PMID: 28193838 DOI: 10.1074/jbc.m117.776310] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/02/2017] [Indexed: 11/06/2022] Open
Abstract
Selenoproteins contain the amino acid selenocysteine (Sec), co-translationally inserted at a predefined UGA opal codon by means of Sec-specific translation machineries. In Escherichia coli, this process is dependent upon binding of the Sec-dedicated elongation factor SelB to a Sec insertion sequence (SECIS) element in the selenoprotein-encoding mRNA and competes with UGA-directed translational termination. Here, we found that Sec can also be efficiently incorporated at a predefined UAG amber codon, thereby competing with RF1 rather than RF2. Subsequently, utilizing the RF1-depleted E. coli strain C321.ΔA, we could produce mammalian selenoprotein thioredoxin reductases with unsurpassed purity and yield. We also found that a SECIS element was no longer absolutely required in such a system. Human glutathione peroxidase 1 could thereby also be produced, and we could confirm a previously proposed catalytic tetrad in this selenoprotein. We believe that the versatility of this new UAG-directed production methodology should enable many further studies of diverse selenoproteins.
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Affiliation(s)
- Qing Cheng
- From the Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Elias S J Arnér
- From the Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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43
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Melo Czekster C, Robertson WE, Walker AS, Söll D, Schepartz A. In Vivo Biosynthesis of a β-Amino Acid-Containing Protein. J Am Chem Soc 2016; 138:5194-7. [PMID: 27086674 DOI: 10.1021/jacs.6b01023] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
It has recently been reported that ribosomes from erythromycin-resistant Escherichia coli strains, when isolated in S30 extracts and incubated with chemically mis-acylated tRNA, can incorporate certain β-amino acids into full length DHFR in vitro. Here we report that wild-type E. coli EF-Tu and phenylalanyl-tRNA synthetase collaborate with these mutant ribosomes and others to incorporate β(3)-Phe analogs into full length DHFR in vivo. E. coli harboring the most active mutant ribosomes are robust, with a doubling time only 14% longer than wild-type. These results reveal the unexpected tolerance of E. coli and its translation machinery to the β(3)-amino acid backbone and should embolden in vivo selections for orthogonal translational machinery components that incorporate diverse β-amino acids into proteins and peptides. E. coli harboring mutant ribosomes may possess the capacity to incorporate many non-natural, non-α-amino acids into proteins and other sequence-programmed polymeric materials.
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Affiliation(s)
- Clarissa Melo Czekster
- Department of Chemistry, ‡Department of Molecular, Cellular, and Developmental Biology, and §Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520-8107, United States
| | - Wesley E Robertson
- Department of Chemistry, ‡Department of Molecular, Cellular, and Developmental Biology, and §Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520-8107, United States
| | - Allison S Walker
- Department of Chemistry, ‡Department of Molecular, Cellular, and Developmental Biology, and §Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520-8107, United States
| | - Dieter Söll
- Department of Chemistry, ‡Department of Molecular, Cellular, and Developmental Biology, and §Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520-8107, United States
| | - Alanna Schepartz
- Department of Chemistry, ‡Department of Molecular, Cellular, and Developmental Biology, and §Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520-8107, United States
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44
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Di Giulio M. The lack of foundation in the mechanism on which are based the physico-chemical theories for the origin of the genetic code is counterposed to the credible and natural mechanism suggested by the coevolution theory. J Theor Biol 2016; 399:134-40. [PMID: 27067244 DOI: 10.1016/j.jtbi.2016.04.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/29/2016] [Accepted: 04/01/2016] [Indexed: 11/25/2022]
Abstract
I analyze the mechanism on which are based the majority of theories that put to the center of the origin of the genetic code the physico-chemical properties of amino acids. As this mechanism is based on excessive mutational steps, I conclude that it could not have been operative or if operative it would not have allowed a full realization of predictions of these theories, because this mechanism contained, evidently, a high indeterminacy. I make that disapproving the four-column theory of the origin of the genetic code (Higgs, 2009) and reply to the criticism that was directed towards the coevolution theory of the origin of the genetic code. In this context, I suggest a new hypothesis that clarifies the mechanism by which the domains of codons of the precursor amino acids would have evolved, as predicted by the coevolution theory. This mechanism would have used particular elongation factors that would have constrained the evolution of all amino acids belonging to a given biosynthetic family to the progenitor pre-tRNA, that for first recognized, the first codons that evolved in a certain codon domain of a determined precursor amino acid. This happened because the elongation factors recognized two characteristics of the progenitor pre-tRNAs of precursor amino acids, which prevented the elongation factors from recognizing the pre-tRNAs belonging to biosynthetic families of different precursor amino acids. Finally, I analyze by means of Fisher's exact test, the distribution, within the genetic code, of the biosynthetic classes of amino acids and the ones of polarity values of amino acids. This analysis would seem to support the biosynthetic classes of amino acids over the ones of polarity values, as the main factor that led to the structuring of the genetic code, with the physico-chemical properties of amino acids playing only a subsidiary role in this evolution. As a whole, the full analysis brings to the conclusion that the coevolution theory of the origin of the genetic code would be a theory highly corroborated.
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Affiliation(s)
- Massimo Di Giulio
- Early Evolution of Life Laboratory, Institute of Biosciences and Bioresources, CNR, Via P. Castellino, 111, 80131 Naples, Italy.
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45
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Lajoie MJ, Söll D, Church GM. Overcoming Challenges in Engineering the Genetic Code. J Mol Biol 2016; 428:1004-21. [PMID: 26348789 PMCID: PMC4779434 DOI: 10.1016/j.jmb.2015.09.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/19/2015] [Accepted: 09/01/2015] [Indexed: 11/24/2022]
Abstract
Withstanding 3.5 billion years of genetic drift, the canonical genetic code remains such a fundamental foundation for the complexity of life that it is highly conserved across all three phylogenetic domains. Genome engineering technologies are now making it possible to rationally change the genetic code, offering resistance to viruses, genetic isolation from horizontal gene transfer, and prevention of environmental escape by genetically modified organisms. We discuss the biochemical, genetic, and technological challenges that must be overcome in order to engineer the genetic code.
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Affiliation(s)
- M J Lajoie
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Program in Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
| | - D Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
| | - G M Church
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
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46
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Ling J, O'Donoghue P, Söll D. Genetic code flexibility in microorganisms: novel mechanisms and impact on physiology. Nat Rev Microbiol 2015; 13:707-721. [PMID: 26411296 DOI: 10.1038/nrmicro3568] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The genetic code, initially thought to be universal and immutable, is now known to contain many variations, including biased codon usage, codon reassignment, ambiguous decoding and recoding. As a result of recent advances in the areas of genome sequencing, biochemistry, bioinformatics and structural biology, our understanding of genetic code flexibility has advanced substantially in the past decade. In this Review, we highlight the prevalence, evolution and mechanistic basis of genetic code variations in microorganisms, and we discuss how this flexibility of the genetic code affects microbial physiology.
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Affiliation(s)
- Jiqiang Ling
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Patrick O'Donoghue
- Department of Biochemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada.,Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.,Department of Chemistry, Yale University, New Haven, Connecticut 06520-8114, USA
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