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Cain A, Krahn N. Overcoming Challenges with Biochemical Studies of Selenocysteine and Selenoproteins. Int J Mol Sci 2024; 25:10101. [PMID: 39337586 PMCID: PMC11431864 DOI: 10.3390/ijms251810101] [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: 08/13/2024] [Revised: 09/16/2024] [Accepted: 09/18/2024] [Indexed: 09/30/2024] Open
Abstract
Selenocysteine (Sec) is an essential amino acid that distinguishes itself from cysteine by a selenium atom in place of a sulfur atom. This single change imparts distinct chemical properties to Sec which are crucial for selenoprotein (Sec-containing protein) function. These properties include a lower pKa, enhanced nucleophilicity, and reversible oxidation. However, studying Sec incorporation in proteins is a complex process. While we find Sec in all domains of life, each domain has distinct translation mechanisms. These mechanisms are unique to canonical translation and are composed of Sec-specific enzymes and an mRNA hairpin to drive recoding of the UGA stop codon with Sec. In this review, we highlight the obstacles that arise when investigating Sec insertion, and the role that Sec has in proteins. We discuss the strategic methods implemented in this field to address these challenges. Though the Sec translation system is complex, a remarkable amount of information has been obtained and specialized tools have been developed. Continued studies in this area will provide a deeper understanding on the role of Sec in the context of proteins, and the necessity that we have for maintaining this complex translation machinery to make selenoproteins.
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Affiliation(s)
- Antavius Cain
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Natalie Krahn
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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2
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Schultz SK, Kothe U. RNA modifying enzymes shape tRNA biogenesis and function. J Biol Chem 2024; 300:107488. [PMID: 38908752 PMCID: PMC11301382 DOI: 10.1016/j.jbc.2024.107488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 06/11/2024] [Accepted: 06/12/2024] [Indexed: 06/24/2024] Open
Abstract
Transfer RNAs (tRNAs) are the most highly modified cellular RNAs, both with respect to the proportion of nucleotides that are modified within the tRNA sequence and with respect to the extraordinary diversity in tRNA modification chemistry. However, the functions of many different tRNA modifications are only beginning to emerge. tRNAs have two general clusters of modifications. The first cluster is within the anticodon stem-loop including several modifications essential for protein translation. The second cluster of modifications is within the tRNA elbow, and roles for these modifications are less clear. In general, tRNA elbow modifications are typically not essential for cell growth, but nonetheless several tRNA elbow modifications have been highly conserved throughout all domains of life. In addition to forming modifications, many tRNA modifying enzymes have been demonstrated or hypothesized to also play an important role in folding tRNA acting as tRNA chaperones. In this review, we summarize the known functions of tRNA modifying enzymes throughout the lifecycle of a tRNA molecule, from transcription to degradation. Thereby, we describe how tRNA modification and folding by tRNA modifying enzymes enhance tRNA maturation, tRNA aminoacylation, and tRNA function during protein synthesis, ultimately impacting cellular phenotypes and disease.
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Affiliation(s)
- Sarah K Schultz
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada; Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada.
| | - Ute Kothe
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada; Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada.
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3
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Liu Z, Wang J, Shi Y, Yee BA, Terrey M, Zhang Q, Lee JC, Lin KI, Wang AHJ, Ackerman S, Yeo G, Cui H, Yang XL. Seryl-tRNA synthetase promotes translational readthrough by mRNA binding and involvement of the selenocysteine incorporation machinery. Nucleic Acids Res 2023; 51:10768-10781. [PMID: 37739431 PMCID: PMC10602924 DOI: 10.1093/nar/gkad773] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 08/17/2023] [Accepted: 09/19/2023] [Indexed: 09/24/2023] Open
Abstract
Translational readthrough of UGA stop codons by selenocysteine-specific tRNA (tRNASec) enables the synthesis of selenoproteins. Seryl-tRNA synthetase (SerRS) charges tRNASec with serine, which is modified into selenocysteine and delivered to the ribosome by a designated elongation factor (eEFSec in eukaryotes). Here we found that components of the human selenocysteine incorporation machinery (SerRS, tRNASec, and eEFSec) also increased translational readthrough of non-selenocysteine genes, including VEGFA, to create C-terminally extended isoforms. SerRS recognizes target mRNAs through a stem-loop structure that resembles the variable loop of its cognate tRNAs. This function of SerRS depends on both its enzymatic activity and a vertebrate-specific domain. Through eCLIP-seq, we identified additional SerRS-interacting mRNAs as potential readthrough genes. Moreover, SerRS overexpression was sufficient to reverse premature termination caused by a pathogenic nonsense mutation. Our findings expand the repertoire of selenoprotein biosynthesis machinery and suggest an avenue for therapeutic targeting of nonsense mutations using endogenous factors.
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Affiliation(s)
- Ze Liu
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Justin Wang
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Yi Shi
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
- Department of Biochemistry, School of Medicine, Nankai University, Tianjin, China
| | - Brian A Yee
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Markus Terrey
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Qian Zhang
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jenq-Chang Lee
- Department of Surgery, National Cheng Kung University Medical College and Hospital, Taiwan
| | - Kuo-I Lin
- Genomics Research Center, Academia Sinica, Taiwan
| | - Andrew H-J Wang
- The Ph.D. Program for Translational Medicine, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei 110, Taiwan
| | - Susan L Ackerman
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA
- Department of Neurobiology, University of California San Diego, La Jolla, CA 92093, USA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Haissi Cui
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Xiang-Lei Yang
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
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4
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Serrão VHB, Fernandes ADF, Basso LGM, Scortecci JF, Crusca Júnior E, Cornélio ML, de Souza BM, Palma MS, de Oliveira Neto M, Thiemann OH. The Specific Elongation Factor to Selenocysteine Incorporation in Escherichia coli: Unique tRNA Sec Recognition and its Interactions. J Mol Biol 2021; 433:167279. [PMID: 34624294 DOI: 10.1016/j.jmb.2021.167279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 10/20/2022]
Abstract
Several molecular mechanisms are involved in the genetic code interpretation during translation, as codon degeneration for the incorporation of rare amino acids. One mechanism that stands out is selenocysteine (Sec), which requires a specific biosynthesis and incorporation pathway. In Bacteria, the Sec biosynthesis pathway has unique features compared with the eukaryote pathway as Ser to Sec conversion mechanism is accomplished by a homodecameric enzyme (selenocysteine synthase, SelA) followed by the action of an elongation factor (SelB) responsible for delivering the mature Sec-tRNASec into the ribosome by the interaction with the Selenocysteine Insertion Sequence (SECIS). Besides this mechanism being already described, the sequential events for Sec-tRNASec and SECIS specific recognition remain unclear. In this study, we determined the order of events of the interactions between the proteins and RNAs involved in Sec incorporation. Dissociation constants between SelB and the native as well as unacylated-tRNASec variants demonstrated that the acceptor stem and variable arm are essential for SelB recognition. Moreover, our data support the sequence of molecular events where GTP-activated SelB strongly interacts with SelA.tRNASec. Subsequently, SelB.GTP.tRNASec recognizes the mRNA SECIS to deliver the tRNASec to the ribosome. SelB in complex with its specific RNAs were examined using Hydrogen/Deuterium exchange mapping that allowed the determination of the molecular envelopes and its secondary structural variations during the complex assembly. Our results demonstrate the ordering of events in Sec incorporation and contribute to the full comprehension of the tRNASec role in the Sec amino acid biosynthesis, as well as extending the knowledge of synthetic biology and the expansion of the genetic code.
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Affiliation(s)
- Vitor Hugo Balasco Serrão
- Physics Institute of Sao Carlos, University of Sao Paulo, Trabalhador Sao Carlense Av., 400, São Carlos, SP CEP 13566-590, Brazil; Department of Chemistry and Biochemistry, University California - Santa Cruz, 1156 High St., Santa Cruz, CA 95060, United States
| | - Adriano de Freitas Fernandes
- Physics Institute of Sao Carlos, University of Sao Paulo, Trabalhador Sao Carlense Av., 400, São Carlos, SP CEP 13566-590, Brazil
| | - Luis Guilherme Mansor Basso
- Physical Sciences Laboratory, State University of Northern Rio de Janeiro Darcy Ribeiro - UENF, Av. Alberto Lamego, 2000, 28013-602 Campos dos Goytacazes, RJ, Brazil; Faculty of Science, Philosophy and Letters, University of Sao Paulo, CEP 14040-901 Ribeirão Preto, SP, Brazil
| | - Jéssica Fernandes Scortecci
- Physics Institute of Sao Carlos, University of Sao Paulo, Trabalhador Sao Carlense Av., 400, São Carlos, SP CEP 13566-590, Brazil; Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Science Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Edson Crusca Júnior
- Department of Physical Chemistry, Chemistry Institute of the São Paulo State University - UNESP, CEP 14800-900 Araraquara, SP, Brazil
| | - Marinônio Lopes Cornélio
- Physics Department, Institute of Biosciences, Letters and Exact Sciences (IBILCE), São Paulo State University - UNESP, São Jose do Rio Preto, SP, Brazil
| | - Bibiana Monson de Souza
- Department of General and Applied Biology, Institute of Biosciences of Rio Claro, São Paulo State University - UNESP, Rio Claro, SP, Brazil
| | - Mário Sérgio Palma
- Department of General and Applied Biology, Institute of Biosciences of Rio Claro, São Paulo State University - UNESP, Rio Claro, SP, Brazil
| | - Mario de Oliveira Neto
- Bioscience Institute of Universidade Estadual Paulista, Rubião Jr., Botucatu, SP CEP 18618-000, Brazil
| | - Otavio Henrique Thiemann
- Physics Institute of Sao Carlos, University of Sao Paulo, Trabalhador Sao Carlense Av., 400, São Carlos, SP CEP 13566-590, Brazil; Department of Genetics and Evolution, Federal University of São Carlos - UFSCar, 13565-905 São Carlos, SP, Brazil.
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5
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Shimizu A, Tobe R, Aono R, Inoue M, Hagita S, Kiriyama K, Toyotake Y, Ogawa T, Kurihara T, Goto K, Prakash NT, Mihara H. Initial Step of Selenite Reduction via Thioredoxin for Bacterial Selenoprotein Biosynthesis. Int J Mol Sci 2021; 22:ijms222010965. [PMID: 34681630 PMCID: PMC8538045 DOI: 10.3390/ijms222010965] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/05/2021] [Accepted: 10/08/2021] [Indexed: 12/11/2022] Open
Abstract
Many organisms reductively assimilate selenite to synthesize selenoprotein. Although the thioredoxin system, consisting of thioredoxin 1 (TrxA) and thioredoxin reductase with NADPH, can reduce selenite and is considered to facilitate selenite assimilation, the detailed mechanism remains obscure. Here, we show that selenite was reduced by the thioredoxin system from Pseudomonas stutzeri only in the presence of the TrxA (PsTrxA), and this system was specific to selenite among the oxyanions examined. Mutational analysis revealed that Cys33 and Cys36 residues in PsTrxA are important for selenite reduction. Free thiol-labeling assays suggested that Cys33 is more reactive than Cys36. Mass spectrometry analysis suggested that PsTrxA reduces selenite via PsTrxA-SeO intermediate formation. Furthermore, an in vivo formate dehydrogenase activity assay in Escherichia coli with a gene disruption suggested that TrxA is important for selenoprotein biosynthesis. The introduction of PsTrxA complemented the effects of TrxA disruption in E. coli cells, only when PsTrxA contained Cys33 and Cys36. Based on these results, we proposed the early steps of the link between selenite and selenoprotein biosynthesis via the formation of TrxA–selenium complexes.
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Affiliation(s)
- Atsuki Shimizu
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
| | - Ryuta Tobe
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
| | - Riku Aono
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
| | - Masao Inoue
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
- R-GIRO, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan
| | - Satoru Hagita
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
| | - Kaito Kiriyama
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
| | - Yosuke Toyotake
- Institute for Chemical Research, Kyoto University, Gokasho, Uji 611-0011, Kyoto, Japan; (Y.T.); (T.O.); (T.K.)
| | - Takuya Ogawa
- Institute for Chemical Research, Kyoto University, Gokasho, Uji 611-0011, Kyoto, Japan; (Y.T.); (T.O.); (T.K.)
| | - Tatsuo Kurihara
- Institute for Chemical Research, Kyoto University, Gokasho, Uji 611-0011, Kyoto, Japan; (Y.T.); (T.O.); (T.K.)
| | - Kei Goto
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan;
| | - N. Tejo Prakash
- School of Energy and Environment, Thapar Institute of Engineering and Technology, Patiala 147004, Punjab, India;
| | - Hisaaki Mihara
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; (A.S.); (R.T.); (R.A.); (M.I.); (S.H.); (K.K.)
- Correspondence: ; Tel.: +81-(0)77-561-2732
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6
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Mojr V, Roghanian M, Tamman H, Do Pham DD, Petrová M, Pohl R, Takada H, Van Nerom K, Ainelo H, Caballero-Montes J, Jimmy S, Garcia-Pino A, Hauryliuk V, Rejman D. Nonhydrolysable Analogues of (p)ppGpp and (p)ppApp Alarmone Nucleotides as Novel Molecular Tools. ACS Chem Biol 2021; 16:1680-1691. [PMID: 34477366 DOI: 10.1021/acschembio.1c00398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
While alarmone nucleotides guanosine-3',5'-bisdiphosphate (ppGpp) and guanosine-5'-triphosphate-3'-diphosphate (pppGpp) are archetypical bacterial second messengers, their adenosine analogues ppApp (adenosine-3',5'-bisdiphosphate) and pppApp (adenosine-5'-triphosphate-3'-diphosphate) are toxic effectors that abrogate bacterial growth. The alarmones are both synthesized and degraded by the members of the RelA-SpoT Homologue (RSH) enzyme family. Because of the chemical and enzymatic liability of (p)ppGpp and (p)ppApp, these alarmones are prone to degradation during structural biology experiments. To overcome this limitation, we have established an efficient and straightforward procedure for synthesizing nonhydrolysable (p)ppNuNpp analogues starting from 3'-azido-3'-deoxyribonucleotides as key intermediates. To demonstrate the utility of (p)ppGNpp as a molecular tool, we show that (i) as an HD substrate mimic, ppGNpp competes with ppGpp to inhibit the enzymatic activity of human MESH1 Small Alarmone Hyrolase, SAH; and (ii) mimicking the allosteric effects of (p)ppGpp, (p)ppGNpp acts as a positive regulator of the synthetase activity of long ribosome-associated RSHs Rel and RelA. Finally, by solving the structure of the N-terminal domain region (NTD) of T. thermophilus Rel complexed with pppGNpp, we show that as an HD substrate mimic, the analogue serves as a bona fide orthosteric regulator that promotes the same intra-NTD structural rearrangements as the native substrate.
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Affiliation(s)
- Viktor Mojr
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Mohammad Roghanian
- Laboratory for Molecular Infection Medicine Sweden (MIMS) and Umea° Centre for Microbial Research (UCMR), Umeå University, 901 87 Umeå, Sweden
- Department of Clinical Microbiology, Rigshospitalet, 2200 Copenhagen, Denmark
| | - Hedvig Tamman
- Cellular and Molecular Microbiology, Faculté des Sciences, Université libre de Bruxelles, Campus La Plaine, Building BC, (1C4 203), Boulevard du Triomphe, 1050, Brussels, Belgium
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Duy Dinh Do Pham
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Magdalena Petrová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Radek Pohl
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Hiraku Takada
- Laboratory for Molecular Infection Medicine Sweden (MIMS) and Umea° Centre for Microbial Research (UCMR), Umeå University, 901 87 Umeå, Sweden
- Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo, Motoyama, Kita-ku, Kyoto 603-8555, Japan
| | - Katleen Van Nerom
- Cellular and Molecular Microbiology, Faculté des Sciences, Université libre de Bruxelles, Campus La Plaine, Building BC, (1C4 203), Boulevard du Triomphe, 1050, Brussels, Belgium
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Hanna Ainelo
- Cellular and Molecular Microbiology, Faculté des Sciences, Université libre de Bruxelles, Campus La Plaine, Building BC, (1C4 203), Boulevard du Triomphe, 1050, Brussels, Belgium
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Julien Caballero-Montes
- Cellular and Molecular Microbiology, Faculté des Sciences, Université libre de Bruxelles, Campus La Plaine, Building BC, (1C4 203), Boulevard du Triomphe, 1050, Brussels, Belgium
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Steffi Jimmy
- Laboratory for Molecular Infection Medicine Sweden (MIMS) and Umea° Centre for Microbial Research (UCMR), Umeå University, 901 87 Umeå, Sweden
- Deutsches Elektronen-Synchrotron DESY, Centre for Structural Systems Biology (CSSB), Notkestr. 85, 22607 Hamburg, Germany
| | - Abel Garcia-Pino
- Cellular and Molecular Microbiology, Faculté des Sciences, Université libre de Bruxelles, Campus La Plaine, Building BC, (1C4 203), Boulevard du Triomphe, 1050, Brussels, Belgium
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Vasili Hauryliuk
- Laboratory for Molecular Infection Medicine Sweden (MIMS) and Umea° Centre for Microbial Research (UCMR), Umeå University, 901 87 Umeå, Sweden
- University of Tartu, Institute of Technology, 50411 Tartu, Estonia
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Dominik Rejman
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
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Paleskava A, Kaiumov MY, Kirillov SV, Konevega AL. Peculiarities in Activation of Hydrolytic Activity of Elongation Factors. BIOCHEMISTRY (MOSCOW) 2021; 85:1422-1433. [PMID: 33280582 DOI: 10.1134/s0006297920110103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Translational GTPases (trGTPases) belong to the family of G proteins and play key roles at all stages of protein biosynthesis on the ribosome. Unidirectional and cyclic functioning of G proteins is ensured by their ability to switch between the active and inactive states due to GTP hydrolysis accelerated by the auxiliary GTPase-activating proteins. Although trGTPases interact with the ribosomes in different conformational states, they bind to the same conserved region, which, unlike in classical GTPase-activating proteins, is represented by ribosomal RNA. The resulting catalytic sites have almost identical structure in all elongation factors suggesting a common mechanism of GTP hydrolysis. However, fine details of the activated state formation and significantly different rates of GTP hydrolysis indicate the existence of distinctive features upon GTP hydrolysis catalyzed by the different factors. Here, we present a contemporary view on the mechanism of GTPase activation and GTP hydrolysis by the elongation factors EF-Tu, EF-G, and SelB based on the analysis of structural, biochemical, and bioinformatics data.
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Affiliation(s)
- A Paleskava
- Petersburg Nuclear Physics Institute named by B.P. Konstantinov of NRC "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia
| | - M Yu Kaiumov
- Petersburg Nuclear Physics Institute named by B.P. Konstantinov of NRC "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia
| | - S V Kirillov
- Petersburg Nuclear Physics Institute named by B.P. Konstantinov of NRC "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia
| | - A L Konevega
- Petersburg Nuclear Physics Institute named by B.P. Konstantinov of NRC "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia.
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8
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Mukai T. Bioinformatic Prediction of an tRNA Sec Gene Nested inside an Elongation Factor SelB Gene in Alphaproteobacteria. Int J Mol Sci 2021; 22:4605. [PMID: 33925673 PMCID: PMC8124441 DOI: 10.3390/ijms22094605] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 04/16/2021] [Accepted: 04/25/2021] [Indexed: 12/02/2022] Open
Abstract
In bacteria, selenocysteine (Sec) is incorporated into proteins via the recoding of a particular codon, the UGA stop codon in most cases. Sec-tRNASec is delivered to the ribosome by the Sec-dedicated elongation factor SelB that also recognizes a Sec-insertion sequence element following the codon on the mRNA. Since the excess of SelB may lead to sequestration of Sec-tRNASec under selenium deficiency or oxidative stress, the expression levels of SelB and tRNASec should be regulated. In this bioinformatic study, I analyzed the Rhizobiales SelB species because they were annotated to have a non-canonical C-terminal extension. I found that the open reading frame (ORF) of diverse Alphaproteobacteria selB genes includes an entire tRNASec sequence (selC) and overlaps with the start codon of the downstream ORF. A remnant tRNASec sequence was found in the Sinorhizobium melilotiselB genes whose products have a shorter C-terminal extension. Similar overlapping traits were found in Gammaproteobacteria and Nitrospirae. I hypothesized that once the tRNASec moiety is folded and processed, the expression of the full-length SelB may be repressed. This is the first report on a nested tRNA gene inside a protein ORF in bacteria.
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Affiliation(s)
- Takahito Mukai
- Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan
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9
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Rodnina MV, Korniy N, Klimova M, Karki P, Peng BZ, Senyushkina T, Belardinelli R, Maracci C, Wohlgemuth I, Samatova E, Peske F. Translational recoding: canonical translation mechanisms reinterpreted. Nucleic Acids Res 2020; 48:1056-1067. [PMID: 31511883 PMCID: PMC7026636 DOI: 10.1093/nar/gkz783] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 08/21/2019] [Accepted: 08/30/2019] [Indexed: 01/15/2023] Open
Abstract
During canonical translation, the ribosome moves along an mRNA from the start to the stop codon in exact steps of one codon at a time. The collinearity of the mRNA and the protein sequence is essential for the quality of the cellular proteome. Spontaneous errors in decoding or translocation are rare and result in a deficient protein. However, dedicated recoding signals in the mRNA can reprogram the ribosome to read the message in alternative ways. This review summarizes the recent advances in understanding the mechanisms of three types of recoding events: stop-codon readthrough, –1 ribosome frameshifting and translational bypassing. Recoding events provide insights into alternative modes of ribosome dynamics that are potentially applicable to other non-canonical modes of prokaryotic and eukaryotic translation.
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Affiliation(s)
- Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Natalia Korniy
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Mariia Klimova
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Prajwal Karki
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Bee-Zen Peng
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Tamara Senyushkina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Riccardo Belardinelli
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Cristina Maracci
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Ingo Wohlgemuth
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Ekaterina Samatova
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Frank Peske
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
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10
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Rother M, Quitzke V. Selenoprotein synthesis and regulation in Archaea. Biochim Biophys Acta Gen Subj 2018; 1862:2451-2462. [DOI: 10.1016/j.bbagen.2018.04.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 01/23/2023]
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11
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On elongation factor eEFSec, its role and mechanism during selenium incorporation into nascent selenoproteins. Biochim Biophys Acta Gen Subj 2018; 1862:2463-2472. [PMID: 29555379 DOI: 10.1016/j.bbagen.2018.03.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 02/28/2018] [Accepted: 03/12/2018] [Indexed: 02/02/2023]
Abstract
BACKGROUND Selenium, an essential dietary micronutrient, is incorporated into proteins as the amino acid selenocysteine (Sec) in response to in-frame UGA codons. Complex machinery ensures accurate recoding of Sec codons in higher organisms. A specialized elongation factor eEFSec is central to the process. SCOPE OF REVIEW Selenoprotein synthesis relies on selenocysteinyl-tRNASec (Sec-tRNASec), selenocysteine inserting sequence (SECIS) and other selenoprotein mRNA elements, an in-trans SECIS binding protein 2 (SBP2) protein factor, and eEFSec. The exact mechanisms of discrete steps of the Sec UGA recoding are not well understood. However, recent studies on mammalian model systems have revealed the first insights into these mechanisms. Herein, we summarize the current knowledge about the structure and role of mammalian eEFSec. MAJOR CONCLUSIONS eEFSec folds into a chalice-like structure resembling that of the archaeal and bacterial orthologues SelB and the initiation protein factor IF2/eIF5B. The three N-terminal domains harbor major functional sites and adopt an EF-Tu-like fold. The C-terminal domain 4 binds to Sec-tRNASec and SBP2, senses distinct binding domains, and modulates the GTPase activity. Remarkably, GTP hydrolysis does not induce a canonical conformational change in eEFSec, but instead promotes a slight ratchet of domains 1 and 2 and a lever-like movement of domain 4, which may be critical for the release of Sec-tRNASec on the ribosome. GENERAL SIGNIFICANCE Based on current findings, a non-canonical mechanism for elongation of selenoprotein synthesis at the Sec UGA codon is proposed. Although incomplete, our understanding of this fundamental biological process is significantly improved, and it is being harnessed for biomedical and synthetic biology initiatives. This article is part of a Special Issue entitled "Selenium research" in celebration of 200 years of selenium discovery, edited by Dr. Elias Arnér and Dr. Regina Brigelius-Flohe.
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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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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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14
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Rodnina MV, Fischer N, Maracci C, Stark H. Ribosome dynamics during decoding. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0182. [PMID: 28138068 PMCID: PMC5311926 DOI: 10.1098/rstb.2016.0182] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 11/24/2022] Open
Abstract
Elongation factors Tu (EF-Tu) and SelB are translational GTPases that deliver aminoacyl-tRNAs (aa-tRNAs) to the ribosome. In each canonical round of translation elongation, aa-tRNAs, assisted by EF-Tu, decode mRNA codons and insert the respective amino acid into the growing peptide chain. Stop codons usually lead to translation termination; however, in special cases UGA codons are recoded to selenocysteine (Sec) with the help of SelB. Recruitment of EF-Tu and SelB together with their respective aa-tRNAs to the ribosome is a multistep process. In this review, we summarize recent progress in understanding the role of ribosome dynamics in aa-tRNA selection. We describe the path to correct codon recognition by canonical elongator aa-tRNA and Sec-tRNASec and discuss the local and global rearrangements of the ribosome in response to correct and incorrect aa-tRNAs. We present the mechanisms of GTPase activation and GTP hydrolysis of EF-Tu and SelB and summarize what is known about the accommodation of aa-tRNA on the ribosome after its release from the elongation factor. We show how ribosome dynamics ensures high selectivity for the cognate aa-tRNA and suggest that conformational fluctuations, induced fit and kinetic discrimination play major roles in maintaining the speed and fidelity of translation. This article is part of the themed issue ‘Perspectives on the ribosome’.
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Affiliation(s)
- Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Niels Fischer
- Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Cristina Maracci
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Holger Stark
- Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
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15
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Fischer N, Neumann P, Bock LV, Maracci C, Wang Z, Paleskava A, Konevega AL, Schröder GF, Grubmüller H, Ficner R, Rodnina MV, Stark H. The pathway to GTPase activation of elongation factor SelB on the ribosome. Nature 2016; 540:80-85. [PMID: 27842381 DOI: 10.1038/nature20560] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 10/24/2016] [Indexed: 01/29/2023]
Abstract
In all domains of life, selenocysteine (Sec) is delivered to the ribosome by selenocysteine-specific tRNA (tRNASec) with the help of a specialized translation factor, SelB in bacteria. Sec-tRNASec recodes a UGA stop codon next to a downstream mRNA stem-loop. Here we present the structures of six intermediates on the pathway of UGA recoding in Escherichia coli by single-particle cryo-electron microscopy. The structures explain the specificity of Sec-tRNASec binding by SelB and show large-scale rearrangements of Sec-tRNASec. Upon initial binding of SelB-Sec-tRNASec to the ribosome and codon reading, the 30S subunit adopts an open conformation with Sec-tRNASec covering the sarcin-ricin loop (SRL) on the 50S subunit. Subsequent codon recognition results in a local closure of the decoding site, which moves Sec-tRNASec away from the SRL and triggers a global closure of the 30S subunit shoulder domain. As a consequence, SelB docks on the SRL, activating the GTPase of SelB. These results reveal how codon recognition triggers GTPase activation in translational GTPases.
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Affiliation(s)
- Niels Fischer
- Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Piotr Neumann
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, GZMB, Georg-August University Göttingen, Justus-von Liebig Weg 11, 37077 Göttingen, Germany
| | - Lars V Bock
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Cristina Maracci
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Zhe Wang
- Institute of Complex Systems (ICS-6), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Alena Paleskava
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Andrey L Konevega
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Gunnar F Schröder
- Institute of Complex Systems (ICS-6), Forschungszentrum Jülich, 52425 Jülich, Germany.,Physics Department, Heinrich-Heine Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Helmut Grubmüller
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, GZMB, Georg-August University Göttingen, Justus-von Liebig Weg 11, 37077 Göttingen, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Holger Stark
- Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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16
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Crystal structures of the human elongation factor eEFSec suggest a non-canonical mechanism for selenocysteine incorporation. Nat Commun 2016; 7:12941. [PMID: 27708257 PMCID: PMC5059743 DOI: 10.1038/ncomms12941] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 08/17/2016] [Indexed: 01/07/2023] Open
Abstract
Selenocysteine is the only proteinogenic amino acid encoded by a recoded in-frame UGA codon that does not operate as the canonical opal stop codon. A specialized translation elongation factor, eEFSec in eukaryotes and SelB in prokaryotes, promotes selenocysteine incorporation into selenoproteins by a still poorly understood mechanism. Our structural and biochemical results reveal that four domains of human eEFSec fold into a chalice-like structure that has similar binding affinities for GDP, GTP and other guanine nucleotides. Surprisingly, unlike in eEF1A and EF-Tu, the guanine nucleotide exchange does not cause a major conformational change in domain 1 of eEFSec, but instead induces a swing of domain 4. We propose that eEFSec employs a non-canonical mechanism involving the distinct C-terminal domain 4 for the release of the selenocysteinyl-tRNA during decoding on the ribosome.
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17
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Protein Elongation, Co-translational Folding and Targeting. J Mol Biol 2016; 428:2165-85. [DOI: 10.1016/j.jmb.2016.03.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Revised: 03/21/2016] [Accepted: 03/22/2016] [Indexed: 11/18/2022]
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18
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Itoh Y, Sekine SI, Yokoyama S. Crystal structure of the full-length bacterial selenocysteine-specific elongation factor SelB. Nucleic Acids Res 2015; 43:9028-38. [PMID: 26304550 PMCID: PMC4605307 DOI: 10.1093/nar/gkv833] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 08/05/2015] [Indexed: 01/23/2023] Open
Abstract
Selenocysteine (Sec), the 21st amino acid in translation, uses its specific tRNA (tRNASec) to recognize the UGA codon. The Sec-specific elongation factor SelB brings the selenocysteinyl-tRNASec (Sec-tRNASec) to the ribosome, dependent on both an in-frame UGA and a Sec-insertion sequence (SECIS) in the mRNA. The bacterial SelB binds mRNA through its C-terminal region, for which crystal structures have been reported. In this study, we determined the crystal structure of the full-length SelB from the bacterium Aquifex aeolicus, in complex with a GTP analog, at 3.2-Å resolution. SelB consists of three EF-Tu-like domains (D1–3), followed by four winged-helix domains (WHD1–4). The spacer region, connecting the N- and C-terminal halves, fixes the position of WHD1 relative to D3. The binding site for the Sec moiety of Sec-tRNASec is located on the interface between D1 and D2, where a cysteine molecule from the crystallization solution is coordinated by Arg residues, which may mimic Sec binding. The Sec-binding site is smaller and more exposed than the corresponding site of EF-Tu. Complex models of Sec-tRNASec, SECIS RNA, and the 70S ribosome suggest that the unique secondary structure of tRNASec allows SelB to specifically recognize tRNASec and characteristically place it at the ribosomal A-site.
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Affiliation(s)
- Yuzuru Itoh
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shun-Ichi Sekine
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan
| | - Shigeyuki Yokoyama
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan RIKEN Structural Biology Laboratory, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan
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19
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Kotini SB, Peske F, Rodnina MV. Partitioning between recoding and termination at a stop codon-selenocysteine insertion sequence. Nucleic Acids Res 2015; 43:6426-38. [PMID: 26040702 PMCID: PMC4513850 DOI: 10.1093/nar/gkv558] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 05/14/2015] [Accepted: 05/17/2015] [Indexed: 11/13/2022] Open
Abstract
Selenocysteine (Sec) is inserted into proteins by recoding a UGA stop codon followed by a selenocysteine insertion sequence (SECIS). UGA recoding by the Sec machinery is believed to be very inefficient owing to RF2-mediated termination at UGA. Here we show that recoding efficiency in vivo is 30-40% independently of the cell growth rate. Efficient recoding requires sufficient selenium concentrations in the medium. RF2 is an unexpectedly poor competitor of Sec. We recapitulate the major characteristics of SECIS-dependent UGA recoding in vitro using a fragment of fdhF-mRNA encoding a natural bacterial selenoprotein. Only 40% of actively translating ribosomes that reach the UGA codon insert Sec, even in the absence of RF2, suggesting that the capacity to insert Sec into proteins is inherently limited. RF2 does not compete with the Sec incorporation machinery; rather, it terminates translation on those ribosomes that failed to incorporate Sec. The data suggest a model in which early recruitment of Sec-tRNA(Sec)-SelB-GTP to the SECIS blocks the access of RF2 to the stop codon, thereby prioritizing recoding over termination at Sec-dedicated stop codons.
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Affiliation(s)
- Suresh Babu Kotini
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Goettingen, Germany
| | - Frank Peske
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Goettingen, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Goettingen, Germany
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20
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Gonzalez-Flores JN, Shetty SP, Dubey A, Copeland PR. The molecular biology of selenocysteine. Biomol Concepts 2015; 4:349-65. [PMID: 25436585 DOI: 10.1515/bmc-2013-0007] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 03/22/2013] [Indexed: 01/11/2023] Open
Abstract
Selenium is an essential trace element that is incorporated into 25 human proteins as the amino acid selenocysteine (Sec). The incorporation of this amino acid turns out to be a fascinating problem in molecular biology because Sec is encoded by a stop codon, UGA. Layered on top of the canonical translation elongation machinery is a set of factors that exist solely to incorporate this important amino acid. The mechanism by which this process occurs, put into the context of selenoprotein biology, is the focus of this review.
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21
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Miller C, Bröcker MJ, Prat L, Ip K, Chirathivat N, Feiock A, Veszprémi M, Söll D. A synthetic tRNA for EF-Tu mediated selenocysteine incorporation in vivo and in vitro. FEBS Lett 2015; 589:2194-9. [PMID: 26160755 DOI: 10.1016/j.febslet.2015.06.039] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 06/24/2015] [Accepted: 06/24/2015] [Indexed: 10/23/2022]
Abstract
Incorporation of selenocysteine (Sec) in bacteria requires a UGA codon that is reassigned to Sec by the Sec-specific elongation factor SelB and a conserved mRNA motif (SECIS element). These requirements severely restrict the engineering of selenoproteins. Earlier, a synthetic tRNASec was reported that allowed canonical Sec incorporation by EF-Tu; however, serine misincorporation limited its scope. We report a superior tRNASec variant (tRNAUTuX) that facilitates EF-Tu dependent stoichiometric Sec insertion in response to UAG both in vivo in Escherichia coli and in vitro in a cellfree protein synthesis system. We also demonstrate recoding of several sense codons in a SelB supplemented cell-free system. These advances in Sec incorporation will aid rational design and directed evolution of selenoproteins.
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Affiliation(s)
- Corwin Miller
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
| | - Markus J Bröcker
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Laure Prat
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Kevan Ip
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Napon Chirathivat
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Alexander Feiock
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Miklós Veszprémi
- 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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22
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García-Márquez A, Gijsbers A, de la Mora E, Sánchez-Puig N. Defective Guanine Nucleotide Exchange in the Elongation Factor-like 1 (EFL1) GTPase by Mutations in the Shwachman-Diamond Syndrome Protein. J Biol Chem 2015; 290:17669-17678. [PMID: 25991726 DOI: 10.1074/jbc.m114.626275] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Indexed: 11/06/2022] Open
Abstract
Ribosome biogenesis is orchestrated by the action of several accessory factors that provide time and directionality to the process. One such accessory factor is the GTPase EFL1 involved in the cytoplasmic maturation of the ribosomal 60S subunit. EFL1 and SBDS, the protein mutated in the Shwachman-Diamond syndrome (SBDS), release the anti-association factor eIF6 from the surface of the ribosomal subunit 60S. Here we report a kinetic analysis of fluorescent guanine nucleotides binding to EFL1 alone and in the presence of SBDS using fluorescence stopped-flow spectroscopy. Binding kinetics of EFL1 to both GDP and GTP suggests a two-step mechanism with an initial binding event followed by a conformational change of the complex. Furthermore, the same behavior was observed in the presence of the SBDS protein irrespective of the guanine nucleotide evaluated. The affinity of EFL1 for GTP is 10-fold lower than that calculated for GDP. Association of EFL1 to SBDS did not modify the affinity for GTP but dramatically decreased that for GDP by increasing the dissociation rate of the nucleotide. Thus, SBDS acts as a guanine nucleotide exchange factor (GEF) for EFL1 promoting its activation by the release of GDP. Finally, fluorescence anisotropy measurements showed that the S143L mutation present in the Shwachman-Diamond syndrome altered a surface epitope for EFL1 and largely decreased the affinity for it. These results suggest that loss of interaction between these proteins due to mutations in the disease consequently prevents the nucleotide exchange regulation the SBDS exerts on EFL1.
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Affiliation(s)
- Adrián García-Márquez
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México
| | - Abril Gijsbers
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México
| | - Eugenio de la Mora
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México
| | - Nuria Sánchez-Puig
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México.
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23
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Thyer R, Robotham SA, Brodbelt JS, Ellington AD. Evolving tRNA(Sec) for efficient canonical incorporation of selenocysteine. J Am Chem Soc 2014; 137:46-9. [PMID: 25521771 DOI: 10.1021/ja510695g] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bacterial selenocysteine incorporation occurs in response to opal stop codons and is dependent on the presence of a selenocysteine insertion sequence (SECIS) element, which recruits the selenocysteine specific elongation factor and tRNA(Sec) needed to reassign the UGA codon. The SECIS element is a stem-loop RNA structure immediately following the UGA codon and forms part of the coding sequence in bacterial selenoproteins. Although the site specific incorporation of selenocysteine is of great interest for protein engineering, the sequence constraints imposed by the adjoining SECIS element severely limit its use. We have evolved an E. coli tRNA(Sec) that is compatible with the canonical translation machinery and can suppress amber stop codons to incorporate selenocysteine with high efficiency. This evolved tRNA(Sec) allows the production of new recombinant selenoproteins containing structural motifs such as selenyl-sulfhydryl and diselenide bonds.
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Affiliation(s)
- Ross Thyer
- Institute for Cellular and Molecular Biology, University of Texas at Austin , Austin, Texas 78712, United States
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24
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Harris RC, Boschitsch AH, Fenley MO. Sensitivities to parameterization in the size-modified Poisson-Boltzmann equation. J Chem Phys 2014; 140:075102. [PMID: 24559370 DOI: 10.1063/1.4864460] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Experimental results have demonstrated that the numbers of counterions surrounding nucleic acids differ from those predicted by the nonlinear Poisson-Boltzmann equation, NLPBE. Some studies have fit these data against the ion size in the size-modified Poisson-Boltzmann equation, SMPBE, but the present study demonstrates that other parameters, such as the Stern layer thickness and the molecular surface definition, can change the number of bound ions by amounts comparable to varying the ion size. These parameters will therefore have to be fit simultaneously against experimental data. In addition, the data presented here demonstrate that the derivative, SK, of the electrostatic binding free energy, ΔGel, with respect to the logarithm of the salt concentration is sensitive to these parameters, and experimental measurements of SK could be used to parameterize the model. However, although better values for the Stern layer thickness and ion size and better molecular surface definitions could improve the model's predictions of the numbers of ions around biomolecules and SK, ΔGel itself is more sensitive to parameters, such as the interior dielectric constant, which in turn do not significantly affect the distributions of ions around biomolecules. Therefore, improved estimates of the ion size and Stern layer thickness to use in the SMPBE will not necessarily improve the model's predictions of ΔGel.
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Affiliation(s)
- Robert C Harris
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-3408, USA
| | | | - Marcia O Fenley
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-3408, USA
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Kuhle B, Ficner R. A monovalent cation acts as structural and catalytic cofactor in translational GTPases. EMBO J 2014; 33:2547-63. [PMID: 25225612 DOI: 10.15252/embj.201488517] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Translational GTPases are universally conserved GTP hydrolyzing enzymes, critical for fidelity and speed of ribosomal protein biosynthesis. Despite their central roles, the mechanisms of GTP-dependent conformational switching and GTP hydrolysis that govern the function of trGTPases remain poorly understood. Here, we provide biochemical and high-resolution structural evidence that eIF5B and aEF1A/EF-Tu bound to GTP or GTPγS coordinate a monovalent cation (M(+)) in their active site. Our data reveal that M(+) ions form constitutive components of the catalytic machinery in trGTPases acting as structural cofactor to stabilize the GTP-bound "on" state. Additionally, the M(+) ion provides a positive charge into the active site analogous to the arginine-finger in the Ras-RasGAP system indicating a similar role as catalytic element that stabilizes the transition state of the hydrolysis reaction. In sequence and structure, the coordination shell for the M(+) ion is, with exception of eIF2γ, highly conserved among trGTPases from bacteria to human. We therefore propose a universal mechanism of M(+)-dependent conformational switching and GTP hydrolysis among trGTPases with important consequences for the interpretation of available biochemical and structural data.
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Affiliation(s)
- Bernhard Kuhle
- Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik Göttinger Zentrum für Molekulare Biowissenschaften Georg-August-Universität Göttingen, Göttingen, Germany
| | - Ralf Ficner
- Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik Göttinger Zentrum für Molekulare Biowissenschaften Georg-August-Universität Göttingen, Göttingen, Germany
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Haruna KI, Alkazemi MH, Liu Y, Söll D, Englert M. Engineering the elongation factor Tu for efficient selenoprotein synthesis. Nucleic Acids Res 2014; 42:9976-83. [PMID: 25064855 PMCID: PMC4150793 DOI: 10.1093/nar/gku691] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Selenocysteine (Sec) is naturally co-translationally incorporated into proteins by recoding the UGA opal codon with a specialized elongation factor (SelB in bacteria) and an RNA structural signal (SECIS element). We have recently developed a SECIS-free selenoprotein synthesis system that site-specifically—using the UAG amber codon—inserts Sec depending on the elongation factor Tu (EF-Tu). Here, we describe the engineering of EF-Tu for improved selenoprotein synthesis. A Sec-specific selection system was established by expression of human protein O6-alkylguanine-DNA alkyltransferase (hAGT), in which the active site cysteine codon has been replaced by the UAG amber codon. The formed hAGT selenoprotein repairs the DNA damage caused by the methylating agent N-methyl-N′-nitro-N-nitrosoguanidine, and thereby enables Escherichia coli to grow in the presence of this mutagen. An EF-Tu library was created in which codons specifying the amino acid binding pocket were randomized. Selection was carried out for enhanced Sec incorporation into hAGT; the resulting EF-Tu variants contained highly conserved amino acid changes within members of the library. The improved UTu-system with EF-Sel1 raises the efficiency of UAG-specific Sec incorporation to >90%, and also doubles the yield of selenoprotein production.
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Affiliation(s)
- Ken-ichi Haruna
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Muhammad H Alkazemi
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Yuchen Liu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA Department of Chemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Markus Englert
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
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Peacock JR, Walvoord RR, Chang AY, Kozlowski MC, Gamper H, Hou YM. Amino acid-dependent stability of the acyl linkage in aminoacyl-tRNA. RNA (NEW YORK, N.Y.) 2014; 20:758-64. [PMID: 24751649 PMCID: PMC4024630 DOI: 10.1261/rna.044123.113] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Aminoacyl-tRNAs are the biologically active substrates for peptide bond formation in protein synthesis. The stability of the acyl linkage in each aminoacyl-tRNA, formed through an ester bond that connects the amino acid carboxyl group with the tRNA terminal 3'-OH group, is thus important. While the ester linkage is the same for all aminoacyl-tRNAs, the stability of each is not well characterized, thus limiting insight into the fundamental process of peptide bond formation. Here, we show, by analysis of the half-lives of 12 of the 22 natural aminoacyl-tRNAs used in peptide bond formation, that the stability of the acyl linkage is effectively determined only by the chemical nature of the amino acid side chain. Even the chirality of the side chain exhibits little influence. Proline confers the lowest stability to the linkage, while isoleucine and valine confer the highest, whereas the nucleotide sequence in the tRNA provides negligible contribution to the stability. We find that, among the variables tested, the protein translation factor EF-Tu is the only one that can protect a weak acyl linkage from hydrolysis. These results suggest that each amino acid plays an active role in determining its own stability in the acyl linkage to tRNA, but that EF-Tu overrides this individuality and protects the acyl linkage stability for protein synthesis on the ribosome.
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Affiliation(s)
- Jacob R. Peacock
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
| | - Ryan R. Walvoord
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Angela Y. Chang
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
| | - Marisa C. Kozlowski
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Howard Gamper
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
- Corresponding authorE-mail
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28
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Peske F, Kuhlenkoetter S, Rodnina MV, Wintermeyer W. Timing of GTP binding and hydrolysis by translation termination factor RF3. Nucleic Acids Res 2013; 42:1812-20. [PMID: 24214994 PMCID: PMC3919579 DOI: 10.1093/nar/gkt1095] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Protein synthesis in bacteria is terminated by release factors 1 or 2 (RF1/2), which, on recognition of a stop codon in the decoding site on the ribosome, promote the hydrolytic release of the polypeptide from the transfer RNA (tRNA). Subsequently, the dissociation of RF1/2 is accelerated by RF3, a guanosine triphosphatase (GTPase) that hydrolyzes GTP during the process. Here we show that—in contrast to a previous report—RF3 binds GTP and guanosine diphosphate (GDP) with comparable affinities. Furthermore, we find that RF3–GTP binds to the ribosome and hydrolyzes GTP independent of whether the P site contains peptidyl-tRNA (pre-termination state) or deacylated tRNA (post-termination state). RF3–GDP in either pre- or post-termination complexes readily exchanges GDP for GTP, and the exchange is accelerated when RF2 is present on the ribosome. Peptide release results in the stabilization of the RF3–GTP–ribosome complex, presumably due to the formation of the hybrid/rotated state of the ribosome, thereby promoting the dissociation of RF1/2. GTP hydrolysis by RF3 is virtually independent of the functional state of the ribosome and the presence of RF2, suggesting that RF3 acts as an unregulated ribosome-activated switch governed by its internal GTPase clock.
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Affiliation(s)
- Frank Peske
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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29
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Effects of combinatorial expression of selA, selB and selC genes on the efficiency of selenocysteine incorporation in Escherichia coli. Chem Res Chin Univ 2013. [DOI: 10.1007/s40242-013-2250-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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30
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Gonzalez-Flores JN, Gupta N, DeMong LW, Copeland PR. The selenocysteine-specific elongation factor contains a novel and multi-functional domain. J Biol Chem 2012; 287:38936-45. [PMID: 22992746 DOI: 10.1074/jbc.m112.415463] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The selenocysteine (Sec)-specific eukaryotic elongation factor (eEFSec) delivers the aminoacylated selenocysteine-tRNA (Sec-tRNA(Sec)) to the ribosome and suppresses UGA codons that are upstream of Sec insertion sequence (SECIS) elements bound by SECIS-binding protein 2 (SBP2). Multiple studies have highlighted the importance of SBP2 forming a complex with the SECIS element, but it is not clear how this regulates eEFSec during Sec incorporation. Compared with the canonical elongation factor eEF1A, eEFSec has a unique C-terminal extension called Domain IV. To understand the role of Domain IV in Sec incorporation, we examined a series of mutant proteins for all of the known molecular functions for eEFSec: GTP hydrolysis, Sec-tRNA(Sec) binding, and SBP2/SECIS binding. In addition, wild-type and mutant versions of eEFSec were analyzed for Sec incorporation activity in a novel eEFSec-dependent translation extract. We have found that Domain IV is essential for both tRNA and SBP2 binding as well as regulating GTPase activity. We propose a model where the SBP2/SECIS complex activates eEFSec by directing functional interactions between Domain IV and the ribosome to promote Sec-tRNA(Sec) binding and accommodation into the ribosomal A-site.
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Affiliation(s)
- Jonathan N Gonzalez-Flores
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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Paleskava A, Konevega AL, Rodnina MV. Thermodynamics of the GTP-GDP-operated conformational switch of selenocysteine-specific translation factor SelB. J Biol Chem 2012; 287:27906-12. [PMID: 22740700 PMCID: PMC3431659 DOI: 10.1074/jbc.m112.366120] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 06/22/2012] [Indexed: 11/06/2022] Open
Abstract
SelB is a specialized translation factor that binds GTP and GDP and delivers selenocysteyl-tRNA (Sec-tRNA(Sec)) to the ribosome. By analogy to elongation factor Tu (EF-Tu), SelB is expected to control the delivery and release of Sec-tRNA(Sec) to the ribosome by the structural switch between GTP- and GDP-bound conformations. However, crystal structures of SelB suggested a similar domain arrangement in the apo form and GDP- and GTP-bound forms of the factor, raising the question of how SelB can fulfill its delivery function. Here, we studied the thermodynamics of guanine nucleotide binding to SelB by isothermal titration calorimetry in the temperature range between 10 and 25 °C using GTP, GDP, and two nonhydrolyzable GTP analogs, guanosine 5'-O-(γ-thio)triphosphate (GTPγS) and guanosine 5'-(β,γ-imido)-triphosphate (GDPNP). The binding of SelB to either guanine nucleotide is characterized by a large heat capacity change (-621, -467, -235, and -275 cal × mol(-1) × K(-1), with GTP, GTPγS, GDPNP, and GDP, respectively), associated with compensatory changes in binding entropy and enthalpy. Changes in heat capacity indicate a large decrease of the solvent-accessible surface area in SelB, amounting to 43 or 32 amino acids buried upon binding of GTP or GTPγS, respectively, and 15-19 amino acids upon binding GDP or GDPNP. The similarity of the GTP and GDP forms in the crystal structures can be attributed to the use of GDPNP, which appears to induce a structure of SelB that is more similar to the GDP than to the GTP-bound form.
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Affiliation(s)
- Alena Paleskava
- From the Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Andrey L. Konevega
- From the Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Marina V. Rodnina
- From the Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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32
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Tuning the affinity of aminoacyl-tRNA to elongation factor Tu for optimal decoding. Proc Natl Acad Sci U S A 2011; 108:5215-20. [PMID: 21402928 DOI: 10.1073/pnas.1102128108] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To better understand why aminoacyl-tRNAs (aa-tRNAs) have evolved to bind bacterial elongation factor Tu (EF-Tu) with uniform affinities, mutant tRNAs with differing affinities for EF-Tu were assayed for decoding on Escherichia coli ribosomes. At saturating EF-Tu concentrations, weaker-binding aa-tRNAs decode their cognate codons similarly to wild-type tRNAs. However, tighter-binding aa-tRNAs show reduced rates of peptide bond formation due to slow release from EF-Tu•GDP. Thus, the affinities of aa-tRNAs for EF-Tu are constrained to be uniform by their need to bind tightly enough to form the ternary complex but weakly enough to release from EF-Tu during decoding. Consistent with available crystal structures, the identity of the esterified amino acid and three base pairs in the T stem of tRNA combine to define the affinity of each aa-tRNA for EF-Tu, both off and on the ribosome.
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33
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Harris RC, Bredenberg JH, Silalahi ARJ, Boschitsch AH, Fenley MO. Understanding the physical basis of the salt dependence of the electrostatic binding free energy of mutated charged ligand-nucleic acid complexes. Biophys Chem 2011; 156:79-87. [PMID: 21458909 DOI: 10.1016/j.bpc.2011.02.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 02/08/2011] [Accepted: 02/21/2011] [Indexed: 12/01/2022]
Abstract
The predictions of the derivative of the electrostatic binding free energy of a biomolecular complex, ΔG(el), with respect to the logarithm of the 1:1 salt concentration, d(ΔG(el))/d(ln[NaCl]), SK, by the Poisson-Boltzmann equation, PBE, are very similar to those of the simpler Debye-Hückel equation, DHE, because the terms in the PBE's predictions of SK that depend on the details of the dielectric interface are small compared to the contributions from long-range electrostatic interactions. These facts allow one to obtain predictions of SK using a simplified charge model along with the DHE that are highly correlated with both the PBE and experimental binding data. The DHE-based model developed here, which was derived from the generalized Born model, explains the lack of correlation between SK and ΔG(el) in the presence of a dielectric discontinuity, which conflicts with the popular use of this supposed correlation to parse experimental binding free energies into electrostatic and nonelectrostatic components. Moreover, the DHE model also provides a clear justification for the correlations between SK and various empirical quantities, like the number of ion pairs, the ligand charge on the interface, the Coulomb binding free energy, and the product of the charges on the complex's components, but these correlations are weak, questioning their usefulness.
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Affiliation(s)
- Robert C Harris
- Department of Physics, Institute of Molecular Biophysics, Florida State University, Tallahasse, 32306, USA.
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Atkinson GC, Hauryliuk V, Tenson T. An ancient family of SelB elongation factor-like proteins with a broad but disjunct distribution across archaea. BMC Evol Biol 2011; 11:22. [PMID: 21255425 PMCID: PMC3037878 DOI: 10.1186/1471-2148-11-22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 01/21/2011] [Indexed: 02/05/2023] Open
Abstract
Background SelB is the dedicated elongation factor for delivery of selenocysteinyl-tRNA to the ribosome. In archaea, only a subset of methanogens utilizes selenocysteine and encodes archaeal SelB (aSelB). A SelB-like (aSelBL) homolog has previously been identified in an archaeon that does not encode selenosysteine, and has been proposed to be a pyrrolysyl-tRNA-specific elongation factor (EF-Pyl). However, elongation factor EF-Tu is capable of binding archaeal Pyl-tRNA in bacteria, suggesting the archaeal ortholog EF1A may also be capable of delivering Pyl-tRNA to the ribosome without the need of a specialized factor. Results We have phylogenetically characterized the aSelB and aSelBL families in archaea. We find the distribution of aSelBL to be wider than both selenocysteine and pyrrolysine usage. The aSelBLs also lack the carboxy terminal domain usually involved in recognition of the selenocysteine insertion sequence in the target mRNA. While most aSelBL-encoding archaea are methanogenic Euryarchaea, we also find aSelBL representatives in Sulfolobales and Thermoproteales of Crenarchaea, and in the recently identified phylum Thaumarchaea, suggesting that aSelBL evolution has involved horizontal gene transfer and/or parallel loss. Severe disruption of the GTPase domain suggests that some family members may employ a hitherto unknown mechanism of nucleotide hydrolysis, or have lost their GTPase ability altogether. However, patterns of sequence conservation indicate that aSelBL is still capable of binding the ribosome and aminoacyl-tRNA. Conclusions Although it is closely related to SelB, aSelBL appears unlikely to either bind selenocysteinyl-tRNA or function as a classical GTP hydrolyzing elongation factor. We propose that following duplication of aSelB, the resultant aSelBL was recruited for binding another aminoacyl-tRNA. In bacteria, aminoacylation with selenocysteine is essential for efficient thermodynamic coupling of SelB binding to tRNA and GTP. Therefore, change in tRNA specificity of aSelBL could have disrupted its GTPase cycle, leading to relaxation of selective pressure on the GTPase domain and explaining its apparent degradation. While the specific role of aSelBL is yet to be experimentally tested, its broad phylogenetic distribution, surpassing that of aSelB, indicates its importance.
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Yuan J, Hohn MJ, Sherrer RL, Palioura S, Su D, Söll D. A tRNA-dependent cysteine biosynthesis enzyme recognizes the selenocysteine-specific tRNA in Escherichia coli. FEBS Lett 2010; 584:2857-61. [PMID: 20493852 DOI: 10.1016/j.febslet.2010.05.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 05/14/2010] [Accepted: 05/14/2010] [Indexed: 12/13/2022]
Abstract
The essential methanogen enzyme Sep-tRNA:Cys-tRNA synthase (SepCysS) converts O-phosphoseryl-tRNA(Cys) (Sep-tRNA(Cys)) into Cys-tRNA(Cys) in the presence of a sulfur donor. Likewise, Sep-tRNA:Sec-tRNA synthase converts O-phosphoseryl-tRNA(Sec) (Sep-tRNA(Sec)) to selenocysteinyl-tRNA(Sec) (Sec-tRNA(Sec)) using a selenium donor. While the Sep moiety of the aminoacyl-tRNA substrates is the same in both reactions, tRNA(Cys) and tRNA(Sec) differ greatly in sequence and structure. In an Escherichia coli genetic approach that tests for formate dehydrogenase activity in the absence of selenium donor we show that Sep-tRNA(Sec) is a substrate for SepCysS. Since Sec and Cys are the only active site amino acids known to sustain FDH activity, we conclude that SepCysS converts Sep-tRNA(Sec) to Cys-tRNA(Sec), and that Sep is crucial for SepCysS recognition.
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Affiliation(s)
- Jing Yuan
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
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36
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Milon P, Carotti M, Konevega AL, Wintermeyer W, Rodnina MV, Gualerzi CO. The ribosome-bound initiation factor 2 recruits initiator tRNA to the 30S initiation complex. EMBO Rep 2010; 11:312-6. [PMID: 20224578 DOI: 10.1038/embor.2010.12] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 12/18/2009] [Accepted: 01/15/2010] [Indexed: 11/09/2022] Open
Abstract
Bacterial translation initiation factor 2 (IF2) is a GTPase that promotes the binding of the initiator fMet-tRNA(fMet) to the 30S ribosomal subunit. It is often assumed that IF2 delivers fMet-tRNA(fMet) to the ribosome in a ternary complex, IF2.GTP.fMet-tRNA(fMet). By using rapid kinetic techniques, we show here that binding of IF2.GTP to the 30S ribosomal subunit precedes and is independent of fMet-tRNA(fMet) binding. The ternary complex formed in solution by IF2.GTP and fMet-tRNA is unstable and dissociates before IF2.GTP and, subsequently, fMet-tRNA(fMet) bind to the 30S subunit. Ribosome-bound IF2 might accelerate the recruitment of fMet-tRNA(fMet) to the 30S initiation complex by providing anchoring interactions or inducing a favourable ribosome conformation. The mechanism of action of IF2 seems to be different from that of tRNA carriers such as EF-Tu, SelB and eukaryotic initiation factor 2 (eIF2), instead resembling that of eIF5B, the eukaryotic subunit association factor.
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Affiliation(s)
- Pohl Milon
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
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