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Ma X, Bakhtina M, Shulgina I, Cantara WA, Kuzmishin Nagy A, Goto Y, Suga H, Foster MP, Musier-Forsyth K. Structural basis of tRNAPro acceptor stem recognition by a bacterial trans-editing domain. Nucleic Acids Res 2023; 51:3988-3999. [PMID: 36951109 PMCID: PMC10164551 DOI: 10.1093/nar/gkad192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 03/03/2023] [Accepted: 03/06/2023] [Indexed: 03/24/2023] Open
Abstract
High fidelity tRNA aminoacylation by aminoacyl-tRNA synthetases is essential for cell viability. ProXp-ala is a trans-editing protein that is present in all three domains of life and is responsible for hydrolyzing mischarged Ala-tRNAPro and preventing mistranslation of proline codons. Previous studies have shown that, like bacterial prolyl-tRNA synthetase, Caulobacter crescentus ProXp-ala recognizes the unique C1:G72 terminal base pair of the tRNAPro acceptor stem, helping to ensure deacylation of Ala-tRNAPro but not Ala-tRNAAla. The structural basis for C1:G72 recognition by ProXp-ala is still unknown and was investigated here. NMR spectroscopy, binding, and activity assays revealed two conserved residues, K50 and R80, that likely interact with the first base pair, stabilizing the initial protein-RNA encounter complex. Modeling studies are consistent with direct interaction between R80 and the major groove of G72. A third key contact between A76 of tRNAPro and K45 of ProXp-ala was essential for binding and accommodating the CCA-3' end in the active site. We also demonstrated the essential role that the 2'OH of A76 plays in catalysis. Eukaryotic ProXp-ala proteins recognize the same acceptor stem positions as their bacterial counterparts, albeit with different nucleotide base identities. ProXp-ala is encoded in some human pathogens; thus, these results have the potential to inform new antibiotic drug design.
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Affiliation(s)
- Xiao Ma
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - Marina Bakhtina
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - Irina Shulgina
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - William A Cantara
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - Alexandra B Kuzmishin Nagy
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - Yuki Goto
- Department of Chemistry, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Mark P Foster
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
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2
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Substrate-assisted mechanism of catalytic hydrolysis of misaminoacylated tRNA required for protein synthesis fidelity. Biochem J 2019; 476:719-732. [PMID: 30718305 DOI: 10.1042/bcj20180910] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/28/2019] [Accepted: 02/01/2019] [Indexed: 11/17/2022]
Abstract
d-aminoacyl-tRNA-deacylase (DTD) prevents the incorporation of d-amino acids into proteins during translation by hydrolyzing the ester bond between mistakenly attached amino acids and tRNAs. Despite extensive study of this proofreading enzyme, the precise catalytic mechanism remains unknown. Here, a combination of biochemical and computational investigations has enabled the discovery of a new substrate-assisted mechanism of d-Tyr-tRNATyr hydrolysis by Thermus thermophilus DTD. Several functional elements of the substrate, misacylated tRNA, participate in the catalysis. During the hydrolytic reaction, the 2'-OH group of the А76 residue of d-Tyr-tRNATyr forms a hydrogen bond with a carbonyl group of the tyrosine residue, stabilizing the transition-state intermediate. Two water molecules participate in this reaction, attacking and assisting ones, resulting in a significant decrease in the activation energy of the rate-limiting step. The amino group of the d-Tyr aminoacyl moiety is unprotonated and serves as a general base, abstracting the proton from the assisting water molecule and forming a more nucleophilic ester-attacking species. Quantum chemical methodology was used to investigate the mechanism of hydrolysis. The DFT-calculated deacylation reaction is in full agreement with the experimental data. The Gibbs activation energies for the first and second steps were 10.52 and 1.05 kcal/mol, respectively, highlighting that the first step of the hydrolysis process is the rate-limiting step. Several amino acid residues of the enzyme participate in the coordination of the substrate and water molecules. Thus, the present work provides new insights into the proofreading details of misacylated tRNAs and can be extended to other systems important for translation fidelity.
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3
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Routh SB, Sankaranarayanan R. Enzyme action at RNA–protein interface in DTD-like fold. Curr Opin Struct Biol 2018; 53:107-114. [DOI: 10.1016/j.sbi.2018.07.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 07/24/2018] [Accepted: 07/30/2018] [Indexed: 02/08/2023]
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4
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Aboelnga MM, Hayward JJ, Gauld JW. Unraveling the Critical Role Played by Ado762'OH in the Post-Transfer Editing by Archaeal Threonyl-tRNA Synthetase. J Phys Chem B 2018; 122:1092-1101. [PMID: 29281289 DOI: 10.1021/acs.jpcb.7b10254] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Archaeal threonyl-tRNA synthetase (ThrRS) possesses an editing active site wherein tRNAThr that has been misaminoacylated with serine (i.e., Ser-tRNAThr) is hydrolytically cleaved to serine and tRNAThr. It has been suggested that the free ribose sugar hydroxyl of Ado76 of the tRNAThr (Ado762'OH) is the mechanistic base, promoting hydrolysis by orienting a nucleophilic water near the scissile Ser-tRNAThr ester bond. We have performed a computational study, involving molecular dynamics (MD) and hybrid ONIOM quantum mechanics/molecular mechanics (QM/MM) methods, considering all possible editing mechanisms to gain an understanding of the role played by Ado762'OH group. More specifically, a range of concerted or stepwise mechanisms involving four-, six-, or eight-membered transition structures (total of seven mechanisms) were considered. In addition, these seven mechanisms were fully optimized using three different DFT functionals, namely, B3LYP, M06-2X, and M06-HF. The M06-HF functional gave the most feasible energy barriers followed by the M06-2X functional. The most favorable mechanism proceeds stepwise through two six-membered ring transition states in which the Ado762'OH group participates, overall, as a shuttle for the proton transfer from the nucleophilic H2O to the bridging oxygen (Ado763'O) of the substrate. More specifically, in the first step, which has a barrier of 25.9 kcal/mol, the Ado762'-OH group accepts a proton from the attacking nucleophilic water while concomitantly transferring its proton onto the substrates C-Ocarb center. Then, in the second step, which also proceeds with a barrier of 25.9 kcal/mol, the Ado762'-OH group transfers its proton on the adjacent Ado763'-oxygen, cleaving the scissile Ccarb-O3'Ado76 bond, while concomitantly accepting a proton from the previously formed C-OcarbH group.
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Affiliation(s)
- Mohamed M Aboelnga
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.,Department of Chemistry, Faculty of Science, Damietta University , New Damietta, Damietta Governorate 34511, Egypt
| | - John J Hayward
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada
| | - James W Gauld
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada
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5
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Dulic M, Cvetesic N, Zivkovic I, Palencia A, Cusack S, Bertosa B, Gruic-Sovulj I. Kinetic Origin of Substrate Specificity in Post-Transfer Editing by Leucyl-tRNA Synthetase. J Mol Biol 2018; 430:1-16. [DOI: 10.1016/j.jmb.2017.10.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/02/2017] [Accepted: 10/08/2017] [Indexed: 10/18/2022]
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6
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Danhart EM, Bakhtina M, Cantara WA, Kuzmishin AB, Ma X, Sanford BL, Vargas-Rodriguez O, Košutić M, Goto Y, Suga H, Nakanishi K, Micura R, Foster MP, Musier-Forsyth K. Conformational and chemical selection by a trans-acting editing domain. Proc Natl Acad Sci U S A 2017; 114:E6774-E6783. [PMID: 28768811 PMCID: PMC5565427 DOI: 10.1073/pnas.1703925114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Molecular sieves ensure proper pairing of tRNAs and amino acids during aminoacyl-tRNA biosynthesis, thereby avoiding detrimental effects of mistranslation on cell growth and viability. Mischarging errors are often corrected through the activity of specialized editing domains present in some aminoacyl-tRNA synthetases or via single-domain trans-editing proteins. ProXp-ala is a ubiquitous trans-editing enzyme that edits Ala-tRNAPro, the product of Ala mischarging by prolyl-tRNA synthetase, although the structural basis for discrimination between correctly charged Pro-tRNAPro and mischarged Ala-tRNAAla is unclear. Deacylation assays using substrate analogs reveal that size discrimination is only one component of selectivity. We used NMR spectroscopy and sequence conservation to guide extensive site-directed mutagenesis of Caulobacter crescentus ProXp-ala, along with binding and deacylation assays to map specificity determinants. Chemical shift perturbations induced by an uncharged tRNAPro acceptor stem mimic, microhelixPro, or a nonhydrolyzable mischarged Ala-microhelixPro substrate analog identified residues important for binding and deacylation. Backbone 15N NMR relaxation experiments revealed dynamics for a helix flanking the substrate binding site in free ProXp-ala, likely reflecting sampling of open and closed conformations. Dynamics persist on binding to the uncharged microhelix, but are attenuated when the stably mischarged analog is bound. Computational docking and molecular dynamics simulations provide structural context for these findings and predict a role for the substrate primary α-amine group in substrate recognition. Overall, our results illuminate strategies used by a trans-editing domain to ensure acceptance of only mischarged Ala-tRNAPro, including conformational selection by a dynamic helix, size-based exclusion, and optimal positioning of substrate chemical groups.
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Affiliation(s)
- Eric M Danhart
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Marina Bakhtina
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - William A Cantara
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Alexandra B Kuzmishin
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Xiao Ma
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Brianne L Sanford
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | | | - Marija Košutić
- Institute of Organic Chemistry, Leopold Franzens University, A-6020 Innsbruck, Austria
- Center for Molecular Biosciences, Leopold Franzens University, A-6020 Innsbruck, Austria
| | - Yuki Goto
- Department of Chemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kotaro Nakanishi
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Ronald Micura
- Institute of Organic Chemistry, Leopold Franzens University, A-6020 Innsbruck, Austria
- Center for Molecular Biosciences, Leopold Franzens University, A-6020 Innsbruck, Austria
| | - Mark P Foster
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210;
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210;
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
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7
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p53-Dependent DNA damage response sensitive to editing-defective tRNA synthetase in zebrafish. Proc Natl Acad Sci U S A 2016; 113:8460-5. [PMID: 27402763 DOI: 10.1073/pnas.1608139113] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Brain and heart pathologies are caused by editing defects of transfer RNA (tRNA) synthetases, which preserve genetic code fidelity by removing incorrect amino acids misattached to tRNAs. To extend understanding of the broader impact of synthetase editing reactions on organismal homeostasis, and based on effects in bacteria ostensibly from small amounts of mistranslation of components of the replication apparatus, we investigated the sensitivity to editing of the vertebrate genome. We show here that in zebrafish embryos, transient overexpression of editing-defective valyl-tRNA synthetase (ValRS(ED)) activated DNA break-responsive H2AX and p53-responsive downstream proteins, such as cyclin-dependent kinase (CDK) inhibitor p21, which promotes cell-cycle arrest at DNA damage checkpoints, and Gadd45 and p53R2, with pivotal roles in DNA repair. In contrast, the response of these proteins to expression of ValRS(ED) was abolished in p53-deficient fish. The p53-activated downstream signaling events correlated with suppression of abnormal morphological changes caused by the editing defect and, in adults, reversed a shortened life span (followed for 2 y). Conversely, with normal editing activities, p53-deficient fish have a normal life span and few morphological changes. Whole-fish deep sequencing showed genomic mutations associated with the editing defect. We suggest that the sensitivity of p53 to expression of an editing-defective tRNA synthetase has a critical role in promoting genome integrity and organismal homeostasis.
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Boyarshin KS, Priss AE, Rayevskiy AV, Ilchenko MM, Dubey IY, Kriklivyi IA, Yaremchuk AD, Tukalo MA. A new mechanism of post-transfer editing by aminoacyl-tRNA synthetases: catalysis of hydrolytic reaction by bacterial-type prolyl-tRNA synthetase. J Biomol Struct Dyn 2016; 35:669-682. [PMID: 26886480 DOI: 10.1080/07391102.2016.1155171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Aminoacyl tRNA synthetases are enzymes that specifically attach amino acids to cognate tRNAs for use in the ribosomal stage of translation. For many aminoacyl tRNA synthetases, the required level of amino acid specificity is achieved either by specific hydrolysis of misactivated aminoacyl-adenylate intermediate (pre-transfer editing) or by hydrolysis of the mischarged aminoacyl-tRNA (post-transfer editing). To investigate the mechanism of post-transfer editing of alanine by prolyl-tRNA synthetase from the pathogenic bacteria Enterococcus faecalis, we used molecular modeling, molecular dynamic simulations, quantum mechanical (QM) calculations, site-directed mutagenesis of the enzyme, and tRNA modification. The results support a new tRNA-assisted mechanism of hydrolysis of misacylated Ala-tRNAPro. The most important functional element of this catalytic mechanism is the 2'-OH group of the terminal adenosine 76 of Ala-tRNAPro, which forms an intramolecular hydrogen bond with the carbonyl group of the alanine residue, strongly facilitating hydrolysis. Hydrolysis was shown by QM methods to proceed via a general acid-base catalysis mechanism involving two functionally distinct water molecules. The transition state of the reaction was identified. Amino acid residues of the editing active site participate in the coordination of substrate and both attacking and assisting water molecules, performing the proton transfer to the 3'-O atom of A76.
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Affiliation(s)
- Konstantin S Boyarshin
- a Department of Protein Synthesis Enzymology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine.,b State Key Laboratory of Molecular and Cellular Biology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Anastasia E Priss
- b State Key Laboratory of Molecular and Cellular Biology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Alexsey V Rayevskiy
- a Department of Protein Synthesis Enzymology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine.,b State Key Laboratory of Molecular and Cellular Biology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Mykola M Ilchenko
- c Department of Synthetic Bioregulators , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Igor Ya Dubey
- c Department of Synthetic Bioregulators , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Ivan A Kriklivyi
- a Department of Protein Synthesis Enzymology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine.,b State Key Laboratory of Molecular and Cellular Biology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Anna D Yaremchuk
- a Department of Protein Synthesis Enzymology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine.,b State Key Laboratory of Molecular and Cellular Biology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
| | - Michael A Tukalo
- a Department of Protein Synthesis Enzymology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine.,b State Key Laboratory of Molecular and Cellular Biology , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , 150 Zabolotnogo Str, 03680 Kyiv , Ukraine
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9
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Fortowsky GB, Simard DJ, Aboelnga MM, Gauld JW. Substrate-Assisted and Enzymatic Pretransfer Editing of Nonstandard Amino Acids by Methionyl-tRNA Synthetase. Biochemistry 2015; 54:5757-65. [PMID: 26322377 DOI: 10.1021/acs.biochem.5b00588] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Aminoacyl-tRNA synthetases (aaRSs) are central to a number of physiological processes, including protein biosynthesis. In particular, they activate and then transfer their corresponding amino acid to the cognate tRNA. This is achieved with a generally remarkably high fidelity by editing against incorrect standard and nonstandard amino acids. Using docking, molecular dynamics (MD), and hybrid quantum mechanical/molecular mechanics methods, we have investigated mechanisms by which methionyl-tRNA synthetase (MetRS) may edit against the highly toxic, noncognate, amino acids homocysteine (Hcy) and its oxygen analogue, homoserine (Hse). Substrate-assisted editing of Hcy-AMP in which its own phosphate acts as the mechanistic base occurs with a rate-limiting barrier of 98.2 kJ mol(-1). This step corresponds to nucleophilic attack of the Hcy side-chain sulfur at its own carbonyl carbon (CCarb). In contrast, a new possible editing mechanism is identified in which an active site aspartate (Asp259) acts as the base. The rate-limiting step is now rotation about the substrate's aminoacyl Cβ-Cγ bond with a barrier of 27.5 kJ mol(-1), while for Hse-AMP, the rate-limiting step is cleavage of the CCarb-OP bond with a barrier of 30.9 kJ mol(-1). A similarly positioned aspartate or glutamate also occurs in the homologous enzymes LeuRS, IleRS, and ValRS, which also discriminate against Hcy. Docking and MD studies suggest that at least in the case of LeuRS and ValRS, a similar editing mechanism may be possible.
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Affiliation(s)
- Grant B Fortowsky
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada
| | - Daniel J Simard
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada
| | - Mohamed M Aboelnga
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada
| | - James W Gauld
- Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada
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10
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Anishkin A, Vanegas JM, Rogers DM, Lorenzi PL, Chan WK, Purwaha P, Weinstein JN, Sukharev S, Rempe SB. Catalytic Role of the Substrate Defines Specificity of Therapeutic l-Asparaginase. J Mol Biol 2015; 427:2867-85. [DOI: 10.1016/j.jmb.2015.06.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 05/20/2015] [Accepted: 06/26/2015] [Indexed: 12/23/2022]
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11
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Nguyen SV, McShan WM. Chromosomal islands of Streptococcus pyogenes and related streptococci: molecular switches for survival and virulence. Front Cell Infect Microbiol 2014; 4:109. [PMID: 25161960 PMCID: PMC4129442 DOI: 10.3389/fcimb.2014.00109] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 07/25/2014] [Indexed: 01/19/2023] Open
Abstract
Streptococcus pyogenes is a significant pathogen of humans, annually causing over 700,000,000 infections and 500,000 deaths. Virulence in S. pyogenes is closely linked to mobile genetic elements like phages and chromosomal islands (CI). S. pyogenes phage-like chromosomal islands (SpyCI) confer a complex mutator phenotype on their host. SpyCI integrate into the 5′ end of DNA mismatch repair (MMR) gene mutL, which also disrupts downstream operon genes lmrP, ruvA, and tag. During early logarithmic growth, SpyCI excise from the bacterial chromosome and replicate as episomes, relieving the mutator phenotype. As growth slows and the cells enter stationary phase, SpyCI reintegrate into the chromosome, again silencing the MMR operon. This system creates a unique growth-dependent and reversible mutator phenotype. Additional CI using the identical attachment site in mutL have been identified in related species, including Streptococcus dysgalactiae subsp. equisimilis, Streptococcus anginosus, Streptococcus intermedius, Streptococcus parauberis, and Streptococcus canis. These CI have small genomes, which range from 13 to 20 kB, conserved integrase and DNA replication genes, and no identifiable genes encoding capsid proteins. SpyCI may employ a helper phage for packaging and dissemination in a fashion similar to the Staphylococcus aureus pathogenicity islands (SaPI). Outside of the core replication and integration genes, SpyCI and related CI show considerable diversity with the presence of many indels that may contribute to the host cell phenotype or fitness. SpyCI are a subset of a larger family of streptococcal CI who potentially regulate the expression of other host genes. The biological and phylogenetic analysis of streptococcal chromosomal islands provides important clues as to how these chromosomal islands help S. pyogenes and other streptococcal species persist in human populations in spite of antibiotic therapy and immune challenges.
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Affiliation(s)
- Scott V Nguyen
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center Oklahoma City, OK, USA
| | - William M McShan
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center Oklahoma City, OK, USA ; Department of Pharmaceutical Sciences, The University of Oklahoma Health Sciences Center Oklahoma City, OK, USA
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12
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Bartholow TG, Sanford BL, Cao B, Schmit HL, Johnson JM, Meitzner J, Bhattacharyya S, Musier-Forsyth K, Hati S. Strictly conserved lysine of prolyl-tRNA Synthetase editing domain facilitates binding and positioning of misacylated tRNA(Pro.). Biochemistry 2014; 53:1059-68. [PMID: 24450765 PMCID: PMC3986007 DOI: 10.1021/bi401279r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
To ensure high fidelity in translation, many aminoacyl-tRNA synthetases, enzymes responsible for attaching specific amino acids to cognate tRNAs, require proof-reading mechanisms. Most bacterial prolyl-tRNA synthetases (ProRSs) misactivate alanine and employ a post-transfer editing mechanism to hydrolyze Ala-tRNA(Pro). This reaction occurs in a second catalytic site (INS) that is distinct from the synthetic active site. The 2'-OH of misacylated tRNA(Pro) and several conserved residues in the Escherichia coli ProRS INS domain are directly involved in Ala-tRNA(Pro) deacylation. Although mutation of the strictly conserved lysine 279 (K279) results in nearly complete loss of post-transfer editing activity, this residue does not directly participate in Ala-tRNA(Pro) hydrolysis. We hypothesized that the role of K279 is to bind the phosphate backbone of the acceptor stem of misacylated tRNA(Pro) and position it in the editing active site. To test this hypothesis, we carried out pKa, charge neutralization, and free-energy of binding calculations. Site-directed mutagenesis and kinetic studies were performed to verify the computational results. The calculations revealed a considerably higher pKa of K279 compared to an isolated lysine and showed that the protonated state of K279 is stabilized by the neighboring acidic residue. However, substitution of this acidic residue with a positively charged residue leads to a significant increase in Ala-tRNA(Pro) hydrolysis, suggesting that enhancement in positive charge density in the vicinity of K279 favors tRNA binding. A charge-swapping experiment and free energy of binding calculations support the conclusion that the positive charge at position 279 is absolutely necessary for tRNA binding in the editing active site.
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Affiliation(s)
- Thomas G Bartholow
- Department of Chemistry, University of Wisconsin-Eau Claire , Eau Claire, Wisconsin, 54702, United States
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13
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Das M, Vargas-Rodriguez O, Goto Y, Suga H, Musier-Forsyth K. Distinct tRNA recognition strategies used by a homologous family of editing domains prevent mistranslation. Nucleic Acids Res 2013; 42:3943-53. [PMID: 24371276 PMCID: PMC3973320 DOI: 10.1093/nar/gkt1332] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Errors in protein synthesis due to mispairing of amino acids with tRNAs jeopardize cell viability. Several checkpoints to prevent formation of Ala- and Cys-tRNAPro have been described, including the Ala-specific editing domain (INS) of most bacterial prolyl-tRNA synthetases (ProRSs) and an autonomous single-domain INS homolog, YbaK, which clears Cys-tRNAPro in trans. In many species where ProRS lacks an INS domain, ProXp-ala, another single-domain INS-like protein, is responsible for editing Ala-tRNAPro. Although the amino acid specificity of these editing domains has been established, the role of tRNA sequence elements in substrate selection has not been investigated in detail. Critical recognition elements for aminoacylation by bacterial ProRS include acceptor stem elements G72/A73 and anticodon bases G35/G36. Here, we show that ProXp-ala and INS require these same acceptor stem and anticodon elements, respectively, whereas YbaK lacks inherent tRNA specificity. Thus, these three related domains use divergent approaches to recognize tRNAs and prevent mistranslation. Whereas some editing domains have borrowed aspects of tRNA recognition from the parent aminoacyl-tRNA synthetase, relaxed tRNA specificity leading to semi-promiscuous editing may offer advantages to cells.
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Affiliation(s)
- Mom Das
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA, Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA and Department of Chemistry, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
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A multiple aminoacyl-tRNA synthetase complex that enhances tRNA-aminoacylation in African trypanosomes. Mol Cell Biol 2013; 33:4872-88. [PMID: 24126051 DOI: 10.1128/mcb.00711-13] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genes for all cytoplasmic and potentially all mitochondrial aminoacyl-tRNA synthetases (aaRSs) were identified, and all those tested by RNA interference were found to be essential for the growth of Trypanosoma brucei. Some of these enzymes were localized to the cytoplasm or mitochondrion, but most were dually localized to both cellular compartments. Cytoplasmic T. brucei aaRSs were organized in a multiprotein complex in both bloodstream and procyclic forms. The multiple aminoacyl-tRNA synthetase (MARS) complex contained at least six aaRS enzymes and three additional non-aaRS proteins. Steady-state kinetic studies showed that association in the MARS complex enhances tRNA-aminoacylation efficiency, which is in part dependent on a MARS complex-associated protein (MCP), named MCP2, that binds tRNAs and increases their aminoacylation by the complex. Conditional repression of MCP2 in T. brucei bloodstream forms resulted in reduced parasite growth and infectivity in mice. Thus, association in a MARS complex enhances tRNA-aminoacylation and contributes to parasite fitness. The MARS complex may be part of a cellular regulatory system and a target for drug development.
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Kumar S, Das M, Hadad CM, Musier-Forsyth K. Aminoacyl-tRNA substrate and enzyme backbone atoms contribute to translational quality control by YbaK. J Phys Chem B 2013; 117:4521-7. [PMID: 23185990 PMCID: PMC3601562 DOI: 10.1021/jp308628y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amino acids are covalently attached to their corresponding transfer RNAs (tRNAs) by aminoacyl-tRNA synthetases. Proofreading mechanisms exist to ensure that high fidelity is maintained in this key step in protein synthesis. Prolyl-tRNA synthetase (ProRS) can misacylate cognate tRNA(Pro) with Ala and Cys. The cis-editing domain of ProRS (INS) hydrolyzes Ala-tRNA(Pro), whereas Cys-tRNA(Pro) is hydrolyzed by a single domain editing protein, YbaK, in trans. Previous studies have proposed a model of substrate-binding by bacterial YbaK and elucidated a substrate-assisted mechanism of catalysis. However, the microscopic steps in this mechanism have not been investigated. In this work, we carried out biochemical experiments together with a detailed hybrid quantum mechanics/molecular mechanics study to investigate the mechanism of catalysis by Escherichia coli YbaK. The results support a mechanism wherein cyclization of the substrate Cys results in cleavage of the Cys-tRNA ester bond. Protein side chains do not play a significant role in YbaK catalysis. Instead, protein backbone atoms play crucial roles in stabilizing the transition state, while the product is stabilized by the 2'-OH of the tRNA.
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Affiliation(s)
- Sandeep Kumar
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210
- Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
| | - Mom Das
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210
- Ohio State Biochemistry Program, Ohio State University, Columbus, Ohio 43210
- Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
| | - Christopher M. Hadad
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210
| | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210
- Ohio State Biochemistry Program, Ohio State University, Columbus, Ohio 43210
- Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
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16
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Vargas-Rodriguez O, Musier-Forsyth K. Exclusive use of trans-editing domains prevents proline mistranslation. J Biol Chem 2013; 288:14391-14399. [PMID: 23564458 DOI: 10.1074/jbc.m113.467795] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Aminoacyl-tRNA synthetases (ARSs) catalyze the attachment of specific amino acids to cognate tRNAs. Although the accuracy of this process is critical for overall translational fidelity, similar sizes of many amino acids provide a challenge to ARSs. For example, prolyl-tRNA synthetases (ProRSs) mischarge alanine and cysteine onto tRNA(Pro). Many bacterial ProRSs possess an alanine-specific proofreading domain (INS) but lack the capability to edit Cys-tRNA(Pro). Instead, Cys-tRNA(Pro) is cleared by a single-domain homolog of INS, the trans-editing YbaK protein. A global bioinformatics analysis revealed that there are six types of "INS-like" proteins. In addition to INS and YbaK, four additional single-domain homologs are widely distributed throughout bacteria: ProXp-ala (formerly named PrdX), ProXp-x (annotated as ProX), ProXp-y (annotated as YeaK), and ProXp-z (annotated as PA2301). The last three are domains of unknown function. Whereas many bacteria encode a ProRS containing an INS domain in addition to YbaK, many other combinations of INS-like proteins exist throughout the bacterial kingdom. Here, we focus on Caulobacter crescentus, which encodes a ProRS with a truncated INS domain that lacks catalytic activity, as well as YbaK and ProXp-ala. We show that C. crescentus ProRS can readily form Cys- and Ala-tRNA(Pro), and deacylation studies confirmed that these species are cleared by C. crescentus YbaK and ProXp-ala, respectively. Substrate specificity of C. crescentus ProXp-ala is determined, in part, by elements in the acceptor stem of tRNA(Pro) and further ensured through collaboration with elongation factor Tu. These results highlight the diversity of approaches used to prevent proline mistranslation and reveal a novel triple-sieve mechanism of editing that relies exclusively on trans-editing factors.
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Affiliation(s)
- Oscar Vargas-Rodriguez
- Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
| | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210.
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