1
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Silveira d'Almeida G, Casius A, Henderson JC, Knuesel S, Aphasizhev R, Aphasizheva I, Manning AC, Lowe TM, Alfonzo JD. tRNA Tyr has an unusually short half-life in Trypanosoma brucei. RNA (NEW YORK, N.Y.) 2023; 29:1243-1254. [PMID: 37197826 PMCID: PMC10351884 DOI: 10.1261/rna.079674.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 04/28/2023] [Indexed: 05/19/2023]
Abstract
Following transcription, tRNAs undergo a series of processing and modification events to become functional adaptors in protein synthesis. Eukaryotes have also evolved intracellular transport systems whereby nucleus-encoded tRNAs may travel out and into the nucleus. In trypanosomes, nearly all tRNAs are also imported from the cytoplasm into the mitochondrion, which lacks tRNA genes. Differential subcellular localization of the cytoplasmic splicing machinery and a nuclear enzyme responsible for queuosine modification at the anticodon "wobble" position appear to be important quality control mechanisms for tRNATyr, the only intron-containing tRNA in T. brucei Since tRNA-guanine transglycosylase (TGT), the enzyme responsible for Q formation, cannot act on an intron-containing tRNA, retrograde nuclear transport is an essential step in maturation. Unlike maturation/processing pathways, the general mechanisms of tRNA stabilization and degradation in T. brucei are poorly understood. Using a combination of cellular and molecular approaches, we show that tRNATyr has an unusually short half-life. tRNATyr, and in addition tRNAAsp, also show the presence of slow-migrating bands during electrophoresis; we term these conformers: alt-tRNATyr and alt-tRNAAsp, respectively. Although we do not know the chemical or structural nature of these conformers, alt-tRNATyr has a short half-life resembling that of tRNATyr; the same is not true for alt-tRNAAsp We also show that RRP44, which is usually an exosome subunit in other organisms, is involved in tRNA degradation of the only intron-containing tRNA in T. brucei and is partly responsible for its unusually short half-life.
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2
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Huang ZX, Li J, Xiong QP, Li H, Wang ED, Liu RJ. Position 34 of tRNA is a discriminative element for m5C38 modification by human DNMT2. Nucleic Acids Res 2021; 49:13045-13061. [PMID: 34871455 PMCID: PMC8682788 DOI: 10.1093/nar/gkab1148] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 10/05/2021] [Accepted: 11/03/2021] [Indexed: 12/05/2022] Open
Abstract
Dnmt2, a member of the DNA methyltransferase superfamily, catalyzes the formation of 5-methylcytosine at position 38 in the anticodon loop of tRNAs. Dnmt2 regulates many cellular biological processes, especially the production of tRNA-derived fragments and intergenerational transmission of paternal metabolic disorders to offspring. Moreover, Dnmt2 is closely related to human cancers. The tRNA substrates of mammalian Dnmt2s are mainly detected using bisulfite sequencing; however, we lack supporting biochemical data concerning their substrate specificity or recognition mechanism. Here, we deciphered the tRNA substrates of human DNMT2 (hDNMT2) as tRNAAsp(GUC), tRNAGly(GCC) and tRNAVal(AAC). Intriguingly, for tRNAAsp(GUC) and tRNAGly(GCC), G34 is the discriminator element; whereas for tRNAVal(AAC), the inosine modification at position 34 (I34), which is formed by the ADAT2/3 complex, is the prerequisite for hDNMT2 recognition. We showed that the C32U33(G/I)34N35 (C/U)36A37C38 motif in the anticodon loop, U11:A24 in the D stem, and the correct size of the variable loop are required for Dnmt2 recognition of substrate tRNAs. Furthermore, mammalian Dnmt2s possess a conserved tRNA recognition mechanism.
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MESH Headings
- 5-Methylcytosine/metabolism
- Adenosine Deaminase/genetics
- Adenosine Deaminase/metabolism
- Animals
- Anticodon/genetics
- Anticodon/metabolism
- Base Sequence
- DNA (Cytosine-5-)-Methyltransferases/chemistry
- DNA (Cytosine-5-)-Methyltransferases/genetics
- DNA (Cytosine-5-)-Methyltransferases/metabolism
- HEK293 Cells
- HeLa Cells
- Humans
- Inosine/metabolism
- Mice
- Models, Molecular
- NIH 3T3 Cells
- Nucleic Acid Conformation
- Protein Binding
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- RNA, Transfer, Asp/chemistry
- RNA, Transfer, Asp/genetics
- RNA, Transfer, Asp/metabolism
- RNA, Transfer, Gly/chemistry
- RNA, Transfer, Gly/genetics
- RNA, Transfer, Gly/metabolism
- RNA, Transfer, Val/chemistry
- RNA, Transfer, Val/genetics
- RNA, Transfer, Val/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Substrate Specificity
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3
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Songsiriritthigul C, Suebka S, Chen CJ, Fuengfuloy P, Chuawong P. Crystal structure of the N-terminal anticodon-binding domain of the nondiscriminating aspartyl-tRNA synthetase from Helicobacter pylori. Acta Crystallogr F Struct Biol Commun 2017; 73:62-69. [PMID: 28177315 PMCID: PMC5297925 DOI: 10.1107/s2053230x16020586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 12/28/2016] [Indexed: 01/25/2023] Open
Abstract
The N-terminal anticodon-binding domain of the nondiscriminating aspartyl-tRNA synthetase (ND-AspRS) plays a crucial role in the recognition of both tRNAAsp and tRNAAsn. Here, the first X-ray crystal structure of the N-terminal domain of this enzyme (ND-AspRS1-104) from the human-pathogenic bacterium Helicobacter pylori is reported at 2.0 Å resolution. The apo form of H. pylori ND-AspRS1-104 shares high structural similarity with the N-terminal anticodon-binding domains of the discriminating aspartyl-tRNA synthetase (D-AspRS) from Escherichia coli and ND-AspRS from Pseudomonas aeruginosa, allowing recognition elements to be proposed for tRNAAsp and tRNAAsn. It is proposed that a long loop (Arg77-Lys90) in this H. pylori domain influences its relaxed tRNA specificity, such that it is classified as nondiscriminating. A structural comparison between D-AspRS from E. coli and ND-AspRS from P. aeruginosa suggests that turns E and F (78GAGL81 and 83NPKL86) in H. pylori ND-AspRS play a crucial role in anticodon recognition. Accordingly, the conserved Pro84 in turn F facilitates the recognition of the anticodons of tRNAAsp (34GUC36) and tRNAAsn (34GUU36). The absence of the amide H atom allows both C and U bases to be accommodated in the tRNA-recognition site.
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MESH Headings
- Amino Acid Sequence
- Anticodon/chemistry
- Anticodon/metabolism
- Apoproteins/chemistry
- Apoproteins/genetics
- Apoproteins/metabolism
- Aspartate-tRNA Ligase/chemistry
- Aspartate-tRNA Ligase/genetics
- Aspartate-tRNA Ligase/metabolism
- Bacterial Proteins/chemistry
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Binding Sites
- Cloning, Molecular
- Crystallography, X-Ray
- Escherichia coli/enzymology
- Escherichia coli/genetics
- Gene Expression
- Helicobacter pylori/chemistry
- Helicobacter pylori/enzymology
- Models, Molecular
- Plasmids/chemistry
- Plasmids/metabolism
- Protein Binding
- Protein Conformation, alpha-Helical
- Protein Conformation, beta-Strand
- Protein Interaction Domains and Motifs
- Pseudomonas aeruginosa/enzymology
- Pseudomonas aeruginosa/genetics
- RNA, Transfer, Asn/chemistry
- RNA, Transfer, Asn/genetics
- RNA, Transfer, Asn/metabolism
- RNA, Transfer, Asp/chemistry
- RNA, Transfer, Asp/genetics
- RNA, Transfer, Asp/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Sequence Alignment
- Structural Homology, Protein
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4
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Manickam N, Nag N, Abbasi A, Patel K, Farabaugh PJ. Studies of translational misreading in vivo show that the ribosome very efficiently discriminates against most potential errors. RNA (NEW YORK, N.Y.) 2014; 20:9-15. [PMID: 24249223 PMCID: PMC3866648 DOI: 10.1261/rna.039792.113] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Protein synthesis must rapidly and repeatedly discriminate between a single correct and many incorrect aminoacyl-tRNAs. We have attempted to measure the frequencies of all possible missense errors by tRNA , tRNA and tRNA . The most frequent errors involve three types of mismatched nucleotide pairs, U•U, U•C, or U•G, all of which can form a noncanonical base pair with geometry similar to that of the canonical U•A or C•G Watson-Crick pairs. Our system is sensitive enough to measure errors at other potential mismatches that occur at frequencies as low as 1 in 500,000 codons. The ribosome appears to discriminate this efficiently against any pair with non-Watson-Crick geometry. This extreme accuracy may be necessary to allow discrimination against the errors involving near Watson-Crick pairing.
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5
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Messmer M, Gaudry A, Sissler M, Florentz C. Pathology-related mutation A7526G (A9G) helps in the understanding of the 3D structural core of human mitochondrial tRNA(Asp). RNA (NEW YORK, N.Y.) 2009; 15:1462-1468. [PMID: 19535463 PMCID: PMC2714750 DOI: 10.1261/rna.1626109] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 05/08/2009] [Indexed: 05/27/2023]
Abstract
More than 130 mutations in human mitochondrial tRNA (mt-tRNA) genes have been correlated with a variety of neurodegenerative and neuromuscular disorders. Their molecular impacts are of mosaic type, affecting various stages of tRNA biogenesis, structure, and/or functions in mt-translation. Knowledge of mammalian mt-tRNA structures per se remains scarce however. Primary and secondary structures deviate from classical tRNAs, while rules for three-dimensional (3D) folding are almost unknown. Here, we take advantage of a myopathy-related mutation A7526G (A9G) in mt-tRNA(Asp) to investigate both the primary molecular impact underlying the pathology and the role of nucleotide 9 in the network of 3D tertiary interactions. Experimental evidence is presented for existence of a 9-12-23 triple in human mt-tRNA(Asp) with a strongly conserved interaction scheme in mammalian mt-tRNAs. Mutation A7526G disrupts the triple interaction and in turn reduces aspartylation efficiency.
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6
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Jurkowski TP, Meusburger M, Phalke S, Helm M, Nellen W, Reuter G, Jeltsch A. Human DNMT2 methylates tRNA(Asp) molecules using a DNA methyltransferase-like catalytic mechanism. RNA (NEW YORK, N.Y.) 2008; 14:1663-70. [PMID: 18567810 PMCID: PMC2491481 DOI: 10.1261/rna.970408] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Accepted: 04/17/2008] [Indexed: 05/21/2023]
Abstract
Although their amino acid sequences and structure closely resemble DNA methyltransferases, Dnmt2 proteins were recently shown by Goll and colleagues to function as RNA methyltransferases transferring a methyl group to the C5 position of C38 in tRNA(Asp). We observe that human DNMT2 methylates tRNA isolated from Dnmt2 knock-out Drosophila melanogaster and Dictyostelium discoideum. RNA extracted from wild type D. melanogaster was methylated to a lower degree, but in the case of Dictyostelium, there was no difference in the methylation of RNA isolated from wild-type and Dnmt2 knock-out strains. Methylation of in vitro transcribed tRNA(Asp) confirms it to be a target of DNMT2. Using site directed mutagenesis, we show here that the enzyme has a DNA methyltransferase-like mechanism, because similar residues from motifs IV, VI, and VIII are involved in catalysis as identified in DNA methyltransferases. In addition, exchange of C292, which is located in a CFT motif conserved among Dnmt2 proteins, strongly reduced the catalytic activity of DNMT2. Dnmt2 represents the first example of an RNA methyltransferase using a DNA methyltransferase type of mechanism.
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7
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Thompson D, Lazennec C, Plateau P, Simonson T. Ammonium Scanning in an Enzyme Active Site. J Biol Chem 2007; 282:30856-68. [PMID: 17690095 DOI: 10.1074/jbc.m704788200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
D-amino acids are largely excluded from protein synthesis, yet they are of great interest in biotechnology. Aspartyl-tRNA synthetase (AspRS) can misacylate tRNA(Asp) with D-aspartate instead of its usual substrate, L-Asp. We investigate how the preference for L-Asp arises, using molecular dynamics simulations. Asp presents a special problem, having pseudosymmetry broken only by its ammonium group, and AspRS must protect not only against D-Asp, but against an "inverted" orientation where the two substrate carboxylates are swapped. We compare L-Asp and D-Asp, in both orientations, and succinate, where the ammonium group is removed and the ligand has an additional negative charge. All possible ammonium positions on the ligand are thus scanned, providing information on electrostatic interactions. As controls, we simulate a Q199E mutation, obtaining a reduction in binding free energy in agreement with experiment, and we simulate TyrRS, which can misacylate tRNA(Tyr) with D-Tyr. For both TyrRS and AspRS, we obtain a moderate binding free energy difference DeltaDeltaG between the L- and D-amino acids, in agreement with their known ability to misacylate their tRNAs. In contrast, we predict that AspRS is strongly protected against inverted L-Asp binding. For succinate, kinetic measurements reveal a DeltaDeltaG of over 5 kcal/mol, favoring L-Asp. The simulations show how chiral discriminations arises from the structures, with two AspRS conformations acting in different ways and proton uptake by nearby histidines playing a role. A complex network of charges protects AspRS against most binding errors, making the engineering of its specificity a difficult challenge.
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8
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Bernard D, Akochy PM, Bernier S, Fisette O, Brousseau OC, Chênevert R, Roy PH, Lapointe J. Inhibition by L-aspartol adenylate of a nondiscriminating aspartyl-tRNA synthetase reveals differences between the interactions of its active site with tRNA(Asp) and tRNA(Asn). J Enzyme Inhib Med Chem 2007; 22:77-82. [PMID: 17373551 DOI: 10.1080/14756360600952316] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Asparaginyl-tRNA formation in Pseudomonas aeruginosa PAO1 involves a nondiscriminating aspartyl-tRNA synthetase (ND-AspRS) which forms Asp-tRNA(Asp) and Asp-tRNA(Asn), and a tRNA-dependent amidotransferase which transamidates the latter into Asn-tRNA(Asn). We report here that the inhibition of this ND-AspRS by L-aspartol adenylate (Asp-ol-AMP), a stable analog of the natural reaction intermediate L-aspartyl adenylate, is biphasic because the aspartylation of the two tRNA substrates of ND-AspRS, tRNA(Asp) and tRNA(Asn), are inhibited with different Ki values (41 microM and 215 microM, respectively). These results reveal that the two tRNA substrates of ND-AspRS interact differently with its active site. Yeast tRNA(Asp) transcripts with some identity elements replaced by those of tRNA(Asn) have their aspartylation inhibited with Ki values different from that for the wild-type transcript. Therefore, aminoacyl adenylate analogs, which are competitive inhibitors of their cognate aminoacyl-tRNA synthetase, can be used to probe rapidly the role of various structural elements in positioning the tRNA acceptor end in the active site.
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9
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Roy H, Becker HD, Mazauric MH, Kern D. Structural elements defining elongation factor Tu mediated suppression of codon ambiguity. Nucleic Acids Res 2007; 35:3420-30. [PMID: 17478519 PMCID: PMC1904265 DOI: 10.1093/nar/gkm211] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In most prokaryotes Asn-tRNAAsn and Gln-tRNAGln are formed by amidation of aspartate and glutamate mischarged onto tRNAAsn and tRNAGln, respectively. Coexistence in the organism of mischarged Asp-tRNAAsn and Glu-tRNAGln and the homologous Asn-tRNAAsn and Gln-tRNAGln does not, however, lead to erroneous incorporation of Asp and Glu into proteins, since EF-Tu discriminates the misacylated tRNAs from the correctly charged ones. This property contrasts with the canonical function of EF-Tu, which is to non-specifically bind the homologous aa-tRNAs, as well as heterologous species formed in vitro by aminoacylation of non-cognate tRNAs. In Thermus thermophilus that forms the Asp-tRNAAsn intermediate by the indirect pathway of tRNA asparaginylation, EF-Tu must discriminate the mischarged aminoacyl-tRNAs (aa-tRNA). We show that two base pairs in the tRNA T-arm and a single residue in the amino acid binding pocket of EF-Tu promote discrimination of Asp-tRNAAsn from Asn-tRNAAsn and Asp-tRNAAsp by the protein. Our analysis suggests that these structural elements might also contribute to rejection of other mischarged aa-tRNAs formed in vivo that are not involved in peptide elongation. Additionally, these structural features might be involved in maintaining a delicate balance of weak and strong binding affinities between EF-Tu and the amino acid and tRNA moieties of other elongator aa-tRNAs.
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MESH Headings
- Base Pairing
- Codon
- Escherichia coli Proteins/metabolism
- Models, Molecular
- Peptide Elongation Factor Tu/chemistry
- Peptide Elongation Factor Tu/metabolism
- Protein Binding
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Amino Acyl/metabolism
- RNA, Transfer, Asn/chemistry
- RNA, Transfer, Asn/metabolism
- RNA, Transfer, Asp/chemistry
- RNA, Transfer, Asp/metabolism
- Thermus thermophilus/genetics
- Transfer RNA Aminoacylation
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10
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Bailly M, Giannouli S, Blaise M, Stathopoulos C, Kern D, Becker HD. A single tRNA base pair mediates bacterial tRNA-dependent biosynthesis of asparagine. Nucleic Acids Res 2006; 34:6083-94. [PMID: 17074748 PMCID: PMC1635274 DOI: 10.1093/nar/gkl622] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In many prokaryotes and in organelles asparagine and glutamine are formed by a tRNA-dependent amidotransferase (AdT) that catalyzes amidation of aspartate and glutamate, respectively, mischarged on tRNAAsn and tRNAGln. These pathways supply the deficiency of the organism in asparaginyl- and glutaminyl-tRNA synthtetases and provide the translational machinery with Asn-tRNAAsn and Gln-tRNAGln. So far, nothing is known about the structural elements that confer to tRNA the role of a specific cofactor in the formation of the cognate amino acid. We show herein, using aspartylated tRNAAsn and tRNAAsp variants, that amidation of Asp acylating tRNAAsn is promoted by the base pair U1-A72 whereas the G1-C72 pair and presence of the supernumerary nucleotide U20A in the D-loop of tRNAAsp prevent amidation. We predict, based on comparison of tRNAGln and tRNAGlu sequence alignments from bacteria using the AdT-dependent pathway to form Gln-tRNAGln, that the same combination of nucleotides also rules specific tRNA-dependent formation of Gln. In contrast, we show that the tRNA-dependent conversion of Asp into Asn by archaeal AdT is mainly mediated by nucleotides G46 and U47 of the variable region. In the light of these results we propose that bacterial and archaeal AdTs use kingdom-specific signals to catalyze the tRNA-dependent formations of Asn and Gln.
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MESH Headings
- Adenine/chemistry
- Asparagine/biosynthesis
- Base Sequence
- Kinetics
- Neisseria meningitidis/enzymology
- Nitrogenous Group Transferases/chemistry
- Nitrogenous Group Transferases/metabolism
- RNA, Archaeal/chemistry
- RNA, Archaeal/metabolism
- RNA, Bacterial/chemistry
- RNA, Bacterial/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/metabolism
- RNA, Transfer, Asn/chemistry
- RNA, Transfer, Asn/metabolism
- RNA, Transfer, Asp/chemistry
- RNA, Transfer, Asp/metabolism
- RNA, Transfer, Gln/chemistry
- RNA, Transfer, Gln/metabolism
- RNA, Transfer, Glu/chemistry
- RNA, Transfer, Glu/metabolism
- Sequence Alignment
- Species Specificity
- Substrate Specificity
- Uridine/chemistry
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11
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Müller S, Shen H, Hofmann D, Schairer HU, Kirby JR. Integration into the phage attachment site, attB, impairs multicellular differentiation in Stigmatella aurantiaca. J Bacteriol 2006; 188:1701-9. [PMID: 16484181 PMCID: PMC1426541 DOI: 10.1128/jb.188.5.1701-1709.2006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Stigmatella aurantiaca displays a complex developmental life cycle in response to starvation conditions that results in the formation of tree-like fruiting bodies capable of producing spores. The phage Mx8, first isolated from the close relative Myxococcus xanthus, is unable to infect S. aurantiaca cells and integrate into the genome. However, plasmids containing Mx8 fragments encoding the integrase and attP are able to integrate at the attB locus in the S. aurantiaca genome by site-specific recombination. After recombination between attP and attB, the S. aurantiaca cells were incapable of building normal fruiting bodies but formed clumps and fungus-like structures characteristic of intermediate stages of development displayed by the wild type. We identified two tRNA genes, trnD and trnV, encoding tRNA(Asp) and tRNA(Val), respectively, composing an operon at the attB locus of S. aurantiaca. Integration of attP-containing plasmids resulted in the incorporation of the t(Mx8) terminator sequence, in addition to a short sequence of Mx8 DNA downstream of trnD. The integrant was unable to process the trnD transcript at the normal 3' processing site and displayed a lower level of expression of the trnVD operon. In addition, several developmentally regulated proteins were no longer produced in mutants following insertion at the attB locus. We hypothesize that the integration of the t(Mx8) terminator sequence results in reduced levels of mature tRNA(Asp) and tRNA(Val) and that altered protein production during development is thereby responsible for the observed phenotype. The trnVD locus thus defines a new developmental checkpoint for Stigmatella aurantiaca.
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MESH Headings
- Attachment Sites, Microbiological/genetics
- Bacterial Proteins/metabolism
- Bacteriophages/enzymology
- Base Sequence
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Genetic Complementation Test
- Integrases/genetics
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Operon/genetics
- Operon/physiology
- Plasmids/genetics
- RNA, Transfer, Asp/genetics
- RNA, Transfer, Asp/metabolism
- RNA, Transfer, Val/genetics
- RNA, Transfer, Val/metabolism
- Sequence Alignment
- Spores, Bacterial/growth & development
- Stigmatella aurantiaca/genetics
- Stigmatella aurantiaca/physiology
- Viral Proteins/genetics
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12
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Fender A, Sauter C, Messmer M, Pütz J, Giegé R, Florentz C, Sissler M. Loss of a primordial identity element for a mammalian mitochondrial aminoacylation system. J Biol Chem 2006; 281:15980-6. [PMID: 16597625 DOI: 10.1074/jbc.m511633200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammalian mitochondria the translational machinery is of dual origin with tRNAs encoded by a simplified and rapidly evolving mitochondrial (mt) genome and aminoacyl-tRNA synthetases (aaRS) coded by the nuclear genome, and imported. Mt-tRNAs are atypical with biased sequences, size variations in loops and stems, and absence of residues forming classical tertiary interactions, whereas synthetases appear typical. This raises questions about identity elements in mt-tRNAs and adaptation of their cognate mt-aaRSs. We have explored here the human mt-aspartate system in which a prokaryotic-type AspRS, highly similar to the Escherichia coli enzyme, recognizes a bizarre tRNA(Asp). Analysis of human mt-tRNA(Asp) transcripts confirms the identity role of the GUC anticodon as in other aspartylation systems but reveals the non-involvement of position 73. This position is otherwise known as the site of a universally conserved major aspartate identity element, G73, also known as a primordial identity signal. In mt-tRNA(Asp), position 73 can be occupied by any of the four nucleotides without affecting aspartylation. Sequence alignments of various AspRSs allowed placing Gly-269 at a position occupied by Asp-220, the residue contacting G73 in the crystallographic structure of E. coli AspRS-tRNA(Asp) complex. Replacing this glycine by an aspartate renders human mt-AspRS more discriminative to G73. Restriction in the aspartylation identity set, driven by a rapid mutagenic rate of the mt-genome, suggests a reverse evolution of the mt-tRNA(Asp) identity elements in regard to its bacterial ancestor.
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13
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Frugier M, Ryckelynck M, Giegé R. tRNA-balanced expression of a eukaryal aminoacyl-tRNA synthetase by an mRNA-mediated pathway. EMBO Rep 2006; 6:860-5. [PMID: 16113655 PMCID: PMC1369159 DOI: 10.1038/sj.embor.7400481] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Revised: 06/09/2005] [Accepted: 06/09/2005] [Indexed: 11/09/2022] Open
Abstract
Aminoacylation of transfer RNAs is a key step during translation. It is catalysed by the aminoacyl-tRNA synthetases (aaRSs) and requires the specific recognition of their cognate substrates, one or several tRNAs, ATP and the amino acid. Whereas the control of certain aaRS genes is well known in prokaryotes, little is known about the regulation of eukaryotic aaRS genes. Here, it is shown that expression of AspRS is regulated in yeast by a feedback mechanism that necessitates the binding of AspRS to its messenger RNA. This regulation leads to a synchronized expression of AspRS and tRNA(Asp). The correlation between AspRS expression and mRNA(AspRS) and tRNA(Asp) concentrations, as well as the presence of AspRS in the nucleus, suggests an original regulation mechanism. It is proposed that the surplus of AspRS, not sequestered by tRNA(Asp), is imported into the nucleus where it binds to mRNA(AspRS) and thus inhibits its accumulation.
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14
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Rueda D, Hsieh J, Day-Storms JJ, Fierke CA, Walter NG. The 5' leader of precursor tRNAAsp bound to the Bacillus subtilis RNase P holoenzyme has an extended conformation. Biochemistry 2006; 44:16130-9. [PMID: 16331973 DOI: 10.1021/bi0519093] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
RNase P catalyzes the 5' maturation of transfer RNA (tRNA). RNase P from Bacillus subtilis comprises a large RNA component (130 kDa, P RNA) and a small protein subunit (14 kDa, P protein). Although P RNA alone can efficiently catalyze the maturation reaction in vitro, P protein is strictly required under physiological conditions. We have used time-resolved fluorescence resonance energy transfer on a series of donor-labeled substrates and two acceptor-labeled P proteins to determine the conformation of the pre-tRNA 5' leader relative to the protein in the holoenzyme-pre-tRNA complex. The resulting distance distribution measurements indicate that the leader binds to the holoenzyme in an extended conformation between nucleotides 3 and 7. The conformational mobility of nucleotides 5-8 in the leader is reduced, providing further evidence that these nucleotides interact with the holoenzyme. The increased fluorescence intensity and lifetime of the 5'-fluorescein label of these leaders indicate a more hydrophobic environment, consistent with the notion that such interactions occur with the central cleft of the P protein. Taken together, our data support a model where the P protein binds to the 5' leader between the fourth and seventh nucleotides upstream of the cleavage site, extending the leader and decreasing its structural dynamics. Thus, P protein acts as a wedge to separate the 5' from the 3' terminus of the pre-tRNA and to position the cleavage site in the catalytic core. These results reveal a structural basis for the P protein dependent discrimination between precursor and mature tRNAs.
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15
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Goll MG, Kirpekar F, Maggert KA, Yoder JA, Hsieh CL, Zhang X, Golic KG, Jacobsen SE, Bestor TH. Methylation of tRNAAsp by the DNA methyltransferase homolog Dnmt2. Science 2006; 311:395-8. [PMID: 16424344 DOI: 10.1126/science.1120976] [Citation(s) in RCA: 743] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The sequence and the structure of DNA methyltransferase-2 (Dnmt2) bear close affinities to authentic DNA cytosine methyltransferases. A combined genetic and biochemical approach revealed that human DNMT2 did not methylate DNA but instead methylated a small RNA; mass spectrometry showed that this RNA is aspartic acid transfer RNA (tRNA(Asp)) and that DNMT2 specifically methylated cytosine 38 in the anticodon loop. The function of DNMT2 is highly conserved, and human DNMT2 protein restored methylation in vitro to tRNA(Asp) from Dnmt2-deficient strains of mouse, Arabidopsis thaliana, and Drosophila melanogaster in a manner that was dependent on preexisting patterns of modified nucleosides. Indirect sequence recognition is also a feature of eukaryotic DNA methyltransferases, which may have arisen from a Dnmt2-like RNA methyltransferase.
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16
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Blaise M, Becker HD, Lapointe J, Cambillau C, Giegé R, Kern D. Glu-Q-tRNAAsp synthetase coded by the yadB gene, a new paralog of aminoacyl-tRNA synthetase that glutamylates tRNAAsp anticodon. Biochimie 2005; 87:847-61. [PMID: 16164993 DOI: 10.1016/j.biochi.2005.03.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Revised: 02/18/2005] [Accepted: 03/17/2005] [Indexed: 10/25/2022]
Abstract
Analysis of the completed genome sequences revealed presence in various bacteria of an open reading frame (ORF) encoding a polypeptide chain presenting important similarities with the catalytic domain of glutamyl-tRNA synthetases but deprived of the C-terminal anticodon-binding domain. This paralog of glutamyl-tRNA synthetases, the YadB protein, activates glutamate in the absence of tRNA and transfers the activated glutamate not on tRNA(Glu) but instead on tRNA(Asp). It has been shown that tRNA(Asp) is able to accept two amino acids: aspartate charged by aspartyl-tRNA synthetase and glutamate charged by YadB. The functional properties of YadB contrast with those of the canonical glutamyl-tRNA synthetases, which activate Glu only in presence of the cognate tRNA before aminoacylation of the 3'-end of tRNA. Biochemical approaches and mass spectrometry investigations revealed that YadB transfers the activated glutamate on the cyclopenthene-diol ring of the modified nucleoside queuosine posttranscriptionally inserted at the wobble position of the anticodon-loop to form glutamyl-queuosine. Unstability of the ester bond between the glutamate residue and the cyclopenthene-diol (half-life 7.5 min) explains why until now this modification escaped detection. Among Escherichia coli tRNAs containing queuosine in the wobble position, only tRNA(Asp) is substrate of YadB. Sequence comparison reveals a structural mimicry between the anticodon-stem and loop of tRNA(Asp) and the amino acid acceptor-stem of tRNA(Glu). YadB, renamed glutamyl-Q-tRNA(Asp) synthetase, constitutes the first enzyme structurally related to aminoacyl-tRNA synthetases which catalyzes a hypermodification in tRNA, and whose function seems to be conserved among prokaryotes. The discovery of glutamyl-Q-tRNA(Asp) synthetase breaks down the current paradigm according to which the catalytic domain of aminoacyl-tRNA synthetases recognizes the amino acid acceptor-stem of tRNA and aminoacylates the 3'-terminal ribose. The evolutionary significance of the existence of an aminoacyl-tRNA synthetase paralog dedicated to the hypermodification of a tRNA anticodon will be discussed.
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17
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Merino EJ, Wilkinson KA, Coughlan JL, Weeks KM. RNA structure analysis at single nucleotide resolution by selective 2'-hydroxyl acylation and primer extension (SHAPE). J Am Chem Soc 2005; 127:4223-31. [PMID: 15783204 DOI: 10.1021/ja043822v] [Citation(s) in RCA: 589] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reactivity of an RNA ribose hydroxyl is shown to be exquisitely sensitive to local nucleotide flexibility because a conformationally constrained adjacent 3'-phosphodiester inhibits formation of the deprotonated, nucleophilic oxyanion form of the 2'-hydroxyl group. Reaction with an appropriate electrophile, N-methylisatoic anhydride, to form a 2'-O-adduct thus can be used to monitor local structure at every nucleotide in an RNA. We develop a quantitative approach involving Selective 2'-Hydroxyl Acylation analyzed by Primer Extension (SHAPE) to map the structure of and to distinguish fine differences in structure for tRNAAsp transcripts at single nucleotide resolution. Modest extensions of the SHAPE approach will allow RNA structure to be monitored comprehensively and at single nucleotide resolution for RNAs of arbitrary sequence and structural complexity and under diverse solution environments.
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18
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Wilkinson KA, Merino EJ, Weeks KM. RNA SHAPE chemistry reveals nonhierarchical interactions dominate equilibrium structural transitions in tRNA(Asp) transcripts. J Am Chem Soc 2005; 127:4659-67. [PMID: 15796531 DOI: 10.1021/ja0436749] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Current models assume that RNA folding is strongly hierarchical such that the base-paired secondary structure is more stable than and forms independently of the tertiary structure. This model has been difficult to test due to the experimental inability to interrogate the local environment at every nucleotide as a comprehensive function of the RNA folding state. Reaction of an RNA 2'-hydroxyl group with N-methylisatoic anhydride to form a nucleotide 2'-ester is governed by the extent to which the nucleotide forms base pairing or tertiary interactions. Selective 2'-Hydroxyl Acylation analyzed by Primer Extension (SHAPE) is shown to be an RNA analogue of the protein hydrogen exchange experiment. Single nucleotide resolution SHAPE analysis emphasizes a complexity for the unfolding of tRNA(Asp) transcripts that is not anticipated by current models for RNA folding. We quantify six well-defined transitions for tRNA(Asp) transcripts between 35 and >75 degrees C, including asymmetric unfolding of the two strands in a single helix, multistep loss of tertiary interactions, and a multihelix conformational shift. The three lowest temperature transitions each involve coupled interactions between the secondary and tertiary structure. Thus, even for this simple RNA, multiple nonhierarchical and complex interactions dominate the equilibrium transitions most accessible from the native state.
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19
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Bonnefond L, Fender A, Rudinger-Thirion J, Giegé R, Florentz C, Sissler M. Toward the Full Set of Human Mitochondrial Aminoacyl-tRNA Synthetases: Characterization of AspRS and TyrRS†. Biochemistry 2005; 44:4805-16. [PMID: 15779907 DOI: 10.1021/bi047527z] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The human mitochondrion possesses a translational machinery devoted to the synthesis of 13 proteins. While the required tRNAs and rRNAs are produced by transcription of the mitochondrial genome, all other factors needed for protein synthesis are synthesized in the cytosol and imported. This is the case for aminoacyl-tRNA synthetases, the enzymes which esterify their cognate tRNA with the specific amino acid. The genes for the full set of cytosolic aaRSs are well defined, but only nine genes for mitochondrial synthetases are known. Here we describe the genes for human mitochondrial aspartyl- and tyrosyl-tRNA synthetases and the initial characterization of the enzymes. Both belong to the expected class of synthetases, have a dimeric organization, and aminoacylate Escherichia coli tRNAs as well as in vitro transcribed human mitochondrial tRNAs. Genes for the remaining missing synthetases were also found with the exception of glutaminyl-tRNA synthetase. Their sequence analysis confirms and further extends the view that, except for lysyl- and glycyl-tRNA synthetases, human mitochondrial and cytosolic enzymes are coded by two different sets of genes.
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20
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Fender A, Geslain R, Eriani G, Giegé R, Sissler M, Florentz C. A yeast arginine specific tRNA is a remnant aspartate acceptor. Nucleic Acids Res 2004; 32:5076-86. [PMID: 15452274 PMCID: PMC521656 DOI: 10.1093/nar/gkh843] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
High specificity in aminoacylation of transfer RNAs (tRNAs) with the help of their cognate aminoacyl-tRNA synthetases (aaRSs) is a guarantee for accurate genetic translation. Structural and mechanistic peculiarities between the different tRNA/aaRS couples, suggest that aminoacylation systems are unrelated. However, occurrence of tRNA mischarging by non-cognate aaRSs reflects the relationship between such systems. In Saccharomyces cerevisiae, functional links between arginylation and aspartylation systems have been reported. In particular, it was found that an in vitro transcribed tRNAAsp is a very efficient substrate for ArgRS. In this study, the relationship of arginine and aspartate systems is further explored, based on the discovery of a fourth isoacceptor in the yeast genome, tRNA4Arg. This tRNA has a sequence strikingly similar to that of tRNAAsp but distinct from those of the other three arginine isoacceptors. After transplantation of the full set of aspartate identity elements into the four arginine isoacceptors, tRNA4Arg gains the highest aspartylation efficiency. Moreover, it is possible to convert tRNA4Arg into an aspartate acceptor, as efficient as tRNAAsp, by only two point mutations, C38 and G73, despite the absence of the major anticodon aspartate identity elements. Thus, cryptic aspartate identity elements are embedded within tRNA4Arg. The latent aspartate acceptor capacity in a contemporary tRNAArg leads to the proposal of an evolutionary link between tRNA4Arg and tRNAAsp genes.
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MESH Headings
- Aspartic Acid/metabolism
- Base Sequence
- Evolution, Molecular
- Molecular Sequence Data
- Point Mutation
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Transfer, Arg/chemistry
- RNA, Transfer, Arg/genetics
- RNA, Transfer, Arg/metabolism
- RNA, Transfer, Asp/chemistry
- RNA, Transfer, Asp/genetics
- RNA, Transfer, Asp/metabolism
- Saccharomyces cerevisiae/genetics
- Sequence Alignment
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21
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Ador L, Jaeger S, Geslain R, Martin F, Cavarelli J, Eriani G. Mutation and evolution of the magnesium-binding site of a class II aminoacyl-tRNA synthetase. Biochemistry 2004; 43:7028-37. [PMID: 15170340 DOI: 10.1021/bi049617+] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aminoacyl-tRNA synthetases contain one or three Mg(2+) ions in their catalytic sites. In addition to their role in ATP binding, these ions are presumed to play a role in catalysis by increasing the electropositivity of the alpha-phosphate and stabilizing the pentavalent transition state. In the class II aaRS, two highly conserved carboxylate residues have been shown to participate with Mg(2+) ions in binding and coordination. It is shown here that these carboxylate residues are absolutely required for the activity of Saccharomyces cerevisiae aspartyl-tRNA synthetase. Mutants of these residues exhibit pleiotropic effects on the kinetic parameters suggesting an effect at an early stage of the aminoacylation reaction, such as the binding of ATP, Mg(2+), aspartic acid, or the amino acid activation. Despite genetic selections in an APS-knockout yeast strain, we were unable to select a single active mutant of these carboxylate residues. Nevertheless, we isolated an intragenic suppressor from a combinatorial library. The active mutant showed a second substitution close to the first one, and exhibited a significant increase of the tRNA aminoacylation rate. Structural analysis suggests that the acceptor stem of the tRNA might be repositioned to give a more productive enzyme:tRNA complex. Thus, the initial defect of the activation reaction was compensated by a significant increase of the aminoacylation rate that led to cellular complementation.
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22
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Blaise M, Becker HD, Keith G, Cambillau C, Lapointe J, Giegé R, Kern D. A minimalist glutamyl-tRNA synthetase dedicated to aminoacylation of the tRNAAsp QUC anticodon. Nucleic Acids Res 2004; 32:2768-75. [PMID: 15150343 PMCID: PMC419609 DOI: 10.1093/nar/gkh608] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Escherichia coli encodes YadB, a protein displaying 34% identity with the catalytic core of glutamyl-tRNA synthetase but lacking the anticodon-binding domain. We show that YadB is a tRNA modifying enzyme that evidently glutamylates the queuosine residue, a modified nucleoside at the wobble position of the tRNA(Asp) QUC anticodon. This conclusion is supported by a variety of biochemical data and by the inability of the enzyme to glutamylate tRNA(Asp) isolated from an E.coli tRNA-guanosine transglycosylase minus strain deprived of the capacity to exchange guanosine 34 with queuosine. Structural mimicry between the tRNA(Asp) anticodon stem and the tRNA(Glu) amino acid acceptor stem in prokaryotes encoding YadB proteins indicates that the function of these tRNA modifying enzymes, which we rename glutamyl-Q tRNA(Asp) synthetases, is conserved among prokaryotes.
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MESH Headings
- Acylation
- Anticodon/chemistry
- Anticodon/genetics
- Anticodon/metabolism
- Base Sequence
- Biological Evolution
- Conserved Sequence
- Escherichia coli/enzymology
- Escherichia coli/genetics
- Glutamate-tRNA Ligase/chemistry
- Glutamate-tRNA Ligase/genetics
- Glutamate-tRNA Ligase/metabolism
- Molecular Mimicry
- Nucleoside Q/genetics
- Nucleoside Q/metabolism
- Periodic Acid/pharmacology
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer, Asp/chemistry
- RNA, Transfer, Asp/genetics
- RNA, Transfer, Asp/metabolism
- RNA, Transfer, Glu/chemistry
- RNA, Transfer, Glu/genetics
- RNA, Transfer, Glu/metabolism
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23
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Dubois DY, Blaise M, Becker HD, Campanacci V, Keith G, Giegé R, Cambillau C, Lapointe J, Kern D. An aminoacyl-tRNA synthetase-like protein encoded by the Escherichia coli yadB gene glutamylates specifically tRNAAsp. Proc Natl Acad Sci U S A 2004; 101:7530-5. [PMID: 15096594 PMCID: PMC419640 DOI: 10.1073/pnas.0401634101] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The product of the Escherichia coli yadB gene is homologous to the N-terminal part of bacterial glutamyl-tRNA synthetases (GluRSs), including the Rossmann fold with the acceptor-binding domain and the stem-contact fold. This GluRS-like protein, which lacks the anticodon-binding domain, does not use tRNA(Glu) as substrate in vitro nor in vivo, but aminoacylates tRNA(Asp) with glutamate. The yadB gene is expressed in wild-type E. coli as an operon with the dksA gene, which encodes a protein involved in the general stress response by means of its action at the translational level. The fate of the glutamylated tRNA(Asp) is not known, but its incapacity to bind elongation factor Tu suggests that it is not involved in ribosomal protein synthesis. Genes homologous to yadB are present only in bacteria, mostly in Proteobacteria. Sequence alignments and phylogenetic analyses show that the YadB proteins form a distinct monophyletic group related to the bacterial and organellar GluRSs (alpha-type GlxRSs superfamily) with ubiquitous function as suggested by the similar functional properties of the YadB homologue from Neisseria meningitidis.
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24
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Salazar JC, Ambrogelly A, Crain PF, McCloskey JA, Söll D. A truncated aminoacyl-tRNA synthetase modifies RNA. Proc Natl Acad Sci U S A 2004; 101:7536-41. [PMID: 15096612 PMCID: PMC419641 DOI: 10.1073/pnas.0401982101] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aminoacyl-tRNA synthetases are modular enzymes composed of a central active site domain to which additional functional domains were appended in the course of evolution. Analysis of bacterial genome sequences revealed the presence of many shorter aminoacyl-tRNA synthetase paralogs. Here we report the characterization of a well conserved glutamyl-tRNA synthetase (GluRS) paralog (YadB in Escherichia coli) that is present in the genomes of >40 species of proteobacteria, cyanobacteria, and actinobacteria. The E. coli yadB gene encodes a truncated GluRS that lacks the C-terminal third of the protein and, consequently, the anticodon binding domain. Generation of a yadB disruption showed the gene to be dispensable for E. coli growth in rich and minimal media. Unlike GluRS, the YadB protein was able to activate glutamate in presence of ATP in a tRNA-independent fashion and to transfer glutamate onto tRNA(Asp). Neither tRNA(Glu) nor tRNA(Gln) were substrates. In contrast to canonical aminoacyl-tRNA, glutamate was not esterified to the 3'-terminal adenosine of tRNA(Asp). Instead, it was attached to the 2-amino-5-(4,5-dihydroxy-2-cyclopenten-1-yl) moiety of queuosine, the modified nucleoside occupying the first anticodon position of tRNA(Asp). Glutamyl-queuosine, like canonical Glu-tRNA, was hydrolyzed by mild alkaline treatment. Analysis of tRNA isolated under acidic conditions showed that this novel modification is present in normal E. coli tRNA; presumably it previously escaped detection as the standard conditions of tRNA isolation include an alkaline deacylation step that also causes hydrolysis of glutamyl-queuosine. Thus, this aminoacyl-tRNA synthetase fragment contributes to standard nucleotide modification of tRNA.
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25
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Fokine A, Lunina N, Lunin V, Urzhumtsev A. Connectivity-based ab initio phasing at different solvent levels. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2003; 59:850-8. [PMID: 12777801 DOI: 10.1107/s0907444903004359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2002] [Accepted: 02/24/2003] [Indexed: 11/10/2022]
Abstract
The connectivity-based phasing method has been applied independently to three neutron diffraction data sets obtained from the same crystal of tRNA(Asp)-aspartyl-tRNA synthetase complex but at different concentrations of D(2)O/H(2)O, thus masking different components of the crystal. The obtained low-resolution images correlate perfectly with the solvent level.
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