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Yakobov N, Mahmoudi N, Grob G, Yokokawa D, Saga Y, Kushiro T, Worrell D, Roy H, Schaller H, Senger B, Huck L, Riera Gascon G, Becker HD, Fischer F. RNA-dependent synthesis of ergosteryl-3β-O-glycine in Ascomycota expands the diversity of steryl-amino acids. J Biol Chem 2022; 298:101657. [PMID: 35131263 PMCID: PMC8913301 DOI: 10.1016/j.jbc.2022.101657] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 01/13/2022] [Accepted: 01/16/2022] [Indexed: 12/11/2022] Open
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2
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Chang CP, Chang CY, Lee YH, Lin YS, Wang CC. Divergent Alanyl-tRNA Synthetase Genes of Vanderwaltozyma polyspora Descended from a Common Ancestor through Whole-Genome Duplication Followed by Asymmetric Evolution. Mol Cell Biol 2015; 35:2242-53. [PMID: 25896914 PMCID: PMC4456443 DOI: 10.1128/mcb.00018-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 02/14/2015] [Accepted: 04/14/2015] [Indexed: 11/20/2022] Open
Abstract
Cytoplasmic and mitochondrial forms of a eukaryotic aminoacyl-tRNA synthetase (aaRS) are generally encoded by two distinct nuclear genes, one of eukaryotic origin and the other of mitochondrial origin. However, in most known yeasts, only the mitochondrial-origin alanyl-tRNA synthetase (AlaRS) gene is retained and plays a dual-functional role. Here, we present a novel scenario of AlaRS evolution in the yeast Vanderwaltozyma polyspora. V. polyspora possesses two significantly diverged AlaRS gene homologues, one encoding the cytoplasmic form and the other its mitochondrial counterpart. Clever selection of transcription and translation initiation sites enables the two isoforms to be localized and thus functional in their respective cellular compartments. However, the two isoforms can also be stably expressed and function in the reciprocal compartments by insertion or removal of a mitochondrial targeting signal. Synteny and phylogeny analyses revealed that the AlaRS homologues of V. polyspora arose from a dual-functional common ancestor through whole-genome duplication (WGD). Moreover, the mitochondrial form had higher synonymous (1.6-fold) and nonsynonymous (2.8-fold) substitution rates than did its cytoplasmic counterpart, presumably due to a lesser constraint imposed on components of the mitochondrial translational apparatus. Our study suggests that asymmetric evolution confers the divergence between the AlaRS paralogues of V. polyspora.
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Affiliation(s)
- Chia-Pei Chang
- Department of Life Sciences, National Central University, Jungli, Taiwan
| | - Chih-Yao Chang
- Department of Life Sciences, National Central University, Jungli, Taiwan
| | - Yi-Hsueh Lee
- Department of Life Sciences, National Central University, Jungli, Taiwan
| | - Yeong-Shin Lin
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Chien-Chia Wang
- Department of Life Sciences, National Central University, Jungli, Taiwan
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3
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Laporte D, Huot JL, Bader G, Enkler L, Senger B, Becker HD. Exploring the evolutionary diversity and assembly modes of multi-aminoacyl-tRNA synthetase complexes: lessons from unicellular organisms. FEBS Lett 2014; 588:4268-78. [PMID: 25315413 DOI: 10.1016/j.febslet.2014.10.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 10/03/2014] [Accepted: 10/06/2014] [Indexed: 10/24/2022]
Abstract
Aminoacyl-tRNA synthetases (aaRSs) are ubiquitous and ancient enzymes, mostly known for their essential role in generating aminoacylated tRNAs. During the last two decades, many aaRSs have been found to perform additional and equally crucial tasks outside translation. In metazoans, aaRSs have been shown to assemble, together with non-enzymatic assembly proteins called aaRSs-interacting multifunctional proteins (AIMPs), into so-called multi-synthetase complexes (MSCs). Metazoan MSCs are dynamic particles able to specifically release some of their constituents in response to a given stimulus. Upon their release from MSCs, aaRSs can reach other subcellular compartments, where they often participate to cellular processes that do not exploit their primary function of synthesizing aminoacyl-tRNAs. The dynamics of MSCs and the expansion of the aaRSs functional repertoire are features that are so far thought to be restricted to higher and multicellular eukaryotes. However, much can be learnt about how MSCs are assembled and function from apparently 'simple' organisms. Here we provide an overview on the diversity of these MSCs, their composition, mode of assembly and the functions that their constituents, namely aaRSs and AIMPs, exert in unicellular organisms.
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Affiliation(s)
- Daphné Laporte
- UMR 'Génétique Moléculaire, Génomique, Microbiologie', CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg Cedex, France
| | - Jonathan L Huot
- UMR 'Génétique Moléculaire, Génomique, Microbiologie', CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg Cedex, France
| | - Gaétan Bader
- UMR 'Génétique Moléculaire, Génomique, Microbiologie', CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg Cedex, France
| | - Ludovic Enkler
- UMR 'Génétique Moléculaire, Génomique, Microbiologie', CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg Cedex, France
| | - Bruno Senger
- UMR 'Génétique Moléculaire, Génomique, Microbiologie', CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg Cedex, France
| | - Hubert Dominique Becker
- UMR 'Génétique Moléculaire, Génomique, Microbiologie', CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg Cedex, France.
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4
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Liao CC, Lin CH, Chen SJ, Wang CC. Trans-kingdom rescue of Gln-tRNAGln synthesis in yeast cytoplasm and mitochondria. Nucleic Acids Res 2012; 40:9171-81. [PMID: 22821561 PMCID: PMC3467082 DOI: 10.1093/nar/gks689] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aminoacylation of transfer RNAGln (tRNAGln) is performed by distinct mechanisms in different kingdoms and represents the most diverged route of aminoacyl-tRNA synthesis found in nature. In Saccharomyces cerevisiae, cytosolic Gln-tRNAGln is generated by direct glutaminylation of tRNAGln by glutaminyl-tRNA synthetase (GlnRS), whereas mitochondrial Gln-tRNAGln is formed by an indirect pathway involving charging by a non-discriminating glutamyl-tRNA synthetase and the subsequent transamidation by a specific Glu-tRNAGln amidotransferase. Previous studies showed that fusion of a yeast non-specific tRNA-binding cofactor, Arc1p, to Escherichia coli GlnRS enables the bacterial enzyme to substitute for its yeast homologue in vivo. We report herein that the same fusion enzyme, upon being imported into mitochondria, substituted the indirect pathway for Gln-tRNAGln synthesis as well, despite significant differences in the identity determinants of E. coli and yeast cytosolic and mitochondrial tRNAGln isoacceptors. Fusion of Arc1p to the bacterial enzyme significantly enhanced its aminoacylation activity towards yeast tRNAGln isoacceptors in vitro. Our study provides a mechanism by which trans-kingdom rescue of distinct pathways of Gln-tRNAGln synthesis can be conferred by a single enzyme.
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Affiliation(s)
- Chih-Chi Liao
- Department of Life Sciences, National Central University, Jung-li 32001, Taiwan, Republic of China
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5
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Fischer F, Huot JL, Lorber B, Diss G, Hendrickson TL, Becker HD, Lapointe J, Kern D. The asparagine-transamidosome from Helicobacter pylori: a dual-kinetic mode in non-discriminating aspartyl-tRNA synthetase safeguards the genetic code. Nucleic Acids Res 2012; 40:4965-76. [PMID: 22362756 PMCID: PMC3367201 DOI: 10.1093/nar/gks167] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Helicobacter pylori catalyzes Asn-tRNA(Asn) formation by use of the indirect pathway that involves charging of Asp onto tRNA(Asn) by a non-discriminating aspartyl-tRNA synthetase (ND-AspRS), followed by conversion of the mischarged Asp into Asn by the GatCAB amidotransferase. We show that the partners of asparaginylation assemble into a dynamic Asn-transamidosome, which uses a different strategy than the Gln-transamidosome to prevent the release of the mischarged aminoacyl-tRNA intermediate. The complex is described by gel-filtration, dynamic light scattering and kinetic measurements. Two strategies for asparaginylation are shown: (i) tRNA(Asn) binds GatCAB first, allowing aminoacylation and immediate transamidation once ND-AspRS joins the complex; (ii) tRNA(Asn) is bound by ND-AspRS which releases the Asp-tRNA(Asn) product much slower than the cognate Asp-tRNA(Asp); this kinetic peculiarity allows GatCAB to bind and transamidate Asp-tRNA(Asn) before its release by the ND-AspRS. These results are discussed in the context of the interrelation between the Asn and Gln-transamidosomes which use the same GatCAB in H. pylori, and shed light on a kinetic mechanism that ensures faithful codon reassignment for Asn.
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Affiliation(s)
- Frédéric Fischer
- Institut de Biologie Moléculaire et Cellulaire, UPR 9002 du CNRS, Architecture et Réactivité de l'ARN, Université de Strasbourg, 15 rue René Descartes, 67084 Strasbourg Cedex, France
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6
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Huot JL, Fischer F, Corbeil J, Madore E, Lorber B, Diss G, Hendrickson TL, Kern D, Lapointe J. Gln-tRNAGln synthesis in a dynamic transamidosome from Helicobacter pylori, where GluRS2 hydrolyzes excess Glu-tRNAGln. Nucleic Acids Res 2011; 39:9306-15. [PMID: 21813455 PMCID: PMC3241645 DOI: 10.1093/nar/gkr619] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In many bacteria and archaea, an ancestral pathway is used where asparagine and glutamine are formed from their acidic precursors while covalently linked to tRNAAsn and tRNAGln, respectively. Stable complexes formed by the enzymes of these indirect tRNA aminoacylation pathways are found in several thermophilic organisms, and are called transamidosomes. We describe here a transamidosome forming Gln-tRNAGln in Helicobacter pylori, an ε-proteobacterium pathogenic for humans; this transamidosome displays novel properties that may be characteristic of mesophilic organisms. This ternary complex containing the non-canonical GluRS2 specific for Glu-tRNAGln formation, the tRNA-dependent amidotransferase GatCAB and tRNAGln was characterized by dynamic light scattering. Moreover, we observed by interferometry a weak interaction between GluRS2 and GatCAB (KD = 40 ± 5 µM). The kinetics of Glu-tRNAGln and Gln-tRNAGln formation indicate that conformational shifts inside the transamidosome allow the tRNAGln acceptor stem to interact alternately with GluRS2 and GatCAB despite their common identity elements. The integrity of this dynamic transamidosome depends on a critical concentration of tRNAGln, above which it dissociates into separate GatCAB/tRNAGln and GluRS2/tRNAGln complexes. Ester bond protection assays show that both enzymes display a good affinity for tRNAGln regardless of its aminoacylation state, and support a mechanism where GluRS2 can hydrolyze excess Glu-tRNAGln, ensuring faithful decoding of Gln codons.
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Affiliation(s)
- Jonathan L Huot
- Département de Biochimie, de Microbiologie et de Bio-informatique, PROTEO et IBIS, Université Laval, 1045 av de la Médecine, Québec, Québec, Canada
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7
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Blaise M, Fréchin M, Oliéric V, Charron C, Sauter C, Lorber B, Roy H, Kern D. Crystal structure of the archaeal asparagine synthetase: interrelation with aspartyl-tRNA and asparaginyl-tRNA synthetases. J Mol Biol 2011; 412:437-52. [PMID: 21820443 DOI: 10.1016/j.jmb.2011.07.050] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 07/19/2011] [Accepted: 07/21/2011] [Indexed: 11/28/2022]
Abstract
Asparagine synthetase A (AsnA) catalyzes asparagine synthesis using aspartate, ATP, and ammonia as substrates. Asparagine is formed in two steps: the β-carboxylate group of aspartate is first activated by ATP to form an aminoacyl-AMP before its amidation by a nucleophilic attack with an ammonium ion. Interestingly, this mechanism of amino acid activation resembles that used by aminoacyl-tRNA synthetases, which first activate the α-carboxylate group of the amino acid to form also an aminoacyl-AMP before they transfer the activated amino acid onto the cognate tRNA. In a previous investigation, we have shown that the open reading frame of Pyrococcus abyssi annotated as asparaginyl-tRNA synthetase (AsnRS) 2 is, in fact, an archaeal asparagine synthetase A (AS-AR) that evolved from an ancestral aspartyl-tRNA synthetase (AspRS). We present here the crystal structure of this AS-AR. The fold of this protein is similar to that of bacterial AsnA and resembles the catalytic cores of AspRS and AsnRS. The high-resolution structures of AS-AR associated with its substrates and end-products help to understand the reaction mechanism of asparagine formation and release. A comparison of the catalytic core of AS-AR with those of archaeal AspRS and AsnRS and with that of bacterial AsnA reveals a strong conservation. This study uncovers how the active site of the ancestral AspRS rearranged throughout evolution to transform an enzyme activating the α-carboxylate group into an enzyme that is able to activate the β-carboxylate group of aspartate, which can react with ammonia instead of tRNA.
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Affiliation(s)
- Mickaël Blaise
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, UPR 9002, 15 rue René Descartes, 67084 Strasbourg Cedex, France.
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8
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Bailly M, Blaise M, Lorber B, Thirup S, Kern D. Isolation, crystallization and preliminary X-ray analysis of the transamidosome, a ribonucleoprotein involved in asparagine formation. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:577-81. [PMID: 19478435 DOI: 10.1107/s1744309109015000] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 04/22/2009] [Indexed: 11/10/2022]
Abstract
Thermus thermophilus deprived of asparagine synthetase synthesizes Asn on tRNA(Asn) via a tRNA-dependent pathway involving a nondiscriminating aspartyl-tRNA synthetase that charges Asp onto tRNA(Asn) prior to conversion of the Asp to Asn by GatCAB, a tRNA-dependent amidotransferase. This pathway also constitutes the route of Asn-tRNA(Asn) formation by bacteria and archaea deprived of asparaginyl-tRNA synthetase. The partners involved in tRNA-dependent Asn formation in T. thermophilus assemble into a ternary complex called the transamidosome. This particule produces Asn-tRNA(Asn) in the presence of free Asp, ATP and an amido-group donor. Crystals of the transamidosome from T. thermophilus were obtained in the presence of PEG 4000 in MES-NaOH buffer pH 6.5. They belonged to the primitive monoclinic space group P2(1), with unit-cell parameters a = 115.9, b = 214.0, c = 127.8 A, beta = 93.3 degrees . A complete data set was collected to 3 A resolution. Here, the isolation and crystallization of the transamidosome from T. thermophilus and preliminary crystallographic data are reported.
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Affiliation(s)
- Marc Bailly
- UPR 9002 'Architecture et Réactivité de l'ARN', Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire du CNRS, 15 Rue René Descartes, F-67084 Strasbourg CEDEX, France
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9
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Crystal structure of glutamyl-queuosine tRNAAsp synthetase complexed with L-glutamate: structural elements mediating tRNA-independent activation of glutamate and glutamylation of tRNAAsp anticodon. J Mol Biol 2008; 381:1224-37. [PMID: 18602926 DOI: 10.1016/j.jmb.2008.06.053] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 06/13/2008] [Accepted: 06/19/2008] [Indexed: 11/24/2022]
Abstract
Glutamyl-queuosine tRNA(Asp) synthetase (Glu-Q-RS) from Escherichia coli is a paralog of the catalytic core of glutamyl-tRNA synthetase (GluRS) that catalyzes glutamylation of queuosine in the wobble position of tRNA(Asp). Despite important structural similarities, Glu-Q-RS and GluRS diverge strongly by their functional properties. The only feature common to both enzymes consists in the activation of Glu to form Glu-AMP, the intermediate of transfer RNA (tRNA) aminoacylation. However, both enzymes differ by the mechanism of selection of the cognate amino acid and by the mechanism of its activation. Whereas GluRS selects l-Glu and activates it only in the presence of the cognate tRNA(Glu), Glu-Q-RS forms Glu-AMP in the absence of tRNA. Moreover, while GluRS transfers the activated Glu to the 3' accepting end of the cognate tRNA(Glu), Glu-Q-RS transfers the activated Glu to Q34 located in the anticodon loop of the noncognate tRNA(Asp). In order to gain insight into the structural elements leading to distinct mechanisms of amino acid activation, we solved the three-dimensional structure of Glu-Q-RS complexed to Glu and compared it to the structure of the GluRS.Glu complex. Comparison of the catalytic site of Glu-Q-RS with that of GluRS, combined with binding experiments of amino acids, shows that a restricted number of residues determine distinct catalytic properties of amino acid recognition and activation by the two enzymes. Furthermore, to explore the structural basis of the distinct aminoacylation properties of the two enzymes and to understand why Glu-Q-RS glutamylates only tRNA(Asp) among the tRNAs possessing queuosine in position 34, we performed a tRNA mutational analysis to search for the elements of tRNA(Asp) that determine recognition by Glu-Q-RS. The analyses made on tRNA(Asp) and tRNA(Asn) show that the presence of a C in position 38 is crucial for glutamylation of Q34. The results are discussed in the context of the evolution and adaptation of the tRNA glutamylation system.
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10
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Deniziak M, Sauter C, Becker HD, Paulus CA, Giegé R, Kern D. Deinococcus glutaminyl-tRNA synthetase is a chimer between proteins from an ancient and the modern pathways of aminoacyl-tRNA formation. Nucleic Acids Res 2007; 35:1421-31. [PMID: 17284460 PMCID: PMC1865053 DOI: 10.1093/nar/gkl1164] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Glutaminyl-tRNA synthetase from Deinococcus radiodurans possesses a C-terminal extension of 215 residues appending the anticodon-binding domain. This domain constitutes a paralog of the Yqey protein present in various organisms and part of it is present in the C-terminal end of the GatB subunit of GatCAB, a partner of the indirect pathway of Gln-tRNAGln formation. To analyze the peculiarities of the structure–function relationship of this GlnRS related to the Yqey domain, a structure of the protein was solved from crystals diffracting at 2.3 Å and a docking model of the synthetase complexed to tRNAGln constructed. The comparison of the modeled complex with the structure of the E. coli complex reveals that all residues of E. coli GlnRS contacting tRNAGln are conserved in D. radiodurans GlnRS, leaving the functional role of the Yqey domain puzzling. Kinetic investigations and tRNA-binding experiments of full length and Yqey-truncated GlnRSs reveal that the Yqey domain is involved in tRNAGln recognition. They demonstrate that Yqey plays the role of an affinity-enhancer of GlnRS for tRNAGln acting only in cis. However, the presence of Yqey in free state in organisms lacking GlnRS, suggests that this domain may exert additional cellular functions.
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Affiliation(s)
| | | | - Hubert Dominique Becker
- *To whom correspondence should be addressed. +33 (0)3 88 41 70 41+33 (0)3 88 60 22 18 Correspondence may also be addressed to Daniel Kern. +33 (0)3 88 41 70 92 +33 (0)3 88 60 22 18;
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11
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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: 40] [Impact Index Per Article: 2.0] [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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Affiliation(s)
- Mickaël Blaise
- Département Mécanismes et Macromolécules de la Synthèse Protéique et Cristallogenèse, UPR 9002, Institut de Biologie Moléculaire et Cellulaire du CNRS, 15 Rue René Descartes, F-67084 Strasbourg Cedex, France
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12
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Campanacci V, Dubois DY, Becker HD, Kern D, Spinelli S, Valencia C, Pagot F, Salomoni A, Grisel S, Vincentelli R, Bignon C, Lapointe J, Giegé R, Cambillau C. The Escherichia coli YadB gene product reveals a novel aminoacyl-tRNA synthetase like activity. J Mol Biol 2004; 337:273-83. [PMID: 15003446 DOI: 10.1016/j.jmb.2004.01.027] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2003] [Revised: 01/08/2004] [Accepted: 01/08/2004] [Indexed: 11/23/2022]
Abstract
In the course of a structural genomics program aiming at solving the structures of Escherichia coli open reading frame products of unknown function, we have determined the structure of YadB at 1.5A using molecular replacement. The YadB protein is 298 amino acid residues long and displays 34% sequence identity with E.coli glutamyl-tRNA synthetase (GluRS). It is much shorter than GluRS, which contains 468 residues, and lacks the complete domain interacting with the tRNA anticodon loop. As E.coli GluRS, YadB possesses a Zn2+ located in the putative tRNA acceptor stem-binding domain. The YadB cluster uses cysteine residues as the first three zinc ligands, but has a weaker tyrosine ligand at the fourth position. It shares with canonical amino acid RNA synthetases a major functional feature, namely activation of the amino acid (here glutamate). It differs, however, from GluRSs by the fact that the activation step is tRNA-independent and that it does not catalyze attachment of the activated glutamate to E.coli tRNAGlu, but to another, as yet unknown tRNA. These results suggest thus a novel function, distinct from that of GluRSs, for the yadB gene family.
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Affiliation(s)
- Valérie Campanacci
- Architecture et Fonction des Macromolécules Biologiques, UMR 6098, CNRS and Universités d'Aix-Marseille I and II, 31 chemin J. Aiguier, F-13402 Marseille Cedex 20, France
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13
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Cura V, Moras D, Kern D. Sequence analysis and modular organization of threonyl-tRNA synthetase from Thermus thermophilus and its interrelation with threonyl-tRNA synthetases of other origins. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:379-93. [PMID: 10632708 DOI: 10.1046/j.1432-1327.2000.01011.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The gene encoding threonyl-tRNA synthetase (Thr-tRNA synthetase) from the extreme thermophilic eubacterium Thermus thermophilus HB8 has been cloned and sequenced. The ORF encodes a polypeptide chain of 659 amino acids (Mr 75 550) that shares strong similarities with other Thr-tRNA synthetases. Comparative analysis with the three-dimensional structure of other subclass IIa synthetases shows it to be organized into four structural modules: two N-terminal modules specific to Thr-tRNA synthetases, a catalytic core and a C-terminal anticodon-binding module. Comparison with the three-dimensional structure of Escherichia coli Thr-tRNA synthetase in complex with tRNAThr enabled identification of the residues involved in substrate binding and catalytic activity. Analysis by atomic absorption spectrometry of the enzyme overexpressed in E. coli revealed the presence in each monomer of one tightly bound zinc atom, which is essential for activity. Despite strong similarites in modular organization, Thr-tRNA synthetases diverge from other subclass IIa synthetases on the basis of their N-terminal extensions. The eubacterial and eukaryotic enzymes possess a large extension folded into two structural domains, N1 and N2, that are not significantly similar to the shorter extension of the archaebacterial enzymes. Investigation of a truncated Thr-tRNA synthetase demonstrated that domain N1 is not essential for tRNA charging. Thr-tRNA synthetase from T. thermophilus is of the eubacterial type, in contrast to other synthetases from this organism, which exhibit archaebacterial characteristics. Alignments show conservation of part of domain N2 in the C-terminal moiety of Ala-tRNA synthetases. Analysis of the nucleotide sequence upstream from the ORF showed the absence of both any anticodon-like stem-loop structure and a loop containing sequences complementary to the anticodon and the CCA end of tRNAThr. This means that the expression of Thr-tRNA synthetase in T. thermophilus is not regulated by the translational and trancriptional mechanisms described for E. coli thrS and Bacillus subtilis thrS and thrZ. Here we discuss our results in the context of evolution of the threonylation systems and of the position of T. thermophilus in the phylogenic tree.
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Affiliation(s)
- V Cura
- UPR 9004 du CNRS, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.
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14
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Abstract
Histidyl-tRNA synthetase (HisRS) is responsible for the synthesis of histidyl-transfer RNA, which is essential for the incorporation of histidine into proteins. This amino acid has uniquely moderate basic properties and is an important group in many catalytic functions of enzymes. A compilation of currently known primary structures of HisRS shows that the subunits of these homo-dimeric enzymes consist of 420-550 amino acid residues. This represents a relatively short chain length among aminoacyl-tRNA synthetases (aaRS), whose peptide chain sizes range from about 300 to 1100 amino acid residues. The crystal structures of HisRS from two organisms and their complexes with histidine, histidyl-adenylate and histidinol with ATP have been solved. HisRS from Escherichia coli and Thermus thermophilus are very similar dimeric enzymes consisting of three domains: the N-terminal catalytic domain containing the six-stranded antiparallel beta-sheet and the three motifs characteristic of class II aaRS, a HisRS-specific helical domain inserted between motifs 2 and 3 that may contact the acceptor stem of the tRNA, and a C-terminal alpha/beta domain that may be involved in the recognition of the anticodon stem and loop of tRNA(His). The aminoacylation reaction follows the standard two-step mechanism. HisRS also belongs to the group of aaRS that can rapidly synthesize diadenosine tetraphosphate, a compound that is suspected to be involved in several regulatory mechanisms of cell metabolism. Many analogs of histidine have been tested for their properties as substrates or inhibitors of HisRS, leading to the elucidation of structure-activity relationships concerning configuration, importance of the carboxy and amino group, and the nature of the side chain. HisRS has been found to act as a particularly important antigen in autoimmune diseases such as rheumatic arthritis or myositis. Successful attempts have been made to identify epitopes responsible for the complexation with such auto-antibodies.
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Affiliation(s)
- W Freist
- Max-Planck-Institut für experimentelle Medizin, Abteilung Molekulare Biologie Neuronaler Signale, Göttingen, Germany
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15
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Mazauric MH, Reinbolt J, Lorber B, Ebel C, Keith G, Giegé R, Kern D. An example of non-conservation of oligomeric structure in prokaryotic aminoacyl-tRNA synthetases. Biochemical and structural properties of glycyl-tRNA synthetase from Thermus thermophilus. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 241:814-26. [PMID: 8944770 DOI: 10.1111/j.1432-1033.1996.00814.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glycyl-tRNA synthetase (Gly-tRNA synthetase) from Thermus thermophilus was purified to homogeneity and with high yield using a five-step purification procedure in amounts sufficient to solve its crystallographic structure [Logan, D.T., Mazauric, M.-H., Kern, D. & Moras, D. (1995) EMBO J. 14, 4156-4167]. Molecular-mass determinations of the native and denatured protein indicate an oligomeric structure of the alpha 2 type consistent with that found for eukaryotic Gly-tRNA synthetases (yeast and Bombyx mori), but different from that of Gly-tRNA synthetases from mesophilic prokaryotes (Escherichia coli and Bacillus brevis) which are alpha 2 beta 2 tetramers. N-terminal sequencing of the polypeptide chain reveals significant identity, reaching 50% with those of the eukaryotic enzymes (B. mori, Homo sapiens, yeast and Caenorhabditis elegans) but no significant identity was found with both alpha and beta chains of the prokaryotic enzymes (E. coli, Haemophilus influenzae and Coxiella burnetii) albeit the enzyme is deprived of the N-terminal extension characterizing eukaryotic synthetases. Thus, the thermophilic Gly-tRNA synthetase combines strong structural homologies of eukaryotic Gly-tRNA synthetases with a feature of prokaryotic synthetases. Heat-stability measurements show that this synthetase keeps its ATP-PPi exchange and aminoacylation activities up to 70 degrees C. Glycyladenylate strongly protects the enzyme against thermal inactivation at higher temperatures. Unexpectedly, tRNA(Gly) does not induce protection. Cross-aminoacylations reveal that the thermophilic Gly-tRNA synthetase charges heterologous E. coli tRNA(gly(GCC)) and tRNA(Gly(GCC)) and yeast tRNA(Gly(GCC)) as efficiently as T. thermophilus tRNA(Gly). All these aminoacylation reactions are characterized by similar activation energies as deduced from Arrhenius plots. Therefore, contrary to the E. coli and H. sapiens Gly-tRNA synthetases, the prokaryotic thermophilic enzyme does not possess a strict species specificity. The results are discussed in the context of the three-dimensional structure of the synthetase and in the view of the particular evolution of the glycinylation systems.
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Affiliation(s)
- M H Mazauric
- UPR 9002 du CNRS, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France
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16
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Airas RK. Differences in the magnesium dependences of the class I and class II aminoacyl-tRNA synthetases from Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 240:223-31. [PMID: 8797857 DOI: 10.1111/j.1432-1033.1996.0223h.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The magnesium dependences of the ATP/PPi exchange and tRNA aminoacylation of reactions were measured for six aminoacyl-tRNA synthetases (isoleucyl-, tyrosyl- and arginyl-tRNA synthetases from class I, and histidyl-, lysyl- and phenylalanyl-tRNA synthetases from class II). The measured values were subjected to best-fit analyses using sum square error calculations between the data and the calculated curves in order to find the mode of participation of the Mg2+ and to optimize the sets of the kinetic constants. The following four dependences were observed: the class II synthetases require three Mg2+ for the activation reaction (including the one in MgATP), but the class I synthetases require only one Mg2+ (in MgATP); in class II synthetases both MgPPi and Mg2PPi participate in the pyrophosphorolysis of the aminoacyl adenylate. Arginyl-tRNA synthetase from class I also shows a better fit if also Mg2PPi reacts, but in the isoleucyl- and tyrosyl-tRNA synthetases only MgPPi but not Mg2PPi is used in the pyrophosphorolysis. Different synthetases have different requirements for the tRNA-bound Mg2+ and spermidine, independent of the enzyme class. 1-4 Mg2+ or spermidines are required in the best fit models. At the end of the reaction in all the synthetases analysed the dissociation of Mg2+ from the product aminoacyl-tRNA essentially enhances the subsequent dissociation of the aminoacyl-tRNA from the enzyme. The binding of ATP to the E. aminoacyl-tRNA complex also speeds up the dissociation of the aminoacyl-tRNA from most of these enzymes.
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Affiliation(s)
- R K Airas
- Department of Biochemistry, University of Turku, Finland
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17
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Ganoza MC, Aoki H, Burkhardt N, Murphy BJ. The ribosome as affinity matrix': efficient purification scheme for translation factors. Biochimie 1996; 78:51-61. [PMID: 8725011 DOI: 10.1016/0300-9084(96)81329-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A convenient method to purify each of the non-ribosomal proteins required to translate a native mRNA in vitro is described. In this scheme, the ribosome is used as an 'affinity' matrix to selectively elute the non-ribosomal proteins required for translation that are bound to these particles. Different sets of these proteins can be eluted with solutions of Mg2+ and NH4+ of various concentrations from either 70S, or 30S and 50S particles. A scheme for the purification of each initiation, elongation and release factor and 20 aminoacyl-tRNA synthetases is described. Specific examples of the purification of the initiation (IF-1, IF-2, IF-3) and elongation (EF-Tu and EF-G) factors and for a protein called 'rescue', which affects the association of native ribosomal subunits, are given. A scheme for the purification of EF-P, which stimulates peptide-bond synthesis and one of the W proteins, which permit reconstitution of translation is also described. The procedure markedly simplifies the isolation, in homogeneous form, of all the non-ribosomal proteins required to reconstruct translation.
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Affiliation(s)
- M C Ganoza
- Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada
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18
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Aoki H, Yaworsky PJ, Patel SD, Margolin-Brzezinski D, Park KS, Ganoza MC. The asparaginyl-tRNA synthetase gene encodes one of the complementing factors for thermosensitive translation in the Escherichia coli mutant strain, N4316. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:511-21. [PMID: 1425658 DOI: 10.1111/j.1432-1033.1992.tb17315.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Escherichia coli strain N4316 is a mutant that exhibits temperature-sensitive growth at 43 degrees C and temperature-sensitive translation in vivo and in vitro. Extracts of the mutant produce an aberrant pattern of translation products of MS2 bacteriophage RNA. Previous work has shown that a protein, called 'rescue', isolated from the parental strain partly corrects the defective translation in vitro. Here we report the purification to homogeneity of a second factor from ribosomal eluates of the wild-type parental strain; the purified protein is a homodimer of 54 kDa. The partial sequence of the second protein was determined, and a recombinant plasmid was isolated based on its ability to complement the temperature-sensitive growth phenotype of the mutant at the non-permissive temperatures. The cloned gene was sequenced, mapped to the 20.9-min region of the E. coli chromosome and shown to code for a 466-amino-acid protein with a molecular mass of 52 kDa. Analysis of the DNA sequence and the correspondence to that of the partial protein sequence has identified the complementing factor as asparaginyl-tRNA synthetase. Marker rescue experiments indicate that the asnS mutation in N4316 resides within the motif 2 domain of the synthetase. A potential role of this synthetase in restoring normal protein synthesis with respect to ribosomal frameshifting, read-through of nonsense codons and protein copy number is discussed.
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Affiliation(s)
- H Aoki
- Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada
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19
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Lin SX, Shi JP, Cheng XD, Wang YL. Arginyl-tRNA synthetase from Escherichia coli, purification by affinity chromatography, properties, and steady-state kinetics. Biochemistry 1988; 27:6343-8. [PMID: 3064807 DOI: 10.1021/bi00417a022] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A Blue Sephadex G-150 affinity column adsorbs the arginyl-tRNA synthetase of Escherichia coli K12 and purifies it with high efficiency. The relatively low enzyme content was conveniently purified by DEAE-cellulose chromatography, affinity chromatography, and fast protein liquid chromatography to a preparation with high activity capable of catalyzing the esterification of about 23,000 nmol of arginine to the cognate tRNA per milligram of enzyme within 1 min, at 37 degrees C, pH 7.4. The turnover number is about 27 s-1. The purification was about 1200-fold, and the overall yield was more than 30%. The enzyme has a single polypeptide chain of about Mr 70,000 and binds arginine and tRNA with 1:1 stoichiometry. For the aminoacylation reaction, the Km values at pH 7.4, 37 degrees C, for various substrates were determined: 12 microM, 0.9 mM, and 2.5 microM for arginine, ATP, and tRNA, respectively. The Km value for cognate tRNA is higher than those of most of the aminoacyl-tRNA synthetase systems so far reported. The ATP-PPi exchange reaction proceeds only in the presence of arginine-specific tRNA. The Km values of the exchange at pH 7.2, 37 degrees C, are 0.11 mM, 2.9 mM, and 0.5 mM for arginine, ATP, and PPi, respectively, with a turnover number of 40 s-1. The pH dependence shows that the reaction is favored toward slightly acidic conditions where the aminoacylation is relatively depressed.
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Affiliation(s)
- S X Lin
- Shanghai Institute of Biochemistry, Academia Sinica, China
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20
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Theobald A, Springer M, Grunberg-Manago M, Ebel JP, Giege R. Tertiary structure of Escherichia coli tRNA(3Thr) in solution and interaction of this tRNA with the cognate threonyl-tRNA synthetase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 175:511-24. [PMID: 2457500 DOI: 10.1111/j.1432-1033.1988.tb14223.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The solution structure of Escherichia coli tRNA(3Thr) (anticodon GGU) and the residues of this tRNA in contact with the alpha 2 dimeric threonyl-tRNA synthetase were studied by chemical and enzymatic footprinting experiments. Alkylation of phosphodiester bonds by ethylnitrosourea and of N-7 positions in guanosines and N-3 positions in cytidines by dimethyl sulphate as well as carbethoxylation of N-7 positions in adenosines by diethyl pyrocarbonate were conducted on different conformers of tRNA(3Thr). The enzymatic structural probes were nuclease S1 and the cobra venom ribonuclease. Results will be compared to those of three other tRNAs, tRNA(Asp), tRNA(Phe) and tRNA(Trp), already mapped with these probes. The reactivity of phosphates towards ethylnitrosourea of the unfolded tRNA was compared to that of the native molecule. The alkylation pattern of tRNA(3Thr) shows some similarities to that of yeast tRNA(Phe) and mammalian tRNA(Trp), especially in the D-arm (positions 19 and 24) and with tRNA(Trp), at position 50, the junction between the variable region and the T-stem. In the T-loop, tRNA(3Thr), similarly to the three other tRNAs, shows protections against alkylation at phosphates 59 and 60. However, tRNA(3Thr) is unique as far as very strong protections are also found for phosphates 55 to 58 in the T-loop. Compared with yeast tRNA(Asp), the main differences in reactivity concern phosphates 19, 24 and 50. Mapping of bases with dimethyl sulphate and diethyl pyrocarbonate reveal conformational similarities with yeast tRNA(Phe). A striking conformational feature of tRNA(3Thr) is found in the 3'-side of its anticodon stem, where G40, surrounded by two G residues, is alkylated under native conditions, in contrast to other G residues in stem regions of tRNAs which are unreactive when sandwiched between two purines. This data is indicative of a perturbed helical conformation in the anticodon stem at the level of the 30-40 base pairs. Footprinting experiments, with chemical and enzymatic probes, on the tRNA complexed with its cognate threonyl-tRNA synthetase indicate significant protections in the anticodon stem and loop region, in the extra-loop, and in the amino acid accepting region. The involvement of the anticodon of tRNA(3Thr) in the recognition process with threonyl-tRNA synthetase was demonstrated by nuclease S1 mapping and by the protection of G34 and G35 against alkylation by dimethyl sulphate. These data are discussed in the light of the tRNA/synthetase recognition problem and of the structural and functional properties of the tRNA-like structure present in the operator region of the thrS mRNA.
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Affiliation(s)
- A Theobald
- Institut de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Strasbourg, France
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21
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Lorber B, Kern D, Mejdoub H, Boulanger Y, Reinbolt J, Giege R. The microheterogeneity of the crystallizable yeast cytoplasmic aspartyl-tRNA synthetase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 165:409-17. [PMID: 3297688 DOI: 10.1111/j.1432-1033.1987.tb11454.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Yeast aspartyl-tRNA synthetase is a dimeric enzyme (alpha 2, Mr 125,000) which can be crystallized either alone or complexed with tRNAAsp. When analyzed by electrophoretic methods, the pure enzyme presents structural heterogeneities even when recovered from crystals. Up to three enzyme populations could be identified by polyacrylamide gel electrophoresis and more than ten by isoelectric focusing. They have similar molecular masses and mainly differ in their charge. All are fully active. This microheterogeneity is also revealed by ion-exchange chromatography and chromatofocusing. Several levels of heterogeneity have been defined. A first type, which is reversible, is linked to redox effects and/or to conformational states of the protein. A second one, revealed by immunological methods, is generated by partial and differential proteolysis occurring during enzyme purification from yeast cells harvested in growth phase. As demonstrated by end-group analysis, the fragmentation concerns exclusively the N-terminal end of the enzyme. The main cleavage points are Gln-19, Val-20 and Gly-26. Six minor cuts are observed between positions 14 and 33. The present data are discussed in the perspective of the crystallographic studies on aspartyl-tRNA synthetase.
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23
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Ratinaud MH, Thomes JC, Julien R. Glutamyl-tRNA synthetases from wheat. Isolation and characterization of three dimeric enzymes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1983; 135:471-7. [PMID: 6617644 DOI: 10.1111/j.1432-1033.1983.tb07675.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Three dimeric glutamyl-tRNA synthetases (GluRS) were isolated from extracts of quiescent wheat germ and wheat chloroplasts. The chloroplast enzyme (Mr = 110 000), called GluRS C, exhibits a prokaryotic (Escherichia coli) tRNA specificity. Two enzymes were found in the quiescent germ and were separated on phosphocellulose P11: one called GluRS P, probably the mitochondrial enzyme, has the same tRNA specificity as GluRS C; the other, called GluRS E, has eukaryotic (wheat germ) tRNA specificity. Both enzymes exhibit a molecular weight close to 160 000. Each of these enzymes co-eluate on hydroxyapatite and phosphocellulose chromatographies with an unstable active monomer whose molecular weight is approximately half that of the corresponding dimer. Two assumptions are discussed about these monomers.
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24
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Sander G. Ribosomal protein L1 from Escherichia coli. Its role in the binding of tRNA to the ribosome and in elongation factor g-dependent gtp hydrolysis. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)44610-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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25
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Abstract
Isoelectric points and isoelectric focusing behaviour of 10 highly purified eukaryotic aminoacyl-tRNA synthetases from 3 sources, Saccharomyces cerevisiae, Euglena gracilis and Phaseolus vulgaris were examined. The pI-values measured on polyacrylamide gels under native conditions are situated between pH 5.0-7.5. A microheterogeneity was observed for 9 enzymes appearing otherwise homogeneous on gel electrophoresis. A compilation of the isoelectric points of aminoacyl-tRNA synthetases is given and literature data are compared with our experimental results.
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26
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Fromant M, Fayat G, Laufer P, Blanquet S. Affinity chromatography of aminoacyl-tRNA syntheses on agarose-hexyl-adenosine-5'-phosphate. Biochimie 1981; 63:541-53. [PMID: 7020774 DOI: 10.1016/s0300-9084(81)80087-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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27
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Kern D, Giegé R, Ebel JP. Purification and some properties of alanyl- and leucyl-tRNA synthetases from baker's yeast. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 653:83-90. [PMID: 7013809 DOI: 10.1016/0005-2787(81)90106-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Alanyl- and leucyl-tRNA synthetases from baker's yeast were purified to homogeneity in the presence of the protease inhibitor phenylmethylsulfonyl fluoride. Both consist of single polypeptide chains of 118 000 and 125 000 daltons, respectively, as determined by polyacrylamide gel electrophoresis under denaturing conditions. The monomeric structure of leucyl-tRNA synthetase differs from the dimeric one obtained previously in the absence of protease inhibitors. This illustrates the sensitivity of the synthetases to proteolytic actions and indicates that native structures can only be obtained under optimal protecting conditions. Alanyl- and leucyl-tRNA synthetases differ with respect to pH optimum (6.5 and 8.5, respectively), Michaelis constant for amino acid (1 mM and 0.03, respectively) and in the rate-limiting step for the tRNA aminoacylation reaction. Whereas the catalytic step itself was rate-limiting for alanyl-tRNA synthetase, a step occurring after this was rate-limiting for leucyl-tRNA synthetase.
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