1
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de Crécy-Lagard V, Hutinet G, Cediel-Becerra JDD, Yuan Y, Zallot R, Chevrette MG, Ratnayake RMMN, Jaroch M, Quaiyum S, Bruner S. Biosynthesis and function of 7-deazaguanine derivatives in bacteria and phages. Microbiol Mol Biol Rev 2024; 88:e0019923. [PMID: 38421302 PMCID: PMC10966956 DOI: 10.1128/mmbr.00199-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024] Open
Abstract
SUMMARYDeazaguanine modifications play multifaceted roles in the molecular biology of DNA and tRNA, shaping diverse yet essential biological processes, including the nuanced fine-tuning of translation efficiency and the intricate modulation of codon-anticodon interactions. Beyond their roles in translation, deazaguanine modifications contribute to cellular stress resistance, self-nonself discrimination mechanisms, and host evasion defenses, directly modulating the adaptability of living organisms. Deazaguanine moieties extend beyond nucleic acid modifications, manifesting in the structural diversity of biologically active natural products. Their roles in fundamental cellular processes and their presence in biologically active natural products underscore their versatility and pivotal contributions to the intricate web of molecular interactions within living organisms. Here, we discuss the current understanding of the biosynthesis and multifaceted functions of deazaguanines, shedding light on their diverse and dynamic roles in the molecular landscape of life.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
- University of Florida Genetics Institute, Gainesville, Florida, USA
| | - Geoffrey Hutinet
- Department of Biology, Haverford College, Haverford, Pennsylvania, USA
| | | | - Yifeng Yuan
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Rémi Zallot
- Department of Life Sciences, Manchester Metropolitan University, Manchester, United Kingdom
| | - Marc G. Chevrette
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | | | - Marshall Jaroch
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Samia Quaiyum
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Steven Bruner
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
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2
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Sievers K, Neumann P, Sušac L, Da Vela S, Graewert M, Trowitzsch S, Svergun D, Tampé R, Ficner R. Structural and functional insights into tRNA recognition by human tRNA guanine transglycosylase. Structure 2024; 32:316-327.e5. [PMID: 38181786 DOI: 10.1016/j.str.2023.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 07/06/2023] [Accepted: 12/08/2023] [Indexed: 01/07/2024]
Abstract
Eukaryotic tRNA guanine transglycosylase (TGT) is an RNA-modifying enzyme which catalyzes the base exchange of the genetically encoded guanine 34 of tRNAsAsp,Asn,His,Tyr for queuine, a hypermodified 7-deazaguanine derivative. Eukaryotic TGT is a heterodimer comprised of a catalytic and a non-catalytic subunit. While binding of the tRNA anticodon loop to the active site is structurally well understood, the contribution of the non-catalytic subunit to tRNA binding remained enigmatic, as no complex structure with a complete tRNA was available. Here, we report a cryo-EM structure of eukaryotic TGT in complex with a complete tRNA, revealing the crucial role of the non-catalytic subunit in tRNA binding. We decipher the functional significance of these additional tRNA-binding sites, analyze solution state conformation, flexibility, and disorder of apo TGT, and examine conformational transitions upon tRNA binding.
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Affiliation(s)
- Katharina Sievers
- Department of Molecular Structural Biology, GZMB, University of Göttingen, 37077 Göttingen, Germany
| | - Piotr Neumann
- Department of Molecular Structural Biology, GZMB, University of Göttingen, 37077 Göttingen, Germany
| | - Lukas Sušac
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, 60438 Frankfurt/Main, Germany
| | - Stefano Da Vela
- European Molecular Biology Laboratory, Hamburg Outstation, EMBL c/o DESY, 22607 Hamburg, Germany
| | - Melissa Graewert
- European Molecular Biology Laboratory, Hamburg Outstation, EMBL c/o DESY, 22607 Hamburg, Germany
| | - Simon Trowitzsch
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, 60438 Frankfurt/Main, Germany
| | - Dmitri Svergun
- European Molecular Biology Laboratory, Hamburg Outstation, EMBL c/o DESY, 22607 Hamburg, Germany
| | - Robert Tampé
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, 60438 Frankfurt/Main, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, GZMB, University of Göttingen, 37077 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37075 Göttingen, Germany.
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3
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Sun Y, Piechotta M, Naarmann-de Vries I, Dieterich C, Ehrenhofer-Murray A. Detection of queuosine and queuosine precursors in tRNAs by direct RNA sequencing. Nucleic Acids Res 2023; 51:11197-11212. [PMID: 37811872 PMCID: PMC10639084 DOI: 10.1093/nar/gkad826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 09/15/2023] [Accepted: 09/28/2023] [Indexed: 10/10/2023] Open
Abstract
Queuosine (Q) is a complex tRNA modification found in bacteria and eukaryotes at position 34 of four tRNAs with a GUN anticodon, and it regulates the translational efficiency and fidelity of the respective codons that differ at the Wobble position. In bacteria, the biosynthesis of Q involves two precursors, preQ0 and preQ1, whereas eukaryotes directly obtain Q from bacterial sources. The study of queuosine has been challenging due to the limited availability of high-throughput methods for its detection and analysis. Here, we have employed direct RNA sequencing using nanopore technology to detect the modification of tRNAs with Q and Q precursors. These modifications were detected with high accuracy on synthetic tRNAs as well as on tRNAs extracted from Schizosaccharomyces pombe and Escherichia coli by comparing unmodified to modified tRNAs using the tool JACUSA2. Furthermore, we present an improved protocol for the alignment of raw sequence reads that gives high specificity and recall for tRNAs ex cellulo that, by nature, carry multiple modifications. Altogether, our results show that 7-deazaguanine-derivatives such as queuosine are readily detectable using direct RNA sequencing. This advancement opens up new possibilities for investigating these modifications in native tRNAs, furthering our understanding of their biological function.
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Affiliation(s)
- Yu Sun
- Institut für Biologie, Lebenswissenschaftliche Fakultät, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
| | - Michael Piechotta
- Klaus Tschira Institute for Integrative Computational Cardiology, University Hospital Heidelberg, Heidelberg, Germany; Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), University Hospital, Heidelberg, Germany; German Centre for Cardiovascular Research (DZHK)-Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Isabel Naarmann-de Vries
- Klaus Tschira Institute for Integrative Computational Cardiology, University Hospital Heidelberg, Heidelberg, Germany; Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), University Hospital, Heidelberg, Germany; German Centre for Cardiovascular Research (DZHK)-Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Christoph Dieterich
- Klaus Tschira Institute for Integrative Computational Cardiology, University Hospital Heidelberg, Heidelberg, Germany; Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), University Hospital, Heidelberg, Germany; German Centre for Cardiovascular Research (DZHK)-Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Ann E Ehrenhofer-Murray
- Institut für Biologie, Lebenswissenschaftliche Fakultät, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
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4
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Hallberg ZF, Seth EC, Thevasundaram K, Taga ME. Comparative Analysis of Corrinoid Profiles across Host-Associated and Environmental Samples. Biochemistry 2022; 61:2791-2796. [PMID: 36037062 DOI: 10.1021/acs.biochem.2c00367] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Vitamin B12 (the cyanated form of cobalamin cofactors) is best known for its essential role in human health. In addition to its function in human metabolism, cobalamin also plays important roles in microbial metabolism and can impact microbial community function. Cobalamin is a member of the structurally diverse family of cofactors known as cobamides that are produced exclusively by certain prokaryotes. Cobamides are considered shared nutrients in microbial communities because the majority of bacteria that possess cobamide-dependent enzymes cannot synthesize cobamides de novo. Furthermore, different microbes have evolved metabolic specificity for particular cobamides, and therefore, the availability of cobamides in the environment is important for cobamide-dependent microbes. Determining the cobamides present in an environment of interest is essential for understanding microbial metabolic interactions. By examining the abundances of different cobamides in diverse environments, including 10 obtained in this study, we find that, contrary to its preeminence in human metabolism, cobalamin is relatively rare in many microbial habitats. Comparison of cobamide profiles of mammalian gastrointestinal samples and wood-feeding insects reveals that host-associated cobamide abundances vary and that fecal cobamide profiles differ from those of their host gastrointestinal tracts. Environmental cobamide profiles obtained from aquatic, soil, and contaminated groundwater samples reveal that the cobamide compositions of environmental samples are highly variable. As the only commercially available cobamide, cobalamin is routinely supplied during microbial culturing efforts. However, these findings suggest that cobamides specific to a given microbiome may yield greater insight into nutrient utilization and physiological processes that occur in these habitats.
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Affiliation(s)
- Zachary F Hallberg
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, California 94720, United States
| | - Erica C Seth
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, California 94720, United States
| | - Kersh Thevasundaram
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, California 94720, United States
| | - Michiko E Taga
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, California 94720, United States
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5
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Sievers K, Welp L, Urlaub H, Ficner R. Structural and functional insights into human tRNA guanine transgylcosylase. RNA Biol 2021; 18:382-396. [PMID: 34241577 DOI: 10.1080/15476286.2021.1950980] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The eukaryotic tRNA guanine transglycosylase (TGT) is an RNA modifying enzyme incorporating queuine, a hypermodified guanine derivative, into the tRNAsAsp,Asn,His,Tyr. While both subunits of the functional heterodimer have been crystallized individually, much of our understanding of its dimer interface or recognition of a target RNA has been inferred from its more thoroughly studied bacterial homolog. However, since bacterial TGT, by incorporating queuine precursor preQ1, deviates not only in function, but as a homodimer, also in its subunit architecture, any inferences regarding the subunit association of the eukaryotic heterodimer or the significance of its unique catalytically inactive subunit are based on unstable footing. Here, we report the crystal structure of human TGT in its heterodimeric form and in complex with a 25-mer stem loop RNA, enabling detailed analysis of its dimer interface and interaction with a minimal substrate RNA. Based on a model of bound tRNA, we addressed a potential functional role of the catalytically inactive subunit QTRT2 by UV-crosslinking and mutagenesis experiments, identifying the two-stranded βEβF-sheet of the QTRT2 subunit as an additional RNA-binding motif.
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Affiliation(s)
- Katharina Sievers
- Department of Molecular Structural Biology, University of Göttingen, Göttingen, Germany
| | - Luisa Welp
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, University of Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (Mbexc), University of Göttingen, Göttingen, Germany
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6
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Winther KS, Sørensen MA, Svenningsen SL. Polyamines are Required for tRNA Anticodon Modification in Escherichia coli. J Mol Biol 2021; 433:167073. [PMID: 34058151 DOI: 10.1016/j.jmb.2021.167073] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/19/2021] [Accepted: 05/23/2021] [Indexed: 11/25/2022]
Abstract
Biogenic polyamines are natural aliphatic polycations formed from amino acids by biochemical pathways that are highly conserved from bacteria to humans. Their cellular concentrations are carefully regulated and dysregulation causes severe cell growth defects. Polyamines have high affinity for nucleic acids and are known to interact with mRNA, tRNA and rRNA to stimulate the translational machinery, but the exact molecular mechanism(s) for this stimulus is still unknown. Here we exploit that Escherichia coli is viable in the absence of polyamines, including the universally conserved putrescine and spermidine. Using global macromolecule labelling approaches we find that ribosome efficiency is reduced by 50-70% in the absence of polyamines and this reduction is caused by slow translation elongation speed. The low efficiency causes rRNA and multiple tRNA species to be overproduced in the absence of polyamines, suggesting an impact on the feedback regulation of stable RNA transcription. Importantly, we find that polyamine deficiency affects both tRNA levels and tRNA modification patterns. Specifically, a large fraction of tRNAhis, tRNAtyr and tRNAasn lack the queuosine modification in the anticodon "wobble" base, which can be reversed by addition of polyamines to the growth medium. In conclusion, we demonstrate that polyamines are needed for modification of specific tRNA, possibly by facilitating the interaction with modification enzymes.
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Affiliation(s)
| | - Michael Askvad Sørensen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark
| | - Sine Lo Svenningsen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark
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7
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Edwards AM, Addo MA, Dos Santos PC. Extracurricular Functions of tRNA Modifications in Microorganisms. Genes (Basel) 2020; 11:genes11080907. [PMID: 32784710 PMCID: PMC7466049 DOI: 10.3390/genes11080907] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 07/29/2020] [Accepted: 08/02/2020] [Indexed: 12/29/2022] Open
Abstract
Transfer RNAs (tRNAs) are essential adaptors that mediate translation of the genetic code. These molecules undergo a variety of post-transcriptional modifications, which expand their chemical reactivity while influencing their structure, stability, and functionality. Chemical modifications to tRNA ensure translational competency and promote cellular viability. Hence, the placement and prevalence of tRNA modifications affects the efficiency of aminoacyl tRNA synthetase (aaRS) reactions, interactions with the ribosome, and transient pairing with messenger RNA (mRNA). The synthesis and abundance of tRNA modifications respond directly and indirectly to a range of environmental and nutritional factors involved in the maintenance of metabolic homeostasis. The dynamic landscape of the tRNA epitranscriptome suggests a role for tRNA modifications as markers of cellular status and regulators of translational capacity. This review discusses the non-canonical roles that tRNA modifications play in central metabolic processes and how their levels are modulated in response to a range of cellular demands.
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8
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Meyer B, Immer C, Kaiser S, Sharma S, Yang J, Watzinger P, Weiß L, Kotter A, Helm M, Seitz HM, Kötter P, Kellner S, Entian KD, Wöhnert J. Identification of the 3-amino-3-carboxypropyl (acp) transferase enzyme responsible for acp3U formation at position 47 in Escherichia coli tRNAs. Nucleic Acids Res 2020; 48:1435-1450. [PMID: 31863583 PMCID: PMC7026641 DOI: 10.1093/nar/gkz1191] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 12/10/2019] [Accepted: 12/11/2019] [Indexed: 02/06/2023] Open
Abstract
tRNAs from all domains of life contain modified nucleotides. However, even for the experimentally most thoroughly characterized model organism Escherichia coli not all tRNA modification enzymes are known. In particular, no enzyme has been found yet for introducing the acp3U modification at position 47 in the variable loop of eight E. coli tRNAs. Here we identify the so far functionally uncharacterized YfiP protein as the SAM-dependent 3-amino-3-carboxypropyl transferase catalyzing this modification and thereby extend the list of known tRNA modification enzymes in E. coli. Similar to the Tsr3 enzymes that introduce acp modifications at U or m1Ψ nucleotides in rRNAs this protein contains a DTW domain suggesting that acp transfer reactions to RNA nucleotides are a general function of DTW domain containing proteins. The introduction of the acp3U-47 modification in E. coli tRNAs is promoted by the presence of the m7G-46 modification as well as by growth in rich medium. However, a deletion of the enzymes responsible for the modifications at position 46 and 47 in the variable loop of E. coli tRNAs did not lead to a clearly discernible phenotype suggesting that these two modifications play only a minor role in ensuring the proper function of tRNAs in E. coli.
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Affiliation(s)
- Britta Meyer
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Carina Immer
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Steffen Kaiser
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5, 81377 Munich, Germany
| | - Sunny Sharma
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany.,Department of Cell Biology and Neurosciences, Rutgers University, Piscataway, NJ 08854, USA
| | - Jun Yang
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany.,Department of Cell Biology and Neurosciences, Rutgers University, Piscataway, NJ 08854, USA
| | - Peter Watzinger
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Lena Weiß
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Annika Kotter
- Institute of Pharmacy and Biochemistry, Johannes-Gutenberg-Universität Mainz, Staudingerweg 5, 55128 Mainz, Germany
| | - Mark Helm
- Institute of Pharmacy and Biochemistry, Johannes-Gutenberg-Universität Mainz, Staudingerweg 5, 55128 Mainz, Germany
| | - Hans-Michael Seitz
- Institute for Geosciences, Research Unit Mineralogy, and Frankfurt Isotope and Element Research Center (FIERCE), Goethe-Universität Frankfurt, Altenhöferallee 1, 60438 Frankfurt/M., Germany
| | - Peter Kötter
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Stefanie Kellner
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5, 81377 Munich, Germany
| | - Karl-Dieter Entian
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Jens Wöhnert
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany.,Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
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9
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Barraud P, Tisné C. To be or not to be modified: Miscellaneous aspects influencing nucleotide modifications in tRNAs. IUBMB Life 2019; 71:1126-1140. [PMID: 30932315 PMCID: PMC6850298 DOI: 10.1002/iub.2041] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 03/10/2019] [Indexed: 12/12/2022]
Abstract
Transfer RNAs (tRNAs) are essential components of the cellular protein synthesis machineries, but are also implicated in many roles outside translation. To become functional, tRNAs, initially transcribed as longer precursor tRNAs, undergo a tightly controlled biogenesis process comprising the maturation of their extremities, removal of intronic sequences if present, addition of the 3'-CCA amino-acid accepting sequence, and aminoacylation. In addition, the most impressive feature of tRNA biogenesis consists in the incorporation of a large number of posttranscriptional chemical modifications along its sequence. The chemical nature of these modifications is highly diverse, with more than hundred different modifications identified in tRNAs to date. All functions of tRNAs in cells are controlled and modulated by modifications, making the understanding of the mechanisms that determine and influence nucleotide modifications in tRNAs an essential point in tRNA biology. This review describes the different aspects that determine whether a certain position in a tRNA molecule is modified or not. We describe how sequence and structural determinants, as well as the presence of prior modifications control modification processes. We also describe how environmental factors and cellular stresses influence the level and/or the nature of certain modifications introduced in tRNAs, and report situations where these dynamic modulations of tRNA modification levels are regulated by active demodification processes. © 2019 IUBMB Life, 71(8):1126-1140, 2019.
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Affiliation(s)
- Pierre Barraud
- Expression génétique microbienneInstitut de biologie physico‐chimique (IBPC), UMR 8261, CNRS, Université Paris DiderotParisFrance
| | - Carine Tisné
- Expression génétique microbienneInstitut de biologie physico‐chimique (IBPC), UMR 8261, CNRS, Université Paris DiderotParisFrance
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10
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Bridwell-Rabb J, Grell TAJ, Drennan CL. A Rich Man, Poor Man Story of S-Adenosylmethionine and Cobalamin Revisited. Annu Rev Biochem 2019; 87:555-584. [PMID: 29925255 DOI: 10.1146/annurev-biochem-062917-012500] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
S-adenosylmethionine (AdoMet) has been referred to as both "a poor man's adenosylcobalamin (AdoCbl)" and "a rich man's AdoCbl," but today, with the ever-increasing number of functions attributed to each cofactor, both appear equally rich and surprising. The recent characterization of an organometallic species in an AdoMet radical enzyme suggests that the line that differentiates them in nature will be constantly challenged. Here, we compare and contrast AdoMet and cobalamin (Cbl) and consider why Cbl-dependent AdoMet radical enzymes require two cofactors that are so similar in their reactivity. We further carry out structural comparisons employing the recently determined crystal structure of oxetanocin-A biosynthetic enzyme OxsB, the first three-dimensional structural data on a Cbl-dependent AdoMet radical enzyme. We find that the structural motifs responsible for housing the AdoMet radical machinery are largely conserved, whereas the motifs responsible for binding additional cofactors are much more varied.
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Affiliation(s)
- Jennifer Bridwell-Rabb
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; , .,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Present address: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Tsehai A J Grell
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; , .,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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11
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Lewis JK, Bruender NA, Bandarian V. QueE: A Radical SAM Enzyme Involved in the Biosynthesis of 7-Deazapurine Containing Natural Products. Methods Enzymol 2018; 606:95-118. [PMID: 30097106 PMCID: PMC6484087 DOI: 10.1016/bs.mie.2018.05.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
7-Carboxy-7-deazaguanine (CDG) is a common intermediate in the biosynthesis of 7-deazapurine-containing natural products. The biosynthesis of CDG from GTP requires three enzymes: GTP cyclohydrolase I, 6-carboxy-5,6,7,8-tetrahydropterin (CPH4) synthase, and CDG synthase (QueE). QueE is a member of the radical S-adenosyl-l-methionine (SAM) superfamily and catalyzes the SAM-dependent radical-mediated ring contraction of CPH4 to generate CDG. This chapter focuses on methods to reconstitute the activity of QueE in vitro.
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Affiliation(s)
- Julia K Lewis
- Department of Chemistry, University of Utah, Salt Lake City, UT, United States
| | - Nathan A Bruender
- Department of Chemistry and Biochemistry, St. Cloud State University, St. Cloud, MN, United States
| | - Vahe Bandarian
- Department of Chemistry, University of Utah, Salt Lake City, UT, United States.
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12
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Behrens C, Biela I, Petiot-Bécard S, Botzanowski T, Cianférani S, Sager CP, Klebe G, Heine A, Reuter K. Homodimer Architecture of QTRT2, the Noncatalytic Subunit of the Eukaryotic tRNA-Guanine Transglycosylase. Biochemistry 2018; 57:3953-3965. [DOI: 10.1021/acs.biochem.8b00294] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Christina Behrens
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany
| | - Inna Biela
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany
| | - Stéphanie Petiot-Bécard
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, IPHC UMR 7178, 67000 Strasbourg, France
| | - Thomas Botzanowski
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, IPHC UMR 7178, 67000 Strasbourg, France
| | - Sarah Cianférani
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, IPHC UMR 7178, 67000 Strasbourg, France
| | - Christoph P. Sager
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany
| | - Gerhard Klebe
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany
| | - Andreas Heine
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany
| | - Klaus Reuter
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany
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13
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Ehrmann FR, Stojko J, Metz A, Debaene F, Barandun LJ, Heine A, Diederich F, Cianférani S, Reuter K, Klebe G. Soaking suggests "alternative facts": Only co-crystallization discloses major ligand-induced interface rearrangements of a homodimeric tRNA-binding protein indicating a novel mode-of-inhibition. PLoS One 2017; 12:e0175723. [PMID: 28419165 PMCID: PMC5395182 DOI: 10.1371/journal.pone.0175723] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 03/30/2017] [Indexed: 01/05/2023] Open
Abstract
For the efficient pathogenesis of Shigella, the causative agent of bacillary dysentery, full functionality of tRNA-guanine transglycosylase (TGT) is mandatory. TGT performs post-transcriptional modifications of tRNAs in the anticodon loop taking impact on virulence development. This suggests TGT as a putative target for selective anti-shigellosis drug therapy. Since bacterial TGT is only functional as homodimer, its activity can be inhibited either by blocking its active site or by preventing dimerization. Recently, we discovered that in some crystal structures obtained by soaking the full conformational adaptation most likely induced in solution upon ligand binding is not displayed. Thus, soaked structures may be misleading and suggest irrelevant binding modes. Accordingly, we re-investigated these complexes by co-crystallization. The obtained structures revealed large conformational rearrangements not visible in the soaked complexes. They result from spatial perturbations in the ribose-34/phosphate-35 recognition pocket and, consequently, an extended loop-helix motif required to prevent access of water molecules into the dimer interface loses its geometric integrity. Thermodynamic profiles of ligand binding in solution indicate favorable entropic contributions to complex formation when large conformational adaptations in the dimer interface are involved. Native MS titration experiments reveal the extent to which the homodimer is destabilized in the presence of each inhibitor. Unexpectedly, one ligand causes a complete rearrangement of subunit packing within the homodimer, never observed in any other TGT crystal structure before. Likely, this novel twisted dimer is catalytically inactive and, therefore, suggests that stabilizing this non-productive subunit arrangement may be used as a further strategy for TGT inhibition.
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Affiliation(s)
| | - Johann Stojko
- Laboratoire de Spectrométrie de Masse Bio-Organique, Université de Strasbourg, CNRS, IPHC UMR 7178, Strasbourg, France
| | - Alexander Metz
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - François Debaene
- Laboratoire de Spectrométrie de Masse Bio-Organique, Université de Strasbourg, CNRS, IPHC UMR 7178, Strasbourg, France
| | | | - Andreas Heine
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | | | - Sarah Cianférani
- Laboratoire de Spectrométrie de Masse Bio-Organique, Université de Strasbourg, CNRS, IPHC UMR 7178, Strasbourg, France
| | - Klaus Reuter
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Gerhard Klebe
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail:
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14
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Zheng C, Black KA, Dos Santos PC. Diverse Mechanisms of Sulfur Decoration in Bacterial tRNA and Their Cellular Functions. Biomolecules 2017; 7:biom7010033. [PMID: 28327539 PMCID: PMC5372745 DOI: 10.3390/biom7010033] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 03/10/2017] [Accepted: 03/16/2017] [Indexed: 01/01/2023] Open
Abstract
Sulfur-containing transfer ribonucleic acids (tRNAs) are ubiquitous biomolecules found in all organisms that possess a variety of functions. For decades, their roles in processes such as translation, structural stability, and cellular protection have been elucidated and appreciated. These thionucleosides are found in all types of bacteria; however, their biosynthetic pathways are distinct among different groups of bacteria. Considering that many of the thio-tRNA biosynthetic enzymes are absent in Gram-positive bacteria, recent studies have addressed how sulfur trafficking is regulated in these prokaryotic species. Interestingly, a novel proposal has been given for interplay among thionucleosides and the biosynthesis of other thiocofactors, through participation of shared-enzyme intermediates, the functions of which are impacted by the availability of substrate as well as metabolic demand of thiocofactors. This review describes the occurrence of thio-modifications in bacterial tRNA and current methods for detection of these modifications that have enabled studies on the biosynthesis and functions of S-containing tRNA across bacteria. It provides insight into potential modes of regulation and potential evolutionary events responsible for divergence in sulfur metabolism among prokaryotes.
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Affiliation(s)
- Chenkang Zheng
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27101, USA.
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15
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Zallot R, Ross R, Chen WH, Bruner SD, Limbach PA, de Crécy-Lagard V. Identification of a Novel Epoxyqueuosine Reductase Family by Comparative Genomics. ACS Chem Biol 2017; 12:844-851. [PMID: 28128549 PMCID: PMC5495094 DOI: 10.1021/acschembio.6b01100] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
![]()
The reduction of epoxyqueuosine (oQ)
is the last step in the synthesis
of the tRNA modification queuosine (Q). While the epoxyqueuosine reductase
(EC 1.17.99.6) enzymatic activity was first described 30 years ago,
the encoding gene queG was only identified in Escherichia coli in 2011. Interestingly, queG is absent from a large number of sequenced genomes that harbor Q
synthesis or salvage genes, suggesting the existence of an alternative
epoxyqueuosine reductase in these organisms. By analyzing phylogenetic
distributions, physical gene clustering, and fusions, members of the
Domain of Unknown Function 208 (DUF208) family were predicted to encode
for an alternative epoxyqueuosine reductase. This prediction was validated
with genetic methods. The Q modification is present in Lactobacillus
salivarius, an organism missing queG but
harboring the duf208 gene. Acinetobacter
baylyi ADP1 is one of the few organisms that harbor both
QueG and DUF208, and deletion of both corresponding genes was required
to observe the absence of Q and the accumulation of oQ in tRNA. Finally,
the conversion oQ to Q was restored in an E. coli queG mutant by complementation with plasmids harboring duf208 genes from different bacteria. Members of the DUF208 family are
not homologous to QueG enzymes, and thus, duf208 is
a non-orthologous replacement of queG. We propose
to name DUF208 encoding genes as queH. While QueH
contains conserved cysteines that could be involved in the coordination
of a Fe/S center in a similar fashion to what has been identified
in QueG, no cobalamin was identified associated with recombinant QueH
protein.
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Affiliation(s)
- Rémi Zallot
- Department
of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611, United States
| | - Robert Ross
- Rieveschl
Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Wei-Hung Chen
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Steven D. Bruner
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Patrick A. Limbach
- Rieveschl
Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Valérie de Crécy-Lagard
- Department
of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611, United States
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16
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part V. {[Fe4S4](SCysγ)4} proteins. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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17
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Zallot R, Yuan Y, de Crécy-Lagard V. The Escherichia coli COG1738 Member YhhQ Is Involved in 7-Cyanodeazaguanine (preQ₀) Transport. Biomolecules 2017; 7:E12. [PMID: 28208705 PMCID: PMC5372724 DOI: 10.3390/biom7010012] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 01/27/2017] [Accepted: 01/30/2017] [Indexed: 11/17/2022] Open
Abstract
Queuosine (Q) is a complex modification of the wobble base in tRNAs with GUN anticodons. The full Q biosynthesis pathway has been elucidated in Escherichia coli. FolE, QueD, QueE and QueC are involved in the conversion of guanosine triphosphate (GTP) to 7-cyano-7-deazaguanine (preQ₀), an intermediate of increasing interest for its central role in tRNA and DNA modification and secondary metabolism. QueF then reduces preQ₀ to 7-aminomethyl-7-deazaguanine (preQ₁). PreQ₁ is inserted into tRNAs by tRNA guanine(34) transglycosylase (TGT). The inserted base preQ₁ is finally matured to Q by two additional steps involving QueA and QueG or QueH. Most Eubacteria harbor the full set of Q synthesis genes and are predicted to synthesize Q de novo. However, some bacteria only encode enzymes involved in the second half of the pathway downstream of preQ₀ synthesis, including the signature enzyme TGT. Different patterns of distribution of the queF, tgt, queA and queG or queH genes are observed, suggesting preQ₀, preQ₁ or even the queuine base being salvaged in specific organisms. Such salvage pathways require the existence of specific 7-deazapurine transporters that have yet to be identified. The COG1738 family was identified as a candidate for a missing preQ₀/preQ₁ transporter in prokaryotes, by comparative genomics analyses. The existence of Q precursor salvage was confirmed for the first time in bacteria, in vivo, through an indirect assay. The involvement of the COG1738 in salvage of a Q precursor was experimentally validated in Escherichia coli, where it was shown that the COG1738 family member YhhQ is essential for preQ₀ transport.
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Affiliation(s)
- Rémi Zallot
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
| | - Yifeng Yuan
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
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18
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Hutinet G, Swarjo MA, de Crécy-Lagard V. Deazaguanine derivatives, examples of crosstalk between RNA and DNA modification pathways. RNA Biol 2016; 14:1175-1184. [PMID: 27937735 PMCID: PMC5699537 DOI: 10.1080/15476286.2016.1265200] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Seven-deazapurine modifications were thought to be highly specific of tRNAs, but have now been discovered in DNA of phages and of phylogenetically diverse bacteria, illustrating the plasticity of these modification pathways. The intermediate 7-cyano-7-deazaguanine (preQ0) is a shared precursor in the pathways leading to the insetion of 7-deazapurine derivatives in both tRNA and DNA. It is also used as an intermediate in the synthesis of secondary metabolites such as toyocamacin. The presence of 7-deazapurine in DNA is proposed to be a protection mechanism against endonucleases. This makes preQ0 a metabolite of underappreaciated but central importance.
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Affiliation(s)
- Geoffrey Hutinet
- a Department of Microbiology and Cell Science , University of Florida , Gainesville , FL , USA
| | - Manal A Swarjo
- b Department of Chemistry and Biochemistry , San Diego State University , San Diego , CA , USA
| | - Valérie de Crécy-Lagard
- a Department of Microbiology and Cell Science , University of Florida , Gainesville , FL , USA
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19
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Dowling DP, Miles ZD, Köhrer C, Maiocco SJ, Elliott SJ, Bandarian V, Drennan CL. Molecular basis of cobalamin-dependent RNA modification. Nucleic Acids Res 2016; 44:9965-9976. [PMID: 27638883 PMCID: PMC5175355 DOI: 10.1093/nar/gkw806] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 08/30/2016] [Accepted: 09/03/2016] [Indexed: 12/22/2022] Open
Abstract
Queuosine (Q) was discovered in the wobble position of a transfer RNA (tRNA) 47 years ago, yet the final biosynthetic enzyme responsible for Q-maturation, epoxyqueuosine (oQ) reductase (QueG), was only recently identified. QueG is a cobalamin (Cbl)-dependent, [4Fe-4S] cluster-containing protein that produces the hypermodified nucleoside Q in situ on four tRNAs. To understand how QueG is able to perform epoxide reduction, an unprecedented reaction for a Cbl-dependent enzyme, we have determined a series of high resolution structures of QueG from Bacillus subtilis. Our structure of QueG bound to a tRNATyr anticodon stem loop shows how this enzyme uses a HEAT-like domain to recognize the appropriate anticodons and position the hypermodified nucleoside into the enzyme active site. We find Q bound directly above the Cbl, consistent with a reaction mechanism that involves the formation of a covalent Cbl-tRNA intermediate. Using protein film electrochemistry, we show that two [4Fe-4S] clusters adjacent to the Cbl have redox potentials in the range expected for Cbl reduction, suggesting how Cbl can be activated for nucleophilic attack on oQ. Together, these structural and electrochemical data inform our understanding of Cbl dependent nucleic acid modification.
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Affiliation(s)
- Daniel P Dowling
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zachary D Miles
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Caroline Köhrer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Sean J Elliott
- Department of Chemistry, Boston University, Boston, MA 02215, USA
| | - Vahe Bandarian
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA .,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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20
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Abstract
Transfer RNA (tRNA) from all organisms on this planet contains modified nucleosides, which are derivatives of the four major nucleosides. tRNA from Escherichia coli/Salmonella enterica contains 31 different modified nucleosides, which are all, except for one (Queuosine[Q]), synthesized on an oligonucleotide precursor, which through specific enzymes later matures into tRNA. The corresponding structural genes for these enzymes are found in mono- and polycistronic operons, the latter of which have a complex transcription and translation pattern. The syntheses of some of them (e.g.,several methylated derivatives) are catalyzed by one enzyme, which is position and base specific, but synthesis of some have a very complex biosynthetic pathway involving several enzymes (e.g., 2-thiouridines, N6-threonyladenosine [t6A],and Q). Several of the modified nucleosides are essential for viability (e.g.,lysidin, t6A, 1-methylguanosine), whereas deficiency in others induces severe growth defects. However, some have no or only a small effect on growth at laboratory conditions. Modified nucleosides that are present in the anticodon loop or stem have a fundamental influence on the efficiency of charging the tRNA, reading cognate codons, and preventing missense and frameshift errors. Those, which are present in the body of the tRNA, have a primarily stabilizing effect on the tRNA. Thus, the ubiquitouspresence of these modified nucleosides plays a pivotal role in the function of the tRNA by their influence on the stability and activity of the tRNA.
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21
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Payne KAP, Fisher K, Sjuts H, Dunstan MS, Bellina B, Johannissen L, Barran P, Hay S, Rigby SEJ, Leys D. Epoxyqueuosine Reductase Structure Suggests a Mechanism for Cobalamin-dependent tRNA Modification. J Biol Chem 2015; 290:27572-81. [PMID: 26378237 PMCID: PMC4646009 DOI: 10.1074/jbc.m115.685693] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Indexed: 01/11/2023] Open
Abstract
Queuosine (Q) is a hypermodified RNA base that replaces guanine in the wobble positions of 5′-GUN-3′ tRNA molecules. Q is exclusively made by bacteria, and the corresponding queuine base is a micronutrient salvaged by eukaryotic species. The final step in Q biosynthesis is the reduction of the epoxide precursor, epoxyqueuosine, to yield the Q cyclopentene ring. The epoxyqueuosine reductase responsible, QueG, shares distant homology with the cobalamin-dependent reductive dehalogenase (RdhA), however the role played by cobalamin in QueG catalysis has remained elusive. We report the solution and structural characterization of Streptococcus thermophilus QueG, revealing the enzyme harbors a redox chain consisting of two [4Fe-4S] clusters and a cob(II)alamin in the base-off form, similar to RdhAs. In contrast to the shared redox chain architecture, the QueG active site shares little homology with RdhA, with the notable exception of a conserved Tyr that is proposed to function as a proton donor during reductive dehalogenation. Docking of an epoxyqueuosine substrate suggests the QueG active site places the substrate cyclopentane moiety in close proximity of the cobalt. Both the Tyr and a conserved Asp are implicated as proton donors to the epoxide leaving group. This suggests that, in contrast to the unusual carbon-halogen bond chemistry catalyzed by RdhAs, QueG acts via Co-C bond formation. Our study establishes the common features of Class III cobalamin-dependent enzymes, and reveals an unexpected diversity in the reductive chemistry catalyzed by these enzymes.
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Affiliation(s)
- Karl A P Payne
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Karl Fisher
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Hanno Sjuts
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Mark S Dunstan
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Bruno Bellina
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Linus Johannissen
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Perdita Barran
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Sam Hay
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Stephen E J Rigby
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - David Leys
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
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22
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Miles ZD, Myers WK, Kincannon WM, Britt RD, Bandarian V. Biochemical and Spectroscopic Studies of Epoxyqueuosine Reductase: A Novel Iron-Sulfur Cluster- and Cobalamin-Containing Protein Involved in the Biosynthesis of Queuosine. Biochemistry 2015; 54:4927-35. [PMID: 26230193 DOI: 10.1021/acs.biochem.5b00335] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Queuosine is a hypermodified nucleoside present in the wobble position of tRNAs with a 5'-GUN-3' sequence in their anticodon (His, Asp, Asn, and Tyr). The 7-deazapurine core of the base is synthesized de novo in prokaryotes from guanosine 5'-triphosphate in a series of eight sequential enzymatic transformations, the final three occurring on tRNA. Epoxyqueuosine reductase (QueG) catalyzes the final step in the pathway, which entails the two-electron reduction of epoxyqueuosine to form queuosine. Biochemical analyses reveal that this enzyme requires cobalamin and two [4Fe-4S] clusters for catalysis. Spectroscopic studies show that the cobalamin appears to bind in a base-off conformation, whereby the dimethylbenzimidazole moiety of the cofactor is removed from the coordination sphere of the cobalt but not replaced by an imidazole side chain, which is a hallmark of many cobalamin-dependent enzymes. The bioinformatically identified residues are shown to have a role in modulating the primary coordination sphere of cobalamin. These studies provide the first demonstration of the cofactor requirements for QueG.
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Affiliation(s)
- Zachary D Miles
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - William K Myers
- ‡Department of Chemistry, University of California-Davis, Davis, California 95616, United States
| | - William M Kincannon
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - R David Britt
- ‡Department of Chemistry, University of California-Davis, Davis, California 95616, United States
| | - Vahe Bandarian
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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23
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Björk GR, Hagervall TG. Transfer RNA Modification: Presence, Synthesis, and Function. EcoSal Plus 2014; 6. [PMID: 26442937 DOI: 10.1128/ecosalplus.esp-0007-2013] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Indexed: 06/05/2023]
Abstract
Transfer RNA (tRNA) from all organisms on this planet contains modified nucleosides, which are derivatives of the four major nucleosides. tRNA from Escherichia coli/Salmonella enterica serovar Typhimurium contains 33 different modified nucleosides, which are all, except one (Queuosine [Q]), synthesized on an oligonucleotide precursor, which by specific enzymes later matures into tRNA. The structural genes for these enzymes are found in mono- and polycistronic operons, the latter of which have a complex transcription and translation pattern. The synthesis of the tRNA-modifying enzymes is not regulated similarly, and it is not coordinated to that of their substrate, the tRNA. The synthesis of some of them (e.g., several methylated derivatives) is catalyzed by one enzyme, which is position and base specific, whereas synthesis of some has a very complex biosynthetic pathway involving several enzymes (e.g., 2-thiouridines, N 6-cyclicthreonyladenosine [ct6A], and Q). Several of the modified nucleosides are essential for viability (e.g., lysidin, ct6A, 1-methylguanosine), whereas the deficiency of others induces severe growth defects. However, some have no or only a small effect on growth at laboratory conditions. Modified nucleosides that are present in the anticodon loop or stem have a fundamental influence on the efficiency of charging the tRNA, reading cognate codons, and preventing missense and frameshift errors. Those that are present in the body of the tRNA primarily have a stabilizing effect on the tRNA. Thus, the ubiquitous presence of these modified nucleosides plays a pivotal role in the function of the tRNA by their influence on the stability and activity of the tRNA.
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Affiliation(s)
- Glenn R Björk
- Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden
| | - Tord G Hagervall
- Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden
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24
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Hazra AB, Tran JLA, Crofts TS, Taga ME. Analysis of substrate specificity in CobT homologs reveals widespread preference for DMB, the lower axial ligand of vitamin B(12). ACTA ACUST UNITED AC 2013; 20:1275-85. [PMID: 24055005 DOI: 10.1016/j.chembiol.2013.08.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 07/02/2013] [Accepted: 08/05/2013] [Indexed: 10/26/2022]
Abstract
Cobamides such as vitamin B12 (cobalamin) are produced exclusively by prokaryotes and used by many other organisms as cofactors for diverse metabolic processes. Cobamides are cobalt-containing tetrapyrroles with upper and lower axial ligands. The structure of the lower ligand varies in cobamides produced by different bacteria. We investigated the biochemical basis of this structural variability by exploring the reactivity of homologs of CobT, the enzyme responsible for activating lower ligand bases for incorporation into cobamides. Our results show that CobT enzymes can activate a range of lower ligand substrates, and the majority of the enzymes tested preferentially attach 5,6-dimethylbenzimidazole (DMB), the lower ligand of cobalamin. This suggests that many bacteria that synthesize cobamides other than cobalamin in pure culture may produce cobalamin in mixed communities by attaching DMB when it is available in the environment.
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Affiliation(s)
- Amrita B Hazra
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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25
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Thoma I, Carell T. Total Synthesis of the Hypermodified tRNA Nucleoside Epoxyqueuosine. European J Org Chem 2013. [DOI: 10.1002/ejoc.201300586] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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26
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Biela I, Tidten-Luksch N, Immekus F, Glinca S, Nguyen TXP, Gerber HD, Heine A, Klebe G, Reuter K. Investigation of specificity determinants in bacterial tRNA-guanine transglycosylase reveals queuine, the substrate of its eucaryotic counterpart, as inhibitor. PLoS One 2013; 8:e64240. [PMID: 23704982 PMCID: PMC3660597 DOI: 10.1371/journal.pone.0064240] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/09/2013] [Indexed: 11/19/2022] Open
Abstract
Bacterial tRNA-guanine transglycosylase (Tgt) catalyses the exchange of the genetically encoded guanine at the wobble position of tRNAs(His,Tyr,Asp,Asn) by the premodified base preQ1, which is further converted to queuine at the tRNA level. As eucaryotes are not able to synthesise queuine de novo but acquire it through their diet, eucaryotic Tgt directly inserts the hypermodified base into the wobble position of the tRNAs mentioned above. Bacterial Tgt is required for the efficient pathogenicity of Shigella sp, the causative agent of bacillary dysentery and, hence, it constitutes a putative target for the rational design of anti-Shigellosis compounds. Since mammalian Tgt is known to be indirectly essential to the conversion of phenylalanine to tyrosine, it is necessary to create substances which only inhibit bacterial but not eucaryotic Tgt. Therefore, it seems of utmost importance to study selectivity-determining features within both types of proteins. Homology models of Caenorhabditis elegans Tgt and human Tgt suggest that the replacement of Cys158 and Val233 in bacterial Tgt (Zymomonas mobilis Tgt numbering) by valine and accordingly glycine in eucaryotic Tgt largely accounts for the different substrate specificities. In the present study we have created mutated variants of Z. mobilis Tgt in order to investigate the impact of a Cys158Val and a Val233Gly exchange on catalytic activity and substrate specificity. Using enzyme kinetics and X-ray crystallography, we gained evidence that the Cys158Val mutation reduces the affinity to preQ1 while leaving the affinity to guanine unaffected. The Val233Gly exchange leads to an enlarged substrate binding pocket, that is necessary to accommodate queuine in a conformation compatible with the intermediately covalently bound tRNA molecule. Contrary to our expectations, we found that a priori queuine is recognised by the binding pocket of bacterial Tgt without, however, being used as a substrate.
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Affiliation(s)
- Inna Biela
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Naomi Tidten-Luksch
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Florian Immekus
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Serghei Glinca
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | | | - Hans-Dieter Gerber
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Andreas Heine
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Gerhard Klebe
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Klaus Reuter
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
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Carell T, Brandmayr C, Hienzsch A, Müller M, Pearson D, Reiter V, Thoma I, Thumbs P, Wagner M. Struktur und Funktion nicht-kanonischer Nukleobasen. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201201193] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Carell T, Brandmayr C, Hienzsch A, Müller M, Pearson D, Reiter V, Thoma I, Thumbs P, Wagner M. Structure and function of noncanonical nucleobases. Angew Chem Int Ed Engl 2012; 51:7110-31. [PMID: 22744788 DOI: 10.1002/anie.201201193] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 05/07/2012] [Indexed: 12/19/2022]
Abstract
DNA and RNA contain, next to the four canonical nucleobases, a number of modified nucleosides that extend their chemical information content. RNA is particularly rich in modifications, which is obviously an adaptation to their highly complex and variable functions. In fact, the modified nucleosides and their chemical structures establish a second layer of information which is of central importance to the function of the RNA molecules. Also the chemical diversity of DNA is greater than originally thought. Next to the four canonical bases, the DNA of higher organisms contains a total of four epigenetic bases: m(5) dC, hm(5) dC, f(5) dC und ca(5) dC. While all cells of an organism contain the same genetic material, their vastly different function and properties inside complex higher organisms require the controlled silencing and activation of cell-type specific genes. The regulation of the underlying silencing and activation process requires an additional layer of epigenetic information, which is clearly linked to increased chemical diversity. This diversity is provided by the modified non-canonical nucleosides in both DNA and RNA.
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Affiliation(s)
- Thomas Carell
- Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany.
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29
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McCarty RM, Bandarian V. Biosynthesis of pyrrolopyrimidines. Bioorg Chem 2012; 43:15-25. [PMID: 22382038 DOI: 10.1016/j.bioorg.2012.01.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 01/05/2012] [Accepted: 01/06/2012] [Indexed: 12/17/2022]
Abstract
Pyrrolopyrimidine containing compounds, also known as 7-deazapurines, are a collection of purine-based metabolites that have been isolated from a variety of biological sources and have diverse functions which range from secondary metabolism to RNA modification. To date, nearly 35 compounds with the common 7-deazapurine core structure have been described. This article will illustrate the structural diversity of these compounds and review the current state of knowledge on the biosynthetic pathways that give rise to them.
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Affiliation(s)
- Reid M McCarty
- Department of Chemistry and Biochemistry, University of Arizona, 1041 E. Lowell St., Tucson, AZ 85721, USA
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30
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Paiva JB, Penha Filho RAC, Junior AB, Lemos MVF. Requirement for cobalamin by Salmonella enterica serovars Typhimurium, Pullorum, Gallinarum and Enteritidis during infection in chickens. Braz J Microbiol 2011; 42:1409-18. [PMID: 24031771 PMCID: PMC3768742 DOI: 10.1590/s1517-838220110004000024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 01/26/2011] [Accepted: 05/16/2011] [Indexed: 11/22/2022] Open
Abstract
Salmonella enterica serovar Typhimurium synthesizes cobalamin (vitamin B12) only during anaerobiosis. Two percent of the S. Typhimurium genome is devoted to the synthesis and uptake of vitamin B12 and to B12-dependent reactions. To understand the requirement for cobalamin synthesis better, we constructed mutants of Salmonella serovars Enteritidis and Pullorum that are double-defective in cobalamin biosynthesis (ΔcobSΔcbiA). We compared the virulence of these mutants to that of their respective wild type strains and found no impairment in their ability to cause disease in chickens. We then assessed B12 production in these mutants and their respective wild type strains, as well as in S. Typhimurium ΔcobSΔcbiA, Salmonella Gallinarum ΔcobSΔcbiA, and their respective wild type strains. None of the mutants was able to produce detectable B12. B12 was detectable in S. Enteritidis, S. Pullorum and S. Typhimurium wild type strains but not in S. Gallinarum. In conclusion, the production of vitamin B12in vitro differed across the tested Salmonella serotypes and the deletion of the cbiA and cobS genes resulted in different levels of alteration in the host parasite interaction according to Salmonella serotype tested.
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Affiliation(s)
- Jacqueline Boldrin Paiva
- Departamento de Patologia Veterinária, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista , Jaboticabal, SP , Brasil
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Miles ZD, McCarty RM, Molnar G, Bandarian V. Discovery of epoxyqueuosine (oQ) reductase reveals parallels between halorespiration and tRNA modification. Proc Natl Acad Sci U S A 2011; 108:7368-72. [PMID: 21502530 PMCID: PMC3088584 DOI: 10.1073/pnas.1018636108] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transfer RNA is one of the most richly modified biological molecules. Biosynthetic pathways that introduce these modifications are underexplored, largely because their absence does not lead to obvious phenotypes under normal growth conditions. Queuosine (Q) is a hypermodified base found in the wobble positions of tRNA Asp, Asn, His, and Tyr from bacteria to mankind. Using liquid chromatography MS methods, we have screened 1,755 single gene knockouts of Escherichia coli and have identified the key final step in the biosynthesis of Q. The protein is homologous to B(12)-dependent iron-sulfur proteins involved in halorespiration. The recombinant Bacillus subtilis epoxyqueuosine (oQ) reductase catalyzes the conversion of oQ to Q in a synthetic substrate, as well as undermodified RNA isolated from an oQ reductase knockout strain. The activity requires inclusion of a reductant and a redox mediator. Finally, exogenously supplied cobalamin stimulates the activity. This work provides the framework for studies of the biosynthesis of other modified RNA components, where lack of accessible phenotype or obvious gene clustering has impeded discovery. Moreover, discovery of the elusive oQ reductase protein completes the biosynthetic pathway of Q.
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Affiliation(s)
- Zachary D. Miles
- Department of Chemistry and Biochemistry, University of Arizona, 1041 East Lowell Street, Tucson, AZ 85721-0088
| | - Reid M. McCarty
- Department of Chemistry and Biochemistry, University of Arizona, 1041 East Lowell Street, Tucson, AZ 85721-0088
| | - Gabriella Molnar
- Department of Chemistry and Biochemistry, University of Arizona, 1041 East Lowell Street, Tucson, AZ 85721-0088
| | - Vahe Bandarian
- Department of Chemistry and Biochemistry, University of Arizona, 1041 East Lowell Street, Tucson, AZ 85721-0088
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32
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Abstract
tRNAs possess a high content of modified nucleosides, which display an incredible structural variety. These modified nucleosides are conserved in their sequence and have important roles in tRNA functions. Most often, hypermodified nucleosides are found in the wobble position of tRNAs, which play a direct role in maintaining translational efficiency and fidelity, codon recognition, etc. One of such hypermodified base is queuine, which is a base analogue of guanine, found in the first anticodon position of specific tRNAs (tyrosine, histidine, aspartate and asparagine tRNAs). These tRNAs of the ‘Q-family’ originally contain guanine in the first position of anticodon, which is post-transcriptionally modified with queuine by an irreversible insertion during maturation. Queuine is ubiquitously present throughout the living system from prokaryotes to eukaryotes, including plants. Prokaryotes can synthesize queuine de novo by a complex biosynthetic pathway, whereas eukaryotes are unable to synthesize either the precursor or queuine. They utilize salvage system and acquire queuine as a nutrient factor from their diet or from intestinal microflora. The tRNAs of the Q-family are completely modified in terminally differentiated somatic cells. However, hypomodification of Q-tRNA (queuosine-modified tRNA) is closely associated with cell proliferation and malignancy. The precise mechanisms of queuine- and Q-tRNA-mediated action are still a mystery. Direct or indirect evidence suggests that queuine or Q-tRNA participates in many cellular functions, such as inhibition of cell proliferation, control of aerobic and anaerobic metabolism, bacterial virulence, etc. The role of Q-tRNA modification in cellular machinery and the signalling pathways involved therein is the focus of this review.
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Kang M, Peterson R, Feigon J. Structural Insights into riboswitch control of the biosynthesis of queuosine, a modified nucleotide found in the anticodon of tRNA. Mol Cell 2009; 33:784-90. [PMID: 19285444 DOI: 10.1016/j.molcel.2009.02.019] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 02/18/2009] [Accepted: 02/25/2009] [Indexed: 12/27/2022]
Abstract
The modified nucleotide queuosine (Q) is almost universally found in the anticodon wobble position of specific tRNAs. In many bacteria, biosynthesis of Q is modulated by a class of regulatory mRNA elements called riboswitches. The preQ(1) riboswitch, found in the 5'UTR of bacterial genes involved in synthesis of the Q precursors preQ(0) and preQ(1), contains the smallest known aptamer domain. We report the solution structure of the preQ(1) riboswitch aptamer domain from Bacillus subtilis bound to preQ(1), which is a unique compact pseudoknot with three loops and two stems that encapsulates preQ(1) at the junction between the two stems. The pseudoknot only forms in the presence of preQ(1), and the 3' A-rich tail of the aptamer domain is an integral part of the pseudoknot. In the absence of preQ(1), the A-rich tail forms part of the antiterminator. These structural studies provide insight into riboswitch transcriptional control of preQ(1) biosynthesis.
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Affiliation(s)
- Mijeong Kang
- UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA
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34
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Biosynthesis of 7-deazaguanosine-modified tRNA nucleosides: a new role for GTP cyclohydrolase I. J Bacteriol 2008; 190:7876-84. [PMID: 18931107 DOI: 10.1128/jb.00874-08] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Queuosine (Q) and archaeosine (G(+)) are hypermodified ribonucleosides found in tRNA. Q is present in the anticodon region of tRNA(GUN) in Eukarya and Bacteria, while G(+) is found at position 15 in the D-loop of archaeal tRNA. Prokaryotes produce these 7-deazaguanosine derivatives de novo from GTP through the 7-cyano-7-deazaguanine (pre-Q(0)) intermediate, but mammals import the free base, queuine, obtained from the diet or the intestinal flora. By combining the results of comparative genomic analysis with those of genetic studies, we show that the first enzyme of the folate pathway, GTP cyclohydrolase I (GCYH-I), encoded in Escherichia coli by folE, is also the first enzyme of pre-Q(0) biosynthesis in both prokaryotic kingdoms. Indeed, tRNA extracted from an E. coli DeltafolE strain is devoid of Q and the deficiency is complemented by expressing GCYH-I-encoding genes from different bacterial or archaeal origins. In a similar fashion, tRNA extracted from a Haloferax volcanii strain carrying a deletion of the GCYH-I-encoding gene contains only traces of G(+). These results link the production of a tRNA-modified base to primary metabolism and further clarify the biosynthetic pathway for these complex modified nucleosides.
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35
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Environmental and growth phase regulation of the Streptococcus gordonii arginine deiminase genes. Appl Environ Microbiol 2008; 74:5023-30. [PMID: 18552185 DOI: 10.1128/aem.00556-08] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A 1,026-bp open reading frame sharing significant similarity with queA, which encodes a predicted S-adenosylmethionine:tRNA ribosyltransferase-isomerase responsible for queosine modification of tRNAs, was found immediately 5' of the gene for the transcriptional activator (ArcR) of the arginine deiminase system (ADS) operon of Streptococcus gordonii. The role of QueA in bacterial physiology is enigmatic, but loss of QueA has been shown to compromise stationary-phase survival or virulence in certain enteric bacteria. Interestingly, S. gordonii appears to be unique among ADS-positive bacteria in the linkage of queA with the ADS genes. A putative sigma(70) promoter (p(queA); TTGCCA-N(21)-TATAAT) was mapped 5' of queA by primer extension, and queA and arcR were shown to be cotranscribed. The expression from p(queA) was found to be constitutive under all conditions tested, but the expression of p(arcA), which drives the expression of the arc structural genes, was enhanced in stationary phase and could be induced by low pH and arginine. QueA and CcpA acted repressively on arc transcription, but neither QueA-deficient strains nor CcpA-deficient strains showed significant differences in arginine deiminase enzyme activities compared with the wild-type strain. The growth rate of a QueA-deficient strain did not differ significantly from that of the parental strain, but the QueA-deficient strain did not compete well with the wild-type during serial passage. In addition to the finding that ADS expression can be regulated separately by growth phase and pH, a significant linkage between the ADS, translational efficiency modulated by QueA, and post-exponential-phase survival of S. gordonii was found.
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36
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Glutamate versus glutamine exchange swaps substrate selectivity in tRNA-guanine transglycosylase: insight into the regulation of substrate selectivity by kinetic and crystallographic studies. J Mol Biol 2007; 374:764-76. [PMID: 17949745 DOI: 10.1016/j.jmb.2007.09.062] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 09/17/2007] [Accepted: 09/21/2007] [Indexed: 11/22/2022]
Abstract
Bacterial tRNA-guanine transglycosylase (Tgt) catalyses the exchange of guanine in the wobble position of particular tRNAs by the modified base preQ(1). In vitro, however, the enzyme is also able to insert the immediate biosynthetic precursor, preQ(0), into those tRNAs. This substrate promiscuity is based on a peptide switch in the active site, gated by the general acid/base Glu235. The switch alters the properties of the binding pocket to allow either the accommodation of guanine or preQ(1). The peptide conformer recognising guanine, however, is also able to bind preQ(0). To investigate selectivity regulation, kinetic data for Zymomonas mobilis Tgt were recorded. They show that selectivity in favour of the actual substrate preQ(1) over preQ(0) is not achieved by a difference in affinity but via a higher turnover rate. Moreover, a Tgt(Glu235Gln) variant was constructed. The mutation was intended to stabilise the peptide switch in the conformation favouring guanine and preQ(0) binding. Kinetic characterisation of the mutated enzyme revealed that the Glu235Gln exchange has, with respect to all substrate bases, no significant influence on k(cat). In contrast, K(M)(preQ(1)) is drastically increased, while K(M)(preQ(0)) seems to be decreased. Hence, regarding k(cat)/K(M) as an indicator for catalytic efficiency, selectivity of Tgt in favour of preQ(1) is abolished or even inverted in favour of preQ(0) for Tgt(Glu235Gln). Crystal structures of the mutated enzyme confirm that the mutation strongly favours the binding pocket conformation required for the accommodation of guanine and preQ(0). The way this is achieved, however, significantly differs from that predicted based on crystal structures of wild-type Tgt.
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37
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Gaur R, Björk GR, Tuck S, Varshney U. Diet-dependent depletion of queuosine in tRNAs in Caenorhabditis elegans does not lead to a developmental block. J Biosci 2007; 32:747-54. [PMID: 17762147 DOI: 10.1007/s12038-007-0074-4] [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: 10/23/2022]
Abstract
Queuosine (Q), a hypermodified nucleoside,occurs at the wobble position of transfer RNAs (tRNAs)with GUN anticodons. In eubacteria, absence of Q affects messenger RNA (mRNA) translation and reduces the virulence of certain pathogenic strains. In animal cells,changes in the abundance of Q have been shown to correlate with diverse phenomena including stress tolerance, cell proliferation and tumour growth but the function of Q in animals is poorly understood. Animals are thought to obtain Q (or its analogues) as a micronutrient from dietary sources such as gut micro flora. However,the difficulty of maintaining animals under bacteria-free conditions on Q-deficient diets has severely hampered the study of Q metabolism and function in animals. In this study,we show that as in higher animals, tRNAs in the nematode Caenorhabditis elegans are modified by Q and its sugar derivatives. When the worms were fed on Q-deficient Escherichia coli, Q modification was absent from the worm tRNAs suggesting that C.elegans lacks a de novo pathway of Q biosynthesis. The inherent advantages of C.elegans as a model organism, and the simplicity of conferring a Q-deficient phenotype on it make it an ideal system to investigate the function of Q modification in tRNA.
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Affiliation(s)
- Rahul Gaur
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
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38
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Roth A, Winkler WC, Regulski EE, Lee BWK, Lim J, Jona I, Barrick JE, Ritwik A, Kim JN, Welz R, Iwata-Reuyl D, Breaker RR. A riboswitch selective for the queuosine precursor preQ1 contains an unusually small aptamer domain. Nat Struct Mol Biol 2007; 14:308-17. [PMID: 17384645 DOI: 10.1038/nsmb1224] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Accepted: 03/05/2007] [Indexed: 01/09/2023]
Abstract
A previous bioinformatics-based search for riboswitches yielded several candidate motifs in eubacteria. One of these motifs commonly resides in the 5' untranslated regions of genes involved in the biosynthesis of queuosine (Q), a hypermodified nucleoside occupying the anticodon wobble position of certain transfer RNAs. Here we show that this structured RNA is part of a riboswitch selective for 7-aminomethyl-7-deazaguanine (preQ(1)), an intermediate in queuosine biosynthesis. Compared with other natural metabolite-binding RNAs, the preQ(1) aptamer appears to have a simple structure, consisting of a single stem-loop and a short tail sequence that together are formed from as few as 34 nucleotides. Despite its small size, this aptamer is highly selective for its cognate ligand in vitro and has an affinity for preQ(1) in the low nanomolar range. Relatively compact RNA structures can therefore serve effectively as metabolite receptors to regulate gene expression.
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Affiliation(s)
- Adam Roth
- Howard Hughes Medical Institute, USA
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39
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Flatt PM, Mahmud T. Biosynthesis of aminocyclitol-aminoglycoside antibiotics and related compounds. Nat Prod Rep 2006; 24:358-92. [PMID: 17390001 DOI: 10.1039/b603816f] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review covers the biosynthesis of aminocyclitol-aminoglycoside antibiotics and related compounds, particularly from the molecular genetic perspectives. 195 references are cited.
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Affiliation(s)
- Patricia M Flatt
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, OR 97331-3507, USA
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40
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Grimm C, Ficner R, Sgraja T, Haebel P, Klebe G, Reuter K. Crystal structure of Bacillus subtilis S-adenosylmethionine:tRNA ribosyltransferase-isomerase. Biochem Biophys Res Commun 2006; 351:695-701. [PMID: 17083917 DOI: 10.1016/j.bbrc.2006.10.096] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2006] [Accepted: 10/19/2006] [Indexed: 11/16/2022]
Abstract
The enzyme S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA) is involved in the biosynthesis of the hypermodified tRNA nucleoside queuosine. It is unprecedented in nature as it uses the cofactor S-adenosylmethionine as the donor of a ribosyl group. We have determined the crystal structure of Bacillus subtilis QueA at a resolution of 2.9A. The structure reveals two domains representing a 6-stranded beta-barrel and an alpha beta alpha-sandwich, respectively. All amino acid residues invariant in the QueA enzymes of known sequence cluster at the interface of the two domains indicating the localization of the substrate binding region and active center. Comparison of the B. subtilis QueA structure with the structure of QueA from Thermotoga maritima suggests a high domain flexibility of this enzyme.
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Affiliation(s)
- Clemens Grimm
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032 Marburg, Germany
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41
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Gaur R, Varshney U. Genetic analysis identifies a function for the queC (ybaX) gene product at an initial step in the queuosine biosynthetic pathway in Escherichia coli. J Bacteriol 2005; 187:6893-901. [PMID: 16199558 PMCID: PMC1251624 DOI: 10.1128/jb.187.20.6893-6901.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Queuosine (Q), one of the most complex modifications occurring at the wobble position of tRNAs with GUN anticodons, is implicated in a number of biological activities, including accuracy of decoding, virulence, and cellular differentiation. Despite these important implications, its biosynthetic pathway has remained unresolved. Earlier, we observed that a naturally occurring strain of Escherichia coli B105 lacked Q modification in the tRNAs. In the present study, we developed a genetic screen to map the defect in E. coli B105 to a single gene, queC (renamed from ybaX), predicted to code for a 231-amino-acid-long protein with a pI of 5.6. As analyzed by mobility of tRNA(Tyr) on acid urea gels and two-dimensional thin-layer chromatography of the modified nucleosides, expression of QueC from a plasmid-borne copy confers a Q+ phenotype to E. coli B105. Further, analyses of tRNA(Tyr) from E. coli JE10651 (queA mutant), its derivative generated by deletion of chromosomal queC (queA deltaqueC), and E. coli JE7325, deficient in converting preQ0 to preQ1, have provided the first genetic evidence for the involvement of QueC at a step leading to production of preQ0, the first known intermediate in the generally accepted pathway that utilizes GTP as the starting molecule. In addition, we discuss the possibilities of collaboration of QueC with other cellular proteins in the production of preQ0.
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Affiliation(s)
- Rahul Gaur
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
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42
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Buan NR, Escalante-Semerena JC. Computer-assisted docking of flavodoxin with the ATP:Co(I)rrinoid adenosyltransferase (CobA) enzyme reveals residues critical for protein-protein interactions but not for catalysis. J Biol Chem 2005; 280:40948-56. [PMID: 16207720 DOI: 10.1074/jbc.m506713200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of the housekeeping ATP:co(I)rrinoid adenosyltransferase (CobA) enzyme of Salmonella enterica sv. Typhimurium is required to adenosylate de novo biosynthetic intermediates of adenosylcobalamin and to salvage incomplete and complete corrinoids from the environment of this bacterium. In vitro, reduced flavodoxin (FldA) provides an electron to generate the co(I)rrinoid substrate in the CobA active site. To understand how CobA and FldA interact, a computer model of a CobA.FldA complex was generated. This model was used to guide the introduction of mutations into CobA using site-directed mutagenesis and the synthesis of a peptide mimic of FldA. Residues Arg-9 and Arg-165 of CobA were critical for FldA-dependent adenosylation but were catalytically as competent as the wild-type protein when cob(I)alamin was provided as substrate. These results indicate that Arg-9 and Arg-165 are important for CobA.FldA docking but not to catalysis. A truncation of the 9-amino acid N-terminal helix of CobA reduced its FldA-dependent cobalamin adenosyltransferase activity by 97.4%. The same protein, however, had a 4-fold higher specific activity than the native enzyme when cob(I)alamin was generated chemically in situ.
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Affiliation(s)
- Nicole R Buan
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53726, USA
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43
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Van Lanen SG, Reader JS, Swairjo MA, de Crécy-Lagard V, Lee B, Iwata-Reuyl D. From cyclohydrolase to oxidoreductase: discovery of nitrile reductase activity in a common fold. Proc Natl Acad Sci U S A 2005; 102:4264-9. [PMID: 15767583 PMCID: PMC555470 DOI: 10.1073/pnas.0408056102] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Indexed: 11/18/2022] Open
Abstract
The enzyme YkvM from Bacillus subtilis was identified previously along with three other enzymes (YkvJKL) in a bioinformatics search for enzymes involved in the biosynthesis of queuosine, a 7-deazaguanine modified nucleoside found in tRNA(GUN) of Bacteria and Eukarya. Genetic analysis of ykvJKLM mutants in Acinetobacter confirmed that each was essential for queuosine biosynthesis, and the genes were renamed queCDEF. QueF exhibits significant homology to the type I GTP cyclohydrolases characterized by FolE. Given that GTP is the precursor to queuosine and that a cyclohydrolase-like reaction was postulated as the initial step in queuosine biosynthesis, QueF was proposed to be the putative cyclohydrolase-like enzyme responsible for this reaction. We have cloned the queF genes from B. subtilis and Escherichia coli and characterized the recombinant enzymes. Contrary to the predictions based on sequence analysis, we discovered that the enzymes, in fact, catalyze a mechanistically unrelated reaction, the NADPH-dependent reduction of 7-cyano-7-deazaguanineto7-aminomethyl-7-deazaguanine, a late step in the biosynthesis of queuosine. We report here in vitro and in vivo studies that demonstrate this catalytic activity, as well as preliminary biochemical and bioinformatics analysis that provide insight into the structure of this family of enzymes.
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Affiliation(s)
- Steven G Van Lanen
- Department of Chemistry, Portland State University, P.O. Box 751, Portland, OR 97207, USA
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44
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Costa A, Païs de Barros JP, Keith G, Baranowski W, Desgrès J. Determination of queuosine derivatives by reverse-phase liquid chromatography for the hypomodification study of Q-bearing tRNAs from various mammal liver cells. J Chromatogr B Analyt Technol Biomed Life Sci 2004; 801:237-47. [PMID: 14751792 DOI: 10.1016/j.jchromb.2003.11.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Three queuosine derivatives (Q-derivatives) have been found at position 34 of four mammalian so-called Q-tRNAs: queuosine (Q) in tRNA(Asn) and tRNA(His), mannosyl-queuosine (manQ) in tRNA(Asp), and galactosyl-queuosine (galQ) in tRNA(Tyr). An analytical procedure based on the combined means of purified tRNA isolation from liver cells and ribonucleoside analysis by reverse-phase high performance liquid chromatography coupled with real-time UV-spectrometry (RPLC-UV) was developed for the quantitative analysis of the three Q-derivatives present in total tRNA from liver tissues and liver cell cultures. Using this analytical procedure, the rates of Q-tRNA modification were studied in total tRNAs from various mammalian hepatic cells. Our results show that the four Q-tRNAs are fully modified in liver tissues from adult mammals, regardless of the mammal species. However, a lack in the Q-modification level was observed in Q-tRNAs from newborn rat liver, as well in Q-tRNAs from normal rat liver cell cultures growing in a low queuine content medium, and from a rat hepatoma cell line. It is noteworthy that in all cases of Q-tRNA hypomodification, our analytical procedure showed that tRNA(Asp) is always the least affected by the hypomodification. The biological significance of this phenomenon is discussed.
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MESH Headings
- Animals
- Cells, Cultured
- Chickens
- Chromatography, High Pressure Liquid
- Hepatocytes/chemistry
- Liver/chemistry
- Liver Neoplasms, Experimental
- Nucleoside Q/analogs & derivatives
- Nucleoside Q/analysis
- RNA, Transfer/chemistry
- RNA, Transfer/isolation & purification
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Asn/chemistry
- Rats
- Tumor Cells, Cultured
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Affiliation(s)
- Annie Costa
- Faculté de Médecine et Centre Hospitalier Universitaire, Université de Bourgogne, 10 Bd de-Lattre-de-Tassigny, 21079 Cedex, Dijon, France
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45
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Kittendorf JD, Sgraja T, Reuter K, Klebe G, Garcia GA. An essential role for aspartate 264 in catalysis by tRNA-guanine transglycosylase from Escherichia coli. J Biol Chem 2003; 278:42369-76. [PMID: 12909636 DOI: 10.1074/jbc.m304323200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
tRNA-guanine transglycosylase (TGT) catalyzes a post-transcriptional base-exchange reaction involved in the incorporation of the modified base queuine (Q) into the wobble position of certain tRNAs. Catalysis by TGT occurs through a double-displacement mechanism that involves the formation of a covalent enzyme-RNA intermediate (Kittendorf, J. D., Barcomb, L. M., Nonekowski, S. T., and Garcia, G. A. (2001) Biochemistry 40, 14123-14133). The TGT chemical mechanism requires the protonation of the displaced guanine and the deprotonation of the incoming heterocyclic base. Based on its position in the active site, it is likely that aspartate 264 is involved in these proton transfer events. To investigate this possibility, site-directed mutagenesis was employed to convert aspartate 264 to alanine, asparagine, glutamate, glutamine, lysine, and histidine. Biochemical characterization of these TGT mutants revealed that only the conservative glutamate mutant retained catalytic activity, with Km values for both tRNA and guanine 3-fold greater than those for wild-type, whereas the kcat was depressed by an order of magnitude. Furthermore, of these six TGT mutants, only the TGT(D264E) was capable of forming a TGT.RNA covalent intermediate; however, unlike wild-type TGT, only hydroxylamine is capable of cleaving the TGT(D264E).RNA covalent complex. In an effort to better understand the unique biochemical properties of the D264E TGT mutant, we solved the crystal structure of the Zymomonas mobilis TGT with the analogous mutation (D280E). The results of these studies support two roles for aspartate 264 in catalysis by TGT, protonation of the leaving guanine and deprotonation of the incoming preQ1.
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Affiliation(s)
- Jeffrey D Kittendorf
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, 428 Chuirch Street, Ann Arbor, MI 48109-1065, USA
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Xie W, Liu X, Huang RH. Chemical trapping and crystal structure of a catalytic tRNA guanine transglycosylase covalent intermediate. Nat Struct Mol Biol 2003; 10:781-8. [PMID: 12949492 DOI: 10.1038/nsb976] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2003] [Accepted: 07/31/2003] [Indexed: 11/09/2022]
Abstract
Prokaryotic tRNA guanine transglycosylase (TGT) catalyzes replacement of guanine (G) by 7-aminomethyl-7-deazaguanine (PreQ1) at the wobble position of four specific tRNAs. Addition of 9-deazaguanine (9dzG) to a reaction mixture of Zymomonas mobilis TGT and an RNA substrate allowed us to trap, purify and crystallize a chemically competent covalent intermediate of the TGT-catalyzed reaction. The crystal structure of the TGT-RNA-9dzG ternary complex at a resolution of 2.9 A reveals, unexpectedly, that RNA is tethered to TGT through the side chain of Asp280. Thus, Asp280, instead of the previously proposed Asp102, acts as the nucleophile for the reaction. The RNA substrate adopts an unusual conformation, with four out of seven nucleotides in the loop region flipped out. Interactions between TGT and RNA revealed by the structure provide the molecular basis of the RNA substrate requirements by TGT. Furthermore, reaction of PreQ1 with the crystallized covalent intermediate provides insight into the necessary structural changes required for the TGT-catalyzed reaction to occur.
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Affiliation(s)
- Wei Xie
- Department of Biochemistry, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
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47
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Van Lanen SG, Iwata-Reuyl D. Kinetic mechanism of the tRNA-modifying enzyme S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA). Biochemistry 2003; 42:5312-20. [PMID: 12731872 DOI: 10.1021/bi034197u] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bacterial enzyme S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA) catalyzes the unprecedented transfer and isomerization of the ribosyl moiety of S-adenosylmethionine (AdoMet) to a modified tRNA nucleoside in the biosynthesis of the hypermodified nucleoside queuosine. The complexity of this reaction makes it a compelling problem in fundamental mechanistic enzymology, and as part of our mechanistic studies of the QueA-catalyzed reaction, we report here the elucidation of the steady-state kinetic mechanism. Bi-substrate kinetic analysis gave initial velocity patterns indicating a sequential mechanism, and provided the following kinetic constants: K (M)(tRNA)= 1.9 +/- 0.7 microM and K (M)(AdoMet)= 98 +/- 5.0 microM. Dead-end inhibition studies with the substrate analogues S-adenosylhomocysteine and sinefungin gave competitive inhibition patterns against AdoMet and noncompetitive patterns against preQ(1)-tRNA(Tyr), with K(i) values of 133 +/- 18 and 4.6 +/- 0.5 microM for sinefungin and S-adenosylhomocysteine, respectively. Product inhibition by adenine was noncompetitive against both substrates under conditions with a subsaturating cosubstrate concentration and uncompetitive against preQ(1)-tRNA(Tyr) when AdoMet was saturating. Inhibition by the tRNA product (oQ-tRNA(Tyr)) was competitive and noncompetitive against the substrates preQ(1)-tRNA(Tyr) and AdoMet, respectively. Inhibition by methionine was uncompetitive versus preQ(1)-tRNA(Tyr), but noncompetitive against AdoMet. However, when methionine inhibition was investigated at high AdoMet concentrations, the pattern was uncompetitive. Taken together, the data are consistent with a fully ordered sequential bi-ter kinetic mechanism in which preQ(1)-tRNA(Tyr) binds first followed by AdoMet, with product release in the order adenine, methionine, and oQ-tRNA. The chemical mechanism that we previously proposed for the QueA-catalyzed reaction [Daoud Kinzie, S., Thern, B., and Iwata-Reuyl, D. (2000) Org. Lett. 2, 1307-1310] is consistent with the constraints imposed by the kinetic mechanism determined here, and we suggest that the magnitude of the inhibition constants for the dead-end inhibitors may provide insight into the catalytic strategy employed by the enzyme.
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Affiliation(s)
- Steven G Van Lanen
- Department of Chemistry, Portland State University, Portland, Oregon 97207-0751, USA
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Brenk R, Naerum L, Grädler U, Gerber HD, Garcia GA, Reuter K, Stubbs MT, Klebe G. Virtual screening for submicromolar leads of tRNA-guanine transglycosylase based on a new unexpected binding mode detected by crystal structure analysis. J Med Chem 2003; 46:1133-43. [PMID: 12646024 DOI: 10.1021/jm0209937] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Eubacterial tRNA-guanine transglycosylase (TGT) is involved in the hypermodification of cognate tRNAs, leading to the exchange of G34 by preQ1 at the wobble position in the anticodon loop. Mutation of the tgt gene in Shigella flexneri results in a significant loss of pathogenicity of the bacterium due to inefficient translation of a virulence protein mRNA. Herein, we describe the discovery of a ligand with an unexpected binding mode. On the basis of this binding mode, three slightly deviating pharmacophore hypotheses have been derived. Virtual screening based on this composite pharmacophore model retrieved a set of potential TGT inhibitors belonging to several compound classes. All nine tested inhibitors being representatives of these classes showed activity in the micromolar range, two of them even in the submicromolar range.
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Affiliation(s)
- Ruth Brenk
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032 Marburg, Germany
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49
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Abstract
Transfer RNA (tRNA) is structurally unique among nucleic acids in harboring an astonishing diversity of post-transcriptionally modified nucleoside. Two of the most radically modified nucleosides known to occur in tRNA are queuosine and archaeosine, both of which are characterized by a 7-deazaguanosine core structure. In spite of the phylogenetic segregation observed for these nucleosides (queuosine is present in Eukarya and Bacteria, while archaeosine is present only in Archaea), their structural similarity suggested a common biosynthetic origin, and recent biochemical and genetic studies have provided compelling evidence that a significant portion of their biosynthesis may in fact be identical. This review covers current understanding of the physiology and biosynthesis of these remarkable nucleosides, with particular emphasis on the only two enzymes that have been discovered in the pathways: tRNA-guanine transglycosylase (TGT), which catalyzes the insertion of a modified base into the polynucleotide with the concomitant elimination of the genetically encoded guanine in the biosynthesis of both nucleosides, and S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA), which catalyzes the penultimate step in the biosynthesis of queuosine, the construction of the carbocyclic side chain.
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Affiliation(s)
- Dirk Iwata-Reuyl
- Department of Chemistry, Portland State University, P.O. Box 751, Portland, OR 97201, USA.
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Durand JMB, Björk GR. Putrescine or a combination of methionine and arginine restores virulence gene expression in a tRNA modification-deficient mutant of Shigella flexneri: a possible role in adaptation of virulence. Mol Microbiol 2003; 47:519-27. [PMID: 12519201 DOI: 10.1046/j.1365-2958.2003.03314.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The wild-type strain YSH6000 of Shigella flexneri growing in minimal medium contains the modified nucleoside epoxy-Q (oQ) in a subset of tRNAs. This nucleoside is lacking in tRNA from a tgt mutant of this bacterium. When these bacteria are growing in minimal medium, the expression of virulence genes is 10-fold lower in the tgt mutant than in the wild type, although only a twofold reduction in the expression of these virulence factors is observed in broth. Such a strong media-dependant expression of virulence genes was not observed in the wild type. Accordingly, the level of the positive regulator of virulence, VirF, is much lower in the mutant than in the wild type. However, the transcription of the virF gene in minimal medium is the same in the wild type and in the tgt mutant. As the undermodification of tRNA is not affected by the quality of the growth medium, we conclude that such an environmental change in growth conditions partly restores virulence gene expression by counteracting poor translation of the virF mRNA mediated by an oQ-deficient tRNA. Virulence gene expression is partly restored in the tgt mutant by the addition of a mixture of arginine and methionine. Addition of the polyamine putrescine, synthesis of which is metabolically related to that of arginine and methionine, has a comparable stimulatory effect on virulence gene expression. These results not only suggest a role for amino acids and polyamines in the environmental regulation of virulence gene expression in S. flexneri, but also demonstrate a strong and specific involvement of tRNA modifications, and especially oQ, in the adaptation of virulence gene expression to the nutritional quality of the growth medium.
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Affiliation(s)
- Jérôme M B Durand
- Department of Molecular Biology, Umeå University, S-90 187 Umeå, Sweden
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