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Isogai S, Nishimura A, Inoue A, Sonohara S, Tsugukuni T, Okada T, Takagi H. Functional analysis of feedback inhibition-insensitive aspartate kinase identified in a threonine-accumulating mutant of Saccharomyces cerevisiae. Appl Environ Microbiol 2024; 90:e0015524. [PMID: 38456673 PMCID: PMC11022571 DOI: 10.1128/aem.00155-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 02/15/2024] [Indexed: 03/09/2024] Open
Abstract
Humans and mammals need to ingest essential amino acids (EAAs) for protein synthesis. In addition to their importance as nutrients, EAAs are involved in brain homeostasis. However, elderly people are unable to efficiently consume EAAs from their daily diet due to reduced appetite and variations in the contents of EAAs in foods. On the other hand, strains of the yeast Saccharomyces cerevisiae that accumulate EAAs would enable elderly people to intakegest adequate amounts of EAAs and thus might slow down the neurodegenerative process, contributing to the extension of their healthy lifespan. In this study, we isolated a mutant (strain HNV-5) that accumulates threonine, an EAA, derived from a diploid laboratory yeast by conventional mutagenesis. Strain HNV-5 carries a novel mutation in the HOM3 gene encoding the Ala462Thr variant of aspartate kinase (AK). Enzymatic analysis revealed that the Ala462Thr substitution significantly decreased the sensitivity of AK activity to threonine feedback inhibition even in the presence of 50 mM threonine. Interestingly, Ala462Thr substitution did not affect the catalytic ability of Hom3, in contrast to previously reported amino acid substitutions that resulted in reduced sensitivity to threonine feedback inhibition. Furthermore, yeast cells expressing the Ala462Thr variant showed an approximately threefold increase in intracellular threonine content compared to that of the wild-type Hom3. These findings will be useful for the development of threonine-accumulating yeast strains that may improve the quality of life in elderly people.IMPORTANCEFor humans and mammals, essential amino acids (EAAs) play an important role in maintaining brain function. Therefore, increasing the intake of EAAs by using strains of the yeast Saccharomyces cerevisiae that accumulate EAAs may inhibit neurodegeneration in elderly people and thus contribute to extending healthy lifespan and improving their quality of life. Threonine, an EAA, is synthesized from aspartate. Aspartate kinase (AK) catalyzes the first step in threonine biosynthesis and is subject to allosteric regulation by threonine. Here, we isolated a threonine-accumulating mutant of S. cerevisiae by conventional mutagenesis and identified a mutant gene encoding a novel variant of AK. In contrast to previously isolated variants, the Hom3 variant exhibited AK activity that was insensitive to feedback inhibition by threonine but retained its catalytic ability. This resulted in increased production of threonine in yeast. These findings open up the possibility for the rational design of AK to increase threonine productivity in yeast.
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Affiliation(s)
- Shota Isogai
- Institute for Research Initiative, Nara Institute of Science and Technology, Takayama, Nara, Japan
| | - Akira Nishimura
- Institute for Research Initiative, Nara Institute of Science and Technology, Takayama, Nara, Japan
| | - Akiko Inoue
- Institute for Research Initiative, Nara Institute of Science and Technology, Takayama, Nara, Japan
| | - Shino Sonohara
- Plant Bio Business Unit, Musashi Seimitsu Industry Co., Ltd., Toyohashi, Aichi, Japan
| | - Takashi Tsugukuni
- Plant Bio Business Unit, Musashi Seimitsu Industry Co., Ltd., Toyohashi, Aichi, Japan
| | - Tomoyuki Okada
- Plant Bio Business Unit, Musashi Seimitsu Industry Co., Ltd., Toyohashi, Aichi, Japan
| | - Hiroshi Takagi
- Institute for Research Initiative, Nara Institute of Science and Technology, Takayama, Nara, Japan
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2
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Aboelnga MM, Gauld JW. Screening a library of potential competitive inhibitors against bacterial threonyl-tRNA synthetase: DFT calculations. J Biomol Struct Dyn 2023:1-9. [PMID: 37909495 DOI: 10.1080/07391102.2023.2276878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 10/24/2023] [Indexed: 11/03/2023]
Abstract
Due to the growing interest in directing aminoacyl-tRNA synthetases for antimicrobial therapies, evaluating the binding proficiency of potential inhibitors against this target holds significant importance. In this work, we proposed potential ligands that could properly bind to the crucial Zn(II) cofactor located in the active site of Threonyl-tRNA synthetases (ThrRS), potentially functioning as competitive inhibitors. Initially, detailed DFT quantum chemical study was conducted to examine the binding ability of threonine against unnatural amino acids to cofactor Zn(II). Then, the binding energy value for each suggested ligand has been determined and compared to the value determined for the native substrate, threonine. Our screening investigation showed that the native threonine should coordinate in a bidentate fashion to this Zn(II) which lead to the highest (binding energy) BE Thereby, the synthetic site of ThrRS rejects unnatural amino acids that cannot afford this type of coordination to Zn(II) ion which has been supported by our calculations. Moreover, based on their binding to the Zn(II) and the obtained BE values compared to the cognate threonine, many potent ligands have been suggested. Importantly, ligands with deprotonated warheads showed the highest binding ability amongst a list of potential hits. Further investigation on the selected ligands using molecular docking and QM/MM calculations confirmed our findings of the suggested ligands being able to bind efficiently in the active site of ThrRS. The suggested hits from this study should be valuable in paving routs for developing candidates as competitive inhibitors against the bacterial ThrRS.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Mohamed M Aboelnga
- Department of Chemistry, Faculty of Science, Damietta University, New Damietta, Egypt
| | - James W Gauld
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Canada
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3
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Ignacio BJ, Dijkstra J, Mora N, Slot EFJ, van Weijsten MJ, Storkebaum E, Vermeulen M, Bonger KM. THRONCAT: metabolic labeling of newly synthesized proteins using a bioorthogonal threonine analog. Nat Commun 2023; 14:3367. [PMID: 37291115 PMCID: PMC10250548 DOI: 10.1038/s41467-023-39063-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 05/26/2023] [Indexed: 06/10/2023] Open
Abstract
Profiling the nascent cellular proteome and capturing early proteomic changes in response to external stimuli provides valuable insights into cellular physiology. Existing metabolic protein labeling approaches based on bioorthogonal methionine- or puromycin analogs allow for the selective visualization and enrichment of newly synthesized proteins. However, their applications are limited as they often require methionine-free conditions, auxotrophic cells and/or are toxic to cells. Here, we introduce THRONCAT, a threonine-derived non-canonical amino acid tagging method based on the bioorthogonal threonine analog β-ethynylserine (βES) that enables efficient labeling of the nascent proteome in complete growth media within minutes. We use THRONCAT for the visualization and enrichment of nascent proteins in bacteria, mammalian cells and Drosophila melanogaster. We profile immediate proteome dynamics of B-cells in response to B-cell receptor activation simply by adding βES to the culture medium, demonstrating the ease-of-use of the method and its potential to address diverse biological questions. In addition, using a Drosophila model of Charcot-Marie-Tooth peripheral neuropathy, we show that THRONCAT enables visualization and quantification of relative protein synthesis rates in specific cell types in vivo.
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Affiliation(s)
- Bob J Ignacio
- Department of Synthetic Organic Chemistry, Chemical Biology Lab, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, the Netherlands
| | - Jelmer Dijkstra
- Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Oncode Institute, Radboud University, Nijmegen, the Netherlands
- Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Natalia Mora
- Molecular Neurobiology Laboratory, Donders Center for Neuroscience, Donders Institute for Brain, Cognition and Behaviour and Faculty of Science, Radboud University, Nijmegen, the Netherlands
| | - Erik F J Slot
- Molecular Neurobiology Laboratory, Donders Center for Neuroscience, Donders Institute for Brain, Cognition and Behaviour and Faculty of Science, Radboud University, Nijmegen, the Netherlands
| | - Margot J van Weijsten
- Department of Synthetic Organic Chemistry, Chemical Biology Lab, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, the Netherlands
| | - Erik Storkebaum
- Molecular Neurobiology Laboratory, Donders Center for Neuroscience, Donders Institute for Brain, Cognition and Behaviour and Faculty of Science, Radboud University, Nijmegen, the Netherlands
| | - Michiel Vermeulen
- Department of Molecular Biology, Radboud Institute for Molecular Life Sciences, Oncode Institute, Radboud University, Nijmegen, the Netherlands
- Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Kimberly M Bonger
- Department of Synthetic Organic Chemistry, Chemical Biology Lab, Radboud University, Heyendaalseweg 135, 6525AJ, Nijmegen, the Netherlands.
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4
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Comparative QM/MM study on the inhibition mechanism of β-Hydroxynorvaline to Threonyl-tRNA synthetase. J Mol Graph Model 2022; 115:108224. [DOI: 10.1016/j.jmgm.2022.108224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/26/2022] [Accepted: 05/13/2022] [Indexed: 11/18/2022]
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5
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Hartman MCT. Non-canonical Amino Acid Substrates of E. coli Aminoacyl-tRNA Synthetases. Chembiochem 2022; 23:e202100299. [PMID: 34416067 PMCID: PMC9651912 DOI: 10.1002/cbic.202100299] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/03/2021] [Indexed: 01/07/2023]
Abstract
In this comprehensive review, I focus on the twenty E. coli aminoacyl-tRNA synthetases and their ability to charge non-canonical amino acids (ncAAs) onto tRNAs. The promiscuity of these enzymes has been harnessed for diverse applications including understanding and engineering of protein function, creation of organisms with an expanded genetic code, and the synthesis of diverse peptide libraries for drug discovery. The review catalogues the structures of all known ncAA substrates for each of the 20 E. coli aminoacyl-tRNA synthetases, including ncAA substrates for engineered versions of these enzymes. Drawing from the structures in the list, I highlight trends and novel opportunities for further exploitation of these ncAAs in the engineering of protein function, synthetic biology, and in drug discovery.
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Affiliation(s)
- Matthew C T Hartman
- Department of Chemistry and Massey Cancer Center, Virginia Commonwealth University, 1001 W Main St., Richmond, VA 23220, USA
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6
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Tawfik DS, Gruic-Sovulj I. How evolution shapes enzyme selectivity - lessons from aminoacyl-tRNA synthetases and other amino acid utilizing enzymes. FEBS J 2020; 287:1284-1305. [PMID: 31891445 DOI: 10.1111/febs.15199] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 12/08/2019] [Accepted: 12/30/2019] [Indexed: 12/21/2022]
Abstract
Aminoacyl-tRNA synthetases (AARSs) charge tRNA with their cognate amino acids. Many other enzymes use amino acids as substrates, yet discrimination against noncognate amino acids that threaten the accuracy of protein translation is a hallmark of AARSs. Comparing AARSs to these other enzymes allowed us to recognize patterns in molecular recognition and strategies used by evolution for exercising selectivity. Overall, AARSs are 2-3 orders of magnitude more selective than most other amino acid utilizing enzymes. AARSs also reveal the physicochemical limits of molecular discrimination. For example, amino acids smaller by a single methyl moiety present a discrimination ceiling of ~200, while larger ones can be discriminated by up to 105 -fold. In contrast, substrates larger by a hydroxyl group challenge AARS selectivity, due to promiscuous H-bonding with polar active site groups. This 'hydroxyl paradox' is resolved by editing. Indeed, when the physicochemical discrimination limits are reached, post-transfer editing - hydrolysis of tRNAs charged with noncognate amino acids, evolved. The editing site often selectively recognizes the edited noncognate substrate using the very same feature that the synthetic site could not efficiently discriminate against. Finally, the comparison to other enzymes also reveals that the selectivity of AARSs is an explicitly evolved trait, showing some clear examples of how selection acted not only to optimize catalytic efficiency with the target substrate, but also to abolish activity with noncognate threat substrates ('negative selection').
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Affiliation(s)
- Dan S Tawfik
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Ita Gruic-Sovulj
- Department of Chemistry, Faculty of Science, University of Zagreb, Croatia
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7
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Francklyn CS, Mullen P. Progress and challenges in aminoacyl-tRNA synthetase-based therapeutics. J Biol Chem 2019; 294:5365-5385. [PMID: 30670594 DOI: 10.1074/jbc.rev118.002956] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aminoacyl-tRNA synthetases (ARSs) are universal enzymes that catalyze the attachment of amino acids to the 3' ends of their cognate tRNAs. The resulting aminoacylated tRNAs are escorted to the ribosome where they enter protein synthesis. By specifically matching amino acids to defined anticodon sequences in tRNAs, ARSs are essential to the physical interpretation of the genetic code. In addition to their canonical role in protein synthesis, ARSs are also involved in RNA splicing, transcriptional regulation, translation, and other aspects of cellular homeostasis. Likewise, aminoacylated tRNAs serve as amino acid donors for biosynthetic processes distinct from protein synthesis, including lipid modification and antibiotic biosynthesis. Thanks to the wealth of details on ARS structures and functions and the growing appreciation of their additional roles regulating cellular homeostasis, opportunities for the development of clinically useful ARS inhibitors are emerging to manage microbial and parasite infections. Exploitation of these opportunities has been stimulated by the discovery of new inhibitor frameworks, the use of semi-synthetic approaches combining chemistry and genome engineering, and more powerful techniques for identifying leads from the screening of large chemical libraries. Here, we review the inhibition of ARSs by small molecules, including the various families of natural products, as well as inhibitors developed by either rational design or high-throughput screening as antibiotics and anti-parasitic therapeutics.
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Affiliation(s)
- Christopher S Francklyn
- From the Department of Biochemistry, College of Medicine, University of Vermont, Burlington, Vermont 05405
| | - Patrick Mullen
- From the Department of Biochemistry, College of Medicine, University of Vermont, Burlington, Vermont 05405
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8
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El Zahed SS, Brown ED. Chemical-Chemical Combinations Map Uncharted Interactions in Escherichia coli under Nutrient Stress. iScience 2018; 2:168-181. [PMID: 30428373 PMCID: PMC6136904 DOI: 10.1016/j.isci.2018.03.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/28/2018] [Accepted: 03/07/2018] [Indexed: 11/16/2022] Open
Abstract
Of the ∼4,400 genes that constitute Escherichia coli's genome, ∼300 genes are indispensable for its growth in nutrient-rich conditions. These encode housekeeping functions, including cell wall, DNA, RNA, and protein syntheses. Under conditions in which nutrients are limited to a carbon source, nitrogen source, essential phosphates, and salts, more than 100 additional genes become essential. These largely code for the synthesis of amino acids, vitamins, and nucleobases. Although much is known about this collection of ∼400 genes, their interactions under nutrient stress are uncharted. Using a chemical biology approach, we focused on 45 chemical probes targeting encoded proteins in this collection and mapped their interactions under nutrient-limited conditions. Encompassing 990 unique pairwise chemical combinations, we revealed a highly connected network of 186 interactions, of which 81 were synergistic and 105 were antagonistic. The network revealed signature interactions for each probe and highlighted new connectivity between housekeeping functions and those essential in nutrient stress. Chemical probes map a complex interaction network in E. coli under nutrient stress A total of 990 unique chemical combinations reveal a dense network of 186 interactions New connections between housekeeping functions and those in nutrient stress
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Affiliation(s)
- Sara S El Zahed
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 3Z5, Canada; Michael G. DeGroote Institute of Infectious Disease Research, McMaster University, Hamilton, ON L8N 3Z5, Canada
| | - Eric D Brown
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 3Z5, Canada; Michael G. DeGroote Institute of Infectious Disease Research, McMaster University, Hamilton, ON L8N 3Z5, Canada.
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9
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Gehrke SS, Kumar G, Yokubynas NA, Côté JP, Wang W, French S, MacNair CR, Wright GD, Brown ED. Exploiting the Sensitivity of Nutrient Transporter Deletion Strains in Discovery of Natural Product Antimetabolites. ACS Infect Dis 2017; 3:955-965. [PMID: 29069544 DOI: 10.1021/acsinfecdis.7b00149] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Actinomycete secondary metabolites are a renowned source of antibacterial chemical scaffolds. Herein, we present a target-specific approach that increases the detection of antimetabolites from natural sources by screening actinomycete-derived extracts against nutrient transporter deletion strains. On the basis of the growth rescue patterns of a collection of 22 Escherichia coli (E. coli) auxotrophic deletion strains representative of the major nutrient biosynthetic pathways, we demonstrate that antimetabolite detection from actinomycete-derived extracts prepared using traditional extraction platforms is masked by nutrient supplementation. In particular, we find poor sensitivity for the detection of antimetabolites targeting vitamin biosynthesis. To circumvent this and as a proof of principle, we exploit the differential activity of actinomycete extracts against E. coli ΔyigM, a biotin transporter deletion strain versus wildtype E. coli. We achieve more than a 100-fold increase in antimetabolite sensitivity using this method and demonstrate a successful bioassay-guided purification of the known biotin antimetabolite, amiclenomycin. Our findings provide a unique solution to uncover the full potential of naturally derived antibiotics.
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Affiliation(s)
- Sebastian S. Gehrke
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Garima Kumar
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Nicole A. Yokubynas
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Jean-Philippe Côté
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Wenliang Wang
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Shawn French
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Craig R. MacNair
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Gerard D. Wright
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Eric D. Brown
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
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10
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Fluorothreonyl-tRNA deacylase prevents mistranslation in the organofluorine producer Streptomyces cattleya. Proc Natl Acad Sci U S A 2017; 114:11920-11925. [PMID: 29078362 DOI: 10.1073/pnas.1711482114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Fluorine is an element with unusual properties that has found significant utility in the design of synthetic small molecules, ranging from therapeutics to materials. In contrast, only a few fluorinated compounds made by living organisms have been found to date, most of which derive from the fluoroacetate/fluorothreonine biosynthetic pathway first discovered in Streptomyces cattleya While fluoroacetate has long been known to act as an inhibitor of the tricarboxylic acid cycle, the fate of the amino acid fluorothreonine is still not well understood. Here, we show that fluorothreonine can be misincorporated into protein in place of the proteinogenic amino acid threonine. We have identified two conserved proteins from the organofluorine biosynthetic locus, FthB and FthC, that are involved in managing fluorothreonine toxicity. Using a combination of biochemical, genetic, physiological, and proteomic studies, we show that FthB is a trans-acting transfer RNA (tRNA) editing protein, which hydrolyzes fluorothreonyl-tRNA 670-fold more efficiently than threonyl-RNA, and assign a role to FthC in fluorothreonine transport. While trans-acting tRNA editing proteins have been found to counteract the misacylation of tRNA with commonly occurring near-cognate amino acids, their role has yet to be described in the context of secondary metabolism. In this regard, the recruitment of tRNA editing proteins to biosynthetic clusters may have enabled the evolution of pathways to produce specialized amino acids, thereby increasing the diversity of natural product structure while also attenuating the risk of mistranslation that would ensue.
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11
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Cvetesic N, Gruic-Sovulj I. Synthetic and editing reactions of aminoacyl-tRNA synthetases using cognate and non-cognate amino acid substrates. Methods 2016; 113:13-26. [PMID: 27713080 DOI: 10.1016/j.ymeth.2016.09.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/29/2016] [Accepted: 09/29/2016] [Indexed: 11/19/2022] Open
Abstract
The covalent coupling of cognate amino acid-tRNA pairs by corresponding aminoacyl-tRNA synthetases (aaRS) defines the genetic code and provides aminoacylated tRNAs for ribosomal protein synthesis. Besides the cognate substrate, some non-cognate amino acids may also compete for tRNA aminoacylation. However, their participation in protein synthesis is generally prevented by an aaRS proofreading activity located in the synthetic site and in a separate editing domain. These mechanisms, coupled with the ability of certain aaRSs to discriminate well against non-cognate amino acids in the synthetic reaction alone, define the accuracy of the aminoacylation reaction. aaRS quality control may also act as a gatekeeper for the standard genetic code and prevents infiltration by natural amino acids that are not normally coded for protein biosynthesis. This latter finding has reinforced interest in understanding the principles that govern discrimination against a range of potential non-cognate amino acids. This paper presents an overview of the kinetic assays that have been established for monitoring synthetic and editing reactions with cognate and non-cognate amino acid substrates. Taking into account the peculiarities of non-cognate reactions, the specific controls needed and the dedicated experimental designs are discussed in detail. Kinetic partitioning within the synthetic and editing sites controls the balance between editing and aminoacylation. We describe in detail steady-state and single-turnover approaches for the analysis of synthetic and editing reactions, which ultimately enable mechanisms of amino acid discrimination to be determined.
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Affiliation(s)
- Nevena Cvetesic
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia
| | - Ita Gruic-Sovulj
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia.
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12
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Wang X, Pan T. Stress Response and Adaptation Mediated by Amino Acid Misincorporation during Protein Synthesis. Adv Nutr 2016; 7:773S-9S. [PMID: 27422514 PMCID: PMC4942860 DOI: 10.3945/an.115.010991] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Translation of genetic information into functional proteins is critical for all cellular life. Accurate protein synthesis relies on proper aminoacylation of transfer RNAs (tRNAs) and decoding of mRNAs by the ribosome with the use of aminoacyl-tRNAs. Mistranslation can lead to pathologic consequences. All cells contain elaborate quality control mechanisms in translation, although translational fidelity may be regulated by various factors such as nutrient limitation or reactive oxygen species. Translation fidelity is maintained via the accuracy of tRNA aminoacylation by the aminoacyl-tRNA synthetases and matching of the mRNA codon with the tRNA anticodon by the ribosome. Stringent substrate discrimination and proofreading are critical in aminoacylating tRNAs with their cognate amino acid to maintain high accuracy of translation. Although the composition of the cellular proteome generally adheres to the genetic code, accumulating evidence indicates that cells can also deliberately mistranslate; they synthesize mutant proteins that deviate from the genetic code in response to stress or environmental changes. Mistranslation with tRNA charged with noncognate amino acids can expand the proteome to enhance stress response and help adaptation. Here, we review current knowledge on mistranslation through tRNA misacylation and describe advances in our understanding of translational control in the regulation of stress response and human diseases.
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Affiliation(s)
- Xiaoyun Wang
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
| | - Tao Pan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
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13
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Commichau FM, Alzinger A, Sande R, Bretzel W, Reuß DR, Dormeyer M, Chevreux B, Schuldes J, Daniel R, Akeroyd M, Wyss M, Hohmann HP, Prágai Z. Engineering Bacillus subtilis for the conversion of the antimetabolite 4-hydroxy-l-threonine to pyridoxine. Metab Eng 2015; 29:196-207. [DOI: 10.1016/j.ymben.2015.03.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 02/12/2015] [Accepted: 03/05/2015] [Indexed: 11/25/2022]
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14
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Perona JJ, Hadd A. Structural diversity and protein engineering of the aminoacyl-tRNA synthetases. Biochemistry 2012; 51:8705-29. [PMID: 23075299 DOI: 10.1021/bi301180x] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Aminoacyl-tRNA synthetases (aaRS) are the enzymes that ensure faithful transmission of genetic information in all living cells, and are central to the developing technologies for expanding the capacity of the translation apparatus to incorporate nonstandard amino acids into proteins in vivo. The 24 known aaRS families are divided into two classes that exhibit functional evolutionary convergence. Each class features an active site domain with a common fold that binds ATP, the amino acid, and the 3'-terminus of tRNA, embellished by idiosyncratic further domains that bind distal portions of the tRNA and enhance specificity. Fidelity in the expression of the genetic code requires that the aaRS be selective for both amino acids and tRNAs, a substantial challenge given the presence of structurally very similar noncognate substrates of both types. Here we comprehensively review central themes concerning the architectures of the protein structures and the remarkable dual-substrate selectivities, with a view toward discerning the most important issues that still substantially limit our capacity for rational protein engineering. A suggested general approach to rational design is presented, which should yield insight into the identities of the protein-RNA motifs at the heart of the genetic code, while also offering a basis for improving the catalytic properties of engineered tRNA synthetases emerging from genetic selections.
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Affiliation(s)
- John J Perona
- Department of Chemistry, Portland State University, Portland, Oregon 97207, United States.
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15
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Cvetesic N, Perona JJ, Gruic-Sovulj I. Kinetic partitioning between synthetic and editing pathways in class I aminoacyl-tRNA synthetases occurs at both pre-transfer and post-transfer hydrolytic steps. J Biol Chem 2012; 287:25381-94. [PMID: 22648413 DOI: 10.1074/jbc.m112.372151] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Comprehensive steady-state and transient kinetic studies of the synthetic and editing activities of Escherichia coli leucyl-tRNA synthetase (LeuRS) demonstrate that the enzyme depends almost entirely on post-transfer editing to endow the cell with specificity against incorporation of norvaline into protein. Among the three class I tRNA synthetases possessing a dedicated post-transfer editing domain (connective peptide 1; CP1 domain), LeuRS resembles valyl-tRNA synthetase in its reliance on post-transfer editing, whereas isoleucyl-tRNA synthetase differs in retaining a distinct tRNA-dependent synthetic site pre-transfer editing activity to clear noncognate amino acids before misacylation. Further characterization of the post-transfer editing activity in LeuRS by single-turnover kinetics demonstrates that the rate-limiting step is dissociation of deacylated tRNA and/or amino acid product and highlights the critical role of a conserved aspartate residue in mediating the first-order hydrolytic steps on the enzyme. Parallel analyses of adenylate and aminoacyl-tRNA formation reactions by wild-type and mutant LeuRS demonstrate that the efficiency of post-transfer editing is controlled by kinetic partitioning between hydrolysis and dissociation of misacylated tRNA and shows that trans editing after rebinding is a competent kinetic pathway. Together with prior analyses of isoleucyl-tRNA synthetase and valyl-tRNA synthetase, these experiments provide the basis for a comprehensive model of editing by class I tRNA synthetases, in which kinetic partitioning plays an essential role at both pre-transfer and post-transfer steps.
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Affiliation(s)
- Nevena Cvetesic
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia
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