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Opuu V, Nigro G, Lazennec‐Schurdevin C, Mechulam Y, Schmitt E, Simonson T. Redesigning methionyl-tRNA synthetase for β-methionine activity with adaptive landscape flattening and experiments. Protein Sci 2023; 32:e4738. [PMID: 37518893 PMCID: PMC10451022 DOI: 10.1002/pro.4738] [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: 05/29/2023] [Revised: 07/21/2023] [Accepted: 07/23/2023] [Indexed: 08/01/2023]
Abstract
Amino acids (AAs) with a noncanonical backbone would be a valuable tool for protein engineering, enabling new structural motifs and building blocks. To incorporate them into an expanded genetic code, the first, key step is to obtain an appropriate aminoacyl-tRNA synthetase. Currently, directed evolution is not available to optimize AAs with noncanonical backbones, since an appropriate selective pressure has not been discovered. Computational protein design (CPD) is an alternative. We used a new CPD method to redesign MetRS and increase its activity towards β-Met, which has an extra backbone methylene. The new method considered a few active site positions for design and used a Monte Carlo exploration of the corresponding sequence space. During the exploration, a bias energy was adaptively learned, such that the free energy landscape of the apo enzyme was flattened. Enzyme variants could then be sampled, in the presence of the ligand and the bias energy, according to their β-Met binding affinities. Eighteen predicted variants were chosen for experimental testing; 10 exhibited detectable activity for β-Met adenylation. Top predicted hits were characterized experimentally in detail. Dissociation constants, catalytic rates, and Michaelis constants for both α-Met and β-Met were measured. The best mutant retained a preference for α-Met over β-Met; however, the preference was reduced, compared to the wildtype, by a factor of 29. For this mutant, high resolution crystal structures were obtained in complex with both α-Met and β-Met, indicating that the predicted, active conformation of β-Met in the active site was retained.
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Affiliation(s)
- Vaitea Opuu
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole PolytechniqueInstitut Polytechnique de ParisPalaiseauFrance
| | - Giuliano Nigro
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole PolytechniqueInstitut Polytechnique de ParisPalaiseauFrance
| | - Christine Lazennec‐Schurdevin
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole PolytechniqueInstitut Polytechnique de ParisPalaiseauFrance
| | - Yves Mechulam
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole PolytechniqueInstitut Polytechnique de ParisPalaiseauFrance
| | - Emmanuelle Schmitt
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole PolytechniqueInstitut Polytechnique de ParisPalaiseauFrance
| | - Thomas Simonson
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole PolytechniqueInstitut Polytechnique de ParisPalaiseauFrance
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2
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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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3
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Adaptive landscape flattening allows the design of both enzyme: Substrate binding and catalytic power. PLoS Comput Biol 2020; 16:e1007600. [PMID: 31917825 PMCID: PMC7041857 DOI: 10.1371/journal.pcbi.1007600] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 02/25/2020] [Accepted: 12/11/2019] [Indexed: 01/30/2023] Open
Abstract
Designed enzymes are of fundamental and technological interest. Experimental directed evolution still has significant limitations, and computational approaches are a complementary route. A designed enzyme should satisfy multiple criteria: stability, substrate binding, transition state binding. Such multi-objective design is computationally challenging. Two recent studies used adaptive importance sampling Monte Carlo to redesign proteins for ligand binding. By first flattening the energy landscape of the apo protein, they obtained positive design for the bound state and negative design for the unbound. We have now extended the method to design an enzyme for specific transition state binding, i.e., for its catalytic power. We considered methionyl-tRNA synthetase (MetRS), which attaches methionine (Met) to its cognate tRNA, establishing codon identity. Previously, MetRS and other synthetases have been redesigned by experimental directed evolution to accept noncanonical amino acids as substrates, leading to genetic code expansion. Here, we have redesigned MetRS computationally to bind several ligands: the Met analog azidonorleucine, methionyl-adenylate (MetAMP), and the activated ligands that form the transition state for MetAMP production. Enzyme mutants known to have azidonorleucine activity were recovered by the design calculations, and 17 mutants predicted to bind MetAMP were characterized experimentally and all found to be active. Mutants predicted to have low activation free energies for MetAMP production were found to be active and the predicted reaction rates agreed well with the experimental values. We suggest the present method should become the paradigm for computational enzyme design. Designed enzymes are of major interest. Experimental directed evolution still has significant limitations, and computational approaches are another route. Enzymes must be stable, bind substrates, and be powerful catalysts. It is challenging to design for all these properties. A method to design substrate binding was proposed recently. It used an adaptive Monte Carlo method to explore mutations of a few amino acids near the substrate. A bias energy was gradually “learned” such that, in the absence of the ligand, the simulation visited most of the possible protein mutations with comparable probabilities. Remarkably, a simulation of the protein:ligand complex, including the bias, will then preferentially sample tight-binding sequences. We generalized the method to design binding specificity. We tested it for the methionyl-tRNA synthetase enzyme, which has been engineered in order to expand the genetic code. We redesigned the enzyme to obtain variants with low activation free energies for the catalytic step. The variants proposed by the simulations were shown experimentally to be active, and the predicted activation free energies were in reasonable agreement with the experimental values. We expect the new method will become the paradigm for computational enzyme design.
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4
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Nigro G, Bourcier S, Lazennec-Schurdevin C, Schmitt E, Marlière P, Mechulam Y. Use of β 3-methionine as an amino acid substrate of Escherichia coli methionyl-tRNA synthetase. J Struct Biol 2019; 209:107435. [PMID: 31862305 DOI: 10.1016/j.jsb.2019.107435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/15/2019] [Accepted: 12/13/2019] [Indexed: 11/17/2022]
Abstract
Polypeptides containing β-amino acids are attractive tools for the design of novel proteins having unique properties of medical or industrial interest. Incorporation of β-amino acids in vivo requires the development of efficient aminoacyl-tRNA synthetases specific of these non-canonical amino acids. Here, we have performed a detailed structural and biochemical study of the recognition and use of β3-Met by Escherichia coli methionyl-tRNA synthetase (MetRS). We show that MetRS binds β3-Met with a 24-fold lower affinity but catalyzes the esterification of the non-canonical amino acid onto tRNA with a rate lowered by three orders of magnitude. Accurate measurements of the catalytic parameters required careful consideration of the presence of contaminating α-Met in β3-Met commercial samples. The 1.45 Å crystal structure of the MetRS: β3-Met complex shows that β3-Met binds the enzyme essentially like α-Met, but the carboxylate moiety is mobile and not adequately positioned to react with ATP for aminoacyl adenylate formation. This study provides structural and biochemical bases for engineering MetRS with improved β3-Met aminoacylation capabilities.
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Affiliation(s)
- Giuliano Nigro
- Laboratoire de Biochimie, BIOC, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Sophie Bourcier
- Laboratoire de Chimie Moléculaire, LCM, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Christine Lazennec-Schurdevin
- Laboratoire de Biochimie, BIOC, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Emmanuelle Schmitt
- Laboratoire de Biochimie, BIOC, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France.
| | - Philippe Marlière
- Xenome Research Group, Institute of Systems and Synthetic Biology, CNRS, UMR8030, UEVE, CEA, GENOPOLE, 5 rue Henri Desbruères, 91030 Evry Cedex, France
| | - Yves Mechulam
- Laboratoire de Biochimie, BIOC, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France.
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5
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Thomas EE, Pandey N, Knudsen S, Ball ZT, Silberg JJ. Programming Post-Translational Control over the Metabolic Labeling of Cellular Proteins with a Noncanonical Amino Acid. ACS Synth Biol 2017; 6:1572-1583. [PMID: 28419802 PMCID: PMC6858787 DOI: 10.1021/acssynbio.7b00100] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Transcriptional control can be used to program cells to label proteins with noncanonical amino acids by regulating the expression of orthogonal aminoacyl tRNA synthetases (aaRSs). However, we cannot yet program cells to control labeling in response to aaRS and ligand binding. To identify aaRSs whose activities can be regulated by interactions with ligands, we used a combinatorial approach to discover fragmented variants of Escherichia coli methionyl tRNA synthetase (MetRS) that require fusion to associating proteins for maximal activity. We found that these split proteins could be leveraged to create ligand-dependent MetRS using two approaches. When a pair of MetRS fragments was fused to FKBP12 and the FKBP-rapamycin binding domain (FRB) of mTOR and mutations were introduced that direct substrate specificity toward azidonorleucine (Anl), Anl metabolic labeling was significantly enhanced in growth medium containing rapamycin, which stabilizes the FKBP12-FRB complex. In addition, fusion of MetRS fragments to the termini of the ligand-binding domain of the estrogen receptor yielded proteins whose Anl metabolic labeling was significantly enhanced when 4-hydroxytamoxifen (4-HT) was added to the growth medium. These findings suggest that split MetRS can be fused to a range of ligand-binding proteins to create aaRSs whose metabolic labeling activities depend upon post-translational interactions with ligands.
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Affiliation(s)
- Emily E. Thomas
- Department of Biosciences, Rice University, Houston, TX 77005, USA
- Biochemistry and Cell Biology Graduate Program, Rice University, Houston, TX 77005, USA
| | - Naresh Pandey
- Department of Biosciences, Rice University, Houston, TX 77005, USA
| | - Sarah Knudsen
- Department of Chemistry, Rice University, Houston, TX 77005, USA
| | - Zachary T. Ball
- Department of Chemistry, Rice University, Houston, TX 77005, USA
| | - Jonathan J. Silberg
- Department of Biosciences, Rice University, Houston, TX 77005, USA
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
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6
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Abstract
Aminoacyl-tRNA synthetases (aaRSs) are modular enzymes globally conserved in the three kingdoms of life. All catalyze the same two-step reaction, i.e., the attachment of a proteinogenic amino acid on their cognate tRNAs, thereby mediating the correct expression of the genetic code. In addition, some aaRSs acquired other functions beyond this key role in translation. Genomics and X-ray crystallography have revealed great structural diversity in aaRSs (e.g., in oligomery and modularity, in ranking into two distinct groups each subdivided in 3 subgroups, by additional domains appended on the catalytic modules). AaRSs show huge structural plasticity related to function and limited idiosyncrasies that are kingdom or even species specific (e.g., the presence in many Bacteria of non discriminating aaRSs compensating for the absence of one or two specific aaRSs, notably AsnRS and/or GlnRS). Diversity, as well, occurs in the mechanisms of aaRS gene regulation that are not conserved in evolution, notably between distant groups such as Gram-positive and Gram-negative Bacteria. The review focuses on bacterial aaRSs (and their paralogs) and covers their structure, function, regulation, and evolution. Structure/function relationships are emphasized, notably the enzymology of tRNA aminoacylation and the editing mechanisms for correction of activation and charging errors. The huge amount of genomic and structural data that accumulated in last two decades is reviewed, showing how the field moved from essentially reductionist biology towards more global and integrated approaches. Likewise, the alternative functions of aaRSs and those of aaRS paralogs (e.g., during cell wall biogenesis and other metabolic processes in or outside protein synthesis) are reviewed. Since aaRS phylogenies present promiscuous bacterial, archaeal, and eukaryal features, similarities and differences in the properties of aaRSs from the three kingdoms of life are pinpointed throughout the review and distinctive characteristics of bacterium-like synthetases from organelles are outlined.
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Affiliation(s)
- Richard Giegé
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 67084 Strasbourg, France
| | - Mathias Springer
- Université Paris Diderot, Sorbonne Cité, UPR9073 CNRS, IBPC, 75005 Paris, France
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7
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Singh G, Singh J, Mangat SS, Singh J, Rani S. Chalcomer assembly of optical chemosensors for selective Cu2+ and Ni2+ ion recognition. RSC Adv 2015. [DOI: 10.1039/c4ra14329a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The o-, m- and p-isomeric units of chalconyl triazole-based, caged organosilicon complexes were efficiently synthesized and explored for their cationic chemosensing activities.
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Affiliation(s)
- Gurjaspreet Singh
- Department of Chemistry and Centre of Advanced Studies
- Panjab University
- Chandigarh
- India
| | - Jandeep Singh
- Department of Chemistry and Centre of Advanced Studies
- Panjab University
- Chandigarh
- India
| | | | - Jasbhinder Singh
- Department of Chemistry and Centre of Advanced Studies
- Panjab University
- Chandigarh
- India
| | - Sunita Rani
- Department of Chemistry and Centre of Advanced Studies
- Panjab University
- Chandigarh
- India
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8
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Lang K, Chin JW. Cellular incorporation of unnatural amino acids and bioorthogonal labeling of proteins. Chem Rev 2014; 114:4764-806. [PMID: 24655057 DOI: 10.1021/cr400355w] [Citation(s) in RCA: 801] [Impact Index Per Article: 80.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Kathrin Lang
- Medical Research Council Laboratory of Molecular Biology , Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
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9
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Mahdavi A, Segall-Shapiro TH, Kou S, Jindal GA, Hoff KG, Liu S, Chitsaz M, Ismagilov RF, Silberg JJ, Tirrell DA. A genetically encoded and gate for cell-targeted metabolic labeling of proteins. J Am Chem Soc 2013; 135:2979-82. [PMID: 23406315 DOI: 10.1021/ja400448f] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We describe a genetic AND gate for cell-targeted metabolic labeling and proteomic analysis in complex cellular systems. The centerpiece of the AND gate is a bisected methionyl-tRNA synthetase (MetRS) that charges the Met surrogate azidonorleucine (Anl) to tRNA(Met). Cellular protein labeling occurs only upon activation of two different promoters that drive expression of the N- and C-terminal fragments of the bisected MetRS. Anl-labeled proteins can be tagged with fluorescent dyes or affinity reagents via either copper-catalyzed or strain-promoted azide-alkyne cycloaddition. Protein labeling is apparent within 5 min after addition of Anl to bacterial cells in which the AND gate has been activated. This method allows spatial and temporal control of proteomic labeling and identification of proteins made in specific cellular subpopulations. The approach is demonstrated by selective labeling of proteins in bacterial cells immobilized in the center of a laminar-flow microfluidic channel, where they are exposed to overlapping, opposed gradients of inducers of the N- and C-terminal MetRS fragments. The observed labeling profile is predicted accurately from the strengths of the individual input signals.
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Affiliation(s)
- Alborz Mahdavi
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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10
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Perona JJ, Gruic-Sovulj I. Synthetic and editing mechanisms of aminoacyl-tRNA synthetases. Top Curr Chem (Cham) 2013; 344:1-41. [PMID: 23852030 DOI: 10.1007/128_2013_456] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Aminoacyl-tRNA synthetases (aaRS) ensure the faithful transmission of genetic information in all living cells. The 24 known aaRS families are divided into 2 structurally distinct classes (class I and class II), each featuring a catalytic domain with a common fold that binds ATP, amino acid, and the 3'-terminus of tRNA. In a common two-step reaction, each aaRS first uses the energy stored in ATP to synthesize an activated aminoacyl adenylate intermediate. In the second step, either the 2'- or 3'-hydroxyl oxygen atom of the 3'-A76 tRNA nucleotide functions as a nucleophile in synthesis of aminoacyl-tRNA. Ten of the 24 aaRS families are unable to distinguish cognate from noncognate amino acids in the synthetic reactions alone. These enzymes possess additional editing activities for hydrolysis of misactivated amino acids and misacylated tRNAs, with clearance of the latter species accomplished in spatially separate post-transfer editing domains. A distinct class of trans-acting proteins that are homologous to class II editing domains also perform hydrolytic editing of some misacylated tRNAs. Here we review essential themes in catalysis with a view toward integrating the kinetic, stereochemical, and structural mechanisms of the enzymes. Although the aaRS have now been the subject of investigation for many decades, it will be seen that a significant number of questions regarding fundamental catalytic functioning still remain unresolved.
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Affiliation(s)
- John J Perona
- Department of Chemistry, Portland State University, 751, Portland, OR, 97207, USA,
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11
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Abstract
Aminoacyl-tRNAsynthetases (aaRSs) are modular enzymesglobally conserved in the three kingdoms of life. All catalyze the same two-step reaction, i.e., the attachment of a proteinogenic amino acid on their cognate tRNAs, thereby mediating the correct expression of the genetic code. In addition, some aaRSs acquired other functions beyond this key role in translation.Genomics and X-ray crystallography have revealed great structural diversity in aaRSs (e.g.,in oligomery and modularity, in ranking into two distinct groups each subdivided in 3 subgroups, by additional domains appended on the catalytic modules). AaRSs show hugestructural plasticity related to function andlimited idiosyncrasies that are kingdom or even speciesspecific (e.g.,the presence in many Bacteria of non discriminating aaRSs compensating for the absence of one or two specific aaRSs, notably AsnRS and/or GlnRS).Diversity, as well, occurs in the mechanisms of aaRS gene regulation that are not conserved in evolution, notably betweendistant groups such as Gram-positive and Gram-negative Bacteria.Thereview focuses on bacterial aaRSs (and their paralogs) and covers their structure, function, regulation,and evolution. Structure/function relationships are emphasized, notably the enzymology of tRNA aminoacylation and the editing mechanisms for correction of activation and charging errors. The huge amount of genomic and structural data that accumulatedin last two decades is reviewed,showing how thefield moved from essentially reductionist biologytowards more global and integrated approaches. Likewise, the alternative functions of aaRSs and those of aaRSparalogs (e.g., during cellwall biogenesis and other metabolic processes in or outside protein synthesis) are reviewed. Since aaRS phylogenies present promiscuous bacterial, archaeal, and eukaryal features, similarities and differences in the properties of aaRSs from the three kingdoms of life are pinpointedthroughout the reviewand distinctive characteristics of bacterium-like synthetases from organelles are outlined.
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12
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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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13
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Abstract
Proteins in living cells can be made receptive to bioorthogonal chemistries through metabolic labeling with appropriately designed noncanonical amino acids (ncAAs). In the simplest approach to metabolic labeling, an amino acid analog replaces one of the natural amino acids specified by the protein's gene (or genes) of interest. Through manipulation of experimental conditions, the extent of the replacement can be adjusted. This approach, often termed residue-specific incorporation, allows the ncAA to be incorporated in controlled proportions into positions normally occupied by the natural amino acid residue. For a protein to be labeled in this way with an ncAA, it must fulfill just two requirements: (i) the corresponding natural amino acid must be encoded within the sequence of the protein at the genetic level, and (ii) the protein must be expressed while the ncAA is in the cell. Because this approach permits labeling of proteins throughout the cell, it has enabled us to develop strategies to track cellular protein synthesis by tagging proteins with reactive ncAAs. In procedures similar to isotopic labeling, translationally active ncAAs are incorporated into proteins during a "pulse" in which newly synthesized proteins are tagged. The set of tagged proteins can be distinguished from those made before the pulse by bioorthogonally ligating the ncAA side chain to probes that permit detection, isolation, and visualization of the labeled proteins. Noncanonical amino acids with side chains containing azide, alkyne, or alkene groups have been especially useful in experiments of this kind. They have been incorporated into proteins in the form of methionine analogs that are substrates for the natural translational machinery. The selectivity of the method can be enhanced through the use of mutant aminoacyl tRNA synthetases (aaRSs) that permit incorporation of ncAAs not used by the endogenous biomachinery. Through expression of mutant aaRSs, proteins can be tagged with other useful ncAAs, including analogs that contain ketones or aryl halides. High-throughput screening strategies can identify aaRS variants that activate a wide range of ncAAs. Controlled expression of mutant synthetases has been combined with ncAA tagging to permit cell-selective metabolic labeling of proteins. Expression of a mutant synthetase in a portion of cells within a complex cellular mixture restricts labeling to that subset of cells. Proteins synthesized in cells not expressing the synthetase are neither labeled nor detected. In multicellular environments, this approach permits the identification of the cellular origins of labeled proteins. In this Account, we summarize the tools and strategies that have been developed for interrogating cellular protein synthesis through residue-specific tagging with ncAAs. We describe the chemical and genetic components of ncAA-tagging strategies and discuss how these methods are being used in chemical biology.
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Affiliation(s)
- John T. Ngo
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
| | - David A. Tirrell
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
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14
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Larson ET, Kim JE, Zucker FH, Kelley A, Mueller N, Napuli AJ, Verlinde CL, Fan E, Buckner FS, Van Voorhis WC, Merritt EA, Hol WG. Structure of Leishmania major methionyl-tRNA synthetase in complex with intermediate products methionyladenylate and pyrophosphate. Biochimie 2011; 93:570-82. [PMID: 21144880 PMCID: PMC3039092 DOI: 10.1016/j.biochi.2010.11.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 11/29/2010] [Indexed: 01/07/2023]
Abstract
Leishmania parasites cause two million new cases of leishmaniasis each year with several hundreds of millions of people at risk. Due to the paucity and shortcomings of available drugs, we have undertaken the crystal structure determination of a key enzyme from Leishmania major in hopes of creating a platform for the rational design of new therapeutics. Crystals of the catalytic core of methionyl-tRNA synthetase from L. major (LmMetRS) were obtained with the substrates MgATP and methionine present in the crystallization medium. These crystals yielded the 2.0 Å resolution structure of LmMetRS in complex with two products, methionyladenylate and pyrophosphate, along with a Mg(2+) ion that bridges them. This is the first class I aminoacyl-tRNA synthetase (aaRS) structure with pyrophosphate bound. The residues of the class I aaRS signature sequence motifs, KISKS and HIGH, make numerous contacts with the pyrophosphate. Substantial differences between the LmMetRS structure and previously reported complexes of Escherichia coli MetRS (EcMetRS) with analogs of the methionyladenylate intermediate product are observed, even though one of these analogs only differs by one atom from the intermediate. The source of these structural differences is attributed to the presence of the product pyrophosphate in LmMetRS. Analysis of the LmMetRS structure in light of the Aquifex aeolicus MetRS-tRNA(Met) complex shows that major rearrangements of multiple structural elements of enzyme and/or tRNA are required to allow the CCA acceptor triplet to reach the methionyladenylate intermediate in the active site. Comparison with sequences of human cytosolic and mitochondrial MetRS reveals interesting differences near the ATP- and methionine-binding regions of LmMetRS, suggesting that it should be possible to obtain compounds that selectively inhibit the parasite enzyme.
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Affiliation(s)
- Eric T. Larson
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org
| | - Jessica E. Kim
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org
| | - Frank H. Zucker
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org
| | - Angela Kelley
- Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org,Department of Medicine, University of Washington, Seattle, WA 98195-7185, USA
| | - Natascha Mueller
- Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org,Department of Medicine, University of Washington, Seattle, WA 98195-7185, USA
| | - Alberto J. Napuli
- Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org,Department of Medicine, University of Washington, Seattle, WA 98195-7185, USA
| | - Christophe L.M.J. Verlinde
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org
| | - Erkang Fan
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org
| | - Frederick S. Buckner
- Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org,Department of Medicine, University of Washington, Seattle, WA 98195-7185, USA
| | - Wesley C. Van Voorhis
- Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org,Department of Medicine, University of Washington, Seattle, WA 98195-7185, USA
| | - Ethan A. Merritt
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org
| | - Wim G.J. Hol
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7742, USA,Medical Structural Genomics of Pathogenic Protozoa (MSGPP), www.msgpp.org,Corresponding author.
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Ingvarsson H, Unge T. Flexibility and communication within the structure of the Mycobacterium smegmatis methionyl-tRNA synthetase. FEBS J 2010; 277:3947-62. [PMID: 20796028 DOI: 10.1111/j.1742-4658.2010.07784.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two structures of monomeric methionyl-tRNA synthetase, from Mycobacterium smegmatis, in complex with the ligands methionine/adenosine and methionine, were analyzed by X-ray crystallography at 2.3 Å and at 2.8 Å, respectively. The structures demonstrated the flexibility of the multidomain enzyme. A new conformation of the structure was identified in which the connective peptide domain bound more closely to the catalytic domain than described previously. The KMSKS(301-305) loop in our structures was in an open and inactive conformation that differed from previous structures by a rotation of the loop of about 90° around hinges located at Asn297 and Val310. The binding of adenosine to the methionyl-tRNA synthetase methionine complex caused a shift in the KMSKS domain that brought it closer to the catalytic domain. The potential use of the adenosine-binding site for inhibitor binding was evaluated and a potential binding site for a specific allosteric inhibitor was identified.
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Affiliation(s)
- Henrik Ingvarsson
- Department of Cell and Molecular Biology, Uppsala Biomedical Center, Uppsala University, Uppsala, Sweden
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