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Chandrasekaran SN, Das J, Dokholyan NV, Carter CW. Microcalorimetry reveals multi-state thermal denaturation of G. stearothermophilus tryptophanyl-tRNA synthetase. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2023; 10:044301. [PMID: 37476003 PMCID: PMC10356175 DOI: 10.1063/4.0000181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 06/21/2023] [Indexed: 07/22/2023]
Abstract
Mechanistic studies of Geobacillus stearothermophilus tryptophanyl-tRNA synthetase (TrpRS) afford an unusually detailed description-the escapement mechanism-for the distinct steps coupling catalysis to domain motion, efficiently converting the free energy of ATP hydrolysis into biologically useful alternative forms of information and work. Further elucidation of the escapement mechanism requires understanding thermodynamic linkages between domain configuration and conformational stability. To that end, we compare experimental thermal melting of fully liganded and apo TrpRS with a computational simulation of the melting of its fully liganded form. The simulation also provides important structural cameos at successively higher temperatures, enabling more confident interpretation. Experimental and simulated melting both proceed through a succession of three transitions at successively higher temperature. The low-temperature transition occurs at approximately the growth temperature of the organism and so may be functionally relevant but remains too subtle to characterize structurally. Structural metrics from the simulation imply that the two higher-temperature transitions entail forming a molten globular state followed by unfolding of secondary structures. Ligands that stabilize the enzyme in a pre-transition (PreTS) state compress the temperature range over which these transitions occur and sharpen the transitions to the molten globule and fully denatured states, while broadening the low-temperature transition. The experimental enthalpy changes provide a key parameter necessary to convert changes in melting temperature of combinatorial mutants into mutationally induced conformational free energy changes. The TrpRS urzyme, an excerpted model representing an early ancestral form, containing virtually the entire catalytic apparatus, remains largely intact at the highest simulated temperatures.
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Affiliation(s)
| | - Jhuma Das
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Nikolay V. Dokholyan
- Department of Pharmacology and Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, Pennsylvania 17033, USA
| | - Charles W. Carter
- Department of Biophysics and Biochemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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2
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Weinreb V, Weinreb G, Carter CW. High-throughput thermal denaturation of tryptophanyl-tRNA synthetase combinatorial mutants reveals high-order energetic coupling determinants of conformational stability. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2023; 10:044304. [PMID: 37637481 PMCID: PMC10449480 DOI: 10.1063/4.0000182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 07/13/2023] [Indexed: 08/29/2023]
Abstract
Landscape descriptions provide a framework for identifying functionally significant dynamic linkages in proteins but cannot supply details. Rate measurements of combinatorial mutations can implicate dynamic linkages in catalysis. A major difficulty is filtering dynamic linkages from the vastly more numerous static interactions that stabilize domain folding. The Geobacillus stearothermophilus (TrpRS) D1 switch is such a dynamic packing motif; it links domain movement to catalysis and specificity. We describe Thermofluor and far UV circular dichroism melting curves for all 16 D1 switch variants to determine their higher-order impact on unliganded TrpRS stability. A prominent transition at intermediate temperatures in TrpRS thermal denaturation is molten globule formation. Combinatorial analysis of thermal melting transcends the protein landscape in four significant respects: (i) bioinformatic methods identify dynamic linkages from coordinates of multiple conformational states. (ii) Relative mutant melting temperatures, δTM, are proportional to free energy changes. (iii) Structural analysis of thermal melting implicates unexpected coupling between the D1 switch packing and regions of high local frustration. Those segments develop molten globular characteristics at the point of greatest complementarity to the chemical transition state and are the first TrpRS structures to melt. (iv) Residue F37 stabilizes both native and molten globular states; its higher-order interactions modify the relative intrinsic impacts of mutations to other D1 switch residues from those estimated for single point mutants. The D1 switch is a central component of an escapement mechanism essential to free energy transduction. These conclusions begin to relate the escapement mechanism to differential TrpRS conformational stabilities.
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Affiliation(s)
- Violetta Weinreb
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260, USA
| | | | - Charles W. Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260, USA
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3
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Fan S, Lv G, Feng X, Wu G, Jin Y, Yan M, Yang Z. Structural insights into the specific interaction between Geobacillus stearothermophilus tryptophanyl-tRNA synthetase and antimicrobial Chuangxinmycin. J Biol Chem 2022; 298:101580. [PMID: 35031320 PMCID: PMC8814664 DOI: 10.1016/j.jbc.2022.101580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/06/2022] [Accepted: 01/08/2022] [Indexed: 11/29/2022] Open
Abstract
The potential antimicrobial compound Chuangxinmycin (CXM) targets the tryptophanyl-tRNA synthetase (TrpRS) of both Gram-negative and Gram-positive bacteria. However, the specific steric recognition mode and interaction mechanism between CXM and TrpRS is unclear. Here, we studied this interaction using recombinant GsTrpRS from Geobacillus stearothermophilus by X-ray crystallography and molecular dynamics (MD) simulations. The crystal structure of the recombinant GsTrpRS in complex with CXM was experimentally determined to a resolution at 2.06 Å. After analysis using a complex-structure probe, MD simulations, and site-directed mutation verification through isothermal titration calorimetry, the interaction between CXM and GsTrpRS was determined to involve the key residues M129, D132, I133, and V141 of GsTrpRS. We further evaluated binding affinities between GsTrpRS WT/mutants and CXM; GsTrpRS was found to bind CXM through hydrogen bonds with D132 and hydrophobic interactions between the lipophilic tricyclic ring of CXM and M129, I133, and V141 in the substrate-binding pockets. This study elucidates the precise interaction mechanism between CXM and its target GsTrpRS at the molecular level and provides a theoretical foundation and guidance for the screening and rational design of more effective CXM analogs against both Gram-negative and Gram-positive bacteria.
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Affiliation(s)
- Shuai Fan
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Guangxin Lv
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Xiao Feng
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Guangteng Wu
- Research and Development Department, ArNuXon Pharm-Sci Co, Ltd, Beijing, China
| | - Yuanyuan Jin
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Maocai Yan
- School of Pharmacy, Jining Medical University, Rizhao, Shandong, China.
| | - Zhaoyong Yang
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
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4
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Grasso KT, Yeo MJR, Hillenbrand CM, Ficaretta ED, Italia JS, Huang RL, Chatterjee A. Structural Robustness Affects the Engineerability of Aminoacyl-tRNA Synthetases for Genetic Code Expansion. Biochemistry 2021; 60:489-493. [PMID: 33560840 DOI: 10.1021/acs.biochem.1c00056] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability to engineer the substrate specificity of natural aminoacyl-tRNA synthetase/tRNA pairs facilitates the site-specific incorporation of noncanonical amino acids (ncAAs) into proteins. The Methanocaldococcus jannaschii-derived tyrosyl-tRNA synthetase (MjTyrRS)/tRNA pair has been engineered to incorporate numerous ncAAs into protein expressed in bacteria. However, it cannot be used in eukaryotic cells due to cross-reactivity with its host counterparts. The Escherichia coli-derived tyrosyl-tRNA synthetase (EcTyrRS)/tRNA pair offers a suitable alternative to this end, but a much smaller subset of ncAAs have been genetically encoded using this pair. Here we report that this discrepancy, at least partly, stems from the structural robustness of EcTyrRS being lower than that of MjTyrRS. We show that the thermostability of engineered TyrRS mutants is generally significantly lower than those of their wild-type counterparts. Derived from a thermophilic archaeon, MjTyrRS is a remarkably sturdy protein and tolerates extensive active site engineering without a catastrophic loss of stability at physiological temperature. In contrast, EcTyrRS exhibits significantly lower thermostability, rendering some of its engineered mutants insufficiently stable at physiological temperature. Our observations identify the structural robustness of an aaRS as an important factor that significantly influences how extensively it can be engineered. To overcome this limitation, we have further developed chimeras between EcTyrRS and its homologue from a thermophilic bacterium, which offer an optimal balance between thermostability and activity. We show that the chimeric bacterial TyrRSs show enhanced tolerance for destabilizing active site mutations, providing a potentially more engineerable platform for genetic code expansion.
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Affiliation(s)
- Katherine T Grasso
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Megan J R Yeo
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Christen M Hillenbrand
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Elise D Ficaretta
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - James S Italia
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Rachel L Huang
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Abhishek Chatterjee
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
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5
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Discovery of indolyl-containing peptides as novel antibacterial agents targeting tryptophanyl-tRNA synthetase. Future Med Chem 2020; 12:877-896. [DOI: 10.4155/fmc-2020-0016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Background: There is an urgent need for antibiotics with novel structures and unexploited targets to counteract bacterial resistance. Methodology & results: Novel tryptophanyl-tRNA synthetase inhibitors were discovered based on virtual screening, surface plasmon resonance binding, enzymatic activity assay and antibacterial activity evaluation. Of the 29 peptide derivatives tested for antibacterial activity, some inhibited the growth of both Staphylococcus aureus and Staphylococcus epidermidis. A13 and A15 exhibited antibacterial activity against methicillin-resistant S. aureus NRS384 at an 8 μg/ml minimum inhibitory concentration. A13 snugly docked into the active site, explaining its improved inhibitory activity. Conclusion: Our results provide us with new structural clues to develop more potent tryptophanyl-tRNA synthetase inhibitors and lay a solid foundation for future drug design efforts.
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6
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Chandrasekaran SN, Carter CW. Augmenting the anisotropic network model with torsional potentials improves PATH performance, enabling detailed comparison with experimental rate data. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:032103. [PMID: 28289692 PMCID: PMC5315668 DOI: 10.1063/1.4976142] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/30/2017] [Indexed: 06/06/2023]
Abstract
PATH algorithms for identifying conformational transition states provide computational parameters-time to the transition state, conformational free energy differences, and transition state activation energies-for comparison to experimental data and can be carried out sufficiently rapidly to use in the "high throughput" mode. These advantages are especially useful for interpreting results from combinatorial mutagenesis experiments. This report updates the previously published algorithm with enhancements that improve correlations between PATH convergence parameters derived from virtual variant structures generated by RosettaBackrub and previously published kinetic data for a complete, four-way combinatorial mutagenesis of a conformational switch in Tryptophanyl-tRNA synthetase.
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Affiliation(s)
- Srinivas Niranj Chandrasekaran
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School , Worcester, Massachusetts 01655, USA
| | - Charles W Carter
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
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7
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Carter CW, Chandrasekaran SN, Weinreb V, Li L, Williams T. Combining multi-mutant and modular thermodynamic cycles to measure energetic coupling networks in enzyme catalysis. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:032101. [PMID: 28191480 PMCID: PMC5272822 DOI: 10.1063/1.4974218] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 12/21/2016] [Indexed: 06/06/2023]
Abstract
We measured and cross-validated the energetics of networks in Bacillus stearothermophilus Tryptophanyl-tRNA synthetase (TrpRS) using both multi-mutant and modular thermodynamic cycles. Multi-dimensional combinatorial mutagenesis showed that four side chains from this "molecular switch" move coordinately with the active-site Mg2+ ion as the active site preorganizes to stabilize the transition state for amino acid activation. A modular thermodynamic cycle consisting of full-length TrpRS, its Urzyme, and the Urzyme plus each of the two domains deleted in the Urzyme gives similar energetics. These dynamic linkages, although unlikely to stabilize the transition-state directly, consign the active-site preorganization to domain motion, assuring coupled vectorial behavior.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Srinivas Niranj Chandrasekaran
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Violetta Weinreb
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Li Li
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Tishan Williams
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
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8
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Carter CW. High-Dimensional Mutant and Modular Thermodynamic Cycles, Molecular Switching, and Free Energy Transduction. Annu Rev Biophys 2017; 46:433-453. [PMID: 28375734 DOI: 10.1146/annurev-biophys-070816-033811] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding how distinct parts of proteins produce coordinated behavior has driven and continues to drive advances in protein science and enzymology. However, despite consensus about the conceptual basis for allostery, the idiosyncratic nature of allosteric mechanisms resists general approaches. Computational methods can identify conformational transition states from structural changes, revealing common switching mechanisms that impose multistate behavior. Thermodynamic cycles use factorial perturbations to measure coupling energies between side chains in molecular switches that mediate shear during domain motion. Such cycles have now been complemented by modular cycles that measure energetic coupling between separable domains. For one model system, energetic coupling between domains has been shown to be quantitatively equivalent to that between dynamic side chains. Linkages between domain motion, switching residues, and catalysis make nucleoside triphosphate hydrolysis conditional on domain movement, confirming an essential yet neglected aspect of free energy transduction and suggesting the potential generality of these studies.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514;
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9
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Moen SO, Edwards TE, Dranow DM, Clifton MC, Sankaran B, Van Voorhis WC, Sharma A, Manoil C, Staker BL, Myler PJ, Lorimer DD. Ligand co-crystallization of aminoacyl-tRNA synthetases from infectious disease organisms. Sci Rep 2017; 7:223. [PMID: 28303005 PMCID: PMC5428304 DOI: 10.1038/s41598-017-00367-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 02/20/2017] [Indexed: 12/15/2022] Open
Abstract
Aminoacyl-tRNA synthetases (aaRSs) charge tRNAs with their cognate amino acid, an essential precursor step to loading of charged tRNAs onto the ribosome and addition of the amino acid to the growing polypeptide chain during protein synthesis. Because of this important biological function, aminoacyl-tRNA synthetases have been the focus of anti-infective drug development efforts and two aaRS inhibitors have been approved as drugs. Several researchers in the scientific community requested aminoacyl-tRNA synthetases to be targeted in the Seattle Structural Genomics Center for Infectious Disease (SSGCID) structure determination pipeline. Here we investigate thirty-one aminoacyl-tRNA synthetases from infectious disease organisms by co-crystallization in the presence of their cognate amino acid, ATP, and/or inhibitors. Crystal structures were determined for a CysRS from Borrelia burgdorferi bound to AMP, GluRS from Borrelia burgdorferi and Burkholderia thailandensis bound to glutamic acid, a TrpRS from the eukaryotic pathogen Encephalitozoon cuniculi bound to tryptophan, a HisRS from Burkholderia thailandensis bound to histidine, and a LysRS from Burkholderia thailandensis bound to lysine. Thus, the presence of ligands may promote aaRS crystallization and structure determination. Comparison with homologous structures shows conformational flexibility that appears to be a recurring theme with this enzyme class.
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Affiliation(s)
- Spencer O Moen
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,Beryllium Discovery Corp, Bainbridge Island, WA, 98110, USA
| | - Thomas E Edwards
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA. .,Beryllium Discovery Corp, Bainbridge Island, WA, 98110, USA.
| | - David M Dranow
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,Beryllium Discovery Corp, Bainbridge Island, WA, 98110, USA
| | - Matthew C Clifton
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,Beryllium Discovery Corp, Bainbridge Island, WA, 98110, USA
| | - Banumathi Sankaran
- Berkeley Center for Structural Biology, Advanced Light Source, Berkeley, CA, 94720, USA
| | - Wesley C Van Voorhis
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,University of Washington, Seattle, WA, 98195-6423, USA
| | - Amit Sharma
- International Center for Genetic Engineering and Biotechnology, New Delhi, 110 067, India
| | - Colin Manoil
- University of Washington, Department of Genome Sciences, Seattle, WA, 98195-5065, USA
| | - Bart L Staker
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, WA, 98109, USA
| | - Peter J Myler
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, WA, 98109, USA.,University of Washington, Department of Medical Education and Biomedical Informatics & Department of Global Health, Seattle, WA, 98195, USA
| | - Donald D Lorimer
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Bethesda, MD, USA.,Beryllium Discovery Corp, Bainbridge Island, WA, 98110, USA
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10
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Koehl P. Minimum action transition paths connecting minima on an energy surface. J Chem Phys 2017; 145:184111. [PMID: 27846680 DOI: 10.1063/1.4966974] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Dynamics is essential to the biological functions of many bio-molecules, yet our knowledge of dynamics remains fragmented. Experimental techniques for studying bio-molecules either provide high resolution information on static conformations of the molecule or provide low-resolution, ensemble information that does not shed light on single molecule dynamics. In parallel, bio-molecular dynamics occur at time scale that are not yet attainable through detailed simulation methods. These limitations are especially noticeable when studying transition paths. To address this issue, we report in this paper two methods that derive meaningful trajectories for proteins between two of their conformations. The first method, MinActionPath, uses approximations of the potential energy surface for the molecule to derive an analytical solution of the equations of motion related to the concept of minimum action path. The second method, RelaxPath, follows the same principle of minimum action path but implements a more sophisticated potential, including a mixed elastic potential and a collision term to alleviate steric clashes. Using this new potential, the equations of motion cannot be solved analytically. We have introduced a relaxation method for solving those equations. We describe both the theories behind the two methods and their implementations, focusing on the specific techniques we have used that make those implementations amenable to study large molecular systems. We have illustrated the performance of RelaxPath on simple 2D systems. We have also compared MinActionPath and RelaxPath to other methods for generating transition paths on a well suited test set of large proteins, for which the end points of the trajectories as well as an intermediate conformation between those end points are known. We have shown that RelaxPath outperforms those other methods, including MinActionPath, in its ability to generate trajectories that get close to the known intermediates. We have also shown that the structures along the RelaxPath trajectories remain protein-like. Open source versions of the two programs MinActionPath and RelaxPath are available by request.
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Affiliation(s)
- Patrice Koehl
- Department of Computer Science and Genome Center, University of California, Davis, California 95616, USA
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11
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Koehl P, Poitevin F, Navaza R, Delarue M. The Renormalization Group and Its Applications to Generating Coarse-Grained Models of Large Biological Molecular Systems. J Chem Theory Comput 2017; 13:1424-1438. [PMID: 28170254 DOI: 10.1021/acs.jctc.6b01136] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Understanding the dynamics of biomolecules is the key to understanding their biological activities. Computational methods ranging from all-atom molecular dynamics simulations to coarse-grained normal-mode analyses based on simplified elastic networks provide a general framework to studying these dynamics. Despite recent successes in studying very large systems with up to a 100,000,000 atoms, those methods are currently limited to studying small- to medium-sized molecular systems due to computational limitations. One solution to circumvent these limitations is to reduce the size of the system under study. In this paper, we argue that coarse-graining, the standard approach to such size reduction, must define a hierarchy of models of decreasing sizes that are consistent with each other, i.e., that each model contains the information of the dynamics of its predecessor. We propose a new method, Decimate, for generating such a hierarchy within the context of elastic networks for normal-mode analysis. This method is based on the concept of the renormalization group developed in statistical physics. We highlight the details of its implementation, with a special focus on its scalability to large systems of up to millions of atoms. We illustrate its application on two large systems, the capsid of a virus and the ribosome translation complex. We show that highly decimated representations of those systems, containing down to 1% of their original number of atoms, still capture qualitatively and quantitatively their dynamics. Decimate is available as an OpenSource resource.
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Affiliation(s)
- Patrice Koehl
- Department of Computer Sciences and Genome Center, University of California, Davis , Davis, California 95616, United States
| | - Frédéric Poitevin
- Department of Structural Biology, Stanford University , Stanford, California 94305, United States.,Stanford PULSE Institute, SLAC National Accelerator Laboratory, Standford University , Menlo Park, California 94025, United States
| | - Rafael Navaza
- Platform of Crystallogenesis and Crystallography, CiTech, Institut Pasteur , 75015 Paris, France
| | - Marc Delarue
- Unité de Dynamique Structurale des Macromolécules, UMR 3528 du CNRS, Institut Pasteur , 75015 Paris, France
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12
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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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13
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Chandrasekaran SN, Das J, Dokholyan NV, Carter CW. A modified PATH algorithm rapidly generates transition states comparable to those found by other well established algorithms. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2016; 3:012101. [PMID: 26958584 PMCID: PMC4769271 DOI: 10.1063/1.4941599] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 01/22/2016] [Indexed: 06/05/2023]
Abstract
PATH rapidly computes a path and a transition state between crystal structures by minimizing the Onsager-Machlup action. It requires input parameters whose range of values can generate different transition-state structures that cannot be uniquely compared with those generated by other methods. We outline modifications to estimate these input parameters to circumvent these difficulties and validate the PATH transition states by showing consistency between transition-states derived by different algorithms for unrelated protein systems. Although functional protein conformational change trajectories are to a degree stochastic, they nonetheless pass through a well-defined transition state whose detailed structural properties can rapidly be identified using PATH.
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Affiliation(s)
- Srinivas Niranj Chandrasekaran
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Jhuma Das
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Nikolay V Dokholyan
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
| | - Charles W Carter
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7260, USA
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14
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Williams TL, Yin YW, Carter CW. Selective Inhibition of Bacterial Tryptophanyl-tRNA Synthetases by Indolmycin Is Mechanism-based. J Biol Chem 2015; 291:255-65. [PMID: 26555258 DOI: 10.1074/jbc.m115.690321] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Indexed: 11/06/2022] Open
Abstract
Indolmycin is a natural tryptophan analog that competes with tryptophan for binding to tryptophanyl-tRNA synthetase (TrpRS) enzymes. Bacterial and eukaryotic cytosolic TrpRSs have comparable affinities for tryptophan (Km ∼ 2 μm), and yet only bacterial TrpRSs are inhibited by indolmycin. Despite the similarity between these ligands, Bacillus stearothermophilus (Bs)TrpRS preferentially binds indolmycin ∼1500-fold more tightly than its tryptophan substrate. Kinetic characterization and crystallographic analysis of BsTrpRS allowed us to probe novel aspects of indolmycin inhibitory action. Previous work had revealed that long range coupling to residues within an allosteric region called the D1 switch of BsTrpRS positions the Mg(2+) ion in a manner that allows it to assist in transition state stabilization. The Mg(2+) ion in the inhibited complex forms significantly closer contacts with non-bridging oxygen atoms from each phosphate group of ATP and three water molecules than occur in the (presumably catalytically competent) pre-transition state (preTS) crystal structures. We propose that this altered coordination stabilizes a ground state Mg(2+)·ATP configuration, accounting for the high affinity inhibition of BsTrpRS by indolmycin. Conversely, both the ATP configuration and Mg(2+) coordination in the human cytosolic (Hc)TrpRS preTS structure differ greatly from the BsTrpRS preTS structure. The effect of these differences is that catalysis occurs via a different transition state stabilization mechanism in HcTrpRS with a yet-to-be determined role for Mg(2+). Modeling indolmycin into the tryptophan binding site points to steric hindrance and an inability to retain the interactions used for tryptophan substrate recognition as causes for the 1000-fold weaker indolmycin affinity to HcTrpRS.
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Affiliation(s)
- Tishan L Williams
- From the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260 and
| | - Yuhui W Yin
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston Texas 77555-0144
| | - Charles W Carter
- From the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260 and
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Koh CY, Wetzel AB, de van der Schueren WJ, Hol WGJ. Comparison of histidine recognition in human and trypanosomatid histidyl-tRNA synthetases. Biochimie 2014; 106:111-20. [PMID: 25151410 DOI: 10.1016/j.biochi.2014.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 08/12/2014] [Indexed: 02/05/2023]
Abstract
As part of a project aimed at obtaining selective inhibitors and drug-like compounds targeting tRNA synthetases from trypanosomatids, we have elucidated the crystal structure of human cytosolic histidyl-tRNA synthetase (Hs-cHisRS) in complex with histidine in order to be able to compare human and parasite enzymes. The resultant structure of Hs-cHisRS•His represents the substrate-bound state (H-state) of the enzyme. It provides an interesting opportunity to compare with ligand-free and imidazole-bound structures Hs-cHisRS published recently, both of which represent the ligand-free state (F-state) of the enzyme. The H-state Hs-cHisRS undergoes conformational changes in active site residues and several conserved motif of HisRS, compared to F-state structures. The histidine forms eight hydrogen bonds with HisRS of which six engage the amino and carboxylate groups of this amino acid. The availability of published imidazole-bound structure provides a unique opportunity to dissect the structural roles of individual chemical groups of histidine. The analysis revealed the importance of the amino and carboxylate groups, of the histidine in leading to these dramatic conformational changes of the H-state. Further, comparison with previously published trypanosomatid HisRS structures reveals a pocket in the F-state of the parasite enzyme that may provide opportunities for developing specific inhibitors of Trypanosoma brucei HisRS.
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Affiliation(s)
- Cho Yeow Koh
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Allan B Wetzel
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | | | - Wim G J Hol
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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16
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Weinreb V, Li L, Chandrasekaran SN, Koehl P, Delarue M, Carter CW. Enhanced amino acid selection in fully evolved tryptophanyl-tRNA synthetase, relative to its urzyme, requires domain motion sensed by the D1 switch, a remote dynamic packing motif. J Biol Chem 2014; 289:4367-76. [PMID: 24394410 DOI: 10.1074/jbc.m113.538660] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We previously showed (Li, L., and Carter, C. W., Jr. (2013) J. Biol. Chem. 288, 34736-34745) that increased specificity for tryptophan versus tyrosine by contemporary Bacillus stearothermophilus tryptophanyl-tRNA synthetase (TrpRS) over that of TrpRS Urzyme results entirely from coupling between the anticodon-binding domain and an insertion into the Rossmann-fold known as Connecting Peptide 1. We show that this effect is closely related to a long range catalytic effect, in which side chain repacking in a region called the D1 Switch, accounts fully for the entire catalytic contribution of the catalytic Mg(2+) ion. We report intrinsic and higher order interaction effects on the specificity ratio, (kcat/Km)Trp/(kcat/Km)Tyr, of 15 combinatorial mutants from a previous study (Weinreb, V., Li, L., and Carter, C. W., Jr. (2012) Structure 20, 128-138) of the catalytic role of the D1 Switch. Unexpectedly, the same four-way interaction both activates catalytic assist by Mg(2+) ion and contributes -4.4 kcal/mol to the free energy of the specificity ratio. A minimum action path computed for the induced-fit and catalytic conformation changes shows that repacking of the four residues precedes a decrease in the volume of the tryptophan-binding pocket. We suggest that previous efforts to alter amino acid specificities of TrpRS and glutaminyl-tRNA synthetase (GlnRS) by mutagenesis without extensive, modular substitution failed because mutations were incompatible with interdomain motions required for catalysis.
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Affiliation(s)
- Violetta Weinreb
- From the Department of Biochemistry and Biophysics, CB 7260, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
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17
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Li L, Carter CW. Full implementation of the genetic code by tryptophanyl-tRNA synthetase requires intermodular coupling. J Biol Chem 2013; 288:34736-45. [PMID: 24142809 DOI: 10.1074/jbc.m113.510958] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Tryptophanyl-tRNA Synthetase (TrpRS) Urzyme (fragments A and C), a 130-residue construct containing only secondary structures positioning the HIGH and KMSKS active site signatures and the specificity helix, accelerates tRNA(Trp) aminoacylation with ∼10-fold specificity toward tryptophan, relative to structurally related tyrosine. We proposed that including the 76-residue connecting peptide 1 insertion (Fragment B) might enhance tryptophan affinity and hence amino acid specificity, because that subdomain constrains the orientation of the specificity helix. We test that hypothesis by characterizing two new constructs: the catalytic domain (fragments A-C) and the Urzyme supplemented with the anticodon-binding domain (fragments A, C, and D). The three constructs, together with the full-length enzyme (fragments A-D), comprise a factorial experiment from which we deduce individual and combined contributions of the two modules to the steady-state kinetics parameters for tryptophan-dependent (32)PPi exchange, specificity for tryptophan versus tyrosine, and aminoacylation of tRNA(Trp). Factorial design directly measures the energetic coupling between the two more recent modules in the contemporary enzyme and demonstrates its functionality. Combining the TrpRS Urzyme individually in cis with each module affords an analysis of long term evolution of amino acid specificity and tRNA aminoacylation, both essential for expanding the genetic code. Either module significantly enhances tryptophan activation but unexpectedly eliminates amino acid specificity for tryptophan, relative to tyrosine, and significantly reduces tRNA aminoacylation. Exclusive dependence of both enhanced functionalities of full-length TrpRS on interdomain coupling energies between the two new modules argues that independent recruitment of connecting peptide 1 and the anticodon-binding domain during evolutionary development of Urzymes would have entailed significant losses of fitness.
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Affiliation(s)
- Li Li
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
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18
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Koh CY, Kim JE, Napoli AJ, Verlinde CL, Fan E, Buckner FS, Van Voorhis WC, Hol WG. Crystal structures of Plasmodium falciparum cytosolic tryptophanyl-tRNA synthetase and its potential as a target for structure-guided drug design. Mol Biochem Parasitol 2013; 189:26-32. [PMID: 23665145 PMCID: PMC3680109 DOI: 10.1016/j.molbiopara.2013.04.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 04/26/2013] [Accepted: 04/29/2013] [Indexed: 01/05/2023]
Abstract
Malaria, most commonly caused by the parasite Plasmodium falciparum, is a devastating disease that remains a large global health burden. Lack of vaccines and drug resistance necessitate the continual development of new drugs and exploration of new drug targets. Due to their essential role in protein synthesis, aminoacyl-tRNA synthetases are potential anti-malaria drug targets. Here we report the crystal structures of P. falciparum cytosolic tryptophanyl-tRNA synthetase (Pf-cTrpRS) in its ligand-free state and tryptophanyl-adenylate (WAMP)-bound state at 2.34 Å and 2.40 Å resolutions, respectively. Large conformational changes are observed when the ligand-free protein is bound to WAMP. Multiple residues, completely surrounding the active site pocket, collapse onto WAMP. Comparison of the structures to those of human cytosolic TrpRS (Hs-cTrpRS) provides information about the possibility of targeting Pf-cTrpRS for inhibitor development. There is a high degree of similarity between Pf-cTrpRS and Hs-cTrpRS within the active site. However, the large motion that Pf-cTrpRS undergoes during transitions between different functional states avails an opportunity to arrive at compounds which selectively perturb the motion, and may provide a starting point for the development of new anti-malaria therapeutics.
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Affiliation(s)
- Cho Yeow Koh
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Jessica E. Kim
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Alberto J. Napoli
- Division of Infectious Diseases, Department of Medicine, University of Washington, Seattle, Washington 98195, USA
| | | | - Erkang Fan
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Frederick S. Buckner
- Division of Infectious Diseases, Department of Medicine, University of Washington, Seattle, Washington 98195, USA
| | - Wesley C. Van Voorhis
- Division of Infectious Diseases, Department of Medicine, University of Washington, Seattle, Washington 98195, USA
| | - Wim G.J. Hol
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
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19
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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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20
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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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21
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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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22
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Weinreb V, Li L, Carter CW. A master switch couples Mg²⁺-assisted catalysis to domain motion in B. stearothermophilus tryptophanyl-tRNA Synthetase. Structure 2012; 20:128-38. [PMID: 22244762 DOI: 10.1016/j.str.2011.10.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 10/22/2011] [Accepted: 10/25/2011] [Indexed: 01/08/2023]
Abstract
We demonstrate how tryptophanyl-tRNA synthetase uses conformation-dependent Mg(2+) activation to couple catalysis of tryptophan activation to specific, functional domain movements. Rate acceleration by Mg(2+) requires ∼-6.0 kcal/mol in protein⋅Mg(2+) interaction energy, none of which arises from the active site. A highly cooperative interaction between Mg(2+) and four residues from a remote, conserved motif that mediates the shear of domain movement (1) destabilizes the pretransition state conformation, thereby (2) inducing the Mg(2+) to stabilize the transition state for k(cat) by ∼-5.0 kcal/mol. Cooperative, long-range conformational effects on the metal therefore convert an inactive Mg(2+) coordination into one that can stabilize the transition state if, and only if, domain motion occurs. Transient, conformation-dependent Mg(2+) activation, analogous to the escapement in mechanical clocks, explains vectorial coupling.
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Affiliation(s)
- Violetta Weinreb
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7260, USA
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23
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Importance of single molecular determinants in the fidelity of expanded genetic codes. Proc Natl Acad Sci U S A 2011; 108:1320-5. [PMID: 21224416 DOI: 10.1073/pnas.1012276108] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The site-selective encoding of noncanonical amino acids (NAAs) is a powerful technique for the installation of novel chemical functional groups in proteins. This is often achieved by recoding a stop codon and requires two additional components: an evolved aminoacyl tRNA synthetase (AARS) and a cognate tRNA. Analysis of the most successful AARSs reveals common characteristics. The highest fidelity NAA systems derived from the Methanocaldococcus jannaschii tyrosyl AARS feature specific mutations to two residues reported to interact with the hydroxyl group of the substrate tyrosine. We demonstrate that the restoration of just one of these determinants for amino acid specificity results in the loss of fidelity as the evolved AARSs become noticeably promiscuous. These results offer a partial explanation of a recently retracted strategy for the synthesis of glycoproteins. Similarly, we reinvestigated a tryptophanyl AARS reported to allow the site-selective incorporation of 5-hydroxy tryptophan within mammalian cells. In multiple experiments, the enzyme displayed elements of promiscuity despite its previous characterization as a high fidelity enzyme. Given the many similarities of the TyrRSs and TrpRSs reevaluated here, our findings can be largely combined, and in doing so they reinforce the long-established central dogma regarding the molecular basis by which these enzymes contribute to the fidelity of translation. Thus, our view is that the central claims of fidelity reported in several NAA systems remain unproven and unprecedented.
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Zhou M, Dong X, Shen N, Zhong C, Ding J. Crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase: new insights into the mechanism of tryptophan activation and implications for anti-fungal drug design. Nucleic Acids Res 2010; 38:3399-413. [PMID: 20123733 PMCID: PMC2879500 DOI: 10.1093/nar/gkp1254] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Specific activation of amino acids by aminoacyl-tRNA synthetases is essential for maintaining translational fidelity. Here, we present crystal structures of Saccharomyces cerevisiae tryptophanyl-tRNA synthetase (sTrpRS) in apo form and in complexes with various ligands. In each complex, there is a sulfate ion bound at the active site which mimics the α- or β-phosphate group of ATP during tryptophan activation. In particular, in one monomer of the sTrpRS–TrpNH2O complex, the sulfate ion appears to capture a snapshot of the α-phosphate of ATP during its movement towards tryptophan. Simulation study of a human TrpRS–Trp–ATP model shows that during the catalytic process the α-phosphate of ATP is driven to an intermediate position equivalent to that of the sulfate ion, then moves further and eventually fluctuates at around 2 Å from the nucleophile. A conserved Arg may interact with the oxygen in the scissile bond at the transition state, indicating its critical role in the nucleophilic substitution. Taken together, eukaryotic TrpRSs may adopt an associative mechanism for tryptophan activation in contrast to a dissociative mechanism proposed for bacterial TrpRSs. In addition, structural analysis of the apo sTrpRS reveals a unique feature of fungal TrpRSs, which could be exploited in rational antifungal drug design.
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Affiliation(s)
- Minyun Zhou
- State Key Laboratory of Molecular Biology and Research Center for Structural Biology, Institute of Biochemistry and Cell Biology, Shanghai, Shanghai 200031, China
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