1
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Tang GQ, Elder JJH, Douglas J, Carter CW. Domain acquisition by class I aminoacyl-tRNA synthetase urzymes coordinated the catalytic functions of HVGH and KMSKS motifs. Nucleic Acids Res 2023; 51:8070-8084. [PMID: 37470821 PMCID: PMC10450160 DOI: 10.1093/nar/gkad590] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/23/2023] [Accepted: 07/11/2023] [Indexed: 07/21/2023] Open
Abstract
Leucyl-tRNA synthetase (LeuRS) is a Class I aminoacyl-tRNA synthetase (aaRS) that synthesizes leucyl-tRNAleu for codon-directed protein synthesis. Two signature sequences, HxGH and KMSKS help stabilize transition-states for amino acid activation and tRNA aminoacylation by all Class I aaRS. Separate alanine mutants of each signature, together with the double mutant, behave in opposite ways in Pyrococcus horikoshii LeuRS and the 129-residue urzyme ancestral model generated from it (LeuAC). Free energy coupling terms, Δ(ΔG‡), for both reactions are large and favourable for LeuRS, but unfavourable for LeuAC. Single turnover assays with 32Pα-ATP show correspondingly different internal products. These results implicate domain motion in catalysis by full-length LeuRS. The distributed thermodynamic cycle of mutational changes authenticates LeuAC urzyme catalysis far more convincingly than do single point mutations. Most importantly, the evolutionary gain of function induced by acquiring the anticodon-binding (ABD) and multiple insertion modules in the catalytic domain appears to be to coordinate the catalytic function of the HxGH and KMSKS signature sequences. The implication that backbone elements of secondary structures achieve a major portion of the overall transition-state stabilization by LeuAC is also consistent with coevolution of the genetic code and metabolic pathways necessary to produce histidine and lysine sidechains.
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Affiliation(s)
- Guo Qing Tang
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, USA
| | - Jessica J H Elder
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, USA
| | - Jordan Douglas
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, USA
- Department of Physics, The University of Auckland, New Zealand
| | - Charles W Carter
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, USA
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2
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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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3
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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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4
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Carter CW, Popinga A, Bouckaert R, Wills PR. Multidimensional Phylogenetic Metrics Identify Class I Aminoacyl-tRNA Synthetase Evolutionary Mosaicity and Inter-Modular Coupling. Int J Mol Sci 2022; 23:ijms23031520. [PMID: 35163448 PMCID: PMC8835825 DOI: 10.3390/ijms23031520] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/17/2022] [Accepted: 01/17/2022] [Indexed: 02/01/2023] Open
Abstract
The role of aminoacyl-tRNA synthetases (aaRS) in the emergence and evolution of genetic coding poses challenging questions concerning their provenance. We seek evidence about their ancestry from curated structure-based multiple sequence alignments of a structurally invariant “scaffold” shared by all 10 canonical Class I aaRS. Three uncorrelated phylogenetic metrics—mutation frequency, its uniformity, and row-by-row cladistic congruence—imply that the Class I scaffold is a mosaic assembled from successive genetic sources. Metrics for different modules vary in accordance with their presumed functionality. Sequences derived from the ATP– and amino acid– binding sites exhibit specific two-way coupling to those derived from Connecting Peptide 1, a third module whose metrics suggest later acquisition. The data help validate: (i) experimental fragmentations of the canonical Class I structure into three partitions that retain catalytic activities in proportion to their length; and (ii) evidence that the ancestral Class I aaRS gene also encoded a Class II ancestor in frame on the opposite strand. A 46-residue Class I “protozyme” roots the Class I tree prior to the adaptive radiation of the Rossmann dinucleotide binding fold that refined substrate discrimination. Such rooting implies near simultaneous emergence of genetic coding and the origin of the proteome, resolving a conundrum posed by previous inferences that Class I aaRS evolved after the genetic code had been implemented in an RNA world. Further, pinpointing discontinuous enhancements of aaRS fidelity establishes a timeline for the growth of coding from a binary amino acid alphabet.
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Affiliation(s)
- Charles W. Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7260, USA
- Correspondence: ; Tel.: +1-919-966-3263
| | - Alex Popinga
- Centre for Computational Evolution, University of Auckland, PB 92019, Auckland 1142, New Zealand; (A.P.); (R.B.)
| | - Remco Bouckaert
- Centre for Computational Evolution, University of Auckland, PB 92019, Auckland 1142, New Zealand; (A.P.); (R.B.)
| | - Peter R. Wills
- Department of Physics and Te Ao Marama Centre for Fundamental Inquiry, University of Auckland, PB 92019, Auckland 1142, New Zealand;
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5
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Carter CW. Simultaneous codon usage, the origin of the proteome, and the emergence of de-novo proteins. Curr Opin Struct Biol 2021; 68:142-148. [PMID: 33529785 DOI: 10.1016/j.sbi.2021.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 01/05/2021] [Indexed: 12/21/2022]
Abstract
Genetic coding generally uses only one of a gene's two strands; its complement serving as template for replication. Aminoacyl-tRNA synthetases, aaRS, apparently first emerged as pairs on bidirectional genes, in which anticodons in the template strand served as codons for an entirely different protein. Interpreting both strands in frame constrained such genes sufficiently that it was rapidly superseded, leaving only traces in the elevated pairing between codon middle bases in antiparallel alignments. Codon assignments actually promote using information from both strands in multiple reading frames. Related phenomena, known as overprinting, are widely associated with viruses. In-frame bidirectional coding and overprinting nevertheless imply different structural and functional relationships, and different roles in generating folded proteins throughout the evolution of the proteome.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry, Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7260, United States.
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6
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Kaiser F, Krautwurst S, Salentin S, Haupt VJ, Leberecht C, Bittrich S, Labudde D, Schroeder M. The structural basis of the genetic code: amino acid recognition by aminoacyl-tRNA synthetases. Sci Rep 2020; 10:12647. [PMID: 32724042 PMCID: PMC7387524 DOI: 10.1038/s41598-020-69100-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/06/2020] [Indexed: 12/29/2022] Open
Abstract
Storage and directed transfer of information is the key requirement for the development of life. Yet any information stored on our genes is useless without its correct interpretation. The genetic code defines the rule set to decode this information. Aminoacyl-tRNA synthetases are at the heart of this process. We extensively characterize how these enzymes distinguish all natural amino acids based on the computational analysis of crystallographic structure data. The results of this meta-analysis show that the correct read-out of genetic information is a delicate interplay between the composition of the binding site, non-covalent interactions, error correction mechanisms, and steric effects.
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Affiliation(s)
- Florian Kaiser
- Biotechnology Center (BIOTEC), TU Dresden, 01307, Dresden, Germany. .,PharmAI GmbH, Tatzberg 47, 01307, Dresden, Germany.
| | - Sarah Krautwurst
- University of Applied Sciences Mittweida, 09648, Mittweida, Germany
| | | | - V Joachim Haupt
- Biotechnology Center (BIOTEC), TU Dresden, 01307, Dresden, Germany.,PharmAI GmbH, Tatzberg 47, 01307, Dresden, Germany
| | | | | | - Dirk Labudde
- University of Applied Sciences Mittweida, 09648, Mittweida, Germany
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7
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Carter CW. Escapement mechanisms: Efficient free energy transduction by reciprocally-coupled gating. Proteins 2019; 88:710-717. [PMID: 31743491 DOI: 10.1002/prot.25856] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 11/05/2019] [Accepted: 11/08/2019] [Indexed: 12/12/2022]
Abstract
Conversion of the free energy of NTP hydrolysis efficiently into mechanical work and/or information by transducing enzymes sustains living systems far from equilibrium, and so has been of interest for many decades. Detailed molecular mechanisms, however, remain puzzling and incomplete. We previously reported that catalysis of tryptophan activation by tryptophanyl-tRNA synthetase, TrpRS, requires relative domain motion to re-position the catalytic Mg2+ ion, noting the analogy between that conditional hydrolysis of ATP and the escapement mechanism of a mechanical clock. The escapement allows the time-keeping mechanism to advance discretely, one gear at a time, if and only if the pendulum swings, thereby converting energy from the weight driving the pendulum into rotation of the hands. Coupling of catalysis to domain motion, however, mimics only half of the escapement mechanism, suggesting that domain motion may also be reciprocally coupled to catalysis, completing the escapement metaphor. Computational studies of the free energy surface restraining the domain motion later confirmed that reciprocal coupling: the catalytic domain motion is thermodynamically unfavorable unless the PPi product is released from the active site. These two conditional phenomena-demonstrated together only for the TrpRS mechanism-function as reciprocally-coupled gates. As we and others have noted, such an escapement mechanism is essential to the efficient transduction of NTP hydrolysis free energy into other useful forms of mechanical or chemical work and/or information. Some implementation of both gating mechanisms-catalysis by domain motion and domain motion by catalysis-will thus likely be found in many other systems.
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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
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8
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Demongeot J, Seligmann H. Bias for 3'-Dominant Codon Directional Asymmetry in Theoretical Minimal RNA Rings. J Comput Biol 2019; 26:1003-1012. [PMID: 31120344 DOI: 10.1089/cmb.2018.0256] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Aminoacyl tRNA synthetases ligate tRNAs specifically with their cognate amino acid. These synthetases are among life's earliest proteins, class II tRNA synthetases (cognates A, D, F, G, H, K, N, P, S, and T) presumably preceding class I tRNA synthetases (cognates C, E, I, L, M, Q, R, V, W, and Y). Classification of codons into palindromic (structure XYX), 5'-dominant (YXX), and 3'-dominant (XXY) (Codon Directional Asymmetry [CDA]) shows that class II tRNA synthetases aminoacylate amino acids associated with XXY. Our working hypothesis expects bias for XXY codons in primordial RNAs, such as theoretical minimal RNA rings, designed in silico to mimic life's earliest RNAs. Twenty-five RNA rings have been computed, which code over a minimal length (22 nucleotides) for a start codon, stop codon, and one and only one codon for each of the 20 amino acids, and form stem-loop hairpins preventing degradation; these 25 minimal RNAs are the only ones matching these constraints and they seem homologous to consensus tRNA sequences. This similarity defined candidate RNA ring anticodons and corresponding cognate amino acids. Here, analyses of RNA ring codon contents confirm bias for XXY codons in 13 among 14 RNA rings with unequal XXY and YXX codon numbers. This bias increases with the genetic code integration order of the RNA ring's cognate amino acid across and within tRNA synthetase classes, suggesting that evolutionary processes, and not physicochemical constraints, produced the association between CDA and tRNA synthetase classes. The self-referential hypothesis for genetic code origin, a very complete genetic code evolutionary hypothesis integrating many translational machinery components, predicts best among genetic code evolutionary hypotheses CDA biases in RNA rings. The RNA rings' simple design inadvertently reproduces CDAs predicted by the genetic code's structure, confirming theoretical minimal RNA rings as good proxies for life's earliest RNAs.
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Affiliation(s)
- Jacques Demongeot
- Laboratory AGEIS EA 7407, Faculty of Medicine, Team Tools for e-Gnosis Medical, Université Grenoble Alpes, La Tronche, France
| | - Hervé Seligmann
- The National Natural History Collections, The Hebrew University of Jerusalem, Jerusalem, Israel
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9
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Abstract
Abundant and essential motifs, such as phosphate-binding loops (P-loops), are presumed to be the seeds of modern enzymes. The Walker-A P-loop is absolutely essential in modern NTPase enzymes, in mediating binding, and transfer of the terminal phosphate groups of NTPs. However, NTPase function depends on many additional active-site residues placed throughout the protein's scaffold. Can motifs such as P-loops confer function in a simpler context? We applied a phylogenetic analysis that yielded a sequence logo of the putative ancestral Walker-A P-loop element: a β-strand connected to an α-helix via the P-loop. Computational design incorporated this element into de novo designed β-α repeat proteins with relatively few sequence modifications. We obtained soluble, stable proteins that unlike modern P-loop NTPases bound ATP in a magnesium-independent manner. Foremost, these simple P-loop proteins avidly bound polynucleotides, RNA, and single-strand DNA, and mutations in the P-loop's key residues abolished binding. Binding appears to be facilitated by the structural plasticity of these proteins, including quaternary structure polymorphism that promotes a combined action of multiple P-loops. Accordingly, oligomerization enabled a 55-aa protein carrying a single P-loop to confer avid polynucleotide binding. Overall, our results show that the P-loop Walker-A motif can be implemented in small and simple β-α repeat proteins, primarily as a polynucleotide binding motif.
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10
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Bittrich S, Schroeder M, Labudde D. Characterizing the relation of functional and Early Folding Residues in protein structures using the example of aminoacyl-tRNA synthetases. PLoS One 2018; 13:e0206369. [PMID: 30376559 PMCID: PMC6207335 DOI: 10.1371/journal.pone.0206369] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/11/2018] [Indexed: 01/10/2023] Open
Abstract
Proteins are chains of amino acids which adopt a three-dimensional structure and are then able to catalyze chemical reactions or propagate signals in organisms. Without external influence, many proteins fold into their native structure, and a small number of Early Folding Residues (EFR) have previously been shown to initiate the formation of secondary structure elements and guide their respective assembly. Using the two diverse superfamilies of aminoacyl-tRNA synthetases (aaRS), it is shown that the position of EFR is preserved over the course of evolution even when the corresponding sequence conservation is small. Folding initiation sites are positioned in the center of secondary structure elements, independent of aaRS class. In class I, the predicted position of EFR resembles an ancient structural packing motif present in many seemingly unrelated proteins. Furthermore, it is shown that EFR and functionally relevant residues in aaRS are almost entirely disjoint sets of residues. The Start2Fold database is used to investigate whether this separation of EFR and functional residues can be observed for other proteins. EFR are found to constitute crucial connectors of protein regions which are distant at sequence level. Especially, these residues exhibit a high number of non-covalent residue-residue contacts such as hydrogen bonds and hydrophobic interactions. This tendency also manifests as energetically stable local regions, as substantiated by a knowledge-based potential. Despite profound differences regarding how EFR and functional residues are embedded in protein structures, a strict separation of structurally and functionally relevant residues cannot be observed for a more general collection of proteins.
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Affiliation(s)
- Sebastian Bittrich
- Applied Computer Sciences & Biosciences, University of Applied Sciences Mittweida, Mittweida, Saxony, Germany
- Biotechnology Center (BIOTEC), Technische Universität Dresden, Dresden, Saxony, Germany
| | - Michael Schroeder
- Biotechnology Center (BIOTEC), Technische Universität Dresden, Dresden, Saxony, Germany
| | - Dirk Labudde
- Applied Computer Sciences & Biosciences, University of Applied Sciences Mittweida, Mittweida, Saxony, Germany
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11
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Carter CW, Wills PR. Interdependence, Reflexivity, Fidelity, Impedance Matching, and the Evolution of Genetic Coding. Mol Biol Evol 2018; 35:269-286. [PMID: 29077934 PMCID: PMC5850816 DOI: 10.1093/molbev/msx265] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Genetic coding is generally thought to have required ribozymes whose functions were taken over by polypeptide aminoacyl-tRNA synthetases (aaRS). Two discoveries about aaRS and their interactions with tRNA substrates now furnish a unifying rationale for the opposite conclusion: that the key processes of the Central Dogma of molecular biology emerged simultaneously and naturally from simple origins in a peptide•RNA partnership, eliminating the epistemological utility of a prior RNA world. First, the two aaRS classes likely arose from opposite strands of the same ancestral gene, implying a simple genetic alphabet. The resulting inversion symmetries in aaRS structural biology would have stabilized the initial and subsequent differentiation of coding specificities, rapidly promoting diversity in the proteome. Second, amino acid physical chemistry maps onto tRNA identity elements, establishing reflexive, nanoenvironmental sensing in protein aaRS. Bootstrapping of increasingly detailed coding is thus intrinsic to polypeptide aaRS, but impossible in an RNA world. These notions underline the following concepts that contradict gradual replacement of ribozymal aaRS by polypeptide aaRS: 1) aaRS enzymes must be interdependent; 2) reflexivity intrinsic to polypeptide aaRS production dynamics promotes bootstrapping; 3) takeover of RNA-catalyzed aminoacylation by enzymes will necessarily degrade specificity; and 4) the Central Dogma's emergence is most probable when replication and translation error rates remain comparable. These characteristics are necessary and sufficient for the essentially de novo emergence of a coupled gene-replicase-translatase system of genetic coding that would have continuously preserved the functional meaning of genetically encoded protein genes whose phylogenetic relationships match those observed today.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Peter R Wills
- Department of Physics, University of Auckland, Auckland, New Zealand
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12
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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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13
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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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14
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Carter CW. Coding of Class I and II Aminoacyl-tRNA Synthetases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 966:103-148. [PMID: 28828732 PMCID: PMC5927602 DOI: 10.1007/5584_2017_93] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The aminoacyl-tRNA synthetases and their cognate transfer RNAs translate the universal genetic code. The twenty canonical amino acids are sufficiently diverse to create a selective advantage for dividing amino acid activation between two distinct, apparently unrelated superfamilies of synthetases, Class I amino acids being generally larger and less polar, Class II amino acids smaller and more polar. Biochemical, bioinformatic, and protein engineering experiments support the hypothesis that the two Classes descended from opposite strands of the same ancestral gene. Parallel experimental deconstructions of Class I and II synthetases reveal parallel losses in catalytic proficiency at two novel modular levels-protozymes and Urzymes-associated with the evolution of catalytic activity. Bi-directional coding supports an important unification of the proteome; affords a genetic relatedness metric-middle base-pairing frequencies in sense/antisense alignments-that probes more deeply into the evolutionary history of translation than do single multiple sequence alignments; and has facilitated the analysis of hitherto unknown coding relationships in tRNA sequences. Reconstruction of native synthetases by modular thermodynamic cycles facilitated by domain engineering emphasizes the subtlety associated with achieving high specificity, shedding new light on allosteric relationships in contemporary synthetases. Synthetase Urzyme structural biology suggests that they are catalytically-active molten globules, broadening the potential manifold of polypeptide catalysts accessible to primitive genetic coding and motivating revisions of the origins of catalysis. Finally, bi-directional genetic coding of some of the oldest genes in the proteome places major limitations on the likelihood that any RNA World preceded the origins of coded proteins.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7260, USA.
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15
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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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Martinez-Rodriguez L, Erdogan O, Jimenez-Rodriguez M, Gonzalez-Rivera K, Williams T, Li L, Weinreb V, Collier M, Chandrasekaran SN, Ambroggio X, Kuhlman B, Carter CW. Functional Class I and II Amino Acid-activating Enzymes Can Be Coded by Opposite Strands of the Same Gene. J Biol Chem 2015; 290:19710-25. [PMID: 26088142 DOI: 10.1074/jbc.m115.642876] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Indexed: 01/11/2023] Open
Abstract
Aminoacyl-tRNA synthetases (aaRS) catalyze both chemical steps that translate the universal genetic code. Rodin and Ohno offered an explanation for the existence of two aaRS classes, observing that codons for the most highly conserved Class I active-site residues are anticodons for corresponding Class II active-site residues. They proposed that the two classes arose simultaneously, by translation of opposite strands from the same gene. We have characterized wild-type 46-residue peptides containing ATP-binding sites of Class I and II synthetases and those coded by a gene designed by Rosetta to encode the corresponding peptides on opposite strands. Catalysis by WT and designed peptides is saturable, and the designed peptides are sensitive to active-site residue mutation. All have comparable apparent second-order rate constants 2.9-7.0E-3 M(-1) s(-1) or ∼750,000-1,300,000 times the uncatalyzed rate. The activities of the two complementary peptides demonstrate that the unique information in a gene can have two functional interpretations, one from each complementary strand. The peptides contain phylogenetic signatures of longer, more sophisticated catalysts we call Urzymes and are short enough to bridge the gap between them and simpler uncoded peptides. Thus, they directly substantiate the sense/antisense coding ancestry of Class I and II aaRS. Furthermore, designed 46-mers achieve similar catalytic proficiency to wild-type 46-mers by significant increases in both kcat and Km values, supporting suggestions that the earliest peptide catalysts activated ATP for biosynthetic purposes.
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Affiliation(s)
- Luis Martinez-Rodriguez
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Ozgün Erdogan
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Mariel Jimenez-Rodriguez
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Katiria Gonzalez-Rivera
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Tishan Williams
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Li Li
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Violetta Weinreb
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Martha Collier
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Srinivas Niranj Chandrasekaran
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Xavier Ambroggio
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Brian Kuhlman
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Charles W Carter
- From the Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
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Carter CW. Urzymology: experimental access to a key transition in the appearance of enzymes. J Biol Chem 2014; 289:30213-30220. [PMID: 25210034 DOI: 10.1074/jbc.r114.567495] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Urzymes are catalysts derived from invariant cores of protein superfamilies. Urzymes from both aminoacyl-tRNA synthetase classes possess sophisticated catalytic mechanisms: pre-steady state bursts, significant transition-state stabilization of both amino acid activation, and tRNA acylation. However, they have insufficient specificity to ensure a fully developed genetic code, suggesting that they participated in synthesizing statistical proteins. They represent a robust experimental platform from which to articulate and test hypotheses both about their own ancestors and about how they, in turn, evolved into modern enzymes. They help reshape numerous paradigms from the RNA World hypothesis to protein structure databases and allostery.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260.
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Carter CW, Li L, Weinreb V, Collier M, Gonzalez-Rivera K, Jimenez-Rodriguez M, Erdogan O, Kuhlman B, Ambroggio X, Williams T, Chandrasekharan SN. The Rodin-Ohno hypothesis that two enzyme superfamilies descended from one ancestral gene: an unlikely scenario for the origins of translation that will not be dismissed. Biol Direct 2014; 9:11. [PMID: 24927791 PMCID: PMC4082485 DOI: 10.1186/1745-6150-9-11] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 05/19/2014] [Indexed: 01/19/2023] Open
Abstract
Background Because amino acid activation is rate-limiting for uncatalyzed protein synthesis, it is a key puzzle in understanding the origin of the genetic code. Two unrelated classes (I and II) of contemporary aminoacyl-tRNA synthetases (aaRS) now translate the code. Observing that codons for the most highly conserved, Class I catalytic peptides, when read in the reverse direction, are very nearly anticodons for Class II defining catalytic peptides, Rodin and Ohno proposed that the two superfamilies descended from opposite strands of the same ancestral gene. This unusual hypothesis languished for a decade, perhaps because it appeared to be unfalsifiable. Results The proposed sense/antisense alignment makes important predictions. Fragments that align in antiparallel orientations, and contain the respective active sites, should catalyze the same two reactions catalyzed by contemporary synthetases. Recent experiments confirmed that prediction. Invariant cores from both classes, called Urzymes after Ur = primitive, authentic, plus enzyme and representing ~20% of the contemporary structures, can be expressed and exhibit high, proportionate rate accelerations for both amino-acid activation and tRNA acylation. A major fraction (60%) of the catalytic rate acceleration by contemporary synthetases resides in segments that align sense/antisense. Bioinformatic evidence for sense/antisense ancestry extends to codons specifying the invariant secondary and tertiary structures outside the active sites of the two synthetase classes. Peptides from a designed, 46-residue gene constrained by Rosetta to encode Class I and II ATP binding sites with fully complementary sequences both accelerate amino acid activation by ATP ~400 fold. Conclusions Biochemical and bioinformatic results substantially enhance the posterior probability that ancestors of the two synthetase classes arose from opposite strands of the same ancestral gene. The remarkable acceleration by short peptides of the rate-limiting step in uncatalyzed protein synthesis, together with the synergy of synthetase Urzymes and their cognate tRNAs, introduce a new paradigm for the origin of protein catalysts, emphasize the potential relevance of an operational RNA code embedded in the tRNA acceptor stems, and challenge the RNA-World hypothesis. Reviewers This article was reviewed by Dr. Paul Schimmel (nominated by Laura Landweber), Dr. Eugene Koonin and Professor David Ardell.
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Affiliation(s)
- Charles W Carter
- Department of Biochemistry and Biophysics, CB 7260 University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7260, USA.
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Carter C, Weinreb V, Li L, Collier M, Chandrasekaran S, Fried H. Urzymology: experimental access to the origins of catalytic activity and translation (967.8). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.967.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Charles Carter
- Biochemistry and Biophysics University of North Carolina at CHAPEL HILLChapel HillNCUnited States
| | - Violetta Weinreb
- Biochemistry and Biophysics University of North Carolina at CHAPEL HILLChapel HillNCUnited States
| | - Li Li
- Biochemistry and Biophysics University of North Carolina at CHAPEL HILLChapel HillNCUnited States
| | - Martha Collier
- Biochemistry and Biophysics University of North Carolina at CHAPEL HILLChapel HillNCUnited States
| | - Srinivas Chandrasekaran
- Biochemistry and Biophysics University of North Carolina at CHAPEL HILLChapel HillNCUnited States
| | - Howard Fried
- Biochemistry and Biophysics University of North Carolina at CHAPEL HILLChapel HillNCUnited States
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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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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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22
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Computational modeling of protein-RNA complex structures. Methods 2013; 65:310-9. [PMID: 24083976 DOI: 10.1016/j.ymeth.2013.09.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/17/2013] [Accepted: 09/19/2013] [Indexed: 12/26/2022] Open
Abstract
Protein-RNA interactions play fundamental roles in many biological processes, such as regulation of gene expression, RNA splicing, and protein synthesis. The understanding of these processes improves as new structures of protein-RNA complexes are solved and the molecular details of interactions analyzed. However, experimental determination of protein-RNA complex structures by high-resolution methods is tedious and difficult. Therefore, studies on protein-RNA recognition and complex formation present major technical challenges for macromolecular structural biology. Alternatively, protein-RNA interactions can be predicted by computational methods. Although less accurate than experimental measurements, theoretical models of macromolecular structures can be sufficiently accurate to prompt functional hypotheses and guide e.g. identification of important amino acid or nucleotide residues. In this article we present an overview of strategies and methods for computational modeling of protein-RNA complexes, including software developed in our laboratory, and illustrate it with practical examples of structural predictions.
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23
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Li L, Francklyn C, Carter CW. Aminoacylating urzymes challenge the RNA world hypothesis. J Biol Chem 2013; 288:26856-63. [PMID: 23867455 DOI: 10.1074/jbc.m113.496125] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We describe experimental evidence that ancestral peptide catalysts substantially accelerated development of genetic coding. Structurally invariant 120-130-residue Urzymes (Ur = primitive plus enzyme) derived from Class I and Class II aminoacyl-tRNA synthetases (aaRSs) acylate tRNA far faster than the uncatalyzed rate of nonribosomal peptide bond formation from activated amino acids. These new data allow us to demonstrate statistically indistinguishable catalytic profiles for Class I and II aaRSs in both amino acid activation and tRNA acylation, over a time period extending to well before the assembly of full-length enzymes and even further before the Last Universal Common Ancestor. Both Urzymes also exhibit ∼60% of the contemporary catalytic proficiencies. Moreover, they are linked by ancestral sense/antisense genetic coding, and their evident modularities suggest descent from even simpler ancestral pairs also coded by opposite strands of the same gene. Thus, aaRS Urzymes substantially pre-date modern aaRS but are, nevertheless, highly evolved. Their unexpectedly advanced catalytic repertoires, sense/antisense coding, and ancestral modularities imply considerable prior protein-tRNA co-evolution. Further, unlike ribozymes that motivated the RNA World hypothesis, Class I and II Urzyme·tRNA pairs represent consensus ancestral forms sufficient for codon-directed synthesis of nonrandom peptides. By tracing aaRS catalytic activities back to simpler ancestral peptides, we demonstrate key steps for a simpler and hence more probable peptide·RNA development of rapid coding systems matching amino acids with anticodon trinucleotides.
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Affiliation(s)
- Li Li
- From the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260 and
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Chandrasekaran SN, Yardimci GG, Erdogan O, Roach J, Carter CW. Statistical evaluation of the Rodin-Ohno hypothesis: sense/antisense coding of ancestral class I and II aminoacyl-tRNA synthetases. Mol Biol Evol 2013; 30:1588-604. [PMID: 23576570 PMCID: PMC3684856 DOI: 10.1093/molbev/mst070] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We tested the idea that ancestral class I and II aminoacyl-tRNA synthetases arose on opposite strands of the same gene. We assembled excerpted 94-residue Urgenes for class I tryptophanyl-tRNA synthetase (TrpRS) and class II Histidyl-tRNA synthetase (HisRS) from a diverse group of species, by identifying and catenating three blocks coding for secondary structures that position the most highly conserved, active-site residues. The codon middle-base pairing frequency was 0.35 ± 0.0002 in all-by-all sense/antisense alignments for 211 TrpRS and 207 HisRS sequences, compared with frequencies between 0.22 ± 0.0009 and 0.27 ± 0.0005 for eight different representations of the null hypothesis. Clustering algorithms demonstrate further that profiles of middle-base pairing in the synthetase antisense alignments are correlated along the sequences from one species-pair to another, whereas this is not the case for similar operations on sets representing the null hypothesis. Most probable reconstructed sequences for ancestral nodes of maximum likelihood trees show that middle-base pairing frequency increases to approximately 0.42 ± 0.002 as bacterial trees approach their roots; ancestral nodes from trees including archaeal sequences show a less pronounced increase. Thus, contemporary and reconstructed sequences all validate important bioinformatic predictions based on descent from opposite strands of the same ancestral gene. They further provide novel evidence for the hypothesis that bacteria lie closer than archaea to the origin of translation. Moreover, the inverse polarity of genetic coding, together with a priori α-helix propensities suggest that in-frame coding on opposite strands leads to similar secondary structures with opposite polarity, as observed in TrpRS and HisRS crystal structures.
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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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26
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Sobolevsky Y, Guimarães RC, Trifonov EN. Towards functional repertoire of the earliest proteins. J Biomol Struct Dyn 2012; 31:1293-300. [PMID: 23140233 DOI: 10.1080/07391102.2012.735623] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The conserved protein sequence motifs present in all prokaryotic proteomes, "omnipresent motifs," presumably, correspond to the earliest proteins of the Last Universal Cellular Ancestor, from which all the proteomes have descended. Fifteen proteomes, each representing one of the total 15 diverse phyla of 131 Eubacteria and Archea, from which the omnipresent elements have been originally derived, are exhaustively screened. All those proteins which harbor the omnipresent motifs are identified. Six "omnipresent" protein types are revealed which are located in all 15 proteomes: ABC cassettes, FtsH proteases, translation initiation factors, translation elongation factors, isoleucyl-tRNA synthases, and RNA polymerases β'. In addition to the omnipresent motifs, these proteins also contain other highly conserved motifs, standing for additional modules of the proteins. Remarkably, the identified tentative earliest proteins are responsible for only three basic functions: supply of monomers (ABC transporters and proteases), protein synthesis (initiation and elongation factors, aminoacyl-tRNA synthases), and RNA synthesis (polymerases). No enzymes involved in metabolic activities are present in the list of the earliest proteins derived by this approach. Some of the omnipresent sequence motifs are found, indeed, in the metabolic enzymes (e.g. NTP binding motifs), but these enzymes do not make a sequence matching collection of 15 sequences, i.e. they are not omnipresent. Future analysis of less conserved sequence motifs may reveal at what degree of conservation (stage of evolution) the metabolic enzymes could have entered the scene.
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Affiliation(s)
- Y Sobolevsky
- a Faculdade de Gama , Universidade de Brasilia , Gama , 72405-610 , Brazil
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27
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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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28
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Cirillo D, Agostini F, Tartaglia GG. Predictions of protein-RNA interactions. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2012. [DOI: 10.1002/wcms.1119] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Banik SD, Nandi N. Mechanism of the activation step of the aminoacylation reaction: a significant difference between class I and class II synthetases. J Biomol Struct Dyn 2012; 30:701-15. [PMID: 22731388 DOI: 10.1080/07391102.2012.689701] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
In the present work we report, for the first time, a novel difference in the molecular mechanism of the activation step of aminoacylation reaction between the class I and class II aminoacyl tRNA synthetases (aaRSs). The observed difference is in the mode of nucleophilic attack by the oxygen atom of the carboxylic group of the substrate amino acid (AA) to the αP atom of adenosine triphosphate (ATP). The syn oxygen atom of the carboxylic group attacks the α-phosphorous atom (αP) of ATP in all class I aaRSs (except TrpRS) investigated, while the anti oxygen atom attacks in the case of class II aaRSs. The class I aaRSs investigated are GluRS, GlnRS, TyrRS, TrpRS, LeuRS, ValRS, IleRS, CysRS, and MetRS and class II aaRSs investigated are HisRS, LysRS, ProRS, AspRS, AsnRS, AlaRS, GlyRS, PheRS, and ThrRS. The variation of the electron density at bond critical points as a function of the conformation of the attacking oxygen atom measured by the dihedral angle ψ (C(α)-C') conclusively proves this. The result shows that the strength of the interaction of syn oxygen and αP is stronger than the interaction with the anti oxygen for class I aaRSs. This indicates that the syn oxygen is the most probable candidate for the nucleophilic attack in class I aaRSs. The result is further supported by the computation of the variation of the nonbonded interaction energies between αP atom and anti oxygen as well as syn oxygen in class I and II aaRSs, respectively. The difference in mechanism is explained based on the analysis of the electrostatic potential of the AA and ATP which shows that the relative arrangement of the ATP with respect to the AA is opposite in class I and class II aaRSs, which is correlated with the organization of the active site in respective aaRSs. A comparative study of the reaction mechanisms of the activation step in a class I aaRS (Glutaminyl tRNA synthetase) and in a class II aaRS (Histidyl tRNA synthetase) is carried out by the transition state analysis. The atoms in molecule analysis of the interaction between active site residues or ions and substrates are carried out in the reactant state and the transition state. The result shows that the observed novel difference in the mechanism is correlated with the organizations of the active sites of the respective aaRSs. The result has implication in understanding the experimentally observed different modes of tRNA binding in the two classes of aaRSs.
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Affiliation(s)
- Sindrila Dutta Banik
- Department of Chemistry, University of Kalyani, Kalyani, Nadia, West Bengal, 741235, India
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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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31
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Computational methods for prediction of protein-RNA interactions. J Struct Biol 2011; 179:261-8. [PMID: 22019768 DOI: 10.1016/j.jsb.2011.10.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 09/28/2011] [Accepted: 10/04/2011] [Indexed: 12/21/2022]
Abstract
Understanding the molecular mechanism of protein-RNA recognition and complex formation is a major challenge in structural biology. Unfortunately, the experimental determination of protein-RNA complexes by X-ray crystallography and nuclear magnetic resonance spectroscopy (NMR) is tedious and difficult. Alternatively, protein-RNA interactions can be predicted by computational methods. Although less accurate than experimental observations, computational predictions can be sufficiently accurate to prompt functional hypotheses and guide experiments, e.g. to identify individual amino acid or nucleotide residues. In this article we review 10 methods for predicting protein-RNA interactions, seven of which predict RNA-binding sites from protein sequences and three from structures. We also developed a meta-predictor that uses the output of top three sequence-based primary predictors to calculate a consensus prediction, which outperforms all the primary predictors. In order to fully cover the software for predicting protein-RNA interactions, we also describe five methods for protein-RNA docking. The article highlights the strengths and shortcomings of existing methods for the prediction of protein-RNA interactions and provides suggestions for their further development.
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Pham Y, Kuhlman B, Butterfoss GL, Hu H, Weinreb V, Carter CW. Tryptophanyl-tRNA synthetase Urzyme: a model to recapitulate molecular evolution and investigate intramolecular complementation. J Biol Chem 2010; 285:38590-601. [PMID: 20864539 PMCID: PMC2992291 DOI: 10.1074/jbc.m110.136911] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 09/14/2010] [Indexed: 01/26/2023] Open
Abstract
We substantiate our preliminary description of the class I tryptophanyl-tRNA synthetase minimal catalytic domain with details of its construction, structure, and steady-state kinetic parameters. Generating that active fragment involved deleting 65% of the contemporary enzyme, including the anticodon-binding domain and connecting peptide 1, CP1, a 74-residue internal segment from within the Rossmann fold. We used protein design (Rosetta), rather than phylogenetic sequence alignments, to identify mutations to compensate for the severe loss of modularity, thus restoring stability, as evidenced by renaturation described previously and by 70-ns molecular dynamics simulations. Sufficient solubility to enable biochemical studies was achieved by expressing the redesigned Urzyme as a maltose-binding protein fusion. Michaelis-Menten kinetic parameters from amino acid activation assays showed that, compared with the native full-length enzyme, TrpRS Urzyme binds ATP with similar affinity. This suggests that neither of the two deleted structural modules has a strong influence on ground-state ATP binding. However, tryptophan has 10(3) lower affinity, and the Urzyme has comparably reduced specificity relative to the related amino acid, tyrosine. Molecular dynamics simulations revealed how CP1 may contribute significantly to cognate amino acid specificity. As class Ia editing domains are nested within the CP1, this finding suggests that this module enhanced amino acid specificity continuously, throughout their evolution. We call this type of reconstructed protein catalyst an Urzyme (Ur prefix indicates original, primitive, or earliest). It establishes a model for recapitulating very early steps in molecular evolution in which fitness may have been enhanced by accumulating entire modules, rather than by discrete amino acid sequence changes.
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Affiliation(s)
- Yen Pham
- From the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Brian Kuhlman
- From the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Glenn L. Butterfoss
- the Biology and Courant Computer Science Department, New York University, New York, New York 10003, and
| | - Hao Hu
- the Chong Yuet Ming Chemistry Building, University of Hong Kong, Pokfulam Road, 999077 Hong Kong, China
| | - Violetta Weinreb
- From the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Charles W. Carter
- From the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
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