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Di Giulio M. Theories of the origin of the genetic code: Strong corroboration for the coevolution theory. Biosystems 2024; 239:105217. [PMID: 38663520 DOI: 10.1016/j.biosystems.2024.105217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 04/16/2024] [Accepted: 04/18/2024] [Indexed: 04/29/2024]
Abstract
I analyzed all the theories and models of the origin of the genetic code, and over the years, I have considered the main suggestions that could explain this origin. The conclusion of this analysis is that the coevolution theory of the origin of the genetic code is the theory that best captures the majority of observations concerning the organization of the genetic code. In other words, the biosynthetic relationships between amino acids would have heavily influenced the origin of the organization of the genetic code, as supported by the coevolution theory. Instead, the presence in the genetic code of physicochemical properties of amino acids, which have also been linked to the physicochemical properties of anticodons or codons or bases by stereochemical and physicochemical theories, would simply be the result of natural selection. More explicitly, I maintain that these correlations between codons, anticodons or bases and amino acids are in fact the result not of a real correlation between amino acids and codons, for example, but are only the effect of the intervention of natural selection. Specifically, in the genetic code table we expect, for example, that the most similar codons - that is, those that differ by only one base - will have more similar physicochemical properties. Therefore, the 64 codons of the genetic code table ordered in a certain way would also represent an ordering of some of their physicochemical properties. Now, a study aimed at clarifying which physicochemical property of amino acids has influenced the allocation of amino acids in the genetic code has established that the partition energy of amino acids has played a role decisive in this. Indeed, under some conditions, the genetic code was found to be approximately 98% optimized on its columns. In this same work, it was shown that this was most likely the result of the action of natural selection. If natural selection had truly allocated the amino acids in the genetic code in such a way that similar amino acids also have similar codons - this, not through a mechanism of physicochemical interaction between, for example, codons and amino acids - then it might turn out that even different physicochemical properties of codons (or anticodons or bases) show some correlation with the physicochemical properties of amino acids, simply because the partition energy of amino acids is correlated with other physicochemical properties of amino acids. It is very likely that this would inevitably lead to a correlation between codons (or anticodons or bases) and amino acids. In other words, since the codons (anticodons or bases) are ordered in the genetic code, that is to say, some of their physicochemical properties should also be ordered by a similar order, and given that the amino acids would also appear to have been ordered in the genetic code by selection natural, then it should inevitably turn out that there is a correlation between, for example, the hydrophobicity of anticodons and that of amino acids. Instead, the intervention of natural selection in organizing the genetic code would appear to be highly compatible with the main mechanism of structuring the genetic code as supported by the coevolution theory. This would make the coevolution theory the only plausible explanation for the origin of the genetic code.
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Affiliation(s)
- Massimo Di Giulio
- The Ionian School, Early Evolution of Life Department, Genetic Code and tRNA Origin Laboratory, Via Roma 19, 67030, Alfedena, L'Aquila, Italy.
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2
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Brown SM, Voráček V, Freeland S. What Would an Alien Amino Acid Alphabet Look Like and Why? ASTROBIOLOGY 2023; 23:536-549. [PMID: 37022727 DOI: 10.1089/ast.2022.0107] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Life on Earth builds genetically encoded proteins by using a standard alphabet of just 20 L-α-amino acids, although many others were available to life's origins and early evolution. To better understand the causes of this foundational evolutionary outcome, we extend previous analyses which have identified a highly unusual distribution of biophysical properties within the set used by life. Specifically, we use a heuristic search algorithm to identify other sets of amino acids, from a library of plausible alternatives, that emulate life's signature. We find that a subset of amino acids seems predisposed to forming such sets. We present other examples of such alphabets under various assumptions, along with analysis and reasoning about why each might be simplistic. We do so to introduce the central, open question that remains: while fundamental biophysics related to protein folding can potentially reduce a library of 1054 possible amino acid alphabets by 7 orders of magnitude, the framework of assumptions that does so leaves a further 1045 possibilities. It is therefore tempting to ask what additional assumptions can further reduce these 45 orders of magnitude? We thus conclude with a focus on library and alphabet construction as a useful target for subsequent research that may help future science speak with more confidence about what an alien amino acid alphabet would look like and why.
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Affiliation(s)
- Sean M Brown
- Department of Biological Sciences, University of Maryland, Baltimore County, Maryland, USA
| | - Václav Voráček
- Department of Computer Science, University of Tübingen, Tübingen, Germany
| | - Stephen Freeland
- Department of Biological Sciences, University of Maryland, Baltimore County, Maryland, USA
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3
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Kondratyeva LG, Dyachkova MS, Galchenko AV. The Origin of Genetic Code and Translation in the Framework of Current Concepts on the Origin of Life. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:150-169. [PMID: 35508902 DOI: 10.1134/s0006297922020079] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The origin of genetic code and translation system is probably the central and most difficult problem in the investigations on the origin of life and one of the most complex problems in the evolutionary biology in general. There are multiple hypotheses on the emergence and development of existing genetic systems that propose the mechanisms for the origin and early evolution of genetic code, as well as for the emergence of replication and translation. Here, we discuss the most well-known of these hypotheses, although none of them provides a description of the early evolution of genetic systems without gaps and assumptions. The RNA world hypothesis is a currently prevailing scientific idea on the early evolution of biological and pre-biological structures, the main advantage of which is the assumption that RNAs as the first living systems were self-sufficient, i.e., capable of functioning as both catalysts and templates. However, this hypothesis has also significant limitations. In particular, no ribozymes with processive polymerase activity have been yet discovered or synthesized. Taking into account the mutual need of proteins and nucleic acids in each other in the current world, many authors propose the early evolution scenarios based on the co-evolution of these two classes of organic molecules. They postulate that the emergence of translation was necessary for the replication of nucleic acids, in contrast to the RNA world hypothesis, according to which the emergence of translation was preceded by the era of self-replicating RNAs. Although such scenarios are less parsimonious from the evolutionary point of view, since they require simultaneous emergence and evolution of two classes of organic molecules, as well as the emergence of synchronized replication and translation, their major advantage is that they explain the development of processive and much more accurate protein-dependent replication.
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Affiliation(s)
- Liya G Kondratyeva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | | | - Alexey V Galchenko
- Peoples' Friendship University of Russia (RUDN University), Moscow, 117198, Russia.
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4
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Abstract
Minimally evolved codes are constructed here; these have randomly chosen standard genetic code (SGC) triplets, completed with completely random triplet assignments. Such "genetic codes" have not evolved, but retain SGC qualities. Retained qualities are basic, part of the underpinning of coding. For example, the sensitivity of coding to arbitrary assignments, which must be < ∼10%, is intrinsic. Such sensitivity comes from the elementary combinatorial properties of coding and constrains any SGC evolution hypothesis. Similarly, assignment of last-evolved functions is difficult because of late kinetic phenomena, likely common across codes. Census of minimally evolved code assignments shows that shape and size of wobble domains controls the code's fit into a coding table, strongly shifting accuracy of codon assignments. Access to the SGC therefore requires a plausible pathway to limited randomness, avoiding difficult completion while fitting a highly ordered, degenerate code into a preset three-dimensional space. Three-dimensional late Crick wobble in a genetic code assembled by lateral transfer between early partial codes satisfies these varied, simultaneous requirements. By allowing parallel evolution of SGC domains, this origin can yield shortened evolution to SGC-level order and allow the code to arise in smaller populations. It effectively yields full codes. Less obviously, it unifies previously studied chemical, biochemical, and wobble order in amino acid assignment, including a stereochemical minority of triplet-amino acid associations. Finally, fusion of intermediates into the final SGC is credible, mirroring broadly accepted later cellular evolution.
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5
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Yarus M. Optimal Evolution of the Standard Genetic Code. J Mol Evol 2021; 89:45-49. [PMID: 33486548 PMCID: PMC7884564 DOI: 10.1007/s00239-020-09984-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Accepted: 12/11/2020] [Indexed: 04/14/2023]
Abstract
The Standard Genetic Code (SGC) exists in every known organism on Earth. SGC evolution via early unique codon assignment, then later wobble, yields coding resembling the near-universal code. Below, later wobble is shown to also create an optimal route to accurate codon assignment. Time of optimal codon assignment matches the previously defined mean time for ordered coding, exhibiting ≥ 90% of SGC order. Accurate evolution is also accessible, sufficiently frequent to appear in populations of 103 to 104 codes. SGC-like coding capacity, code order, and accurate assignments therefore arise together, in one attainable evolutionary intermediate. Examples, which plausibly resemble coding at evolutionary domain separation, are characterized.
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Affiliation(s)
- Michael Yarus
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, CO, 80309-0347, USA.
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6
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Abstract
A near-universal Standard Genetic Code (SGC) implies a single origin for present Earth life. To study this unique event, I compute paths to the SGC, comparing different plausible histories. Notably, SGC-like coding emerges from traditional evolutionary mechanisms, and a superior route can be identified. To objectively measure evolution, progress values from 0 (random coding) to 1 (SGC-like) are defined: these measure fractions of random-code-to-SGC distance. Progress types are spacing/distance/delta Polar Requirement, detecting space between identical assignments/mutational distance to the SGC/chemical order, respectively. The coding system is based on selected RNAs performing aminoacyl-RNA synthetase reactions. Acceptor RNAs exhibit SGC-like Crick wobble; alternatively, non-wobbling triplets uniquely encode 20 amino acids/start/stop. Triplets acquire 22 functions by stereochemistry, selection, coevolution, or at random. Assignments also propagate to an assigned triplet’s neighborhood via single mutations, but can also decay. A vast code universe makes futile evolutionary paths plentiful. Thus, SGC evolution is critically sensitive to disorder from random assignments. Evolution also inevitably slows near coding completion. The SGC likely avoided these difficulties, and two suitable paths are compared. In late wobble, a majority of non-wobble assignments are made before wobble is adopted. In continuous wobble, a uniquely advantageous early intermediate yields an ordered SGC. Revised coding evolution (limited randomness, late wobble, concentration on amino acid encoding, chemically conservative coevolution with a chemically ordered elite) produces varied full codes with excellent joint progress values. A population of only 600 independent coding tables includes SGC-like members; a Bayesian path toward more accurate SGC evolution is available.
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Affiliation(s)
- Michael Yarus
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, CO, 80309-0347, USA.
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Muchowska KB, Varma SJ, Moran J. Nonenzymatic Metabolic Reactions and Life's Origins. Chem Rev 2020; 120:7708-7744. [PMID: 32687326 DOI: 10.1021/acs.chemrev.0c00191] [Citation(s) in RCA: 110] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Prebiotic chemistry aims to explain how the biochemistry of life as we know it came to be. Most efforts in this area have focused on provisioning compounds of importance to life by multistep synthetic routes that do not resemble biochemistry. However, gaining insight into why core metabolism uses the molecules, reactions, pathways, and overall organization that it does requires us to consider molecules not only as synthetic end goals. Equally important are the dynamic processes that build them up and break them down. This perspective has led many researchers to the hypothesis that the first stage of the origin of life began with the onset of a primitive nonenzymatic version of metabolism, initially catalyzed by naturally occurring minerals and metal ions. This view of life's origins has come to be known as "metabolism first". Continuity with modern metabolism would require a primitive version of metabolism to build and break down ketoacids, sugars, amino acids, and ribonucleotides in much the same way as the pathways that do it today. This review discusses metabolic pathways of relevance to the origin of life in a manner accessible to chemists, and summarizes experiments suggesting several pathways might have their roots in prebiotic chemistry. Finally, key remaining milestones for the protometabolic hypothesis are highlighted.
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Affiliation(s)
| | - Sreejith J Varma
- University of Strasbourg, CNRS, ISIS UMR 7006, 67000 Strasbourg, France
| | - Joseph Moran
- University of Strasbourg, CNRS, ISIS UMR 7006, 67000 Strasbourg, France
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8
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Abstract
Since the origin of life, metabolism and protein synthesis have evolved together to balance the vast amounts of ATP and amino acids required for genetic translation with the rest of the cell's energy needs. A new study offers satisfying insights into a long-standing evolutionary mystery surrounding a fused, bifunctional aminoacyl-tRNA synthetase. To avoid depleting cells from an essential amino acid generated by the Krebs cycle, harvesting for Glu and Pro by the translation machinery was unified in animals, thus preventing a Pro-hungry translational apparatus from depleting the cell of essential Glu reserves.
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Affiliation(s)
- Lluís Ribas de Pouplana
- From the Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Parc Científic de Barcelona, C/Baldiri Reixac 10, 08028 Barcelona, Catalonia, Spain and Catalan Institution for Research and Advanced Studies (ICREA), P/Lluís Companys 23, 08010 Barcelona, Catalonia, Spain
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Newton MS, Morrone DJ, Lee KH, Seelig B. Genetic Code Evolution Investigated through the Synthesis and Characterisation of Proteins from Reduced-Alphabet Libraries. Chembiochem 2019; 20:846-856. [PMID: 30511381 DOI: 10.1002/cbic.201800668] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Indexed: 11/08/2022]
Abstract
The universal genetic code of 20 amino acids is the product of evolution. It is believed that earlier versions of the code had fewer residues. Many theories for the order in which amino acids were integrated into the code have been proposed, considering factors ranging from prebiotic chemistry to codon capture. Several meta-analyses combined these theories to yield a feasible consensus chronology of the genetic code's evolution, but there is a dearth of experimental data to test the hypothesised order. We used combinatorial chemistry to synthesise libraries of random polypeptides that were based on different subsets of the 20 standard amino acids, thus representing different stages of a plausible history of the alphabet. Four libraries were comprised of the five, nine, and 16 most ancient amino acids, and all 20 extant residues for a direct side-by-side comparison. We characterised numerous variants from each library for their solubility and propensity to form secondary, tertiary or quaternary structures. Proteins from the two most ancient libraries were more likely to be soluble than those from the extant library. Several individual protein variants exhibited inducible protein folding and other traits typical of intrinsically disordered proteins. From these libraries, we can infer how primordial protein structure and function might have evolved with the genetic code.
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Affiliation(s)
- Matilda S Newton
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA.,BioTechnology Institute, University of Minnesota, 1479 Gortner Avenue, 140 Gortner Laboratory, St. Paul, MN, 55108-6106, USA
| | - Dana J Morrone
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA.,BioTechnology Institute, University of Minnesota, 1479 Gortner Avenue, 140 Gortner Laboratory, St. Paul, MN, 55108-6106, USA
| | - Kun-Hwa Lee
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA.,BioTechnology Institute, University of Minnesota, 1479 Gortner Avenue, 140 Gortner Laboratory, St. Paul, MN, 55108-6106, USA
| | - Burckhard Seelig
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA.,BioTechnology Institute, University of Minnesota, 1479 Gortner Avenue, 140 Gortner Laboratory, St. Paul, MN, 55108-6106, USA
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10
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Błażej P, Wnętrzak M, Mackiewicz D, Mackiewicz P. Optimization of the standard genetic code according to three codon positions using an evolutionary algorithm. PLoS One 2018; 13:e0201715. [PMID: 30092017 PMCID: PMC6084934 DOI: 10.1371/journal.pone.0201715] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 07/21/2018] [Indexed: 12/28/2022] Open
Abstract
Many biological systems are typically examined from the point of view of adaptation to certain conditions or requirements. One such system is the standard genetic code (SGC), which generally minimizes the cost of amino acid replacements resulting from mutations or mistranslations. However, no full consensus has been reached on the factors that caused the evolution of this feature. One of the hypotheses suggests that code optimality was directly selected as an advantage to preserve information about encoded proteins. An important feature that should be considered when studying the SGC is the different roles of the three codon positions. Therefore, we investigated the robustness of this code regarding the cost of amino acid replacements resulting from substitutions in these positions separately and the sum of these costs. We applied a modified evolutionary algorithm and included four models of the genetic code assuming various restrictions on its structure. The SGC was compared both with the codes that minimize the objective function and those that maximize it. This approach allowed us to place the SGC in the global space of possible codes, which is a more appropriate and unbiased comparison than that with randomly generated codes because they are characterized by relatively uniform amino acid assignments to codons. The SGC appeared to be well optimized at the global scale, but its individual positions were not fully optimized because there were codes that were optimized for only one codon position and simultaneously outperformed the SGC at the other positions. We also found that different code structures may lead to the same optimality and that random codes can show a tendency to minimize costs under some of the genetic code models. Our results suggest that the optimality of SGC could be a by-product of other processes.
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Affiliation(s)
- Paweł Błażej
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Małgorzata Wnętrzak
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Dorota Mackiewicz
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Paweł Mackiewicz
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
- * E-mail:
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11
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Wagner A, Ortman S, Maxfield R. From the primordial soup to self-driving cars: standards and their role in natural and technological innovation. J R Soc Interface 2016; 13:20151086. [PMID: 26864893 DOI: 10.1098/rsif.2015.1086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Standards are specifications to which the elements of a technology must conform. Here, we apply this notion to the biochemical 'technologies' of nature, where objects like DNA and proteins, as well as processes like the regulation of gene activity are highly standardized. We introduce the concept of standards with multiple examples, ranging from the ancient genetic material RNA, to Palaeolithic stone axes, and digital electronics, and we discuss common ways in which standards emerge in nature and technology. We then focus on the question of how standards can facilitate technological and biological innovation. Innovation-enhancing standards include those of proteins and digital electronics. They share common features, such as that few standardized building blocks can be combined through standard interfaces to create myriad useful objects or processes. We argue that such features will also characterize the most innovation-enhancing standards of future technologies.
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Affiliation(s)
- Andreas Wagner
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland Swiss Institute of Bioinformatics, Lausanne, Switzerland Santa Fe Institute, Santa Fe, NM, USA
| | - Scott Ortman
- Santa Fe Institute, Santa Fe, NM, USA Department of Anthropology, University of Colorado Boulder, Boulder, CO, USA
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12
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Grosjean H, Westhof E. An integrated, structure- and energy-based view of the genetic code. Nucleic Acids Res 2016; 44:8020-40. [PMID: 27448410 PMCID: PMC5041475 DOI: 10.1093/nar/gkw608] [Citation(s) in RCA: 177] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 06/11/2016] [Accepted: 06/17/2016] [Indexed: 12/25/2022] Open
Abstract
The principles of mRNA decoding are conserved among all extant life forms. We present an integrative view of all the interaction networks between mRNA, tRNA and rRNA: the intrinsic stability of codon-anticodon duplex, the conformation of the anticodon hairpin, the presence of modified nucleotides, the occurrence of non-Watson-Crick pairs in the codon-anticodon helix and the interactions with bases of rRNA at the A-site decoding site. We derive a more information-rich, alternative representation of the genetic code, that is circular with an unsymmetrical distribution of codons leading to a clear segregation between GC-rich 4-codon boxes and AU-rich 2:2-codon and 3:1-codon boxes. All tRNA sequence variations can be visualized, within an internal structural and energy framework, for each organism, and each anticodon of the sense codons. The multiplicity and complexity of nucleotide modifications at positions 34 and 37 of the anticodon loop segregate meaningfully, and correlate well with the necessity to stabilize AU-rich codon-anticodon pairs and to avoid miscoding in split codon boxes. The evolution and expansion of the genetic code is viewed as being originally based on GC content with progressive introduction of A/U together with tRNA modifications. The representation we present should help the engineering of the genetic code to include non-natural amino acids.
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Affiliation(s)
- Henri Grosjean
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Eric Westhof
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Institut de biologie moléculaire et cellulaire du CNRS, 15 rue René Descartes, 67084 Strasbourg, France
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13
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Macé K, Gillet R. Origins of tmRNA: the missing link in the birth of protein synthesis? Nucleic Acids Res 2016; 44:8041-51. [PMID: 27484476 PMCID: PMC5041485 DOI: 10.1093/nar/gkw693] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 07/22/2016] [Accepted: 07/26/2016] [Indexed: 12/20/2022] Open
Abstract
The RNA world hypothesis refers to the early period on earth in which RNA was central in assuring both genetic continuity and catalysis. The end of this era coincided with the development of the genetic code and protein synthesis, symbolized by the apparition of the first non-random messenger RNA (mRNA). Modern transfer-messenger RNA (tmRNA) is a unique hybrid molecule which has the properties of both mRNA and transfer RNA (tRNA). It acts as a key molecule during trans-translation, a major quality control pathway of modern bacterial protein synthesis. tmRNA shares many common characteristics with ancestral RNA. Here, we present a model in which proto-tmRNAs were the first molecules on earth to support non-random protein synthesis, explaining the emergence of early genetic code. In this way, proto-tmRNA could be the missing link between the first mRNA and tRNA molecules and modern ribosome-mediated protein synthesis.
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Affiliation(s)
- Kevin Macé
- Université de Rennes 1, CNRS UMR 6290 IGDR, Translation and Folding Team, 35042 Rennes cedex, France
| | - Reynald Gillet
- Université de Rennes 1, CNRS UMR 6290 IGDR, Translation and Folding Team, 35042 Rennes cedex, France Institut Universitaire de France
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14
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Kumar B, Saini S. Analysis of the optimality of the standard genetic code. MOLECULAR BIOSYSTEMS 2016; 12:2642-51. [DOI: 10.1039/c6mb00262e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Many theories have been proposed attempting to explain the origin of the genetic code. In this work, we compare performance of the standard genetic code against millions of randomly generated codes. On left, ability of genetic codes to encode additional information and their robustness to frameshift mutations.
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Affiliation(s)
- Balaji Kumar
- Department of Chemical Engineering
- Indian Institute of Technology Bombay
- Mumbai – 400 076
- India
| | - Supreet Saini
- Department of Chemical Engineering
- Indian Institute of Technology Bombay
- Mumbai – 400 076
- India
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15
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Pathways of Genetic Code Evolution in Ancient and Modern Organisms. J Mol Evol 2015; 80:229-43. [DOI: 10.1007/s00239-015-9686-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 06/03/2015] [Indexed: 10/23/2022]
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16
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Novoa EM, Vargas-Rodriguez O, Lange S, Goto Y, Suga H, Musier-Forsyth K, Ribas de Pouplana L. Ancestral AlaX editing enzymes for control of genetic code fidelity are not tRNA-specific. J Biol Chem 2015; 290:10495-503. [PMID: 25724653 DOI: 10.1074/jbc.m115.640060] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Indexed: 01/15/2023] Open
Abstract
Accurate protein synthesis requires the hydrolytic editing of tRNAs incorrectly aminoacylated by aminoacyl-tRNA synthetases (ARSs). Recognition of cognate tRNAs by ARS is less error-prone than amino acid recognition, and, consequently, editing domains are generally believed to act only on the tRNAs cognate to their related ARSs. For example, the AlaX family of editing domains, including the editing domain of alanyl-tRNA synthetase and the related free-standing trans-editing AlaX enzymes, are thought to specifically act on tRNA(Ala), whereas the editing domains of threonyl-tRNA synthetases are specific for tRNA(Thr). Here we show that, contrary to this belief, AlaX-S, the smallest of the extant AlaX enzymes, deacylates Ser-tRNA(Thr) in addition to Ser-tRNA(Ala) and that a single residue is important to determine this behavior. Our data indicate that promiscuous forms of AlaX are ancestral to tRNA-specific AlaXs. We propose that former AlaX domains were used to maintain translational fidelity in earlier stages of genetic code evolution when mis-serylation of several tRNAs was possible.
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Affiliation(s)
- Eva Maria Novoa
- From the Institute for Research in Biomedicine, c/ Baldiri Reixac 10, 08028 Barcelona, Catalonia, Spain
| | - Oscar Vargas-Rodriguez
- the Department of Chemistry and Biochemistry, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
| | - Stefanie Lange
- From the Institute for Research in Biomedicine, c/ Baldiri Reixac 10, 08028 Barcelona, Catalonia, Spain
| | - Yuki Goto
- the Department of Chemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan, and
| | - Hiroaki Suga
- the Department of Chemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan, and
| | - Karin Musier-Forsyth
- the Department of Chemistry and Biochemistry, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
| | - Lluís Ribas de Pouplana
- From the Institute for Research in Biomedicine, c/ Baldiri Reixac 10, 08028 Barcelona, Catalonia, Spain, the Catalan Institution for Research and Advanced Studies, Passeig Lluís Companys 23, 08010 Barcelona, Catalonia, Spain
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17
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The genetic code did not originate from an mRNA codifying polyglycine because the proto-mRNAs already codified for an amino acid number greater than one. J Theor Biol 2014; 361:204-5. [DOI: 10.1016/j.jtbi.2014.09.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Revised: 08/28/2014] [Accepted: 09/03/2014] [Indexed: 11/30/2022]
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18
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Genetic code evolution started with the incorporation of glycine, followed by other small hydrophilic amino acids. J Mol Evol 2014; 78:307-9. [PMID: 24916657 DOI: 10.1007/s00239-014-9627-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 05/23/2014] [Indexed: 10/25/2022]
Abstract
We propose that glycine was the first amino acid to be incorporated into the genetic code, followed by serine, aspartic and/or glutamic acid-small hydrophilic amino acids that all have codons in the bottom right-hand corner of the standard genetic code table. Because primordial ribosomal synthesis is presumed to have been rudimentary, this stage would have been characterized by the synthesis of short, water-soluble peptides, the first of which would have comprised polyglycine. Evolution of the code is proposed to have occurred by the duplication and mutation of tRNA sequences, which produced a radiation of codon assignment outwards from the bottom right-hand corner. As a result of this expansion, we propose a trend from small hydrophilic to hydrophobic amino acids, with selection for longer polypeptides requiring a hydrophobic core for folding and stability driving the incorporation of hydrophobic amino acids into the code.
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Biro JC. Coding nucleic acids are chaperons for protein folding: a novel theory of protein folding. Gene 2012; 515:249-57. [PMID: 23266645 DOI: 10.1016/j.gene.2012.12.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 12/04/2012] [Accepted: 12/06/2012] [Indexed: 11/29/2022]
Abstract
The arguments for nucleic acid chaperons are reviewed and three new lines of evidence are added. (1) It was found that amino acids encoded by codons in short nucleic acid loops frequently form turns and helices in the corresponding protein structures. (2) The amino acids encoded by partially complementary (1st and 3rd nucleotides) codons are more frequently co-located in the encoded proteins than expected by chance. (3) There are significant correlations between thermodynamic changes (ddG) caused by codon mutations in nucleic acids and the thermodynamic changes caused by the corresponding amino acid mutations in the encoded proteins. We conclude that the concept of the Proteomic Code and nucleic acid chaperons seems correct from the bioinformatics point of view, and we expect to see direct biochemical experiments and evidence in the near future.
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Affiliation(s)
- Jan C Biro
- Karolinska Institute, Stockholm, Sweden.
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20
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Mutuality in Discrete and Compositional Information: Perspectives for Synthetic Genetic Codes. Cognit Comput 2011. [DOI: 10.1007/s12559-011-9116-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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21
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Abstract
The establishment of the genetic code remains elusive nearly five decades after the code was elucidated. The stereochemical hypothesis postulates that the code developed from interactions between nucleotides and amino acids, yet supporting evidence in a biological context is lacking. We show here that anticodons are selectively enriched near their respective amino acids in the ribosome, and that such enrichment is significantly correlated with the canonical code over random codes. Ribosomal anticodon-amino acid enrichment further reveals that specific codons were reassigned during code evolution, and that the code evolved through a two-stage transition from ancient amino acids without anticodon interaction to newer additions with anticodon interaction. The ribosome thus serves as a molecular fossil, preserving biological evidence that anticodon-amino acid interactions shaped the evolution of the genetic code.
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22
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Koonin EV, Novozhilov AS. Origin and evolution of the genetic code: the universal enigma. IUBMB Life 2009; 61:99-111. [PMID: 19117371 DOI: 10.1002/iub.146] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The genetic code is nearly universal, and the arrangement of the codons in the standard codon table is highly nonrandom. The three main concepts on the origin and evolution of the code are the stereochemical theory, according to which codon assignments are dictated by physicochemical affinity between amino acids and the cognate codons (anticodons); the coevolution theory, which posits that the code structure coevolved with amino acid biosynthesis pathways; and the error minimization theory under which selection to minimize the adverse effect of point mutations and translation errors was the principal factor of the code's evolution. These theories are not mutually exclusive and are also compatible with the frozen accident hypothesis, that is, the notion that the standard code might have no special properties but was fixed simply because all extant life forms share a common ancestor, with subsequent changes to the code, mostly, precluded by the deleterious effect of codon reassignment. Mathematical analysis of the structure and possible evolutionary trajectories of the code shows that it is highly robust to translational misreading but there are numerous more robust codes, so the standard code potentially could evolve from a random code via a short sequence of codon series reassignments. Thus, much of the evolution that led to the standard code could be a combination of frozen accident with selection for error minimization although contributions from coevolution of the code with metabolic pathways and weak affinities between amino acids and nucleotide triplets cannot be ruled out. However, such scenarios for the code evolution are based on formal schemes whose relevance to the actual primordial evolution is uncertain. A real understanding of the code origin and evolution is likely to be attainable only in conjunction with a credible scenario for the evolution of the coding principle itself and the translation system.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA.
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23
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The close relationship between the biosynthetic families of amino acids and the organisation of the genetic code. Gene 2009; 435:9-12. [PMID: 19393191 DOI: 10.1016/j.gene.2008.12.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 12/18/2008] [Accepted: 12/23/2008] [Indexed: 11/21/2022]
Abstract
By generating random codes and applying Fisher's exact test, we confirm that the biosynthetic families of amino acids are intimately involved in the organisation of the genetic code. This observation corroborates the coevolution theory of genetic code origin. As the amino acids belonging to the single biosynthetic families have codons that are contiguous in the genetic code, they must have entered the code itself by means of a clustering mechanism, which must clearly have been compatible with the mechanism on which this theory is based because this too envisages the clustering of biosynthetically correlated amino acids within the code.
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24
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Di Giulio M. An extension of the coevolution theory of the origin of the genetic code. Biol Direct 2008; 3:37. [PMID: 18775066 PMCID: PMC2538516 DOI: 10.1186/1745-6150-3-37] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 09/05/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The coevolution theory of the origin of the genetic code suggests that the genetic code is an imprint of the biosynthetic relationships between amino acids. However, this theory does not seem to attribute a role to the biosynthetic relationships between the earliest amino acids that evolved along the pathways of energetic metabolism. As a result, the coevolution theory is unable to clearly define the very earliest phases of genetic code origin. In order to remove this difficulty, I here suggest an extension of the coevolution theory that attributes a crucial role to the first amino acids that evolved along these biosynthetic pathways and to their biosynthetic relationships, even when defined by the non-amino acid molecules that are their precursors. RESULTS It is re-observed that the first amino acids to evolve along these biosynthetic pathways are predominantly those codified by codons of the type GNN, and this observation is found to be statistically significant. Furthermore, the close biosynthetic relationships between the sibling amino acids Ala-Ser, Ser-Gly, Asp-Glu, and Ala-Val are not random in the genetic code table and reinforce the hypothesis that the biosynthetic relationships between these six amino acids played a crucial role in defining the very earliest phases of genetic code origin. CONCLUSION All this leads to the hypothesis that there existed a code, GNS, reflecting the biosynthetic relationships between these six amino acids which, as it defines the very earliest phases of genetic code origin, removes the main difficulty of the coevolution theory. Furthermore, it is here discussed how this code might have naturally led to the code codifying only for the domains of the codons of precursor amino acids, as predicted by the coevolution theory. Finally, the hypothesis here suggested also removes other problems of the coevolution theory, such as the existence for certain pairs of amino acids with an unclear biosynthetic relationship between the precursor and product amino acids and the collocation of Ala between the amino acids Val and Leu belonging to the pyruvate biosynthetic family, which the coevolution theory considered as belonging to different biosyntheses. REVIEWERS This article was reviewed by Rob Knight, Paul Higgs (nominated by Laura Landweber), and Eugene Koonin.
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Affiliation(s)
- Massimo Di Giulio
- Laboratory for Molecular Evolution, Institute of Genetics and Biophysics Adriano Buzzati Traverso, CNR, Via P. Castellino, 111, 80131 Naples, Napoli, Italy.
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Sun FJ, Caetano-Anollés G. Evolutionary patterns in the sequence and structure of transfer RNA: a window into early translation and the genetic code. PLoS One 2008; 3:e2799. [PMID: 18665254 PMCID: PMC2474678 DOI: 10.1371/journal.pone.0002799] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 07/02/2008] [Indexed: 01/06/2023] Open
Abstract
Transfer RNA (tRNA) molecules play vital roles during protein synthesis. Their acceptor arms are aminoacylated with specific amino acid residues while their anticodons delimit codon specificity. The history of these two functions has been generally linked in evolutionary studies of the genetic code. However, these functions could have been differentially recruited as evolutionary signatures were left embedded in tRNA molecules. Here we built phylogenies derived from the sequence and structure of tRNA, we forced taxa into monophyletic groups using constraint analyses, tested competing evolutionary hypotheses, and generated timelines of amino acid charging and codon discovery. Charging of Sec, Tyr, Ser and Leu appeared ancient, while specificities related to Asn, Met, and Arg were derived. The timelines also uncovered an early role of the second and then first codon bases, identified codons for Ala and Pro as the most ancient, and revealed important evolutionary take-overs related to the loss of the long variable arm in tRNA. The lack of correlation between ancestries of amino acid charging and encoding indicated that the separate discoveries of these functions reflected independent histories of recruitment. These histories were probably curbed by co-options and important take-overs during early diversification of the living world.
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Affiliation(s)
- Feng-Jie Sun
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Gustavo Caetano-Anollés
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
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26
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Goodarzi H, Torabi N, Najafabadi HS, Archetti M. Amino acid and codon usage profiles: Adaptive changes in the frequency of amino acids and codons. Gene 2008; 407:30-41. [DOI: 10.1016/j.gene.2007.09.020] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2007] [Revised: 05/29/2007] [Accepted: 09/24/2007] [Indexed: 10/22/2022]
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27
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Abstract
The evolution of the transfer RNA (tRNA) molecule is controversial but embeds the history of protein biosynthesis, the genetic code, and the origins of diversified life. A new phylogenetic method based on RNA structure that we developed provides new lines of evidence to support the genome tag hypothesis and confirms that the 'top half' of tRNA is more ancient than the 'bottom half'. Timelines of amino acid charging function generated from constraint analyses showed that selenocysteine, tyrosine, serine, and leucine specificities were ancient, while those related to asparagine, methionine, and arginine were more recent. The timelines also uncovered an early role of the second and then first codon bases, identified codons for alanine and proline as the most ancient, and revealed important evolutionary take-overs related to the loss of the long variable arm of tRNA. Furthermore, organismal timelines showed Archaea was the oldest superkingdom, followed by viruses, and superkingdoms Eukarya and Bacteria in that order supporting conclusions from recent phylogenomic studies of protein architecture. Strikingly, results showed that the origin of viruses was not only ancient but was linked to Archaea, supporting the notion that the archaeal lineage is the most ancient on earth and its origin predated diversification of tRNA function and specificity.
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Affiliation(s)
- Feng-Jie Sun
- Department of Crop Sciences at the University of Illinois at Urbana-Champaign, 61801, USA
| | - Gustavo Caetano-Anollés
- Department of Crop Sciences, University of Illinois, 332 NSRC, 1101 West Peabody Drive, Urbana, Illinois, 61801, USA
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28
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Abstract
The codon table for the canonical genetic code can be rearranged in such a way that the code is divided into four quarters and two halves according to the variability of their GC and purine contents, respectively. For prokaryotic genomes, when the genomic GC content increases, their amino acid contents tend to be restricted to the GC-rich quarter and the purine-content insensitive half, where all codons are fourfold degenerate and relatively mutation-tolerant. Conversely, when the genomic GC content decreases, most of the codons retract to the AU-rich quarter and the purine-content sensitive half; most of the codons not only remain encoding physicochemically diversified amino acids but also vary when transversion (between purine and pyrimidine) happens. Amino acids with sixfold-degenerate codons are distributed into all four quarters and across the two halves; their fourfold-degenerate codons are all partitioned into the purine-insensitive half in favorite of robustness against mutations. The features manifested in the rearranged codon table explain most of the intrinsic relationship between protein coding sequences (the informational content) and amino acid compositions (the functional content). The renovated codon table is useful in predicting abundant amino acids and positioning the amino acids with related or distinct physicochemical properties.
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Affiliation(s)
- Jun Yu
- Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101300, China.
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29
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Davis BK. Coevolution theory of the genetic code: is the precursor-product hypothesis invalid? Bioessays 2006; 27:1308; author reply 1309; discussion 1310. [PMID: 16299768 DOI: 10.1002/bies.20332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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30
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Caporaso JG, Yarus M, Knight R. Error Minimization and Coding Triplet/Binding Site Associations Are Independent Features of the Canonical Genetic Code. J Mol Evol 2005; 61:597-607. [PMID: 16211428 DOI: 10.1007/s00239-004-0314-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Accepted: 05/05/2005] [Indexed: 10/25/2022]
Abstract
The canonical genetic code has been reported both to be error minimizing and to show stereochemical associations between coding triplets and binding sites. In order to test whether these two properties are unexpectedly overlapping, we generated 200,000 randomized genetic codes using each of five randomization schemes, with and without randomization of stop codons. Comparison of the code error (difference in polar requirement for single-nucleotide codon interchanges) with the coding triplet concentrations in RNA binding sites for eight amino acids shows that these properties are independent and uncorrelated. Thus, one is not the result of the other, and error minimization and triplet associations probably arose independently during the history of the genetic code. We explicitly show that prior fixation of a stereochemical core is consistent with an effective later minimization of error.
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Affiliation(s)
- J Gregory Caporaso
- Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Mail Stop 8303, P.O. Box 6511, Aurora, CO 80045, USA
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31
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Abstract
There is very significant evidence that cognate codons and/or anticodons are unexpectedly frequent in RNA-binding sites for seven of eight biological amino acids that have been tested. This suggests that a substantial fraction of the genetic code has a stereochemical basis, the triplets having escaped from their original function in amino acid-binding sites to become modern codons and anticodons. We explicitly show that this stereochemical basis is consistent with subsequent optimization of the code to minimize the effect of coding mistakes on protein structure. These data also strengthen the argument for invention of the genetic code in an RNA world and for the RNA world itself.
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Affiliation(s)
- Michael Yarus
- Department of Molecular Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309-0347, USA.
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32
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Goodarzi H, Najafabadi HS, Torabi N. Designing a neural network for the constraint optimization of the fitness functions devised based on the load minimization of the genetic code. Biosystems 2005; 81:91-100. [PMID: 15936137 DOI: 10.1016/j.biosystems.2005.02.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Revised: 01/16/2005] [Accepted: 02/02/2005] [Indexed: 11/20/2022]
Abstract
Nonrandom patterns in codon assignments are supported by many statistical and biochemical studies in the last two decades. The canonical genetic code is known to be highly efficient in minimizing the effects of mistranslational errors and point mutations, an ability, which in term is designated "load minimization". Prior studies have included many attempts at quantitative estimation of the fraction of randomly generated codes, which in terms of load minimization, score higher than the canonical genetic code. In this study, a neural network, which estimates a highly optimized genetic code in a relatively short period of time has been devised. Several fitness functions were used throughout this text. Meanwhile, we have made use of two cost measure matrices, PAM74-100 and mutation matrix.
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Affiliation(s)
- Hani Goodarzi
- Department of Biotechnology, Faculty of Science, University of Tehran, Enghelab St., Tehran, Iran.
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33
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Goodarzi H, Najafabadi HS, Hassani K, Nejad HA, Torabi N. On the optimality of the genetic code, with the consideration of coevolution theory by comparison of prominent cost measure matrices. J Theor Biol 2005; 235:318-25. [PMID: 15882694 DOI: 10.1016/j.jtbi.2005.01.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Revised: 01/20/2005] [Accepted: 01/24/2005] [Indexed: 11/22/2022]
Abstract
Statistical and biochemical studies have revealed non-random patterns in codon assignments. The canonical genetic code is known to be highly efficient in minimizing the effects of mistranslation errors and point mutations, since it is known that when an amino acid is converted to another due to error, the biochemical properties of the resulted amino acid are usually very similar to those of the original one. In this study, using altered forms of the fitness functions used in the prior studies, we have optimized the parameters involved in the calculation of the error minimizing property of the genetic code so that the genetic code outscores the random codes as much as possible. This work also compares two prominent matrices, the Mutation Matrix and Point Accepted Mutations 74-100 (PAM(74-100)). It has been resulted that the hypothetical properties of the coevolution theory of the genetic code are already considered in PAM(74-100), giving more evidence on the existence of bias towards the genetic code in this matrix. Furthermore, our results indicate that PAM(74-100) is biased towards the single base mistranslation occurrences in second codon position as well as the frequency of amino acids. Thus PAM(74-100) is not a suitable substitution matrix for the studies conducted on the evolution of the genetic code.
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Affiliation(s)
- Hani Goodarzi
- Department of Biotechnology, Faculty of Science, University of Tehran, Enghelab Ave., Tehran, Iran.
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34
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Yang CM. On the structural regularity in nucleobases and amino acids and relationship to the origin and evolution of the genetic code. ORIGINS LIFE EVOL B 2005; 35:275-95. [PMID: 16228642 DOI: 10.1007/s11084-005-1078-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2003] [Revised: 02/19/2004] [Accepted: 02/19/2004] [Indexed: 10/25/2022]
Abstract
To explore how chemical structures of both nucleobases and amino acids may have played a role in shaping the genetic code, numbers of sp2 hybrid nitrogen atoms in nucleobases were taken as a determinative measure for empirical stereo-electronic property to analyze the genetic code. Results revealed that amino acid hydropathy correlates strongly with the sp2 nitrogen atom numbers in nucleobases rather than with the overall electronic property such as redox potentials of the bases, reflecting that stereo-electronic property of bases may play a role. In the rearranged code, five simple but stereo-structurally distinctive amino acids (Gly, Pro, Val, Thr and Ala) and their codon quartets form a crossed intersection "core". Secondly, a re-categorization of the amino acids according to their beta-carbon stereochemistry, verified by charge density (at beta-carbon) calculation, results in five groups of stereo-structurally distinctive amino acids, the group leaders of which are Gly, Pro, Val, Thr and Ala, remarkably overlapping the above "core". These two lines of independent observations provide empirical arguments for a contention that a seemingly "frozen" "core" could have formed at a certain evolutionary stage. The possible existence of this codon "core" is in conformity with a previous evolutionary model whereby stereochemical interactions may have shaped the code. Moreover, the genetic code listed in UCGA succession together with this codon "core" has recently facilitated an identification of the unprecedented icosikaioctagon symmetry and bi-pyramidal nature of the genetic code.
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Affiliation(s)
- Chi Ming Yang
- Neurochemistry and System Chemical Biology, Nankai University, Tian Jin, 300071, China.
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35
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Abstract
Since the early days of the discovery of the genetic code nonrandom patterns have been searched for in the code in the hope of providing information about its origin and early evolution. Here we present a new classification scheme of the genetic code that is based on a binary representation of the purines and pyrimidines. This scheme reveals known patterns more clearly than the common one, for instance, the classification of strong, mixed, and weak codons as well as the ordering of codon families. Furthermore, new patterns have been found that have not been described before: Nearly all quantitative amino acid properties, such as Woese's polarity and the specific volume, show a perfect correlation to Lagerkvist's codon-anticodon binding strength. Our new scheme leads to new ideas about the evolution of the genetic code. It is hypothesized that it started with a binary doublet code and developed via a quaternary doublet code into the contemporary triplet code. Furthermore, arguments are presented against suggestions that a "simpler" code, where only the midbase was informational, was at the origin of the genetic code.
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Affiliation(s)
- Thomas Wilhelm
- Institute of Molecular Biotechnology, Beutenbergstr. 11, 07745 Jena, Germany.
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36
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37
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Abstract
Although chemists can synthesize virtually any small organic molecule, our ability to rationally manipulate the structures of proteins is quite limited, despite their involvement in virtually every life process. For most proteins, modifications are largely restricted to substitutions among the common 20 amino acids. Herein we describe recent advances that make it possible to add new building blocks to the genetic codes of both prokaryotic and eukaryotic organisms. Over 30 novel amino acids have been genetically encoded in response to unique triplet and quadruplet codons including fluorescent, photoreactive, and redox-active amino acids, glycosylated amino acids, and amino acids with keto, azido, acetylenic, and heavy-atom-containing side chains. By removing the limitations imposed by the existing 20 amino acid code, it should be possible to generate proteins and perhaps entire organisms with new or enhanced properties.
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Affiliation(s)
- Lei Wang
- Department of Pharmacology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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38
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Abstract
The coevolution theory of the genetic code, which postulates that prebiotic synthesis was an inadequate source of all twenty protein amino acids, and therefore some of them had to be derived from the coevolving pathways of amino acid biosynthesis, has been assessed in the light of the discoveries of the past three decades. Its four fundamental tenets regarding the essentiality of amino acid biosynthesis, role of pretran synthesis, biosynthetic imprint on codon allocations and mutability of the encoded amino acids are proven by the new knowledge. Of the factors that guided the evolutionary selection of the universal code, the relative contributions of Amino Acid Biosynthesis: Error Minimization: Stereochemical Interaction are estimated to first approximation as 40,000,000:400:1, which suggests that amino acid biosynthesis represents the dominant factor shaping the code. The utility of the coevolution theory is demonstrated by its opening up experimental expansions of the code and providing a basis for locating the root of life.
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Affiliation(s)
- J Tze-Fei Wong
- Applied Genomics Laboratory and Department of Biochemistry, Hong Kong University of Science & Technology, Hong Kong, China.
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39
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Goodarzi H, Nejad HA, Torabi N. On the optimality of the genetic code, with the consideration of termination codons. Biosystems 2004; 77:163-73. [PMID: 15527955 DOI: 10.1016/j.biosystems.2004.05.031] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2004] [Revised: 05/09/2004] [Accepted: 05/25/2004] [Indexed: 11/18/2022]
Abstract
The existence of nonrandom patterns in codon assignments is supported by many statistical and biochemical studies. The canonical genetic code is known to be highly efficient in minimizing the effects of mistranslation errors and point mutations. For example, it is known that when an error induces the conversion of an amino acid to another, the biochemical properties of the resulting amino acid are usually very similar to that of the original. Prior studies include many attempts at quantitative estimation of the fraction of randomly generated codes which, based upon load minimization, score higher than the canonical genetic code. In this study, we took into consideration both the relative frequencies of amino acids and nonsense mistranslations, factors which had been previously ignored. Incorporation of these parameters, resulted in a fitness function (phi) which rendered the canonical genetic code to be highly optimized with respect to load minimization. Considering termination codons, we applied a biosynthetic version of the coevolution theory, however, with low significance. We employed a revised cost for the precursor-product pairs of amino acids and showed that the significance of this approach depends on the cost measure matrix used by the researcher. Thus, we have compared the two prominent matrices, point accepted mutations 74-100 (PAM(74-100)) and mutation matrix in our study.
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Affiliation(s)
- Hani Goodarzi
- Department of Biotechnology, Faculty of Science, University of Tehran, Enghelab Avenue, Tehran, Iran.
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40
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41
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Abstract
Since discovering the pattern by which amino acids are assigned to codons within the standard genetic code, investigators have explored the idea that natural selection placed biochemically similar amino acids near to one another in coding space so as to minimize the impact of mutations and/or mistranslations. The analytical evidence to support this theory has grown in sophistication and strength over the years, and counterclaims questioning its plausibility and quantitative support have yet to transcend some significant weaknesses in their approach. These weaknesses are illustrated here by means of a simple simulation model for adaptive genetic code evolution. There remain ill explored facets of the 'error minimizing' code hypothesis, however, including the mechanism and pathway by which an adaptive pattern of codon assignments emerged, the extent to which natural selection created synonym redundancy, its role in shaping the amino acid and nucleotide languages, and even the correct interpretation of the adaptive codon assignment pattern: these represent fertile areas for future research.
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Affiliation(s)
- Stephen J Freeland
- Department of Biology, University of Maryland, Baltimore County, Catonsville, MD, USA.
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42
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Abstract
The primordial genetic code probably has been a drastically simplified ancestor of the canonical code that is used by contemporary cells. In order to understand how the present-day code came about we first need to explain how the language of the building plan can change without destroying the encoded information. In this work we introduce a minimal organism model that is based on biophysically reasonable descriptions of RNA and protein, namely secondary structure folding and knowledge based potentials. The evolution of a population of such organism under competition for a common resource is simulated explicitly at the level of individual replication events. Starting with very simple codes, and hence greatly reduced amino acid alphabets, we observe a diversification of the codes in most simulation runs. The driving force behind this effect is the possibility to produce fitter proteins when the repertoire of amino acids is enlarged.
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Affiliation(s)
- Günter Weberndorfer
- Institut für Theoretische Chemie und Molekulare Strukturbiologie, Universität Wien, Wien, Austria
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43
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Biro JC, Benyó B, Sansom C, Szlávecz A, Fördös G, Micsik T, Benyó Z. A common periodic table of codons and amino acids. Biochem Biophys Res Commun 2003; 306:408-15. [PMID: 12804578 DOI: 10.1016/s0006-291x(03)00974-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A periodic table of codons has been designed where the codons are in regular locations. The table has four fields (16 places in each) one with each of the four nucleotides (A, U, G, C) in the central codon position. Thus, AAA (lysine), UUU (phenylalanine), GGG (glycine), and CCC (proline) were placed into the corners of the fields as the main codons (and amino acids) of the fields. They were connected to each other by six axes. The resulting nucleic acid periodic table showed perfect axial symmetry for codons. The corresponding amino acid table also displaced periodicity regarding the biochemical properties (charge and hydropathy) of the 20 amino acids and the position of the stop signals. The table emphasizes the importance of the central nucleotide in the codons and predicts that purines control the charge while pyrimidines determine the polarity of the amino acids. This prediction was experimentally tested.
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Affiliation(s)
- J C Biro
- Karolinska Institute, Stockholm, Sweden.
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Mehl RA, Anderson JC, Santoro SW, Wang L, Martin AB, King DS, Horn DM, Schultz PG. Generation of a bacterium with a 21 amino acid genetic code. J Am Chem Soc 2003; 125:935-9. [PMID: 12537491 DOI: 10.1021/ja0284153] [Citation(s) in RCA: 196] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have generated a completely autonomous bacterium with a 21 amino acid genetic code. This bacterium can biosynthesize a nonstandard amino acid from basic carbon sources and incorporate this amino acid into proteins in response to the amber nonsense codon. The biosynthetic pathway for the amino acid p-aminophenylalanine (pAF) as well as a unique pAF synthetase and cognate tRNA were added to Escherichia coli. Denaturing gel electrophoresis and mass spectrometric analysis show that pAF is incorporated into myoglobin with fidelity and efficiency rivaling those of the common 20 amino acids. This and other such organisms may provide an opportunity to examine the evolutionary consequences of adding new amino acids to the genetic repertoire, as well as generate proteins with new or enhanced biological functions.
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Affiliation(s)
- Ryan A Mehl
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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45
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Davis BK. Molecular evolution before the origin of species. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2002; 79:77-133. [PMID: 12225777 DOI: 10.1016/s0079-6107(02)00012-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amino acids at conserved sites in the residue sequence of 10 ancient proteins, from 844 phylogenetically diverse sources, were used to specify their time of origin in the interval before species divergence from the last common ancestor (LCA). The order of amino acid addition to the genetic code, based on biosynthesis path length and other molecular evidence, provided a reference for evaluating the 'code age' of each residue profile examined. Significantly earlier estimates were obtained for conserved amino acid residues in these proteins than non-conserved residues. Evidence from the primary structure of 'fossil' proteins thus corroborated the biosynthetic order of amino acid addition to the code.Low potential ferredoxin (Fdxn) had the earliest residue profile among the proteins in this study. A phylogenetic tree for 82 prokaryote Fdxn sequences was rooted midway between bacteria and archaea branches. LCA Fdxn had a 23-residue antecedent whose residue profile matched mid-expansion phase codon assignments and included an amide residue. It contained a highly acidic N-terminal region and a non-charged C-terminal region, with all four cysteine residues. This small protein apparently anchored a [4Fe-4S] cluster, ligated by C-terminal cysteines, to a positively charged mineral surface, consistent with mediating e(-) transfer in a primordial surface system before cells appeared. Its negatively charged N-terminal 'attachment site' was highly mutable during evolution of ancestral Fdxn for Bacteria and Archaea, consistent with a loss of function after cell formation. An initial glutamate to lysine substitution may link 'attachment site' removal to early post-expansion phase entry of basic amino acids to the code. As proteins evidently anchored non-charged amide residues initially, surface attachment of cofactors and other functional groups emerges as a general function of pre-cell proteins.A phylogenetic tree of 107 proteolipid (PL) helix-1 sequences from H(+)-ATPase of bacteria, archaea and eukaryotes had its root between prokaryote branches. LCA PL h1 residue profile optimally fit a late expansion phase codon array. Sequence repeats in transmembrane PL helices h1 and h2 indicated formation of the archetypal PL hairpin structure involved successive tandem duplications, initiated within the gene for an 11-residue (or 4-residue) hydrophobic peptide. Ancestral PL h1 lacked acidic residues, in a fundamental departure from the prototype pre-cell protein. By this stage, proteins with a hydrophobic domain had evolved. Its non-polar, late expansion phase residue profile point to ancestral PL being a component of an early permeable cell membrane. Other indicators of cell formation about this stage of code evolution include phospholipid biosynthesis path length, FtsZ residue profile, and late entry of basic amino acids into the genetic code. Estimates based on conserved residues in prokaryote cell septation protein, FtsZ, and proteins involved with synthesis, transcription and replication of DNA revealed FtsZ, ribonucleotide reductase, RNA polymerase core subunits and 5'-->3' flap exonuclease, FEN-1, originated soon after cells putatively evolved. While reverse transcriptase and topoisomerase I, Topo I, appeared late in the pre-divergence era, when the genetic code was essentially complete. The transition from RNA genes to a DNA genome seemingly proceeded via formation of a DNA-RNA heteroduplex. These results suggest formation of DNA awaited evolution of a catalyst with a hydrophobic domain, capable of sequestering radical bearing intermediates in its synthesis from ribonucleotide precursors. Late formation of topology altering protein, Topo I, further suggests consolidation of genes into chromosomes followed synthesis of comparatively thermostable DNA strands.
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Affiliation(s)
- Brian K Davis
- Research Foundation of Southern California, Inc., La Jolla, CA 92037, USA.
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46
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Gilis D, Massar S, Cerf NJ, Rooman M. Optimality of the genetic code with respect to protein stability and amino-acid frequencies. Genome Biol 2001; 2:RESEARCH0049. [PMID: 11737948 PMCID: PMC60310 DOI: 10.1186/gb-2001-2-11-research0049] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2001] [Revised: 07/06/2001] [Accepted: 09/28/2001] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND The genetic code is known to be efficient in limiting the effect of mistranslation errors. A misread codon often codes for the same amino acid or one with similar biochemical properties, so the structure and function of the coded protein remain relatively unaltered. Previous studies have attempted to address this question quantitatively, by estimating the fraction of randomly generated codes that do better than the genetic code in respect of overall robustness. We extended these results by investigating the role of amino-acid frequencies in the optimality of the genetic code. RESULTS We found that taking the amino-acid frequency into account decreases the fraction of random codes that beat the natural code. This effect is particularly pronounced when more refined measures of the amino-acid substitution cost are used than hydrophobicity. To show this, we devised a new cost function by evaluating in silico the change in folding free energy caused by all possible point mutations in a set of protein structures. With this function, which measures protein stability while being unrelated to the code's structure, we estimated that around two random codes in a billion (109) are fitter than the natural code. When alternative codes are restricted to those that interchange biosynthetically related amino acids, the genetic code appears even more optimal. CONCLUSIONS These results lead us to discuss the role of amino-acid frequencies and other parameters in the genetic code's evolution, in an attempt to propose a tentative picture of primitive life.
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Affiliation(s)
- D Gilis
- Biomolecular Engineering, Université Libre de Bruxelles, ave F D Roosevelt, 1050 Bruxelles, Belgium.
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47
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Abstract
This computer simulation is based on a model of the origin of life proposed by H. Kuhn and J. Waser, where the evolution of short molecular strands is assumed to take place in a distinct spatiotemporal structured environment. In their model, the prebiotic situation is strongly simplified to grasp essential features of the evolution of the genetic apparatus without attempts to trace the historic path. With the tool of computer implementation confining to principle aspects and focused on critical features of the model, a deeper understanding of the model's premises is achieved. Each generation consists of three steps: (i) construction of devices (entities exposed to selection) presently available; (ii) selection; and (iii) multiplication of the isolated strands (R oligomers) by complementary copying with occasional variation by copying mismatch. In the beginning, the devices are single strands with random sequences; later, increasingly complex aggregates of strands form devices such as a hairpin-assembler device which develop in favorable cases. A monomers interlink by binding to the hairpin-assembler device, and a translation machinery, called the hairpin-assembler-enzyme device, emerges, which translates the sequence of R(1) and R(2) monomers in the assembler strand to the sequence of A(1) and A(2) monomers in the A oligomer, working as an enzyme.
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Affiliation(s)
- C Kuhn
- Gruppe Biophysik, Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule Hönggerberg, CH-8093 Zürich, Switzerland.
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48
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Genes can't tell us everything. Nature 2000. [DOI: 10.1038/news001221-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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