1
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Tang GQ, Hu H, Douglas J, Carter C. Primordial aminoacyl-tRNA synthetases preferred minihelices to full-length tRNA. Nucleic Acids Res 2024; 52:7096-7111. [PMID: 38783009 PMCID: PMC11229368 DOI: 10.1093/nar/gkae417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/30/2024] [Accepted: 05/10/2024] [Indexed: 05/25/2024] Open
Abstract
Aminoacyl-tRNA synthetases (AARS) and tRNAs translate the genetic code in all living cells. Little is known about how their molecular ancestors began to enforce the coding rules for the expression of their own genes. Schimmel et al. proposed in 1993 that AARS catalytic domains began by reading an 'operational' code in the acceptor stems of tRNA minihelices. We show here that the enzymology of an AARS urzyme•TΨC-minihelix cognate pair is a rich in vitro realization of that idea. The TΨC-minihelixLeu is a very poor substrate for full-length Leucyl-tRNA synthetase. It is a superior RNA substrate for the corresponding urzyme, LeuAC. LeuAC active-site mutations shift the choice of both amino acid and RNA substrates. AARS urzyme•minihelix cognate pairs are thus small, pliant models for the ancestral decoding hardware. They are thus an ideal platform for detailed experimental study of the operational RNA code.
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Affiliation(s)
- Guo Qing Tang
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, USA
| | - Hao Hu
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, USA
| | - Jordan Douglas
- Department of Physics, The University of Auckland, New Zealand
- Centre for Computational Evolution, University of Auckland, New Zealand
- Department of Computer Science, 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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Kocher CD, Dill KA. The prebiotic emergence of biological evolution. ROYAL SOCIETY OPEN SCIENCE 2024; 11:240431. [PMID: 39050718 PMCID: PMC11265915 DOI: 10.1098/rsos.240431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 05/10/2024] [Indexed: 07/27/2024]
Abstract
The origin of life must have been preceded by Darwin-like evolutionary dynamics that could propagate it. How did that adaptive dynamics arise? And from what prebiotic molecules? Using evolutionary invasion analysis, we develop a universal framework for describing any origin story for evolutionary dynamics. We find that cooperative autocatalysts, i.e. autocatalysts whose per-unit reproductive rate grows as their population increases, have the special property of being able to cross a barrier that separates their initial degradation-dominated state from a growth-dominated state with evolutionary dynamics. For some model parameters, this leap to persistent propagation is likely, not rare. We apply this analysis to the Foldcat Mechanism, wherein peptides fold and help catalyse the elongation of each other. Foldcats are found to have cooperative autocatalysis and be capable of emergent evolutionary dynamics.
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Affiliation(s)
- Charles D. Kocher
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
| | - Ken A. Dill
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA
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3
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Fontecilla-Camps JC. Reflections on the Origin of Coded Protein Biosynthesis. Biomolecules 2024; 14:518. [PMID: 38785925 PMCID: PMC11117964 DOI: 10.3390/biom14050518] [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: 04/09/2024] [Revised: 04/23/2024] [Accepted: 04/24/2024] [Indexed: 05/25/2024] Open
Abstract
The principle of continuity posits that some central features of primordial biocatalytic mechanisms should still be present in the genetically dependent pathway of protein synthesis, a crucial step in the emergence of life. Key bimolecular reactions of this process are catalyzed by DNA-dependent RNA polymerases, aminoacyl-tRNA synthetases, and ribosomes. Remarkably, none of these biocatalysts contribute chemically active groups to their respective reactions. Instead, structural and functional studies have demonstrated that nucleotidic α-phosphate and β-d-ribosyl 2' OH and 3' OH groups can help their own catalysis, a process which, consequently, has been called "substrate-assisted". Furthermore, upon binding, the substrates significantly lower the entropy of activation, exclude water from these catalysts' active sites, and are readily positioned for a reaction. This binding mode has been described as an "entropy trap". The combination of this effect with substrate-assisted catalysis results in reactions that are stereochemically and mechanistically simpler than the ones found in most modern enzymes. This observation is consistent with the way in which primordial catalysts could have operated; it may also explain why, thanks to their complementary reactivities, β-d-ribose and phosphate were naturally selected to be the central components of early coding polymers.
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4
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Garte S. Accurate phenotypic self-replication as a necessary cause for biological evolution. Biosystems 2024; 237:105154. [PMID: 38346554 DOI: 10.1016/j.biosystems.2024.105154] [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: 10/27/2023] [Revised: 01/29/2024] [Accepted: 02/09/2024] [Indexed: 02/17/2024]
Abstract
Since the Origin of Species, it has been known that evolution depends on what Darwin called the "strong principle of inheritance." Highly accurate replication of cellular phenotype is a universal phenomenon in all of life since LUCA and is often taken for granted as a constant in evolutionary theory. It is not known how self-replication arose during the origin of life. In this report I use the simple mathematics of evolutionary theory to investigate the dynamics of self-replication accuracy and allelic selection. Results indicate that the degree of self-replication accuracy must be greater than a threshold related to the selection coefficients of the alleles in a population in order for evolution to occur. Accurate replication of cellular phenotype and of the molecules involved in genotype/phenotype linkage is necessary for the origin of evolution and may be considered the fundamental principle of life.
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Affiliation(s)
- Seymour Garte
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, 160 Frelinghuysen Road, Piscataway, NJ, 08854-8020, USA.
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5
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Brunk CF, Marshall CR. Opinion: The Key Steps in the Origin of Life to the Formation of the Eukaryotic Cell. Life (Basel) 2024; 14:226. [PMID: 38398735 PMCID: PMC10890422 DOI: 10.3390/life14020226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 01/16/2024] [Accepted: 01/29/2024] [Indexed: 02/25/2024] Open
Abstract
The path from life's origin to the emergence of the eukaryotic cell was long and complex, and as such it is rarely treated in one publication. Here, we offer a sketch of this path, recognizing that there are points of disagreement and that many transitions are still shrouded in mystery. We assume life developed within microchambers of an alkaline hydrothermal vent system. Initial simple reactions were built into more sophisticated reflexively autocatalytic food-generated networks (RAFs), laying the foundation for life's anastomosing metabolism, and eventually for the origin of RNA, which functioned as a genetic repository and as a catalyst (ribozymes). Eventually, protein synthesis developed, leading to life's biology becoming dominated by enzymes and not ribozymes. Subsequent enzymatic innovation included ATP synthase, which generates ATP, fueled by the proton gradient between the alkaline vent flux and the acidic sea. This gradient was later internalized via the evolution of the electron transport chain, a preadaptation for the subsequent emergence of the vent creatures from their microchamber cradles. Differences between bacteria and archaea suggests cellularization evolved at least twice. Later, the bacterial development of oxidative phosphorylation and the archaeal development of proteins to stabilize its DNA laid the foundation for the merger that led to the formation of eukaryotic cells.
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Affiliation(s)
- Clifford F. Brunk
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095-1606, USA
| | - Charles R. Marshall
- Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA 94720-4780, USA
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6
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Lopez A, Vauchez A, Ajram G, Shvetsova A, Leveau G, Fiore M, Strazewski P. From the RNA-Peptide World: Prebiotic Reaction Conditions Compatible with Lipid Membranes for the Formation of Lipophilic Random Peptides in the Presence of Short Oligonucleotides, and More. Life (Basel) 2024; 14:108. [PMID: 38255723 PMCID: PMC10817532 DOI: 10.3390/life14010108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 12/25/2023] [Accepted: 01/05/2024] [Indexed: 01/24/2024] Open
Abstract
Deciphering the origins of life on a molecular level includes unravelling the numerous interactions that could occur between the most important biomolecules being the lipids, peptides and nucleotides. They were likely all present on the early Earth and all necessary for the emergence of cellular life. In this study, we intended to explore conditions that were at the same time conducive to chemical reactions critical for the origins of life (peptide-oligonucleotide couplings and templated ligation of oligonucleotides) and compatible with the presence of prebiotic lipid vesicles. For that, random peptides were generated from activated amino acids and analysed using NMR and MS, whereas short oligonucleotides were produced through solid-support synthesis, manually deprotected and purified using HPLC. After chemical activation in prebiotic conditions, the resulting mixtures were analysed using LC-MS. Vesicles could be produced through gentle hydration in similar conditions and observed using epifluorescence microscopy. Despite the absence of coupling or ligation, our results help to pave the way for future investigations on the origins of life that may gather all three types of biomolecules rather than studying them separately, as it is still too often the case.
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Affiliation(s)
- Augustin Lopez
- Laboratoire de Chimie Organique 2 (LCO2), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS, UMR CNRS 5246), Bâtiment Edgar Lederer, Université Claude Bernard Lyon 1, Université de Lyon, 1 rue Victor Grignard, 69100 Villeurbanne, France (M.F.)
| | - Antoine Vauchez
- Centre Commun de la Spectrométrie de Masse (CCSM), ICBMS, Bâtiment Edgar Lederer, 1 rue Victor Grignard, 69100 Villeurbanne, France;
| | - Ghinwa Ajram
- Laboratoire de Chimie Organique 2 (LCO2), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS, UMR CNRS 5246), Bâtiment Edgar Lederer, Université Claude Bernard Lyon 1, Université de Lyon, 1 rue Victor Grignard, 69100 Villeurbanne, France (M.F.)
| | - Anastasiia Shvetsova
- Laboratoire de Chimie Organique 2 (LCO2), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS, UMR CNRS 5246), Bâtiment Edgar Lederer, Université Claude Bernard Lyon 1, Université de Lyon, 1 rue Victor Grignard, 69100 Villeurbanne, France (M.F.)
| | - Gabrielle Leveau
- Laboratoire de Chimie Organique 2 (LCO2), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS, UMR CNRS 5246), Bâtiment Edgar Lederer, Université Claude Bernard Lyon 1, Université de Lyon, 1 rue Victor Grignard, 69100 Villeurbanne, France (M.F.)
| | - Michele Fiore
- Laboratoire de Chimie Organique 2 (LCO2), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS, UMR CNRS 5246), Bâtiment Edgar Lederer, Université Claude Bernard Lyon 1, Université de Lyon, 1 rue Victor Grignard, 69100 Villeurbanne, France (M.F.)
| | - Peter Strazewski
- Laboratoire de Chimie Organique 2 (LCO2), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS, UMR CNRS 5246), Bâtiment Edgar Lederer, Université Claude Bernard Lyon 1, Université de Lyon, 1 rue Victor Grignard, 69100 Villeurbanne, France (M.F.)
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7
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Wills PR. Origins of Genetic Coding: Self-Guided Molecular Self-Organisation. ENTROPY (BASEL, SWITZERLAND) 2023; 25:1281. [PMID: 37761580 PMCID: PMC10527755 DOI: 10.3390/e25091281] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 08/22/2023] [Accepted: 08/28/2023] [Indexed: 09/29/2023]
Abstract
The origin of genetic coding is characterised as an event of cosmic significance in which quantum mechanical causation was transcended by constructive computation. Computational causation entered the physico-chemical processes of the pre-biotic world by the incidental satisfaction of a condition of reflexivity between polymer sequence information and system elements able to facilitate their own production through translation of that information. This event, which has previously been modelled in the dynamics of Gene-Replication-Translation systems, is properly described as a process of self-guided self-organisation. The spontaneous emergence of a primordial genetic code between two-letter alphabets of nucleotide triplets and amino acids is easily possible, starting with random peptide synthesis that is RNA-sequence-dependent. The evident self-organising mechanism is the simultaneous quasi-species bifurcation of the populations of information-carrying genes and enzymes with aminoacyl-tRNA synthetase-like activities. This mechanism allowed the code to evolve very rapidly to the ~20 amino acid limit apparent for the reflexive differentiation of amino acid properties using protein catalysts. The self-organisation of semantics in this domain of physical chemistry conferred on emergent molecular biology exquisite computational control over the nanoscopic events needed for its self-construction.
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Affiliation(s)
- Peter R Wills
- Department of Physics, University of Auckland, Auckland PB 92019, New Zealand
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8
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Russell MJ. A self-sustaining serpentinization mega-engine feeds the fougerite nanoengines implicated in the emergence of guided metabolism. Front Microbiol 2023; 14:1145915. [PMID: 37275164 PMCID: PMC10236563 DOI: 10.3389/fmicb.2023.1145915] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/22/2023] [Indexed: 06/07/2023] Open
Abstract
The demonstration by Ivan Barnes et al. that the serpentinization of fresh Alpine-type ultramafic rocks results in the exhalation of hot alkaline fluids is foundational to the submarine alkaline vent theory (AVT) for life's emergence to its 'improbable' thermodynamic state. In AVT, such alkaline fluids ≤ 150°C, bearing H2 > CH4 > HS--generated and driven convectively by a serpentinizing exothermic mega-engine operating in the ultramafic crust-exhale into the iron-rich, CO2> > > NO3--bearing Hadean ocean to result in hydrothermal precipitate mounds comprising macromolecular ferroferric-carbonate oxyhydroxide and minor sulfide. As the nanocrystalline minerals fougerite/green rust and mackinawite (FeS), they compose the spontaneously precipitated inorganic membranes that keep the highly contrasting solutions apart, thereby maintaining redox and pH disequilibria. They do so in the form of fine chimneys and chemical gardens. The same disequilibria drive the reduction of CO2 to HCOO- or CO, and the oxidation of CH4 to a methyl group-the two products reacting to form acetate in a sequence antedating the 'energy-producing' acetyl coenzyme-A pathway. Fougerite is a 2D-layered mineral in which the hydrous interlayers themselves harbor 2D solutions, in effect constricted to ~ 1D by preferentially directed electron hopping/tunneling, and proton Gröthuss 'bucket-brigading' when subject to charge. As a redox-driven nanoengine or peristaltic pump, fougerite forces the ordered reduction of nitrate to ammonium, the amination of pyruvate and oxalate to alanine and glycine, and their condensation to short peptides. In turn, these peptides have the flexibility to sequester the founding inorganic iron oxyhydroxide, sulfide, and pyrophosphate clusters, to produce metal- and phosphate-dosed organic films and cells. As the feed to the hydrothermal mound fails, the only equivalent sustenance on offer to the first autotrophs is the still mildly serpentinizing upper crust beneath. While the conditions here are very much less bountiful, they do offer the similar feed and disequilibria the survivors are accustomed to. Sometime during this transition, a replicating non-ribosomal guidance system is discovered to provide the rules to take on the incrementally changing surroundings. The details of how these replicating apparatuses emerged are the hard problem, but by doing so the progenote archaea and bacteria could begin to colonize what would become the deep biosphere. Indeed, that the anaerobic nitrate-respiring methanotrophic archaea and the deep-branching Acetothermia presently comprise a portion of that microbiome occupying serpentinizing rocks offers circumstantial support for this notion. However, the inescapable, if jarring conclusion is drawn that, absent fougerite/green rust, there would be no structured channelway to life.
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Affiliation(s)
- Michael J. Russell
- Dipartimento di Chimica, Università degli Studi di Torino, Torino, Italy
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9
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Wozniak K, Brzezinski K. Biological Catalysis and Information Storage Have Relied on N-Glycosyl Derivatives of β-D-Ribofuranose since the Origins of Life. Biomolecules 2023; 13:biom13050782. [PMID: 37238652 DOI: 10.3390/biom13050782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/24/2023] [Accepted: 04/29/2023] [Indexed: 05/28/2023] Open
Abstract
Most naturally occurring nucleotides and nucleosides are N-glycosyl derivatives of β-d-ribose. These N-ribosides are involved in most metabolic processes that occur in cells. They are essential components of nucleic acids, forming the basis for genetic information storage and flow. Moreover, these compounds are involved in numerous catalytic processes, including chemical energy production and storage, in which they serve as cofactors or coribozymes. From a chemical point of view, the overall structure of nucleotides and nucleosides is very similar and simple. However, their unique chemical and structural features render these compounds versatile building blocks that are crucial for life processes in all known organisms. Notably, the universal function of these compounds in encoding genetic information and cellular catalysis strongly suggests their essential role in the origins of life. In this review, we summarize major issues related to the role of N-ribosides in biological systems, especially in the context of the origin of life and its further evolution, through the RNA-based World(s), toward the life we observe today. We also discuss possible reasons why life has arisen from derivatives of β-d-ribofuranose instead of compounds based on other sugar moieties.
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Affiliation(s)
- Katarzyna Wozniak
- Department of Structural Biology of Prokaryotic Organisms, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-074 Poznan, Poland
| | - Krzysztof Brzezinski
- Department of Structural Biology of Prokaryotic Organisms, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-074 Poznan, Poland
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10
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Kocher C, Dill KA. Origins of life: first came evolutionary dynamics. QRB DISCOVERY 2023; 4:e4. [PMID: 37529034 PMCID: PMC10392681 DOI: 10.1017/qrd.2023.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/07/2023] [Accepted: 03/08/2023] [Indexed: 08/03/2023] Open
Abstract
When life arose from prebiotic molecules 3.5 billion years ago, what came first? Informational molecules (RNA, DNA), functional ones (proteins), or something else? We argue here for a different logic: rather than seeking a molecule type, we seek a dynamical process. Biology required an ability to evolve before it could choose and optimise materials. We hypothesise that the evolution process was rooted in the peptide folding process. Modelling shows how short random peptides can collapse in water and catalyse the elongation of others, powering both increased folding stability and emergent autocatalysis through a disorder-to-order process.
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Affiliation(s)
- Charles Kocher
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Ken A. Dill
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- Department of Chemistry, Stony Brook University, Stony Brook, NY, USA
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11
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Jia TZ, Nishikawa S, Fujishima K. Sequencing the Origins of Life. BBA ADVANCES 2022; 2:100049. [PMID: 37082609 PMCID: PMC10074849 DOI: 10.1016/j.bbadva.2022.100049] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 02/27/2022] [Accepted: 03/02/2022] [Indexed: 01/10/2023] Open
Abstract
One goal of origins of life research is to understand how primitive informational and catalytic biopolymers emerged and evolved. Recently, a number of sequencing techniques have been applied to analysis of replicating and evolving primitive biopolymer systems, providing a sequence-specific and high-resolution view of primitive chemical processes. Here, we review application of sequencing techniques to analysis of synthetic and primitive nucleic acids and polypeptides. This includes next-generation sequencing of primitive polymerization and evolution processes, followed by discussion of other novel biochemical techniques that could contribute to sequence analysis of primitive biopolymer driven chemical systems. Further application of sequencing to origins of life research, perhaps as a life detection technology, could provide insight into the origin and evolution of informational and catalytic biopolymers on early Earth or elsewhere.
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Affiliation(s)
- Tony Z. Jia
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1-IE-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
- Blue Marble Space Institute of Science, 600 1st Ave, Floor 1, Seattle, WA 98104, USA
- Corresponding author
| | - Shota Nishikawa
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1-IE-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8501, Japan
| | - Kosuke Fujishima
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1-IE-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
- Graduate School of Media and Governance, Keio University, 5322 Endo, Fujisawa-shi, Kanagawa 252-0882, Japan
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12
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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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13
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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: 6] [Impact Index Per Article: 3.0] [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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14
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Abstract
Codon-dependent translation underlies genetics and phylogenetic inferences, but its origins pose two challenges. Prevailing narratives cannot account for the fact that aminoacyl-tRNA synthetases (aaRSs), which translate the genetic code, must collectively enforce the rules used to assemble themselves. Nor can they explain how specific assignments arose from rudimentary differentiation between ancestral aaRSs and corresponding transfer RNAs (tRNAs). Experimental deconstruction of the two aaRS superfamilies created new experimental tools with which to analyze the emergence of the code. Amino acid and tRNA substrate recognition are linked to phase transfer free energies of amino acids and arise largely from aaRS class-specific differences in secondary structure. Sensitivity to protein folding rules endowed ancestral aaRS-tRNA pairs with the feedback necessary to rapidly compare alternative genetic codes and coding sequences. These and other experimental data suggest that the aaRS bidirectional genetic ancestry stabilized the differentiation and interdependence required to initiate and elaborate the genetic coding table.
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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;
| | - Peter R Wills
- Department of Physics, University of Auckland, Auckland 1142, New Zealand
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15
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Carter CW, Wills PR. Reciprocally-Coupled Gating: Strange Loops in Bioenergetics, Genetics, and Catalysis. Biomolecules 2021; 11:265. [PMID: 33670192 PMCID: PMC7916928 DOI: 10.3390/biom11020265] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/04/2021] [Accepted: 02/06/2021] [Indexed: 12/12/2022] Open
Abstract
Bioenergetics, genetic coding, and catalysis are all difficult to imagine emerging without pre-existing historical context. That context is often posed as a "Chicken and Egg" problem; its resolution is concisely described by de Grasse Tyson: "The egg was laid by a bird that was not a chicken". The concision and generality of that answer furnish no details-only an appropriate framework from which to examine detailed paradigms that might illuminate paradoxes underlying these three life-defining biomolecular processes. We examine experimental aspects here of five examples that all conform to the same paradigm. In each example, a paradox is resolved by coupling "if, and only if" conditions for reciprocal transitions between levels, such that the consequent of the first test is the antecedent for the second. Each condition thus restricts fluxes through, or "gates" the other. Reciprocally-coupled gating, in which two gated processes constrain one another, is self-referential, hence maps onto the formal structure of "strange loops". That mapping uncovers two different kinds of forces that may help unite the axioms underlying three phenomena that distinguish biology from chemistry. As a physical analog for Gödel's logic, biomolecular strange-loops provide a natural metaphor around which to organize a large body of experimental data, linking biology to information, free energy, and the second law of thermodynamics.
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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
| | - 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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16
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Abstract
What were the physico-chemical forces that drove the origins of life? We discuss four major prebiotic 'discoveries': persistent sampling of chemical reaction space; sequence-encodable foldable catalysts; assembly of functional pathways; and encapsulation and heritability. We describe how a 'proteins-first' world gives plausible mechanisms. We note the importance of hydrophobic and polar compositions of matter in these advances.
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Affiliation(s)
- K. A. Dill
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY, USA
- Department of Chemistry, Stony Brook University, Stony Brook, NY, USA
- Department Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - L. Agozzino
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY, USA
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17
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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: 10] [Impact Index Per Article: 3.3] [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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18
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Is it possible that cells have had more than one origin? Biosystems 2021; 202:104371. [PMID: 33524470 DOI: 10.1016/j.biosystems.2021.104371] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/22/2021] [Accepted: 01/22/2021] [Indexed: 01/03/2023]
Abstract
Cells occupy a prominent place in the history of life in Earth. The central role of cellular organization can be understood by the fact that "cellular life" is often used as a synonym for life itself. Thus, most characteristics used to define cell overlap with those ones used to define life. However, innovative scenarios for the origin of life are bringing alternative views to describe how cells may have evolved from the open biological systems named progenotes. Here, using a logical and conceptual analysis, we re-evaluate the characteristics used to infer a single origin for cells. We argue that some evidences used to support cell monophyly, such as the presence of elements from the translation mechanism together with the universality of the genetic code, actually indicate a unique origin for all "biological systems", a term used to define not only cells, but also viruses and progenotes. Besides, we present evidence that at least two biochemical pathways as important as (i) DNA replication and (ii) lipid biosynthesis are not homologous between Bacteria and Archaea. The identities observed between the proteins involved in those pathways along representatives of these two ancestral domains of life are too low to indicate common genic ancestry. Altogether these facts can be seen as an indication that cellular organization has possibly evolved two or more times and that LUCA (the Last Universal Common Ancestor) may not have existed as a cellular entity. Thus, we aim to consider the possibility that different strategies acquired by biological systems to exist, such as viral, bacterial and archaeal were most likely originated independently from the evolution of different progenote populations.
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19
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Fontecilla-Camps JC. Primordial bioenergy sources: The two facets of adenosine triphosphate. J Inorg Biochem 2020; 216:111347. [PMID: 33450675 DOI: 10.1016/j.jinorgbio.2020.111347] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/14/2020] [Accepted: 12/21/2020] [Indexed: 01/10/2023]
Abstract
Life requires energy to exist, to reproduce and to survive. Two major hypotheses have been put forward concerning the source of this energy at the very early stages of life evolution: (i) abiotic organics either brought to Earth by comets and/or meteorites, or produced at its atmosphere, and (ii) mineral surface-dependent bioinorganic catalytic reactions. Considering the latter possibility, I propose that, besides being a precursor of nucleic acids, adenosine triphosphate (ATP), which probably was used very early to improve the fidelity of nucleic acid polymerization, played an essential role in the transition between mineral-bound protocells and their free counterparts. Indeed, phosphorylation by ATP renders carboxylate groups electrophilic enough to react with nucleophiles such as amines, an effect that, thanks to their Lewis acid character, also have dehydrated metal ions on mineral surfaces. Early ATP synthesis for metabolic processes most likely depended on substrate level phosphorylation. However, the exaptation of a hexameric helicase-like ATPase and a transmembrane H+ pump (which evolved to counteract the acidity caused by fermentation reactions within the protocell) generated a much more efficient membrane-bound ATP synthase that uses chemiosmosis to make ATP.
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20
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Kunnev D. Origin of Life: The Point of No Return. Life (Basel) 2020; 10:life10110269. [PMID: 33153087 PMCID: PMC7693465 DOI: 10.3390/life10110269] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/01/2020] [Accepted: 11/01/2020] [Indexed: 12/13/2022] Open
Abstract
Origin of life research is one of the greatest scientific frontiers of mankind. Many hypotheses have been proposed to explain how life began. Although different hypotheses emphasize different initial phenomena, all of them agree around one important concept: at some point, along with the chain of events toward life, Darwinian evolution emerged. There is no consensus, however, how this occurred. Frequently, the mechanism leading to Darwinian evolution is not addressed and it is assumed that this problem could be solved later, with experimental proof of the hypothesis. Here, the author first defines the minimum components required for Darwinian evolution and then from this standpoint, analyzes some of the hypotheses for the origin of life. Distinctive features of Darwinian evolution and life rooted in the interaction between information and its corresponding structure/function are then reviewed. Due to the obligatory dependency of the information and structure subject to Darwinian evolution, these components must be locked in their origin. One of the most distinctive characteristics of Darwinian evolution in comparison with all other processes is the establishment of a fundamentally new level of matter capable of evolving and adapting. Therefore, the initiation of Darwinian evolution is the "point of no return" after which life begins. In summary: a definition and a mechanism for Darwinian evolution are provided together with a critical analysis of some of the hypotheses for the origin of life.
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Affiliation(s)
- Dimiter Kunnev
- Department of Oral Biology, University at Buffalo, Buffalo, NY 14263, USA
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21
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Wills PR, Carter CW. Impedance Matching and the Choice Between Alternative Pathways for the Origin of Genetic Coding. Int J Mol Sci 2020; 21:E7392. [PMID: 33036401 PMCID: PMC7582391 DOI: 10.3390/ijms21197392] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 09/28/2020] [Accepted: 09/30/2020] [Indexed: 01/07/2023] Open
Abstract
We recently observed that errors in gene replication and translation could be seen qualitatively to behave analogously to the impedances in acoustical and electronic energy transducing systems. We develop here quantitative relationships necessary to confirm that analogy and to place it into the context of the minimization of dissipative losses of both chemical free energy and information. The formal developments include expressions for the information transferred from a template to a new polymer, Iσ; an impedance parameter, Z; and an effective alphabet size, neff; all of which have non-linear dependences on the fidelity parameter, q, and the alphabet size, n. Surfaces of these functions over the {n,q} plane reveal key new insights into the origin of coding. Our conclusion is that the emergence and evolutionary refinement of information transfer in biology follow principles previously identified to govern physical energy flows, strengthening analogies (i) between chemical self-organization and biological natural selection, and (ii) between the course of evolutionary trajectories and the most probable pathways for time-dependent transitions in physics. Matching the informational impedance of translation to the four-letter alphabet of genes uncovers a pivotal role for the redundancy of triplet codons in preserving as much intrinsic genetic information as possible, especially in early stages when the coding alphabet size was small.
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Affiliation(s)
- Peter R. Wills
- Department of Physics and Te Ao Marama Centre for Fundamental Inquiry, University of Auckland, PB 92019, Auckland 1142, New Zealand
| | - 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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22
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Piette BMAG, Heddle JG. A Peptide-Nucleic Acid Replicator Origin for Life. Trends Ecol Evol 2020; 35:397-406. [PMID: 32294421 DOI: 10.1016/j.tree.2020.01.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 12/19/2019] [Accepted: 01/15/2020] [Indexed: 12/20/2022]
Abstract
Evolution requires self-replication. But, what was the very first self-replicator directly ancestral to all life? The currently favoured RNA World theory assigns this role to RNA alone but suffers from a number of seemingly intractable problems. Instead, we suggest that the self-replicator consisted of both peptides and nucleic acid strands. Such a nucleopeptide replicator is more feasible both in the light of the replication machinery currently found in cells and the complexity of the evolutionary path required to reach them. Recent theoretical and mathematical work supports this idea and provide a blueprint for future investigations.
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Affiliation(s)
| | - Jonathan G Heddle
- Bionanoscience and Biochemistry Laboratory, Malopolska Centre of Biotechnology, Jagiellonian University, Krakow, Poland.
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23
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Mayer C. Life in The Context of Order and Complexity. Life (Basel) 2020; 10:life10010005. [PMID: 31963637 PMCID: PMC7175320 DOI: 10.3390/life10010005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/06/2020] [Accepted: 01/16/2020] [Indexed: 11/17/2022] Open
Abstract
It is generally accepted that life requires structural complexity. However, a chaotic mixture of organic compounds like the one formed by extensive reaction sequences over time may be extremely complex, but could just represent a static asphalt-like dead end situation. Likewise, it is accepted that life requires a certain degree of structural order. However, even extremely ordered structures like mineral crystals show no tendency to be alive. So neither complexity nor order alone can characterize a living organism. In order to come close to life, and in order for life to develop to higher organisms, both conditions have to be fulfilled and advanced simultaneously. Only a combination of the two requirements, complexity and structural order, can mark the difference between living and dead matter. It is essential for the development of prebiotic chemistry into life and characterizes the course and the result of Darwinian evolution. For this reason, it is worthwhile to define complexity and order as an essential pair of characteristics of life and to use them as fundamental parameters to evaluate early steps in prebiotic development. A combination of high order and high complexity also represents a universal type of biosignature which could be used to identify unknown forms of life or remnants thereof.
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Affiliation(s)
- Christian Mayer
- Institute of Physical Chemistry, CENIDE, University of Duisburg-Essen, 45141 Essen, Germany
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24
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The Ancient Operational Code is Embedded in the Amino Acid Substitution Matrix and aaRS Phylogenies. J Mol Evol 2019; 88:136-150. [PMID: 31781936 DOI: 10.1007/s00239-019-09918-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 11/14/2019] [Indexed: 10/25/2022]
Abstract
The underlying structure of the canonical amino acid substitution matrix (aaSM) is examined by considering stepwise improvements in the differential recognition of amino acids according to their chemical properties during the branching history of the two aminoacyl-tRNA synthetase (aaRS) superfamilies. The evolutionary expansion of the genetic code is described by a simple parameterization of the aaSM, in which (i) the number of distinguishable amino acid types, (ii) the matrix dimension and (iii) the number of parameters, each increases by one for each bifurcation in an aaRS phylogeny. Parameterized matrices corresponding to trees in which the size of an amino acid sidechain is the only discernible property behind its categorization as a substrate, exclusively for a Class I or II aaRS, provide a significantly better fit to empirically determined aaSM than trees with random bifurcation patterns. A second split between polar and nonpolar amino acids in each Class effects a vastly greater further improvement. The earliest Class-separated epochs in the phylogenies of the aaRS reflect these enzymes' capability to distinguish tRNAs through the recognition of acceptor stem identity elements via the minor (Class I) and major (Class II) helical grooves, which is how the ancient operational code functioned. The advent of tRNA recognition using the anticodon loop supports the evolution of the optimal map of amino acid chemistry found in the later genetic code, an essentially digital categorization, in which polarity is the major functional property, compensating for the unrefined, haphazard differentiation of amino acids achieved by the operational code.
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25
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Grabow WW, Andrews GE. On the nature and origin of biological information: The curious case of RNA. Biosystems 2019; 185:104031. [PMID: 31525398 DOI: 10.1016/j.biosystems.2019.104031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 09/11/2019] [Accepted: 09/12/2019] [Indexed: 11/18/2022]
Abstract
Biological information is most commonly thought of in terms of biology's Central Dogma where DNA is viewed as a linearized code used to synthesize proteins. Using DNA's chemical cousin, RNA, as a case study we consider how biological information operates outside the linear arrangement of its polymeric subunits. Much like individual pieces of a jigsaw puzzle, particular structures enable biomolecules to undergo precise molecular interactions with one another based on their respective shapes. By exploring the relationship between sequence and structure in RNA we argue that biological information finds its ultimate functional fulfillment in the three-dimensional structural arrangement of its atoms. We show how recurrent structural RNA motifs-operating at the tertiary level of a molecule-provide robust building blocks for the formation of new structural configurations and thereby convey the information required for emergent biological functions. We posit that these same RNA structures, guided by their respective thermodynamic stabilities, experience selective pressure to maintain particular three-dimensional architectures over and above pressures to maintain a particular sequence of nucleotides. Ultimately, this framework for understanding the nature of biological information provides a useful paradigm for understanding its origins and how biological information can result from chaotic prebiotic conditions.
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Affiliation(s)
- Wade W Grabow
- Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA, 918119-1997, USA.
| | - Grace E Andrews
- Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA, 918119-1997, USA
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26
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Reflexivity, coding and quantum biology. Biosystems 2019; 185:104027. [PMID: 31494127 DOI: 10.1016/j.biosystems.2019.104027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/29/2019] [Accepted: 08/31/2019] [Indexed: 12/31/2022]
Abstract
Biological systems are fundamentally computational in that they process information in an apparently purposeful fashion rather than just transferring bits of it in a purely syntactical manner. Biological information, such has genetic information stored in DNA sequences, has semantic content. It carries meaning that is defined by the molecular context of its cellular environment. Information processing in biological systems displays an inherent reflexivity, a tendency for the computational information-processing to be "about" the behaviour of the molecules that participate in the computational process. This is most evident in the operation of the genetic code, where the specificity of the reactions catalysed by the aminoacyl-tRNA synthetase (aaRS) enzymes is required to be self-sustaining. A cell's suite of aaRS enzymes completes a reflexively autocatalytic set of molecular components capable of making themselves through the operation of the code. This set requires the existence of a body of reflexive information to be stored in an organism's genome. The genetic code is a reflexively self-organised mapping of the chemical properties of amino acid sidechains onto codon "tokens". It is a highly evolved symbolic system of chemical self-description. Although molecular biological coding is generally portrayed in terms of classical bit-transfer events, various biochemical events explicitly require quantum coherence for their occurrence. Whether the implicit transfer of quantum information, qbits, is indicative of wide-ranging quantum computation in living systems is currently the subject of extensive investigation and speculation in the field of Quantum Biology.
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27
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Carter CW, Wills PR. Experimental solutions to problems defining the origin of codon-directed protein synthesis. Biosystems 2019; 183:103979. [PMID: 31176803 PMCID: PMC6693952 DOI: 10.1016/j.biosystems.2019.103979] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 05/27/2019] [Accepted: 05/29/2019] [Indexed: 12/13/2022]
Abstract
How genetic coding differentiated biology from chemistry is a long-standing challenge in Biology, for which there have been few experimental approaches, despite a wide-ranging speculative literature. We summarize five coordinated areas-experimental characterization of functional approximations to the minimal peptides (protozymes and urzymes) necessary to activate amino acids and acylate tRNA; showing that specificities of these experimental models match those expected from the synthetase Class division; population of disjoint regions of amino acid sequence space via bidirectional coding ancestry of the two synthetase Classes; showing that the phase transfer equilibria of amino acid side chains that form a two-dimensional basis set for protein folding are embedded in patterns of bases in the tRNA acceptor stem and anticodon; and identification of molecular signatures of ancestral synthetases and tRNAs necessary to define the earliest cognate synthetase:tRNA pairs-that now compose an extensive experimentally testable paradigm for progress toward understanding the coordinated emergence of the codon table and viable mRNA coding sequences. We briefly discuss recent progress toward identifying the remaining outstanding questions-the nature of the earliest amino acid alphabets and the origin of binding discrimination via distinct amino acid sequence-independent protein secondary structures-and how these, too, might be addressed experimentally.
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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, United States
| | - 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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28
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The difficult case of an RNA-only origin of life. Emerg Top Life Sci 2019; 3:469-475. [PMID: 33523163 PMCID: PMC7289000 DOI: 10.1042/etls20190024] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 08/08/2019] [Accepted: 08/09/2019] [Indexed: 11/17/2022]
Abstract
The RNA world hypothesis is probably the most extensively studied model for the emergence of life on Earth. Despite a large body of evidence supporting the idea that RNA is capable of kick-starting autocatalytic self-replication and thus initiating the emergence of life, seemingly insurmountable weaknesses in the theory have also been highlighted. These problems could be overcome by novel experimental approaches, including out-of-equilibrium environments, and the exploration of an early co-evolution of RNA and other key biomolecules such as peptides and DNA, which might be necessary to mitigate the shortcomings of RNA-only systems.
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29
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Carter CW, Wills PR. Hierarchical groove discrimination by Class I and II aminoacyl-tRNA synthetases reveals a palimpsest of the operational RNA code in the tRNA acceptor-stem bases. Nucleic Acids Res 2019; 46:9667-9683. [PMID: 30016476 PMCID: PMC6182185 DOI: 10.1093/nar/gky600] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 07/12/2018] [Indexed: 01/01/2023] Open
Abstract
Class I and II aaRS recognition of opposite grooves was likely among the earliest determinants fixed in the tRNA acceptor stem bases. A new regression model identifies those determinants in bacterial tRNAs. Integral coefficients relate digital dependent to independent variables with perfect agreement between observed and calculated grooves for all twenty isoaccepting tRNAs. Recognition is mediated by the Discriminator base 73, the first base pair, and base 2 of the acceptor stem. Subsets of these coefficients also identically compute grooves recognized by smaller numbers of aaRS. Thus, the model is hierarchical, suggesting that new rules were added to pre-existing ones as new amino acids joined the coding alphabet. A thermodynamic rationale for the simplest model implies that Class-dependent aaRS secondary structures exploited differential tendencies of the acceptor stem to form the hairpin observed in Class I aaRS•tRNA complexes, enabling the earliest groove discrimination. Curiously, groove recognition also depends explicitly on the identity of base 2 in a manner consistent with the middle bases of the codon table, confirming a hidden ancestry of codon-anticodon pairing in the acceptor stem. That, and the lack of correlation with anticodon bases support prior productive coding interaction of tRNA minihelices with proto-mRNA.
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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
| | - Peter R Wills
- Department of Physics, Centre for Computational Evolution, and Te Ao Marama Centre for Fundamental Enquiry, University of Auckland, PB 92109, Auckland 1142, New Zealand
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30
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Lopez A, Fiore M. Investigating Prebiotic Protocells for A Comprehensive Understanding of the Origins of Life: A Prebiotic Systems Chemistry Perspective. Life (Basel) 2019; 9:E49. [PMID: 31181679 PMCID: PMC6616946 DOI: 10.3390/life9020049] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 05/21/2019] [Accepted: 06/06/2019] [Indexed: 01/06/2023] Open
Abstract
Protocells are supramolecular systems commonly used for numerous applications, such as the formation of self-evolvable systems, in systems chemistry and synthetic biology. Certain types of protocells imitate plausible prebiotic compartments, such as giant vesicles, that are formed with the hydration of thin films of amphiphiles. These constructs can be studied to address the emergence of life from a non-living chemical network. They are useful tools since they offer the possibility to understand the mechanisms underlying any living cellular system: Its formation, its metabolism, its replication and its evolution. Protocells allow the investigation of the synergies occurring in a web of chemical compounds. This cooperation can explain the transition between chemical (inanimate) and biological systems (living) due to the discoveries of emerging properties. The aim of this review is to provide an overview of relevant concept in prebiotic protocell research.
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Affiliation(s)
- Augustin Lopez
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, Université de Lyon, Claude Bernard Lyon 1, 1 Rue Victor Grignard, Bâtiment Lederer, 69622 Villeurbanne CEDEX, France.
- Master de Biologie, École Normale Supérieure de Lyon, Université Claude Bernard Lyon I, Université de Lyon, 69342 Lyon CEDEX 07, France.
| | - Michele Fiore
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, Université de Lyon, Claude Bernard Lyon 1, 1 Rue Victor Grignard, Bâtiment Lederer, 69622 Villeurbanne CEDEX, France.
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31
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Collins-Hed AI, Ardell DH. Match fitness landscapes for macromolecular interaction networks: Selection for translational accuracy and rate can displace tRNA-binding interfaces of non-cognate aminoacyl-tRNA synthetases. Theor Popul Biol 2019; 129:68-80. [PMID: 31042487 DOI: 10.1016/j.tpb.2019.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 01/26/2019] [Accepted: 03/13/2019] [Indexed: 12/21/2022]
Abstract
Advances in structural biology of aminoacyl-tRNA synthetases (aaRSs) have revealed incredible diversity in how aaRSs bind their tRNA substrates. The causes of this diversity remain mysterious. We developed a new class of highly rugged fitness landscape models called match landscapes, through which genes encode the assortative interactions of their gene products through the complementarity and identifiability of their structural features. We used results from coding theory to prove bounds and equalities on fitness in match landscapes assuming additive interaction energies, macroscopic aminoacylation kinetics including proofreading, site-specific modifiers of interaction, and selection for translational accuracy in multiple, perfectly encoded site-types. Using genotypes based on extended Hamming codes we show that over a wide array of interface sizes and numbers of encoded cognate pairs, selection for translational accuracy alone is insufficient to displace the tRNA-binding interfaces of aaRSs. Yet, under combined selection for translational accuracy and rate, site-specific modifiers are selected to adaptively displace the tRNA-binding interfaces of non-cognate aaRS-tRNA pairs. We describe a remarkable correspondence between the lengths of perfect RNA (quaternary) codes and the modal sizes of small non-coding RNA families.
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Affiliation(s)
- Andrea I Collins-Hed
- Quantitative and Systems Biology Program, University of California, Merced, CA, 95306, United States
| | - David H Ardell
- Quantitative and Systems Biology Program, University of California, Merced, CA, 95306, United States; Molecular and Cell Biology Department, School of Natural Sciences, University of California, Merced, CA, 95306, United States.
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32
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Strazewski P. Low-Digit and High-Digit Polymers in the Origin of Life. Life (Basel) 2019; 9:life9010017. [PMID: 30717360 PMCID: PMC6463190 DOI: 10.3390/life9010017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 01/23/2019] [Accepted: 01/26/2019] [Indexed: 01/22/2023] Open
Abstract
Extant life uses two kinds of linear biopolymers that mutually control their own production, as well as the cellular metabolism and the production and homeostatic maintenance of other biopolymers. Nucleic acids are linear polymers composed of a relatively low structural variety of monomeric residues, and thus a low diversity per accessed volume. Proteins are more compact linear polymers that dispose of a huge compositional diversity even at the monomeric level, and thus bear a much higher catalytic potential. The fine-grained diversity of proteins makes an unambiguous information transfer from protein templates too error-prone, so they need to be resynthesized in every generation. But proteins can catalyse both their own reproduction as well as the efficient and faithful replication of nucleic acids, which resolves in a most straightforward way an issue termed “Eigen’s paradox”. Here the importance of the existence of both kinds of linear biopolymers is discussed in the context of the emergence of cellular life, be it for the historic orgin of life on Earth, on some other habitable planet, or in the test tube. An immediate consequence of this analysis is the necessity for translation to appear early during the evolution of life.
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Affiliation(s)
- Peter Strazewski
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (Unité Mixte de Recherche 5246), Université de Lyon, Claude Bernard Lyon 1, 43 bvd du 11 Novembre 1918, 69622 Villeurbanne CEDEX, France.
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Biscans A. Exploring the Emergence of RNA Nucleosides and Nucleotides on the Early Earth. Life (Basel) 2018; 8:life8040057. [PMID: 30404133 PMCID: PMC6316623 DOI: 10.3390/life8040057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 10/31/2018] [Accepted: 11/03/2018] [Indexed: 01/02/2023] Open
Abstract
Understanding how life began is one of the most fascinating problems to solve. By approaching this enigma from a chemistry perspective, the goal is to define what series of chemical reactions could lead to the synthesis of nucleotides, amino acids, lipids, and other cellular components from simple feedstocks under prebiotically plausible conditions. It is well established that evolution of life involved RNA which plays central roles in both inheritance and catalysis. In this review, we present historically important and recently published articles aimed at understanding the emergence of RNA nucleosides and nucleotides on the early Earth.
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Affiliation(s)
- Annabelle Biscans
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, 01605 MA, USA.
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Kunnev D, Gospodinov A. Possible Emergence of Sequence Specific RNA Aminoacylation via Peptide Intermediary to Initiate Darwinian Evolution and Code Through Origin of Life. Life (Basel) 2018; 8:E44. [PMID: 30279401 PMCID: PMC6316189 DOI: 10.3390/life8040044] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/30/2018] [Accepted: 09/30/2018] [Indexed: 12/12/2022] Open
Abstract
One of the most intriguing questions in biological science is how life originated on Earth. A large number of hypotheses have been proposed to explain it, each putting an emphasis on different events leading to functional translation and self-sustained system. Here, we propose a set of interactions that could have taken place in the prebiotic environment. According to our hypothesis, hybridization-induced proximity of short aminoacylated RNAs led to the synthesis of peptides of random sequence. We postulate that among these emerged a type of peptide(s) capable of stimulating the interaction between specific RNAs and specific amino acids, which we call "bridge peptide" (BP). We conclude that translation should have emerged at the same time when the standard genetic code begun to evolve due to the stabilizing effect on RNA-peptide complexes with the help of BPs. Ribosomes, ribozymes, and the enzyme-directed RNA replication could co-evolve within the same period, as logical outcome of RNA-peptide world without the need of RNA only self-sustained step.
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Affiliation(s)
- Dimiter Kunnev
- Roswell Park Cancer Institute, Department of Molecular & Cellular Biology, Buffalo, NY 14263, USA.
| | - Anastas Gospodinov
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. 21, Sofia 1113, Bulgaria.
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Vitas M, Dobovišek A. In the Beginning was a Mutualism - On the Origin of Translation. ORIGINS LIFE EVOL B 2018; 48:223-243. [PMID: 29713988 DOI: 10.1007/s11084-018-9557-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Accepted: 04/23/2018] [Indexed: 12/28/2022]
Abstract
The origin of translation is critical for understanding the evolution of life, including the origins of life. The canonical genetic code is one of the most dominant aspects of life on this planet, while the origin of heredity is one of the key evolutionary transitions in living world. Why the translation apparatus evolved is one of the enduring mysteries of molecular biology. Assuming the hypothesis, that during the emergence of life evolution had to first involve autocatalytic systems which only subsequently acquired the capacity of genetic heredity, we propose and discuss possible mechanisms, basic aspects of the emergence and subsequent molecular evolution of translation and ribosomes, as well as enzymes as we know them today. It is possible, in this sense, to view the ribosome as a digital-to-analogue information converter. The proposed mechanism is based on the abilities and tendencies of short RNA and polypeptides to fold and to catalyse biochemical reactions. The proposed mechanism is in concordance with the hypothesis of a possible chemical co-evolution of RNA and proteins in the origin of the genetic code or even more generally at the early evolution of life on Earth. The possible abundance and availability of monomers at prebiotic conditions are considered in the mechanism. The hypothesis that early polypeptides were folding on the RNA scaffold is also considered and mutualism in molecular evolutionary development of RNA and peptides is favoured.
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Affiliation(s)
- Marko Vitas
- , Laze pri Borovnici 38, Borovnica, Slovenia.
| | - Andrej Dobovišek
- Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, 2000, Maribor, Slovenia
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Pak D, Kim Y, Burton ZF. Aminoacyl-tRNA synthetase evolution and sectoring of the genetic code. Transcription 2018; 9:205-224. [PMID: 29727262 PMCID: PMC6104698 DOI: 10.1080/21541264.2018.1467718] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/13/2018] [Indexed: 02/08/2023] Open
Abstract
The genetic code sectored via tRNA charging errors, and the code progressed toward closure and universality because of evolution of aminoacyl-tRNA synthetase (aaRS) fidelity and translational fidelity mechanisms. Class I and class II aaRS folds are identified as homologs. From sequence alignments, a structurally conserved Zn-binding domain common to class I and class II aaRS was identified. A model for the class I and class II aaRS alternate folding pathways is posited. Five mechanisms toward code closure are highlighted: 1) aaRS proofreading to remove mischarged amino acids from tRNA; 2) accurate aaRS active site specification of amino acid substrates; 3) aaRS-tRNA anticodon recognition; 4) conformational coupling proofreading of the anticodon-codon interaction; and 5) deamination of tRNA wobble adenine to inosine. In tRNA anticodons there is strong wobble sequence preference that results in a broader spectrum of contacts to synonymous mRNA codon wobble bases. Adenine is excluded from the anticodon wobble position of tRNA unless it is modified to inosine. Uracil is generally preferred to cytosine in the tRNA anticodon wobble position. Because of wobble ambiguity when tRNA reads mRNA, the maximal coding capacity of the three nucleotide code read by tRNA is 31 amino acids + stops.
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Affiliation(s)
- Daewoo Pak
- Center for Statistical Training and Consulting, Michigan State University, E. Lansing, MI 48824, USA
| | | | - Zachary F. Burton
- Department of Biochemistry and Molecular Biology, Michigan State University, 603 Wilson Rd, E. Lansing, MI 48824-1319, USA
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Kaiser F, Bittrich S, Salentin S, Leberecht C, Haupt VJ, Krautwurst S, Schroeder M, Labudde D. Backbone Brackets and Arginine Tweezers delineate Class I and Class II aminoacyl tRNA synthetases. PLoS Comput Biol 2018; 14:e1006101. [PMID: 29659563 PMCID: PMC5919687 DOI: 10.1371/journal.pcbi.1006101] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 04/26/2018] [Accepted: 03/20/2018] [Indexed: 12/22/2022] Open
Abstract
The origin of the machinery that realizes protein biosynthesis in all organisms is still unclear. One key component of this machinery are aminoacyl tRNA synthetases (aaRS), which ligate tRNAs to amino acids while consuming ATP. Sequence analyses revealed that these enzymes can be divided into two complementary classes. Both classes differ significantly on a sequence and structural level, feature different reaction mechanisms, and occur in diverse oligomerization states. The one unifying aspect of both classes is their function of binding ATP. We identified Backbone Brackets and Arginine Tweezers as most compact ATP binding motifs characteristic for each Class. Geometric analysis shows a structural rearrangement of the Backbone Brackets upon ATP binding, indicating a general mechanism of all Class I structures. Regarding the origin of aaRS, the Rodin-Ohno hypothesis states that the peculiar nature of the two aaRS classes is the result of their primordial forms, called Protozymes, being encoded on opposite strands of the same gene. Backbone Brackets and Arginine Tweezers were traced back to the proposed Protozymes and their more efficient successors, the Urzymes. Both structural motifs can be observed as pairs of residues in contemporary structures and it seems that the time of their addition, indicated by their placement in the ancient aaRS, coincides with the evolutionary trace of Proto- and Urzymes. Aminoacyl tRNA synthetases (aaRS) are primordial enzymes essential for interpretation and transfer of genetic information. Understanding the origin of the peculiarities observed with aaRS can explain what constituted the earliest life forms and how the genetic code was established. The increasing amount of experimentally determined three-dimensional structures of aaRS opens up new avenues for high-throughput analyses of molecular mechanisms. In this study, we present an exhaustive structural analysis of ATP binding motifs. We unveil an oppositional implementation of enzyme substrate binding in each aaRS Class. While Class I binds via interactions mediated by backbone hydrogen bonds, Class II uses a pair of arginine residues to establish salt bridges to its ATP ligand. We show how nature realized the binding of the same ligand species with completely different mechanisms. In addition, we demonstrate that sequence or even structure analysis for conserved residues may miss important functional aspects which can only be revealed by ligand interaction studies. Additionally, the placement of those key residues in the structure supports a popular hypothesis, which states that prototypic aaRS were once coded on complementary strands of the same gene.
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Affiliation(s)
- Florian Kaiser
- University of Applied Sciences Mittweida, Mittweida, Germany
- Biotechnology Center (BIOTEC), TU Dresden, Dresden, Germany
- * E-mail:
| | - Sebastian Bittrich
- University of Applied Sciences Mittweida, Mittweida, Germany
- Biotechnology Center (BIOTEC), TU Dresden, Dresden, Germany
| | | | - Christoph Leberecht
- University of Applied Sciences Mittweida, Mittweida, Germany
- Biotechnology Center (BIOTEC), TU Dresden, Dresden, Germany
| | | | | | | | - Dirk Labudde
- University of Applied Sciences Mittweida, Mittweida, Germany
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Branciamore S, Gogoshin G, Di Giulio M, Rodin AS. Intrinsic Properties of tRNA Molecules as Deciphered via Bayesian Network and Distribution Divergence Analysis. Life (Basel) 2018; 8:life8010005. [PMID: 29419741 PMCID: PMC5871937 DOI: 10.3390/life8010005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 01/22/2018] [Accepted: 01/23/2018] [Indexed: 12/27/2022] Open
Abstract
The identity/recognition of tRNAs, in the context of aminoacyl tRNA synthetases (and other molecules), is a complex phenomenon that has major implications ranging from the origins and evolution of translation machinery and genetic code to the evolution and speciation of tRNAs themselves to human mitochondrial diseases to artificial genetic code engineering. Deciphering it via laboratory experiments, however, is difficult and necessarily time- and resource-consuming. In this study, we propose a mathematically rigorous two-pronged in silico approach to identifying and classifying tRNA positions important for tRNA identity/recognition, rooted in machine learning and information-theoretic methodology. We apply Bayesian Network modeling to elucidate the structure of intra-tRNA-molecule relationships, and distribution divergence analysis to identify meaningful inter-molecule differences between various tRNA subclasses. We illustrate the complementary application of these two approaches using tRNA examples across the three domains of life, and identify and discuss important (informative) positions therein. In summary, we deliver to the tRNA research community a novel, comprehensive methodology for identifying the specific elements of interest in various tRNA molecules, which can be followed up by the corresponding experimental work and/or high-resolution position-specific statistical analyses.
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Affiliation(s)
- Sergio Branciamore
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolism Research Institute, City of Hope, Duarte, 91010 CA, USA.
| | - Grigoriy Gogoshin
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolism Research Institute, City of Hope, Duarte, 91010 CA, USA.
| | - Massimo Di Giulio
- Early Evolution of Life Laboratory, Institute of Biosciences and Bioresources, CNR, 80131 Naples, Italy.
| | - Andrei S Rodin
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolism Research Institute, City of Hope, Duarte, 91010 CA, USA.
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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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Affiliation(s)
- Jan-Hendrik S Hofmeyr
- Centre for Complex Systems in Transition and Dept. of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa.
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Ma W. What Does "the RNA World" Mean to "the Origin of Life"? Life (Basel) 2017; 7:life7040049. [PMID: 29186049 PMCID: PMC5745562 DOI: 10.3390/life7040049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 10/30/2017] [Accepted: 11/24/2017] [Indexed: 12/30/2022] Open
Abstract
Corresponding to life’s two distinct aspects: Darwinian evolution and self-sustainment, the origin of life should also split into two issues: the origin of Darwinian evolution and the arising of self-sustainment. Because the “self-sustainment” we concern about life should be the self-sustainment of a relevant system that is “defined” by its genetic information, the self-sustainment could not have arisen before the origin of Darwinian evolution, which was just marked by the emergence of genetic information. The logic behind the idea of the RNA world is not as tenable as it has been believed. That is, genetic molecules and functional molecules, even though not being the same material, could have emerged together in the beginning and launched the evolution—provided that the genetic molecules can “simply” code the functional molecules. However, due to these or those reasons, alternative scenarios are generally much less convincing than the RNA world. In particular, when considering the accumulating experimental evidence that is supporting a de novo origin of the RNA world, it seems now quite reasonable to believe that such a world may have just stood at the very beginning of life on the Earth. Therewith, we acquire a concrete scenario for our attempts to appreciate those fundamental issues that are involved in the origin of life. In the light of those possible scenes included in this scenario, Darwinian evolution may have originated at the molecular level, realized upon a functional RNA. When two or more functional RNAs emerged, for their efficient cooperation, there should have been a selective pressure for the emergence of protocells. But it was not until the appearance of the “unitary-protocell”, which had all of its RNA genes linked into a chromosome, that Darwinian evolution made its full step towards the cellular level—no longer severely constrained by the low-grade evolution at the molecular level. Self-sustainment did not make sense before protocells emerged. The selection pressure that was favoring the exploration of more and more fundamental raw materials resulted in an evolutionary tendency of life to become more and more self-sustained. New functions for the entities to adapt to environments, including those that are involved in the self-sustainment per se, would bring new burdens to the self-sustainment—the advantage of these functions must overweigh the corresponding disadvantage.
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Affiliation(s)
- Wentao Ma
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan 430072, China.
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