Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.448
Filtrar
1.
DNA Cell Biol ; 39(2): 177-186, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31804855

RESUMO

The chemical or prebiotic evolution referred also to as pre-Darwinian evolution describes chemical reactions up to the origin of a self-replicating system that was capable of Darwinian evolution. These chemical processes took place on Earth between about 3.7 and 4.5 billion years ago when cellular life came into being. The pre-Darwinian chemical evolution usually assumes hereditary elements, but does not regard them as self-organizing processes. Physical and chemical self-organization led to uninterrupted pre-Darwinian and Darwinian evolution. Thus, it is not justified to distinguish between different types of evolution. From the many possible solutions, evolution selected among those reactions that generated catalytic networks incorporating chemical sequence information and under gradually changing circumstances produced a reproducible and stable living system that adapted to these conditions. Major issues in this review involve prebiotic reactions leading to genetic evolution involving (1) abiotic sources of components of ribonucleotides and xenobiotic nucleotides, (2) formation of prebiotic RNA, (3) development of genetic RNA from random-sequence noncoding RNA, (4) transition from RNA World to DNA Empire, (5) the role of oxygenic photosynthesis in genetic transitions, and (6) hierarchical arrangement of processes involved in the optimized genetic system.


Assuntos
Nucleotídeos/genética , Origem da Vida , RNA/genética , Ribose/metabolismo , Animais , Evolução Química , Evolução Molecular , Humanos
2.
Chem Asian J ; 15(2): 214-230, 2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-31714665

RESUMO

Catalysis by nucleic acids is indispensable for extant cellular life, and it is widely accepted that nucleic acid enzymes were crucial for the emergence of primitive life 3.5-4 billion years ago. However, geochemical conditions on early Earth must have differed greatly from the constant internal milieus of today's cells. In order to explore plausible scenarios for early molecular evolution, it is therefore essential to understand how different physicochemical parameters, such as temperature, pH, and ionic composition, influence nucleic acid catalysis and to explore to what extent nucleic acid enzymes can adapt to non-physiological conditions. In this article, we give an overview of the research on catalysis of nucleic acids, in particular catalytic RNAs (ribozymes) and DNAs (deoxyribozymes), under extreme and/or unusual conditions that may relate to prebiotic environments.


Assuntos
DNA Catalítico/química , RNA Catalítico/química , Sequência de Bases , Catálise , DNA Catalítico/efeitos da radiação , Concentração de Íons de Hidrogênio , Pressão Hidrostática , Metais/química , Origem da Vida , RNA Catalítico/efeitos da radiação , Temperatura Ambiente , Raios Ultravioleta
3.
Mol Biol Evol ; 37(1): 71-83, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31504724

RESUMO

Most scenarios for the origin of life assume that RNA played a key role in both catalysis and information storage. The A, U, G, and C nucleobases in modern RNA all participate in secondary structure formation and replication. However, the rapid deamination of C to U and the absence of C in meteorite samples suggest that prebiotic RNA may have been deficient in cytosine. Here, we assess the ability of RNA sequences formed from a three-letter AUG alphabet to perform both structural and genetic roles in comparison to sequences formed from the AUGC alphabet. Despite forming less thermodynamically stable helices, the AUG alphabet can find a broad range of structures and thus appears sufficient for catalysis in the RNA World. However, in the AUG case, longer sequences are required to form structures with an equivalent complexity. Replication in the AUG alphabet requires GU pairing. Sequence fidelity in the AUG alphabet is low whenever G's are present in the sequence. We find that AUG sequences evolve to AU sequences if GU pairing is rare, and to RU sequences if GU pairing is common (R denotes A or G). It is not possible to conserve a G at a specific site in either case. These problems do not rule out the possibility of an RNA World based on AUG, but they show that it wouldbe significantly more difficult than with a four-base alphabet.


Assuntos
Origem da Vida , RNA/fisiologia , Estrutura Molecular
4.
Phys Chem Chem Phys ; 22(3): 971-975, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31854402

RESUMO

An environment far from equilibrium is thought to be a necessary condition for the origin and persistence of life. In this context we report open-flow simulations of a non-enzymic proto-metabolic system, in which hydrogen peroxide acts both as oxidant and driver of thermochemical cycling. We find that a Gaussian perturbed input produces a non-Boltzmann output fluctuation distribution around the mean oscillation maximum. Our main result is that net biosynthesis can occur under fluctuating cyclical but not steady drive. Consequently we may revise the necessary condition to "dynamically far from equilibrium".


Assuntos
Fenômenos Bioquímicos/fisiologia , Origem da Vida , Termodinâmica , Simulação por Computador , Modelos Químicos
5.
Orig Life Evol Biosph ; 49(3): 187-196, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31642022

RESUMO

This work addresses the supramolecular self-organization in the xerogels of formose reaction products. The UV-induced formose reaction was held in over-saturated formaldehyde solutions at 70∘C without a catalyst. The solutions of the obtained carbohydrates were dried on a glass slide, and the obtained xerogels demonstrated a prominent optical activity, while the initial solutions were optically inactive. The xerogels contained highly elongated crystalline elements of a helical structure as well as the isometric ones. Thus xerogel formation was accompanied by a spontaneous resolution of enantiomers and separation of different-shaped supramolecular structures. The thick helices were twisted of thinner ones, while the latter were twisted of elementary structures having a diameter much smaller than 400 nm. Similar structural hierarchy is typical of biological macromolecules (DNA, proteins, and cellulose). Summarizing the obtained results, we proposed a hypothetical mechanism explaining the amplification of the initial enantiomeric excess, as well as chiral and chemical purification of the substances which were essential for the evolution of Life to start.


Assuntos
Carboidratos/química , Formaldeído/química , Géis , Origem da Vida , Estereoisomerismo
6.
PLoS Genet ; 15(10): e1008271, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31622336

RESUMO

Viral quasispecies refers to a population structure that consists of extremely large numbers of variant genomes, termed mutant spectra, mutant swarms or mutant clouds. Fueled by high mutation rates, mutants arise continually, and they change in relative frequency as viral replication proceeds. The term quasispecies was adopted from a theory of the origin of life in which primitive replicons) consisted of mutant distributions, as found experimentally with present day RNA viruses. The theory provided a new definition of wild type, and a conceptual framework for the interpretation of the adaptive potential of RNA viruses that contrasted with classical studies based on consensus sequences. Standard clonal analyses and deep sequencing methodologies have confirmed the presence of myriads of mutant genomes in viral populations, and their participation in adaptive processes. The quasispecies concept applies to any biological entity, but its impact is more evident when the genome size is limited and the mutation rate is high. This is the case of the RNA viruses, ubiquitous in our biosphere, and that comprise many important pathogens. In virology, quasispecies are defined as complex distributions of closely related variant genomes subjected to genetic variation, competition and selection, and that may act as a unit of selection. Despite being an integral part of their replication, high mutation rates have an upper limit compatible with inheritable information. Crossing such a limit leads to RNA virus extinction, a transition that is the basis of an antiviral design termed lethal mutagenesis.


Assuntos
Quase-Espécies , Vírus de RNA/fisiologia , Evolução Molecular , Sequenciamento de Nucleotídeos em Larga Escala , Taxa de Mutação , Origem da Vida , Vírus de RNA/genética , Vírus de RNA/imunologia , Vacinas Virais/imunologia , Replicação Viral
7.
Mol Biol Evol ; 36(12): 2737-2747, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31504731

RESUMO

Reverse gyrase (RG) is the only protein found ubiquitously in hyperthermophilic organisms, but absent from mesophiles. As such, its simple presence or absence allows us to deduce information about the optimal growth temperature of long-extinct organisms, even as far as the last universal common ancestor of extant life (LUCA). The growth environment and gene content of the LUCA has long been a source of debate in which RG often features. In an attempt to settle this debate, we carried out an exhaustive search for RG proteins, generating the largest RG data set to date. Comprising 376 sequences, our data set allows for phylogenetic reconstructions of RG with unprecedented size and detail. These RG phylogenies are strikingly different from those of universal proteins inferred to be present in the LUCA, even when using the same set of species. Unlike such proteins, RG does not form monophyletic archaeal and bacterial clades, suggesting RG emergence after the formation of these domains, and/or significant horizontal gene transfer. Additionally, the branch lengths separating archaeal and bacterial groups are very short, inconsistent with the tempo of evolution from the time of the LUCA. Despite this, phylogenies limited to archaeal RG resolve most archaeal phyla, suggesting predominantly vertical evolution since the time of the last archaeal ancestor. In contrast, bacterial RG indicates emergence after the last bacterial ancestor followed by significant horizontal transfer. Taken together, these results suggest a nonhyperthermophilic LUCA and bacterial ancestor, with hyperthermophily emerging early in the evolution of the archaeal and bacterial domains.


Assuntos
DNA Topoisomerases Tipo I/genética , Evolução Molecular , Origem da Vida , Filogenia , Transferência Genética Horizontal
8.
Biochemistry (Mosc) ; 84(8): 870-883, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31522669

RESUMO

It has been suggested that RNA polymerase ribozyme displaying reverse transcriptase and integrase activities has played a vital role in the origin of life on Earth. Here, we present a hypothesis that formation of universal ancestral units of all living organisms - retroelements - in the evolution was mediated by reverse transcriptase. The propensity of retroelements to mutations and their insertion capacity have formed a basis for the origin of complex DNA structures - primary genomes - that have given rise to archaea, eukaryotes, bacteria, and viruses. Conserved properties of retroelements have been preserved throughout the evolution; their modifications have facilitated the emergence of mechanisms for the interactions between proteins and nucleic acids. Life has evolved due to insertional mutagenesis and competition of autonomously replicating polynucleotides that allowed to preserve structures with adaptive properties. We hypothesize that natural selection of mechanisms for the defense against insertions based on the ribonuclease activity of reverse transcriptase ribozyme has led to the emergence of all universal enzymatic systems for the processing of RNA molecules. These systems have been and still remain the key sources of structural and functional transformations of genomes in the course of evolution. The data presented in this review suggest that the process of translation, which unifies the nucleic acid and protein worlds, has developed as a modification of the defense mechanisms against insertions. Polypeptides formed by this defense system have potentiated the activity of ribozymes in the composition of ribonucleoproteins (RNPs) and even functionally replaced them as more efficient catalysts of biological reactions. Here, we analyze the mechanisms of retroelement involvement in the structural and regulatory transformations of eukaryotic genomes supposedly reflecting the adaptive principles that had originated during the beginning of life on Earth. Simultaneously with the evolution of existing proteins, retroelements have served as sources of new ribozymes, such as long non-coding RNAs. These ribozymes can function in complexes with proteins in the composition of RNPs, as well as display independent catalytic and translational activities; their genes have a potential for the transformation into protein-coding genes. Hence, the conserved principles of RNA, DNA, and proteins interregulation formed at the time of life origin on Earth have been used throughout the evolution.


Assuntos
Evolução Molecular , Origem da Vida , DNA Polimerase Dirigida por RNA/fisiologia , Animais , Elementos de DNA Transponíveis/genética , RNA Polimerases Dirigidas por DNA , Escherichia coli/enzimologia , Escherichia coli/genética , Eucariotos/genética , Humanos , Íntrons/genética , Biossíntese de Proteínas , RNA Catalítico/fisiologia , RNA Longo não Codificante/genética , RNA de Transferência/genética , RNA de Transferência/metabolismo , Retroelementos
9.
Orig Life Evol Biosph ; 49(3): 111-145, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31399826

RESUMO

In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we provide brief summaries of debates with respect to (1) definitions (or theories) of life, what life is and how research should be conducted in the absence of an accepted theory of life, (2) the distinctions between synthetic, historical, and universal projects in origins-of-life studies, issues with strategies for inferring the origins of life, such as (3) the nature of the first living entities (the "bottom up" approach) and (4) how to infer the nature of the last universal common ancestor (the "top down" approach), and (5) the status of origins of life as a science. Each of these debates influences the others. Although there are clusters of researchers that agree on some answers to these issues, each of these debates is still open. With respect to history, we outline several independent paths that have led to some of the approaches now prevalent in origins-of-life studies. These include one path from early views of life through the scientific revolutions brought about by Linnaeus (von Linn.), Wöhler, Miller, and others. In this approach, new theories, tools, and evidence guide new thoughts about the nature of life and its origin. We also describe another family of paths motivated by a" circularity" approach to life, which is guided by such thinkers as Maturana & Varela, Gánti, Rosen, and others. These views echo ideas developed by Kant and Aristotle, though they do so using modern science in ways that produce exciting avenues of investigation. By exploring the history of these ideas, we can see how many of the issues that currently interest us have been guided by the contexts in which the ideas were developed. The disciplinary backgrounds of each of these scholars has influenced the questions they sought to answer, the experiments they envisioned, and the kinds of data they collected. We conclude by encouraging scientists and scholars in the humanities and social sciences to explore ways in which they can interact to provide a deeper understanding of the conceptual assumptions, structure, and history of origins-of-life research. This may be useful to help frame future research agendas and bring awareness to the multifaceted issues facing this challenging scientific question.


Assuntos
Biologia/história , Química/história , Historiografia , Informática/história , Origem da Vida , Paleontologia/história , Filosofia/história , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , Biologia Molecular/história
10.
Chem Commun (Camb) ; 55(71): 10563-10566, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31417990

RESUMO

Besides delivering plausible prebiotic feedstock molecules and high-energy initiators, extraterrestrial impacts could also affect the process of abiogenesis by altering the early Earth's geological environment in which primitive life was conceived. We show that iron-rich smectites formed by reprocessing of basalts due to the residual post-impact heat could catalyze the synthesis and accumulation of important prebiotic building blocks such as nucleobases, amino acids and urea.


Assuntos
Argila/química , Ferro/química , Meteoroides , Silicatos/química , Aminoácidos/química , Catálise , Evolução Química , Meio Ambiente Extraterreno/química , Origem da Vida , Ureia/química
11.
Orig Life Evol Biosph ; 49(3): 147-162, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31444635

RESUMO

The synthesis of prebiotic molecules from simple precursors is believed to be a crucial scheme in order to study the origin of life processes. The present study describes the one-pot synthesis of purine and pyrimidine nucleic acid bases in the presence of pre-biologically significant binary metal oxide nanoparticles, metal ferrites, namely NiFe2O4, CoFe2O4, CuFe2O4, ZnFe2O4 and MnFe2O4. The products identified are cytosine, isocytosine, 4(3H)-pyrimidinone, adenine, hypoxanthine and purine. The ability of isocytosine (a constitutional isomer of cytosine) to recognize cytosine and guanine through normal and reversed Watson-Crick pairing respectively, demonstrates an important storyline for the genesis of ancient nucleic acids. The relevance of other synthesized nucleic acid bases with respect to the origin of life is also discussed. The divalent metal ions in iron oxide make it an appropriate catalytic system because it demonstrates excellent catalytic performance for the nucleic acid bases synthesis with significantly high yield, as compared to pure iron oxide and some other minerals like silica, alumina, manganese oxides and double metal cyanide complexes.


Assuntos
Compostos Férricos/química , Formamidas/química , Nanopartículas Metálicas/química , Ácidos Nucleicos/síntese química , Origem da Vida , Carbono/química
12.
BMC Evol Biol ; 19(1): 158, 2019 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-31362700

RESUMO

BACKGROUND: There is wide agreement that only a subset of the twenty standard amino acids existed prebiotically in sufficient concentrations to form functional polypeptides. We ask how this subset, postulated as {A,D,E,G,I,L,P,S,T,V}, could have formed structures stable enough to found metabolic pathways. Inspired by alphabet reduction experiments, we undertook a computational analysis to measure the structural coding behavior of sequences simplified by reduced alphabets. We sought to discern characteristics of the prebiotic set that would endow it with unique properties relevant to structure, stability, and folding. RESULTS: Drawing on a large dataset of single-domain proteins, we employed an information-theoretic measure to assess how well the prebiotic amino acid set preserves fold information against all other possible ten-amino acid sets. An extensive virtual mutagenesis procedure revealed that the prebiotic set excellently preserves sequence-dependent information regarding both backbone conformation and tertiary contact matrix of proteins. We observed that information retention is fold-class dependent: the prebiotic set sufficiently encodes the structure space of α/ß and α + ß folds, and to a lesser extent, of all-α and all-ß folds. The prebiotic set appeared insufficient to encode the small proteins. Assessing how well the prebiotic set discriminates native vs. incorrect sequence-structure matches, we found that α/ß and α + ß folds exhibit more pronounced energy gaps with the prebiotic set than with nearly all alternatives. CONCLUSIONS: The prebiotic set optimally encodes local backbone structures that appear in the folded environment and near-optimally encodes the tertiary contact matrix of extant proteins. The fold-class-specific patterns observed from our structural analysis confirm the postulated timeline of fold appearance in proteogenesis derived from proteomic sequence analyses. Polypeptides arising in a prebiotic environment will likely form α/ß and α + ß-like folds if any at all. We infer that the progressive expansion of the alphabet allowed the increased conformational stability and functional specificity of later folds, including all-α, all-ß, and small proteins. Our results suggest that prebiotic sequences are amenable to mutations that significantly lower native conformational energies and increase discrimination amidst incorrect folds. This property may have assisted the genesis of functional proto-enzymes prior to the expansion of the full amino acid alphabet.


Assuntos
Aminoácidos/metabolismo , Origem da Vida , Proteínas/química , Sequência de Aminoácidos , Método de Monte Carlo , Mutagênese/genética , Conformação Proteica , Domínios Proteicos , Dobramento de Proteína , Proteínas/genética
13.
Nature ; 571(7766): 546-549, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31292542

RESUMO

Amide bond formation is one of the most important reactions in both chemistry and biology1-4, but there is currently no chemical method of achieving α-peptide ligation in water that tolerates all of the 20 proteinogenic amino acids at the peptide ligation site. The universal genetic code establishes that the biological role of peptides predates life's last universal common ancestor and that peptides played an essential part in the origins of life5-9. The essential role of sulfur in the citric acid cycle, non-ribosomal peptide synthesis and polyketide biosynthesis point towards thioester-dependent peptide ligations preceding RNA-dependent protein synthesis during the evolution of life5,9-13. However, a robust mechanism for aminoacyl thioester formation has not been demonstrated13. Here we report a chemoselective, high-yielding α-aminonitrile ligation that exploits only prebiotically plausible molecules-hydrogen sulfide, thioacetate12,14 and ferricyanide12,14-17 or cyanoacetylene8,14-to yield α-peptides in water. The ligation is extremely selective for α-aminonitrile coupling and tolerates all of the 20 proteinogenic amino acid residues. Two essential features enable peptide ligation in water: the reactivity and pKaH of α-aminonitriles makes them compatible with ligation at neutral pH and N-acylation stabilizes the peptide product and activates the peptide precursor to (biomimetic) N-to-C peptide ligation. Our model unites prebiotic aminonitrile synthesis and biological α-peptides, suggesting that short N-acyl peptide nitriles were plausible substrates during early evolution.


Assuntos
Evolução Química , Nitrilos/química , Nitrilos/síntese química , Origem da Vida , Peptídeos/química , Peptídeos/síntese química , Água/química , Acetileno/análogos & derivados , Acetileno/química , Dipeptídeos/síntese química , Dipeptídeos/química , Ferricianetos/química , Sulfeto de Hidrogênio/química , Concentração de Íons de Hidrogênio , Oxirredução , Compostos de Sulfidrila/química , Sulfetos/química
14.
Orig Life Evol Biosph ; 49(3): 163-185, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31327111

RESUMO

In line with the postulated intermediacy of aminoxazoles derived from small sugars toward the direct assembly of nucleoside precursors, we show here a potential prebiotic scenario where aminoxazolines might have also played further roles as complexing and/or sequestering agents of other primeval blocks, namely amino acids. To this end, a bis-aminoxazoline derivative, generated from dihydroxyacetone and cyanamide, gives rise to stable co-crystal forms with dicarboxylic amino acids (Asp and Glu), while ionic interactions owing to proton transfer are inferred from spectroscopic data in aqueous solution. The structure of a 1:2 aminoxazoline: aspartic acid complex, discussed in detail, was elucidated by X-ray diffractometry. Optimized geometries of such ionic structures with bulk aqueous solvation were assessed by DFT calculations, which disclose preferential arrangements that validate the experimental data. Peripherally, we were able to detect in a few cases amino acid dimerization (i.e. dipeptide formation) after prolonged incubation with the bis-aminoxazole derivative. A mechanistic simulation aided by computation provides some predictive conclusions for future explorations and catalytic design.


Assuntos
Aminoácidos/química , Origem da Vida , Oxazóis/química , Biologia Computacional
15.
J Phys Chem Lett ; 10(15): 4192-4196, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31305079

RESUMO

We report the successful one-pot synthesis of adenosine mono-, di-, and triphosphate in the confined space of a mordenite zeolite. This is also the first report of ATP synthesized onto a porous mineral surface. The results revealed a plausible prebiotic route to ribonucleotides and highlighted the contribution of microporous minerals in the origins of life.


Assuntos
Difosfato de Adenosina/síntese química , Monofosfato de Adenosina/síntese química , Trifosfato de Adenosina/síntese química , Silicatos de Alumínio/química , Nanopartículas/química , Técnicas de Síntese em Fase Sólida/métodos , Zeolitas/química , Adenina/química , Organofosfatos/química , Origem da Vida , Porosidade , Ribose/química , Propriedades de Superfície , Termodinâmica , Fatores de Tempo
16.
Biosystems ; 183: 103984, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31201829

RESUMO

Cells must have preceded by simpler chemical systems (protocells) that had the capacity of a spontaneous self-assembly process and the ability to confine chemical reaction networks together with a form of information. The presence of lipid molecules in the early Earth conditions is sufficient to ensure the occurrence of spontaneous self-assembly processes, not defined by genetic information, but related to their chemical amphiphilic nature. Ribozymes are plausible molecules for early life, being the first small polynucleotides made up of random oligomers or formed by non-enzymatic template copying. Compartmentalization represents a strategy for the evolution of ribozymes; the attachment of ribozymes to surfaces, such as formed by lipid micellar aggregates may be particular relevant if the surface itself catalyzes RNA polymerization.It is conceivable that the transition from pre-biotic molecular aggregates to cellular life required the coevolution of the RNA world, capable of synthesizing specific, instead of statistical proteins, and of the Lipid world, with a transition from micellar aggregates to semipermeable vesicles. Small molecules available in the prebiotic inventory might promote RNA stability and the evolution of hydrophobic micellar aggregates into membrane-delimited vesicles. The transition from ribozymes catalyzing the assembly of statistical polypeptides to the synthesis of proteins, required the appearance of the genetic code; the transition from hydrophobic platforms favoring the stability of ribozymes and of nascent polypeptides to the selective transport of reagents through a membrane, required the appearance of the signal transduction code.A further integration between the RNA and Lipid worlds can be advanced, taking into account the emerging roles of phospholipid aggregates not only in ensuring stability to ribozymes by compartmentalization, but also in a crucial step of evolution through natural selection mechanisms, based on signal transduction pathways that convert environmental changes into biochemical responses that could vary according to the context. Here I present evidences on the presence of traces of the evolution of a signal transduction system in extant cells, which utilize a phosphoinositide signaling system located both at nucleoplasmic level as well as at the plasma membrane, based on the very same molecules but responding to different rules. The model herewith proposed is based on the following assumptions on the biomolecules of extant organisms: i) amphiphils can be converted into structured aggregates by hydrophobic forces thus giving rise to functional platforms for the interaction of other biomolecules and to their compartmentalization; ii) fundamental biochemical pathways, including protein synthesis, can be sustained by natural ribozymes of ancient origin; iii) ribozymes and nucleotide-derived coenzymes could have existed long before protein enzymes emerged; iv) signaling molecules, both derived from phospholipids and from RNAs could have guided the evolution of complex metabolic processes before the emergence of proteins.


Assuntos
Código Genético , Origem da Vida , RNA Catalítico/fisiologia , RNA/genética , Animais , Archaea , Células Artificiais , Bactérias , Evolução Biológica , Núcleo Celular/metabolismo , Humanos , Lipoproteínas/metabolismo , Modelos Biológicos , Nucleotídeos , Biossíntese de Proteínas , Seleção Genética , Transdução de Sinais
17.
Nucleic Acids Res ; 47(13): 6569-6577, 2019 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-31170298

RESUMO

The RNA World hypothesis posits that RNA was once responsible for genetic information storage and catalysis. However, a prebiotic mechanism has yet to be reported for the replication of duplex RNA that could have operated before the emergence of polymerase ribozymes. Previously, we showed that a viscous solvent enables information transfer from one strand of long RNA duplex templates, overcoming 'the strand inhibition problem'. Here, we demonstrate that the same approach allows simultaneous information transfer from both strands of long duplex templates. An additional challenge for the RNA World is that structured RNAs (like those with catalytic activity) function poorly as templates in model prebiotic RNA synthesis reactions, raising the question of how a single sequence could serve as both a catalyst and as a replication template. Here, we show that a viscous solvent also facilitates the transition of a newly synthesized hammerhead ribozyme sequence from its inactive, duplex state to its active, folded state. These results demonstrate how fluctuating environmental conditions can allow a ribozyme sequence to alternate between acting as a template for replication and functioning as a catalyst, and illustrate the potential for temporally changing environments to enable molecular processes necessary for the origin of life.


Assuntos
Modelos Genéticos , Origem da Vida , RNA Catalítico/efeitos dos fármacos , RNA de Cadeia Dupla/genética , Solventes/farmacologia , Moldes Genéticos , Catálise , Eletroforese em Gel de Ágar , Técnicas In Vitro , Conformação de Ácido Nucleico , Oligorribonucleotídeos/genética , Oligorribonucleotídeos/metabolismo , RNA Catalítico/metabolismo , RNA de Cadeia Dupla/biossíntese , Viscosidade
18.
ACS Chem Biol ; 14(6): 1243-1248, 2019 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-31181897

RESUMO

Owing to their ability to encapsulate biomolecules, complex coacervates formed by associative phase separation of oppositely charged polyelectrolytes have been postulated as prebiotic nonmembranous compartments (NMCs). Recent studies show that NMCs sequester RNA and enhance ribozyme reactions, a critical tenet of the RNA World Hypothesis. As RNA is negatively charged, it is expected to interact with polycationic coacervate components. The molecular basis for how identity and concentration of polyanionic components of complex coacervates affect ribozyme catalysis remains unexplored. We report here a general mechanism wherein diverse polyanions enhance ribozyme catalysis in complex coacervates. By competing for unproductive RNA-polycation interactions, polyanions enhance ribozyme reaction more than 12-fold. The generality of our findings is supported by similar behavior in three polyanions-polycarboxylates, polysulfates, and polysulfates/carboxylates-as well as two different ribozymes, the hammerhead and hairpin. These results reveal potential roles for polyanions in prebiotic chemistry and extant biology.


Assuntos
Polímeros/metabolismo , RNA Catalítico/metabolismo , Catálise , Origem da Vida
19.
Orig Life Evol Biosph ; 49(1-2): 77-88, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31222432

RESUMO

A new definition of life is proposed and discussed in the present article. It is formulated by modifying and extending NASA's working definition of life, which postulates that life is a "self-sustaining chemical system capable of Darwinian evolution". The new definition includes a thermodynamical aspect of life as a far from equilibrium system and considers the flow of information from the environment to the living system. In our derivation of the definition of life we have assumed the hypothesis, that during the emergence of life evolution had to first involve autocatalytic systems that only subsequently acquired the capacity of genetic heredity. The new proposed definition of life is independent of the mode of evolution, regardless of whether Lamarckian or Darwinian evolution operated at the origins of life and throughout evolutionary history. The new definition of life presented herein is formulated in a minimal manner and it is general enough that it does not distinguish between individual (metabolic) network and the collective (ecological) one. The newly proposed definition of life may be of interest for astrobiology, research into the origins of life or for efforts to produce synthetic or artificial life, and it furthermore may also have implications in the cognitive and computer sciences.


Assuntos
Evolução Biológica , Vida , Origem da Vida , Termodinâmica
20.
Nature ; 569(7754): 47-49, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-31043723

Assuntos
Ferro , Origem da Vida
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA