Prebiotic Chemistry and the Origin of the RNA World

The Salk Institute, La Jolla, California 92097, USA.
Critical Reviews in Biochemistry and Molecular Biology (Impact Factor: 7.71). 03/2010; 39(2):99-123. DOI: 10.1080/10409230490460765
Source: PubMed

ABSTRACT The demonstration that ribosomal peptide synthesis is a ribozyme-catalyzed reaction makes it almost certain that there was once an RNA World. The central problem for origin-of-life studies, therefore, is to understand how a protein-free RNA World became established on the primitive Earth. We first review the literature on the prebiotic synthesis of the nucleotides, the nonenzymatic synthesis and copying of polynucleotides, and the selection of ribozyme catalysts of a kind that might have facilitated polynucleotide replication. This leads to a brief outline of the Molecular Biologists' Dream, an optimistic scenario for the origin of the RNA World. In the second part of the review we point out the many unresolved problems presented by the Molecular Biologists' Dream. This in turn leads to a discussion of genetic systems simpler than RNA that might have "invented" RNA. Finally, we review studies of prebiotic membrane formation.

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    • "ej. Orgel, 2004) 7 . El ARN en el mundo primitivo habría funcionado como una molécula autoreplicante hasta que eventualmente se desarrollaron estructuras con funciones catalíticas mínimas confinadas por una membrana de lípidos semi-impermeable (protocélula), donde luego se sintetizó el ADN, molécula precursora e indispensable para el funcionamiento de todos los seres vivos en el mundo celular que conocemos. "
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    ABSTRACT: The origin of life is rooted in the most primitive events of planetary evolution, events which were faithfully registered by the extraterrestrial bodies today called meteorites, and which formed the main constituent of rocky planets, such as Mercury, Venus, Earth and Mars. This register includes the chemical compounds precursors of life, as well as those high-energy events, whose nature could have accelerated the process of chemical evolution leading to life or delaying it.
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    • "Yet, we have no other choice at present but assuming that the RNA-World was initially absolutely " heterotrophic " , that is, the first RNA(-like) macromolecules were randomly assembled from activated modules which in turn were the products of so far largely unknown geochemical processes. " Black smokers " (hot and high pressure volcanic vents thousands of meters below sea level in the oceanbeds ) seem to be reasonably good candidates for having supplied the modules (Deamer and Weber, 2010; LaRowe and Regnier, 2008; Orgel, 2004), but we are still far from even an established hypothesis on this topic. Fortunately, there is much more known about the possibilities of non-template-directed RNA synthesis from activated monomers (nucleotides). "
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    ABSTRACT: Metabolically Coupled Replicator Systems (MCRS) are a family of models implementing a simple, physico-chemically and ecologically feasible scenario for the first steps of chemical evolution towards life. Evolution in an abiotically produced RNA-population sets in as soon as any one of the RNA molecules become autocatalytic by engaging in template directed self-replication from activated monomers, and starts increasing exponentially. Competition for the finite external supply of monomers ignites selection favouring RNA molecules with catalytic activity helping self-replication by any possible means. One way of providing such autocatalytic help is to become a replicase ribozyme. An additional way is through increasing monomer supply by contributing to monomer synthesis from external resources, i.e., by evolving metabolic enzyme activity. Retroevolution may build up an increasingly autotrophic, cooperating community of metabolic ribozymes running an increasingly complicated and ever more efficient metabolism. Maintaining such a cooperating community of metabolic replicators raises two serious ecological problems: one is keeping the system coexistent in spite of the different replicabilities of the cooperating replicators; the other is constraining parasitism, i.e., keeping "cheaters" in check. Surface-bound MCRS provide an automatic solution to both problems: coexistence and parasite resistance are the consequences of assuming the local nature of metabolic interactions. In this review we present an overview of results published in previous articles, showing that these effects are, indeed, robust in different MCRS implementations, by considering different environmental setups and realistic chemical details in a few different models. We argue that the MCRS model framework naturally offers a suitable starting point for the future modelling of membrane evolution and extending the theory to cover the emergence of the first protocell in a self-consistent manner. The coevolution of metabolic, genetic and membrane functions is hypothesized to follow the progressive sequestration scenario, the conceptual blueprint for the earliest steps of protocell evolution. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Theoretical Biology 06/2015; 381. DOI:10.1016/j.jtbi.2015.06.002 · 2.12 Impact Factor
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    • "amino acids, nucleic acid bases, phosphate and sugars etc.), which were either supplied abundantly or sufficiently stable to accumulate under primitive Earth conditions . Prebiotic syntheses of biomolecules from chemical precursors often suffer from low yields (Lucrezia et al. 2007; Orgel 2004; Lambert 2008; Shapiro 1999), thus the steady-state concentrations of amino acids (AAs) in the primitive oceans has been estimated to be on the order of 4 to 10 −7 mM (Lahav and Chang 1976; Stribling and Miller 1987).The stability of these molecules under the conditions (viz. ultra-violet, thermal, electric discharge etc.) prevalent on Earth when life started ~4.4–3.5 Ga ago may also have been an impediment to their accumulation (Cleaves et al. 2012). "
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    ABSTRACT: Earth is the only known planet bestowed with life. Several attempts have been made to explore the pathways of the origin of life on planet Earth. The search for the chemistry which gave rise to life has given answers related to the formation of biomonomers, and their adsorption on solid surfaces has gained much attention for the catalysis and stabilization processes related to the abiotic chemical evolution of the complex molecules of life. In this communication, surface interactions of L-leucine (Leu) on smectite (SMT) group of clay (viz. bentonite and montmorillonite) and their divalent metal ion (Mg2+, Ca2+ and Cu2+) incorporated on SMT has been studied to find the optimal conditions of time, pH, and concentration at ambient temperature (298 K). The progress of adsorption was followed spectrophotometrically and further characterized by FTIR, SEM/EDS and XRD. Leu, a neutral/non polar amino acid, was found to have more affinity in its zwitterionic form towards Cu2+- exchanged SMT and minimal affinity for Mg2+- exchanged SMT. The vibrational frequency shifts of —NH3 + and —COO− favor Van der Waal’s forces during the course of surface interaction. Quantum calculations using density functional theory (DFT) have been applied to investigate the absolute value of metal ion affinities of Leu (Leu—M2+ complex, M = Mg2+, Ca2+, Cu2+) with the help of their physico-chemical parameters. The hydration effect on the relative stability and geometry of the individual species of Leu—M2+ × (H2O)n, (n =2 and 4) has also been evaluated within the supermolecule approach. Evidence gathered from investigations of surface interactions, divalent metal ions affinities and hydration effects with biomolecules may be important for better understanding of chemical evolution, the stabilization of biomolecules on solid surfaces and biomolecular-metal interactions. These results may have implications for understanding the origin of life and the preservation of biomarkers.
    Origins of Life and Evolution of Biospheres 05/2015; · 1.11 Impact Factor
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