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


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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    • "" In a review, Leslie Orgel expressed that, " The relevance of all of this early work to the origin of life has been questioned because it now seems very unlikely that the Earth's atmosphere was ever as strongly reducing as Miller and Urey assumed. " (Orgel, 2004). "
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    DESCRIPTION: This article was presented as an invited talk at 100th Indian Science Congress (Video: ) and also presented in several universities and colleges. A html version of the same can also be found at:
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    • "HCN provides a biologically accessible source of reduced nitrogen (Zahnle 1986). Its presence has been invoked for a variety of prebiotic chemistry studies (see e.g., Ritson and Sutherland 2012, Ferris and Hagan 1984, Orgel 2004). "
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    ABSTRACT: Ultraviolet (UV) radiation is common to most planetary environments, and could play a key role in the chemistry of molecules relevant to abiogenesis (prebiotic chemistry). In this work, we explore the impact of UV light on prebiotic chemistry that might occur in liquid water on the surface of a planet with an atmosphere. We consider effects including atmospheric absorption, attenuation by water, and stellar variability to constrain the UV input as a function of wavelength. We conclude that the UV environment would be characterized by broadband input, and wavelengths below 204 nm and 168 nm would be shielded out by atmospheric CO2 and water, respectively. We compare this broadband prebiotic UV input to the narrowband UV sources (e.g. mercury lamps) often used in laboratory studies of prebiotic chemistry, and explore the implications for the conclusions drawn from these experiments. We consider as case studies the ribonucleotide synthesis pathway of Powner et al (2009) and the sugar synthesis pathway of Ritson et al (2012). Irradiation by narrowband UV light from a mercury lamp formed an integral component of these studies: we quantitatively explore the impact of more realistic UV input on the conclusions that can be drawn from these experiments. Finally, we explore the constraints solar UV input places on the buildup of prebiotically important feedstock gasses like CH4 and HCN. Our results demonstrate the importance of characterizing the wavelength dependence (action spectra) of prebiotic synthesis pathways to determine how pathways derived under laboratory irradiation conditions will function under planetary prebiotic conditions. Keywords: Laboratory Investigations; Origin of Life; Planetary Environments; UV Radiation; RNA World
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    • "The question can largely be reduced to the question of what was the first informational system that was able to self-replicate and evolve under the assumedly very harsh early Earth conditions. Of the origin-of-life hypotheses, the RNA world hypothesis (Gilbert, 1986; Orgel, 2004; Robertson and Joyce, 2012) has received most attention. However, RNA with both replicative and catalytic functions is difficult to produce and would probably not have been stable under the harsh prebiotic conditions. "
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    ABSTRACT: The question of the origin of life on Earth can largely be reduced to the question of what was the first molecular replicator system that was able to replicate and evolve under the presumably very harsh conditions on the early Earth. It is unlikely that a functional RNA could have existed under such conditions and it is generally assumed that some other kind of information system preceded the RNA world. Here, I present an informational molecular system that is stable, self-replicative, environmentally responsive, and evolvable under conditions characterized by high temperatures, ultraviolet and cosmic radiation. This postulated pregenetic system is based on the amyloid fold, a functionally unique polypeptide fold characterized by a cross beta-sheet structure in which the beta strands are arranged perpendicular to the fiber axis. Beside an extraordinary structural robustness, the amyloid fold posses a unique ability to transmit information by a three-dimensional templating mechanism. In amyloidogenesis short peptide monomers are added one by one to the growing end of the fiber. From the same monomeric subunits several structural variants of amyloid may be formed. Then, in a self-replicative mode, a specific amyloid conformer can act as a template and confer its spatially encoded information to daughter molecular entities in a repetitive way. In this process, the specific conformational information, the spatially changed organization, is transmitted; the coding element is the steric zipper structure, and recognition occurs by amino acid side chain complementarity. The amyloid information system fulfills several basic requirements of a primordial evolvable replicator system: (i) it is stable under the presumed primitive Earth conditions, (ii) the monomeric building blocks of the informational polymer can be formed from available prebiotic compounds, (iii) the system is self-assembling and self-replicative and (iv) it is adaptive to changes in the environment and evolvable. Copyright © 2015. Published by Elsevier Ltd.
    Journal of Theoretical Biology 07/2015; 382. DOI:10.1016/j.jtbi.2015.07.008 · 2.12 Impact Factor
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