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Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life
The present study proposes to search our solar system (Mars, Enceladus, Europa) for patterns of organic molecules that are universally associated with biological functions and structures. The functions are primarily catalytic because life could only have originated within volume/space-constrained co...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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Mary Ann Liebert, Inc., publishers
2018
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6211371/ https://www.ncbi.nlm.nih.gov/pubmed/30129781 http://dx.doi.org/10.1089/ast.2018.1868 |
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author | Georgiou, Christos D. |
author_facet | Georgiou, Christos D. |
author_sort | Georgiou, Christos D. |
collection | PubMed |
description | The present study proposes to search our solar system (Mars, Enceladus, Europa) for patterns of organic molecules that are universally associated with biological functions and structures. The functions are primarily catalytic because life could only have originated within volume/space-constrained compartments containing chemical reactions catalyzed by certain polymers. The proposed molecular structures are specific groups in the side chains of amino acids with the highest catalytic propensities related to life on Earth, that is, those that most frequently participate as key catalytic groups in the active sites of enzymes such as imidazole, thiol, guanidinium, amide, and carboxyl. Alternatively, these or other catalytic groups can be searched for on non-amino-acid organic molecules, which can be tested for certain hydrolytic catalytic activities. The first scenario assumes that life may have originated in a similar manner as the terrestrial set of α-amino acids, while the second scenario does not set such a requirement. From the catalytic propensity perspective proposed in the first scenario, life must have invented amino acids with high catalytic propensity (His, Cys, Arg) in order to overcome, and be complemented by, the low catalytic propensity of the initially available abiogenic amino acids. The abiogenic and the metabolically invented amino acids with the lowest catalytic propensity can also serve as markers of extraterrestrial life when searching for patterns on the basis of the following functional propensities related to protein secondary/quaternary structure: (1) amino acids that are able to form α-helical intramembrane peptide domains, which can serve as primitive transporters in protocell membrane bilayers and catalysts of simple biochemical reactions; (2) amino acids that tend to accumulate in extremophile proteins of Earth and possibly extraterrestrial life. The catalytic/structural functional propensity approach offers a new perspective in the search for extraterrestrial life and could help unify previous amino acid–based approaches. |
format | Online Article Text |
id | pubmed-6211371 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | Mary Ann Liebert, Inc., publishers |
record_format | MEDLINE/PubMed |
spelling | pubmed-62113712018-11-02 Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life Georgiou, Christos D. Astrobiology Hypothesis Article The present study proposes to search our solar system (Mars, Enceladus, Europa) for patterns of organic molecules that are universally associated with biological functions and structures. The functions are primarily catalytic because life could only have originated within volume/space-constrained compartments containing chemical reactions catalyzed by certain polymers. The proposed molecular structures are specific groups in the side chains of amino acids with the highest catalytic propensities related to life on Earth, that is, those that most frequently participate as key catalytic groups in the active sites of enzymes such as imidazole, thiol, guanidinium, amide, and carboxyl. Alternatively, these or other catalytic groups can be searched for on non-amino-acid organic molecules, which can be tested for certain hydrolytic catalytic activities. The first scenario assumes that life may have originated in a similar manner as the terrestrial set of α-amino acids, while the second scenario does not set such a requirement. From the catalytic propensity perspective proposed in the first scenario, life must have invented amino acids with high catalytic propensity (His, Cys, Arg) in order to overcome, and be complemented by, the low catalytic propensity of the initially available abiogenic amino acids. The abiogenic and the metabolically invented amino acids with the lowest catalytic propensity can also serve as markers of extraterrestrial life when searching for patterns on the basis of the following functional propensities related to protein secondary/quaternary structure: (1) amino acids that are able to form α-helical intramembrane peptide domains, which can serve as primitive transporters in protocell membrane bilayers and catalysts of simple biochemical reactions; (2) amino acids that tend to accumulate in extremophile proteins of Earth and possibly extraterrestrial life. The catalytic/structural functional propensity approach offers a new perspective in the search for extraterrestrial life and could help unify previous amino acid–based approaches. Mary Ann Liebert, Inc., publishers 2018-11-01 2018-10-26 /pmc/articles/PMC6211371/ /pubmed/30129781 http://dx.doi.org/10.1089/ast.2018.1868 Text en © Christos D. Georgiou, 2018; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. |
spellingShingle | Hypothesis Article Georgiou, Christos D. Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life |
title | Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life |
title_full | Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life |
title_fullStr | Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life |
title_full_unstemmed | Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life |
title_short | Functional Properties of Amino Acid Side Chains as Biomarkers of Extraterrestrial Life |
title_sort | functional properties of amino acid side chains as biomarkers of extraterrestrial life |
topic | Hypothesis Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6211371/ https://www.ncbi.nlm.nih.gov/pubmed/30129781 http://dx.doi.org/10.1089/ast.2018.1868 |
work_keys_str_mv | AT georgiouchristosd functionalpropertiesofaminoacidsidechainsasbiomarkersofextraterrestriallife |