Journal
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Volume 12, Issue 7, Pages 4745-4757Publisher
MDPI
DOI: 10.3390/ijms12074745
Keywords
homochirality; amino acid; RNA; aminoacylation; stereochemistry; extended double helix; origin of life
Funding
- PRESTO
- Japan Science and Technology Agency (JST), Japan
- Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
- Grants-in-Aid for Scientific Research [23657160] Funding Source: KAKEN
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The chiral-selective aminoacylation of an RNA minihelix is a potential progenitor to modern tRNA-based protein synthesis using L-amino acids. This article describes the molecular basis for this chiral selection. The extended double helical form of an RNA minihelix with a CCA triplet (acceptor of an amino acid), an aminoacyl phosphate donor nucleotide (mimic of aminoacyl-AMP), and a bridging nucleotide facilitates chiral-selective aminoacylation. Energetically, the reaction is characterized by a downhill reaction wherein an amino acid migrates from a high-energy acyl phosphate linkage to a lower-energy carboxyl ester linkage. The reaction occurs under the restriction that the nucleophilic attack of O, from 3'-OH in the terminal CCA, to C, from C=O in the acyl phosphate linkage, must occur at a Burgi-Dunitz angle, which is defined as the O-C=O angle of approximately 105 degrees. The extended double helical form results in a steric hindrance at the side chain of the amino acid leading to chiral preference combined with cation coordinations in the amino acid and the phosphate oxygen. Such a system could have developed into the protein biosynthetic system with an exclusively chiral component (L-amino acids) via (proto) ribosomes.
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