Journal
BIOSYSTEMS
Volume 114, Issue 3, Pages 155-163Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.biosystems.2013.09.002
Keywords
Suppressor tRNAs; Genetic code expansion; Synonymous codon usage; tRNA cloverleaf structure; Developmental stability
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Funding
- Fondecyt [1120181]
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Codons expanded by a silent position (quadruplet or tetracodons) may solve the conundrum that at life's origins, the weak tricodon-anticodon interactions could not promote translation in the absence of complex ribosomes. Modern genomes have isolated tetracodons resulting from insertion mutations. Some bioinformatic analyses suggest that tetracoding stretches overlap with regular mitochondrial protein coding genes. These tetragenes are probably decoded by (antisense) tRNAs with expanded anticodons. They are GC-rich, which produce stronger basepairs than A:T interactions, suggesting expression at high temperatures. The hypothesis that tetracoding is an adaptation to high temperatures is tested here by comparing predicted mitochondrial tetracoding in Lepidosauria (lizards, amphisbaenia, and Sphenodon), in relation to body temperature, expecting more tetracoding in species with high body temperature. The association between tRNAs with expanded anticodons and tetracoding previously described for mammals and Drosophila is confirmed for Lepidosauria. Independent evidence indicates that tetracoding increases with body temperature, supporting the hypothesis that tetracoding is an adaptation for efficient translation when conditions (temperature) make triplet codon-anticodons too unstable to allow efficient protein elongation. (C) 2013 Elsevier Ireland Ltd. All rights reserved.
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