Alternative genetic code for amino acids and transfer RNA revisited

2013 ◽  
Vol 4 (3) ◽  
pp. 309-318 ◽  
Author(s):  
Kiyofumi Hamashima ◽  
Akio Kanai
Keyword(s):  
Genetic Code ◽  
Translational Control ◽  
Trna Synthetase ◽  
Evolutionary Divergence ◽  
Aminoacyl Trna Synthetase ◽  
Standard Genetic Code ◽  
Standard Code ◽  
Rna Biosynthesis ◽  
Nematode Worm ◽  
Eukaryotic Genomes

AbstractThe genetic code is highly conserved among all organisms and its evolution is thought to be strictly limited. However, an increasing number of studies have reported non-standard codes in prokaryotic and eukaryotic genomes. Most of these deviations from the standard code are attributable to tRNA changes relating to, for example, codon/anticodon base pairing and tRNA/aminoacyl-tRNA synthetase recognition. In this review, we focus on tRNA, a key molecule in the translation of the genetic code, and summarize the most recently published information on the evolutionary divergence of the tRNAs. Surprisingly, although higher eukaryotes, such as the nematode (worm), utilize the standard genetic code, newly identified nematode-specific tRNAs (nev-tRNAs) translate nucleotides in a manner that transgresses the code. Furthermore, a variety of additional functions of tRNAs, beyond their translation of the genetic code, have emerged rapidly. We also review these intriguing new aspects of tRNA, which have potential impacts on translational control, RNA silencing, antibiotic resistance, RNA biosynthesis, and transcriptional regulation.

scholarly journals Combinatorial Fusion Rules to Describe Codon Assignment in the Standard Genetic Code

Life ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 4
Author(s):  
Alexander Nesterov-Mueller ◽  
Roman Popov ◽  
Hervé Seligmann
Keyword(s):  
Amino Acids ◽  
Genetic Code ◽  
State Of The Art ◽  
Trna Synthetase ◽  
Aminoacyl Trna Synthetase ◽  
Standard Genetic Code ◽  
Fusion Rules ◽  
Hydrophobic Amino Acids ◽  
Combinatorial Fusion ◽  
Small Hydrophobic

We propose combinatorial fusion rules that describe the codon assignment in the standard genetic code simply and uniformly for all canonical amino acids. These rules become obvious if the origin of the standard genetic code is considered as a result of a fusion of four protocodes: Two dominant AU and GC protocodes and two recessive AU and GC protocodes. The biochemical meaning of the fusion rules consists of retaining the complementarity between cognate codons of the small hydrophobic amino acids and large charged or polar amino acids within the protocodes. The proto tRNAs were assembled in form of two kissing hairpins with 9-base and 10-base loops in the case of dominant protocodes and two 9-base loops in the case of recessive protocodes. The fusion rules reveal the connection between the stop codons, the non-canonical amino acids, pyrrolysine and selenocysteine, and deviations in the translation of mitochondria. Using fusion rules, we predicted the existence of additional amino acids that are essential for the development of the standard genetic code. The validity of the proposed partition of the genetic code into dominant and recessive protocodes is considered referring to state-of-the-art hypotheses. The formation of two aminoacyl-tRNA synthetase classes is compatible with four-protocode partition.

scholarly journals Pyrrolysyl-tRNA Synthetase, an Aminoacyl-tRNA Synthetase for Genetic Code Expansion

2016 ◽  
Vol 89 (2) ◽  
Author(s):  
Ana Crnković ◽  
Tateki Suzuki ◽  
Dieter Söll ◽  
Noah M. Reynolds
Keyword(s):  
Genetic Code ◽  
Trna Synthetase ◽  
Aminoacyl Trna Synthetase ◽  
Genetic Code Expansion

scholarly journals Did Amino Acid Side Chain Reactivity Dictate the Composition and Timing of Aminoacyl-tRNA Synthetase Evolution?

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 409
Author(s):  
Tamara L. Hendrickson ◽  
Whitney N. Wood ◽  
Udumbara M. Rathnayake
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Genetic Code ◽  
Chemical Reactivity ◽  
Trna Synthetase ◽  
Amino Acid Side Chain ◽  
Standard Genetic Code ◽  
Last Universal Common Ancestor ◽  
Trna Synthetases ◽  
Universal Common Ancestor

The twenty amino acids in the standard genetic code were fixed prior to the last universal common ancestor (LUCA). Factors that guided this selection included establishment of pathways for their metabolic synthesis and the concomitant fixation of substrate specificities in the emerging aminoacyl-tRNA synthetases (aaRSs). In this conceptual paper, we propose that the chemical reactivity of some amino acid side chains (e.g., lysine, cysteine, homocysteine, ornithine, homoserine, and selenocysteine) delayed or prohibited the emergence of the corresponding aaRSs and helped define the amino acids in the standard genetic code. We also consider the possibility that amino acid chemistry delayed the emergence of the glutaminyl- and asparaginyl-tRNA synthetases, neither of which are ubiquitous in extant organisms. We argue that fundamental chemical principles played critical roles in fixation of some aspects of the genetic code pre- and post-LUCA.

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