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Residue-specific Incorporation of Noncanonical Amino Acids into Model Proteins Using an Escherichia coli Cell-free Transcription-translation System
Published on: August 1, 2016
Transfer RNA paralogs: evidence for genetic code-amino acid biosynthesis coevolution and an archaeal root of life
Hong Xue1, Ka-Lok Tong, Christian Marck
1Department of Biochemistry and Applied Genomics Center, Hong Kong University of Science and Technology, Hong Kong, China.
Abstract:
A search has been performed on 2878 tRNA sequences from 60 different genomes in order to detect the existence of closely related 'alloacceptor' tRNAs accepting dissimilar amino acids that could be paralogs generated by gene duplications. This has led to the identification of extremely conserved tRNA(Phe)-tRNA(Tyr) pairs displaying as high as 94% identity between them, and also other potentially paralogous tRNA pairs in archaeal species. These paralogous pairs are enriched for amino acid pairs belonging to the same amino acid biosynthetic family, thus providing evidence for the coevolution of genetic code and amino acid biosynthesis. Overall, the genetic distances between alloacceptor tRNAs yield estimates of how closely clustered in sequence space are the tRNAs in a genome. Among 34 Bacteria, 18 Archaea and 8 Eukarya, Methanopyrus kandleri and Aeropyrum pernix have yielded the lowest alloacceptor distances and largest number of paralogous pairs. Based on a cluster-dispersion model of tRNA evolution, such tight alloacceptor clustering is a measure of primitiveness of tRNA genotypes, and places last universal common ancestor (LUCA) between the branches leading to these two archaea in the tRNA phylogenetic tree.
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