Evolution and Relatedness in Two Aminoacyl-tRNA Synthetase Families

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 18; pp. 8121 - 8125
• Main Authors: Nagel, Glenn M., Doolittle, Russell F.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15.09.1991; National Acad Sciences
• Subjects: Acidic amino acids; Amino Acid Sequence; Amino acids; Biological and medical sciences; Biological Evolution; Enzymes; Evolution; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Mathematical sequences; Molecular Sequence Data; Multigene Family; Protein synthesis; Regional identity; RNA, Transfer, Amino Acyl - chemistry; RNA, Transfer, Amino Acyl - classification; RNA, Transfer, Amino Acyl - genetics; Sequence Alignment; Transfer RNA; Yeasts; Yeast; Rhizobium meliloti; Enzyme; Consensus sequence; Biological evolution; Bacteria; Multigene family; Rhizobiaceae; Aminoacyl-tRNA synthetase; Computer aid
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.18.8121

Sequence segments of about 140 amino acids in length, each containing a selected consensus region, were used in alignments of the aminoacyl-tRNA synthetases with the aim of discerning their evolutionary relationships. In all cases tested, enzymes specific for the same amino acid from a variety of organisms grouped together, reinforcing the supposition that the aminoacyl-tRNA synthetases are very ancient enzymes that evolved to include the full complement of 20 amino acids long before the divergence leading to prokaryotes and eukaryotes. The enzymes are divided into two mutually exclusive groups that appear to have evolved from independent roots. Group I, for which two sequence segments were analyzed, contains the enzymes specific for glutamic acid, glutamine, tryptophan, tyrosine, valine, leucine, isoleucine, methionine, and arginine. Group II enzymes include those activating threonine, proline, serine, lysine, aspartic acid, asparagine, histidine, alanine, glycine, and phenylalanine. Both groups contain a spectrum of amino acid types, suggesting the possibility that each could have once supported an independent system for protein synthesis. Within each group, enzymes specific for chemically similar amino acids tend to cluster together, indicating that a major theme of synthetase evolution involved the adaptation of binding sites to accommodate related amino acids with subsequent specialization to a single amino acid. In a few cases, however, synthetases activating dissimilar amino acids are grouped together.