title: Transfer RNA mutation and the malleability of the genetic code.
abstract: We propose that evolutionary reassignment of codons is facilitated by a translationally ambiguous intermediate. For example, recently discovered tRNA mutations that allow relatively efficient simultaneous cognate and near-cognate coding (sharing 2 contiguous nt) in vivo may speed reassignment of the near-cognate codon. As predicted by this notion, characterized codon reassignments are strikingly non-random, and half can be immediately explained by unusual tRNA activities already demonstrated. In addition, sequences of reassigned tRNAs contain sequences that promote ambiguity. tRNA structural change may provide a transitional pathway that allows rapid selection of a new specificity, rather than slow mutation toward a new codon-amino acid association.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309-0347.
authors.forename: D W
authors.initials: DW
authors.lastname: Schultz
authors.forename: M
authors.initials: M
authors.lastname: Yarus
mesh_terms: D005075:Biological Evolution; D003062:Codon; D004926:Escherichia coli / Q000235:genetics; D005815:Genetic Code; D008957:Models, Genetic; D009154:Mutation; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D003062:Codon; D012343:RNA, Transfer