PMID:15941983
| Citation |
Das, G, Dineshkumar, TK, Thanedar, S and Varshney, U (2005) Acquisition of a stable mutation in metY allows efficient initiation from an amber codon in Escherichia coli. Microbiology (Reading, Engl.) 151:1741-50 |
|---|---|
| Abstract |
Escherichia coli strains harbouring elongator tRNAs that insert amino acids in response to a termination codon during elongation have been generated for various applications. Additionally, it was shown that expression of an initiator tRNA containing a CUA anticodon from a multicopy plasmid in E. coli resulted in initiation from an amber codon. Even though the initiation-based system remedies toxicity-related drawbacks, its usefulness has remained limited for want of a strain with a chromosomally encoded initiator tRNA 'suppressor'. E. coli K strains possess four initiator tRNA genes: the metZ, metW and metV genes, located at a single locus, encode tRNA(1)(fMet), and a distantly located metY gene encodes a variant, tRNA(2)(fMet). In this study, a stable strain of E. coli K-12 that affords efficient initiation from an amber initiation codon was isolated. Genetic analysis revealed that the metY gene in this strain acquired mutations to encode tRNA(2)(fMet) with a CUA anticodon (a U35A36 mutation). The acquisition of the mutations depended on the presence of a plasmid-borne copy of the mutant metY and recA(+) host background. The mutations were observed when the plasmid-borne gene encoded tRNA(2)(fMet) (U35A36) with additional changes in the acceptor stem (G72; G72G73) but not in the anticodon stem (U29C30A31/U35A36/psi39G40A41). The usefulness of this strain, and a possible role for multiple tRNA(1)(fMet) genes in E. coli in safeguarding their intactness, are discussed. |
| Links |
PubMed Online version:10.1099/mic.0.27915-0 |
| Keywords |
Anticodon/genetics; Base Sequence; Codon, Terminator; Escherichia coli/genetics; Gene Dosage; Molecular Sequence Data; Peptide Chain Initiation, Translational/genetics; Plasmids; Point Mutation; RNA, Bacterial/genetics; RNA, Bacterial/physiology; RNA, Transfer, Met/genetics; RNA, Transfer, Met/physiology; Rec A Recombinases |
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