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Life without the essential bacterial tRNA Ile2 –lysidine synthetase TilS: a case of tRNA gene recruitment in Bacillus subtilis
Author(s) -
Fabret Céline,
Dervyn Etienne,
Dalmais Bérengère,
Guillot Alain,
Marck Christian,
Grosjean Henri,
Noirot Philippe
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07630.x
Subject(s) - transfer rna , biology , bacillus subtilis , gene , wobble base pair , genetics , cytidine , mutant , methanococcus , genetic code , biochemistry , microbiology and biotechnology , rna , escherichia coli , enzyme , bacteria
Summary In eubacteria, the post‐transcriptional modification of the wobble cytidine of the C AU anticodon in a precursor tRNA Ile2 to a lysidine residue (2‐lysyl‐cytidine, abbreviated as L) allows the amino acid specificity to change from methionine to isoleucine and the codon decoding specificity to shift from AU G to AU A . The tilS gene encoding the enzyme that catalyses this modification is widely distributed. However, some microbial species lack a tilS gene, indicating that an alternative strategy exists to accurately translate the AU A codon into Ile. To determine whether a TilS‐dependent bacterium, such as Bacillus subtilis , can overcome the absence of lysidine in its tRNA Ile2 (CAU), we analysed the suppressor mutants of a tilS ‐thermosensitive allele. These tilS ‐suppressor mutants carry a substitution of the wobble guanosine into thymidine in one of the tRNA Ile1 genes (the original G AT anticodon is changed to a T AT). In absence of TilS activity, the AU A codons are translated into isoleucine by the suppressor tRNA Ile1 , although a low level of AU A codons is also mistranslated into methionine. Results are in agreement with rare cases of eubacteria (and archaea), which naturally lack the tilS gene (or tiaS in archaea) but contain a tRNA Ile2 gene containing a T AT instead of a C AT anticodon.