Characterization Of Redundant Trna(Ile)S With Cau And Uau Anticodons In Lactobacillus Plantarum

In most eubacteria, the minor AUA isoleucine codon is decoded by tRNA(Ile2), which has a lysidine (L) in the anticodon loop. The lysidine is introduced by tRNA(Ile)-lysidine synthetase (TilS) through post-transcriptional modification of cytidine to yield an LAU anticodon. Some bacteria, Lactobacillus plantarum for example, possess two tRNA(Ile2)(UAU) genes in addition to, two tRNA(Ile2)(CAU) genes and the tilS gene. tRNA expression from all these genes would generate redundancy in a tRNA that decodes a rare AUA codon. In this study, we investigated the tRNA expression from these genes in L. plantarum and characterized the corresponding tRNAs. The tRNA(Ile2)(CAU) gene products are modified by TilS to produce tRNA(Ile2)(LAU), while tRNA(Ile2)(UAU) lacks modification especially in the anticodon sequence. We found that tRNA(Ile2)(LAU) is charged with isoleucine but tRNA(Ile2)(UAU) is not. Our results suggest that the tRNA(Ile2) redundancy may be related to different roles of these tRNAs in the cell.