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An RNA-Modifying Enzyme that Governs Both the Codon and Amino Acid Specificities of Isoleucine tRNA

2003; Elsevier BV; Volume: 12; Issue: 3 Linguagem: Inglês

10.1016/s1097-2765(03)00346-0

1097-4164

Akiko Soma, Yoshiho Ikeuchi, Satoru Kanemasa, Kazuo Kobayashi, Naotake Ogasawara, Tomotake Ote, Junichi Kato, Kimitsuna Watanabe, Yasuhiko Sekine, Tsutomu Suzuki,

Bacterial Genetics and Biotechnology

The AUA codon-specific isoleucine tRNA (tRNAIle) in eubacteria has the posttranscriptionally modified nucleoside lysidine (L) at the wobble position of the anticodon (position 34). This modification is a lysine-containing cytidine derivative that converts both the codon specificity of tRNAIle from AUG to AUA and its amino acid specificity from methionine to isoleucine. We identified an essential gene (tilS; tRNAIle-lysidine synthetase) that is responsible for lysidine formation in both Bacillus subtilis and Escherichia coli. The recombinant enzyme complexed specifically with tRNAIle and synthesized L by utilizing ATP and lysine as substrates. The lysidine synthesis of this enzyme was shown to directly convert the amino acid specificity of tRNAIle from methionine to isoleucine in vitro. Partial inactivation of tilS in vivo resulted in an AUA codon-dependent translational defect, which supports the notion that TilS is an RNA-modifying enzyme that plays a critical role in the accurate decoding of genetic information.