title: Decoding system for the AUA codon by tRNAIle with the UAU anticodon in Mycoplasma mobile.
abstract: Deciphering the genetic code is a fundamental process in all living organisms. In many bacteria, AUA codons are deciphered by tRNA(Ile2) bearing lysidine (L) at the wobble position. L is a modified cytidine introduced post-transcriptionally by tRNA(Ile)-lysidine synthetase (TilS). Some bacteria, including Mycoplasma mobile, do not carry the tilS gene, indicating that they have established a different system to decode AUA codons. In this study, tRNA(Ile2) has been isolated from M. mobile and was found to contain a UAU anticodon without any modification. Mycoplasma mobile isoleucyl-tRNA synthetase (IleRS) recognized the UAU anticodon, whereas Escherichia coli IleRS did not efficiently aminoacylate tRNA(Ile2)(UAU). In M. mobile IleRS, a single Arg residue at position 865 was critical for specificity for the UAU anticodon and, when the corresponding site (W905) in E. coli IleRS was substituted with Arg, the W905R mutant efficiently aminoacylated tRNA with UAU anticodon. Mycoplasma mobile tRNA(Ile2) cannot distinguish between AUA and AUG codon on E. coli ribosome. However, on M. mobile ribosome, M. mobile tRNA(Ile2)(UAU) specifically recognized AUA codon, and not AUG codon, suggesting M. mobile ribosome has a property that prevents misreading of AUG codon. These findings provide an insight into the evolutionary reorganization of the AUA decoding system.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Kenjyo
authors.initials: K
authors.lastname: Miyauchi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nakane
authors.forename: Makoto
authors.initials: M
authors.lastname: Miyata
authors.forename: Akira
authors.initials: A
authors.lastname: Muto
authors.forename: Susumu
authors.initials: S
authors.lastname: Nishimura
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000595:Amino Acid Sequence; D000926:Anticodon / Q000737:chemistry*; D001120:Arginine / Q000737:chemistry; D003062:Codon / Q000737:chemistry*; D007533:Isoleucine-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009174:Mycoplasma / Q000201:enzymology / Q000235:genetics*; D012355:RNA, Transfer, Ile / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D000926:Anticodon; D003062:Codon; D012355:RNA, Transfer, Ile; D001120:Arginine; D007533:Isoleucine-tRNA Ligase