title: Crystal structure of tRNA adenosine deaminase (TadA) from Aquifex aeolicus.
abstract: The bacterial tRNA adenosine deaminase (TadA) generates inosine by deaminating the adenosine residue at the wobble position of tRNA(Arg-2). This modification is essential for the decoding system. In this study, we determined the crystal structure of Aquifex aeolicus TadA at a 1.8-A resolution. This is the first structure of a deaminase acting on tRNA. A. aeolicus TadA has an alpha/beta/alpha three-layered fold and forms a homodimer. The A. aeolicus TadA dimeric structure is completely different from the tetrameric structure of yeast CDD1, which deaminates mRNA and cytidine, but is similar to the dimeric structure of yeast cytosine deaminase. However, in the A. aeolicus TadA structure, the shapes of the C-terminal helix and the regions between the beta4 and beta5 strands are quite distinct from those of yeast cytosine deaminase and a large cavity is produced. This cavity contains many conserved amino acid residues that are likely to be involved in either catalysis or tRNA binding. We made a docking model of TadA with the tRNA anticodon stem loop.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kuratani
authors.forename: Ryohei
authors.initials: R
authors.lastname: Ishii
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Bessho
authors.forename: Ryuya
authors.initials: R
authors.lastname: Fukunaga
authors.forename: Toru
authors.initials: T
authors.lastname: Sengoku
authors.forename: Mikako
authors.initials: M
authors.lastname: Shirouzu
authors.forename: Shun-Ichi
authors.initials: S
authors.lastname: Sekine
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000243:Adenosine Deaminase / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D006090:Gram-Negative Bacteria / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012347:RNA, Transfer, Arg / Q000378:metabolism; D016601:RNA-Binding Proteins; D016415:Sequence Alignment; D015032:Zinc / Q000378:metabolism
chemical_list: D012347:RNA, Transfer, Arg; D016601:RNA-Binding Proteins; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase; D015032:Zinc