title: The C-terminal domain of the archaeal leucyl-tRNA synthetase prevents misediting of isoleucyl-tRNA(Ile).
abstract: In the archaeal leucyl-tRNA synthetase (LeuRS), the C-terminal domain recognizes the long variable arm of tRNA(Leu) for aminoacylation, and the so-called editing domain deacylates incorrectly formed Ile-tRNA(Leu). We previously reported, for Pyrococcus horikoshii LeuRS, that a deletion mutant lacking the C-terminal domain (LeuRS_delta(811-967)) retains normal editing activity, but has severely reduced aminoacylation activity. In this study, we found that LeuRS_delta(811-967), but not the wild-type LeuRS, exhibited surprisingly robust deacylation activity against Ile-tRNA(Ile), correctly formed by isoleucyl-tRNA synthetase ("misediting"). Structural superposition of tRNA(Ile) onto the LeuRS x tRNA(Leu) complex indicated that Ile911, Lys912, and Glu913 of the LeuRS C-terminal domain clash with U20 of tRNA(Ile), which is bulged out as compared to the corresponding nucleotide of tRNA(Leu). The deletion of amino acid residues 911-913 of LeuRS enhanced the Ile-tRNA(Ile) deacylation activity, without affecting the Ile-tRNA(Leu) deacylation activity. These results demonstrate that the clashing between U20 of tRNA(Ile) and residues 911-913 of the LeuRS C-terminal domain is the structural mechanism that prevents misediting. In contrast, the deletion of the C-terminal domains of the isoleucyl- and valyl-tRNA synthetases impaired both the aminoacylation (Ile-tRNA(Ile) and Val-tRNA(Val) formation, respectively) and editing (Val-tRNA(Ile) and Thr-tRNA(Val) deacylation, respectively) activities, and did not cause misediting (Val-tRNA(Val) and Thr-tRNA(Thr) deacylation, respectively) activity. Thus, the requirement of the C-terminal domain for misediting prevention is unique to LeuRS, which does not recognize the anticodon of the cognate tRNA, unlike the common aminoacyl-tRNA synthetases.
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: Ryuya
authors.initials: R
authors.lastname: Fukunaga
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000215:Acylation; D001483:Base Sequence; D007935:Leucine-tRNA Ligase / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D043902:Pyrococcus horikoshii / Q000201:enzymology*; D017393:RNA Editing; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012346:RNA, Transfer, Amino Acyl; D007935:Leucine-tRNA Ligase