title: Shifted positioning of the anticodon nucleotide residues of amber suppressor tRNA species by Escherichia coli arginyl-tRNA synthetase.
abstract: Cytidine in the anticodon second position (position 35) and G or U in position 36 of tRNAArg are required for aminoacylation by arginyl-tRNA synthetase (ArgRS) from Escherichia coli. Nevertheless, an arginine-accepting amber suppressor tRNA with a CUA anticodon (FTOR1Delta26) exhibits suppression activity in vivo [McClain, W.H. & Foss, K. (1988) Science, 241, 1804-1807]. By an in vitro kinetic study with mutagenized tRNAs, we showed that the arginylation of FTOR1Delta26 involves C34 and U35, and that U35 can be replaced by G without affecting the activity. Thus, the positioning of the essential nucleotides for the arginylation is shifted to the 5' side, by one residue, in the suppressor tRNAArg. We found that the shifted positioning does not depend on the tRNA sequence outside the anticodon. Furthermore, by a genetic method, we isolated a mutant ArgRS that aminoacylates FTOR1Delta26 more efficiently than the wild-type ArgRS. The isolated mutant has mutations at two nonsurface amino-acid residues that interact with each other near the anticodon-binding site.
authors.affiliation: Yokoyama CytoLogic Project, ERATO, JST c/o RIKEN, Hirosawa, Wako-shi, Saitama, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Kiga
authors.forename: K
authors.initials: K
authors.lastname: Sakamoto
authors.forename: S
authors.initials: S
authors.lastname: Sato
authors.forename: I
authors.initials: I
authors.lastname: Hirao
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000926:Anticodon / Q000235:genetics*; D001126:Arginine-tRNA Ligase / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D005798:Genes, Bacterial; D016153:Genes, Suppressor; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics
chemical_list: D000926:Anticodon; D012329:RNA, Bacterial; D012343:RNA, Transfer; D001126:Arginine-tRNA Ligase