TAILIEUCHUNG - Báo cáo Y học: Shifted positioning of the anticodon nucleotide residues of amber suppressor tRNA species by Escherichia coli arginyl-tRNA synthetase

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 (FTOR1D26) exhibits suppression activity in vivo [McClain, . & Foss, K. (1988) Science, 241, 1804 –1807]. By an in vitro kinetic study with mutagenized tRNAs, we showed that the arginylation of FTOR1D26 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 50. | Eur. J. Biochem. 268 6207-6213 2001 FEBS 2001 Shifted positioning of the anticodon nucleotide residues of amber suppressor tRNA species by Escherichia coli arginyl-tRNA synthetase Daisuke Kiga1 2 Kensaku Sakamoto2 Saori Sato1 Ichiro Hirao1 and Shigeyuki Yokoyama1 2 1 Yokoyama CytoLogic Project ERATO JST c o RIKEN Hirosawa Wako-shi Saitama Japan -Department of Biophysics and Biochemistry Graduate School of Science University of Tokyo Bunkyo-ku Japan 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 FTOR1D26 exhibits suppression activity in vivo McClain . Foss K. 1988 Science 241 1804-1807 . By an in vitro kinetic study with mutagenized tRNAs we showed that the arginylation of FTOR1D26 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 50 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 FTOR1D26 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. Keywords tRNA identity anticodon aminoacyl-tRNA synthetase genetic screen kinetic analysis. The accurate recognition of a tRNA by its aminoacyl-tRNA synthetase aaRS is a vital step in ensuring the fidelity of translation. An aaRS distinguishes its cognate tRNAs from the tRNA species existing in the same cell by the recognition of the particular nucleotide residues identity determinants that are found only in the cognate tRNAs as one set. In most tRNA species these nucleotides are located in the .

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