D. Kiga et al., Shifted positioning of the anticodon nucleotide residues of amber suppressor tRNA species by Escherichia coli arginyl-tRNA synthetase, EUR J BIOCH, 268(23), 2001, pp. 6207-6213
Cytidine in the anticodon second position (position 35) and G or U in posit
ion 36 of tRNA(Arg) are required for aminoacylation by arginyl-tRNA synthet
ase (ArgRS) from Escherichia coli. Nevertheless, an arginine-accepting ambe
r suppressor tRNA with a CUA anticodon (FTOR1 Delta 26) exhibits suppressio
n 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 FTOR1 Delta 26 involves C34 and U35, and that U35 can be re
placed by G without affecting the activity. Thus, the positioning of the es
sential nucleotides for the arginylation is shifted to the 5' side, by one
residue, in the suppressor tRNA(Arg). We found that the shifted positioning
does not depend on the tRNA sequence outside the anticodon. Furthermore, b
y a genetic method, we isolated a mutant ArgRS that aminoacylates FTOR1 Del
ta 26 more efficiently than the wild-type ArgRS. The isolated mutant has mu
tations at two nonsurface amino-acid residues that interact with each other
near the anticodon-binding site.