title: Specific substitution into the anticodon loop of yeast tyrosine transfer RNA.
abstract: The aminoacylation kinetics of 19 different variants of yeast tRNATyr with nucleotide substitutions in positions 33-35 were determined. Substitution of the conserved uridine-33 does not alter the rate of aminoacylation. However, substitution of the anticodon position 34 or position 35 reduces Km from 2- to 10-fold and Vmax as much as 2-fold, depending on the nucleotide inserted. The ochre and amber suppressor tRNAsTyr both showed about a 7-fold reduction in Vmax/Km. Data from tRNATyr with different modified nucleotides at position 35 suggest that specific hydrogen bonds form between the synthetase and both the N1 and N3 hydrogens of psi-35. The effect of simultaneous substitutions at positions 34 and 35 can be predicted reasonably well by combining the effects of single substitutions. These data suggest that yeast tyrosyl-tRNA synthetase interacts with positions 34 and 35 of the anticodon of tRNATyr and opens the possibility that nonsense suppressor efficiency may be mediated by the level of aminoacylation.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000926:Anticodon; D004926:Escherichia coli / Q000235:genetics*; D014644:Genetic Variation; D007700:Kinetics; D012343:RNA, Transfer; D012346:RNA, Transfer, Amino Acyl / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013329:Structure-Activity Relationship; D014448:Tyrosine-tRNA Ligase / Q000378:metabolism*
chemical_list: D000926:Anticodon; D012346:RNA, Transfer, Amino Acyl; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D014448:Tyrosine-tRNA Ligase