title: Conformation transitions of a tRNA--aminoacyl-tRNA synthetase complex induced by tRNAs bearing different modifications in the 3' terminus.
abstract: The influence of modifications of the 3'-terminal adenosine of tRNAPhe (yeast) on the complex formation between this tRNA and phenylalanyl-tRNA synthetase (yeast) has been investigated by using fluorescence titrations and fast kinetic techniques. Subtle changes in the 3' terminus are reflected by distinct alterations in the two-step recognition process which had been demonstrated earlier for the native substrate tRNAPheCCA [Krauss, G., Riesner, D., & Maass, G. (1977) Nucleic Acids Res. 4, 2253--2262]. Binding experiments with tRNAPheCC, tRNAPheCCA-ox-red, tRNAPheCC2'dA, tRNAPheCC3'dA, tRNAPheCC-formycin, and tRNAPheCC-formycin-ox-red confirm that the 3'-terminal adenosine participates in a conformational change of the tRNA--synthetase complex. This is valid in both the absence and presence of phenylalaninyl-5'-AMP, the alkyl analogue of the aminoacyladenylate. As compared to tRNAPheCCA, a slower conformational change is observed with the competitive inhibitor tRNAPheCC-formycin-ox-red. The reaction enthalpy and/or the quench of the Y-base fluorescence that accompany the conformational change are altered upon binding of tRNAPheC2'dA, tRNAPheCC3'dA, and tRNAPheCC-formycin. It is evident that the final adaptation between tRNA and its synthetase in the complex is determined by the chemical nature of the 3'-terminal nucleotide. This is of vital importance for the specificity of the aminoacylation process.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D009690:Nucleic Acid Conformation; D010649:Phenylalanine; D010652:Phenylalanine-tRNA Ligase / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D012343:RNA, Transfer; D012441:Saccharomyces cerevisiae / Q000201:enzymology
chemical_list: D046911:Macromolecular Substances; D010649:Phenylalanine; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D010652:Phenylalanine-tRNA Ligase