Lefevre J F, Bacha H, Renaud M, Ehrlich R, Gangloff J, Von der Haar F, Remy P
Eur J Biochem. 1981 Jul;117(3):439-47.
The fluorescence properties of yeast tRNAPheCCF (tRNAPhe in which the 3'-terminal adenosine has been replaced by formycin) and tRNAPheCCFoxi-red (tRNAPheCCF after periodate oxidation followed by borohydride reduction) were studied in the complex with the cognate aminoacyl-tRNA synthetase. In both cases a conformational change affecting the 3' end was observed in a magnesium concentration range close to 1 mM. The modification of formycin fluorescence could be ascribed simultaneously to the existence of a tautomeric equilibrium of the fluorescent probe and to a pH effect raising from a prototropic effect at the active site of phenylalanyl-tRNA synthetase, and to a partial destacking of the 3'-formycin from the adjacent C residue. The observed transconformation, which can be related to the structure modification of the anticodon loop previously reported [Ehrlich, Lefèvre, and Remy (1980) Eur. J. Biochem. 103, 145-153], takes place in the magnesium concentration range allowing the transfer of the activated amino acid from the adenylate to the tRNA. The interconnection between the anticodon loop and the accepting end was further supported by the observation that wybutine excision hinders the specific structure modification of 3'-formycin upon binding to the synthetase. The tRNAPhe transconformations occurring in the complex with the cognate synthetase probably reflect a reciprocal adaptation of both macromolecules which might lead to the optimal aminoacylation velocity and thus contribute to the specificity of aminoacylation, since it was previously established that this specificity relies more strongly on the kinetics of the reaction than on a discrimination of tRNAs according to different affinities.
研究了酵母苯丙氨酸tRNAPheCCF（3'-末端腺苷被间型霉素取代的苯丙氨酸tRNA）和tRNAPheCCFoxi-red（高碘酸盐氧化后硼氢化还原的tRNAPheCCF）与同源氨酰-tRNA合成酶形成复合物时的荧光特性。在这两种情况下，在接近1 mM的镁浓度范围内都观察到了影响3'末端的构象变化。间型霉素荧光的修饰可同时归因于荧光探针互变异构平衡的存在、苯丙氨酰-tRNA合成酶活性位点质子转移效应引起的pH效应以及3'-间型霉素与相邻C残基的部分解堆叠。观察到的反式构象与先前报道的反密码子环结构修饰有关[Ehrlich、Lefèvre和Remy（1980年），《欧洲生物化学杂志》103卷，145 - 153页]，发生在允许活化氨基酸从腺苷酸转移到tRNA的镁浓度范围内。反密码子环与接受端之间的相互联系进一步得到了以下观察结果的支持：怀丁切除阻碍了3'-间型霉素与合成酶结合时的特定结构修饰。与同源合成酶形成复合物时发生的苯丙氨酸tRNA反式构象可能反映了两种大分子的相互适应，这可能导致最佳的氨酰化速度，从而有助于氨酰化的特异性，因为先前已经确定这种特异性更强烈地依赖于反应动力学而不是根据不同亲和力对tRNA的区分。
