Haruki M, Matsumoto R, Hara-Yokoyama M, Miyazawa T, Yokoyama S
Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
FEBS Lett. 1990 Apr 24;263(2):361-4. doi: 10.1016/0014-5793(90)81414-j.
The conformation change of Thermus thermophilus tRNA(1Ile) upon complex formation with T. thermophilus elongation factor Tu (EF-Tu) was studied by analysis of the circular dichroism (CD) bands at 315 nm (due to the 2-thioribothymidine residue in the T-loop) and at 295 nm (due to the core structure of tRNA). Formation of the ternary complex of isoleucyl-tRNA(1Ile) and EF-Tu.GTP increased the intensities of these CD bands, indicating stabilization of the association between the T-loop and the D-loop and also a significant conformation change of the core region. Upon complex formation of EF-Tu.GTP and uncharged tRNA, however, the conformation of the core region is not changed, while the association of the two loops is still stabilized. On the other hand, the binding with EF-Tu.GDP does not appreciably affect the conformation of isoleucyl-tRNA or uncharged tRNA. These indicate the importance of the gamma-phosphate group of GTP and the aminoacyl group in the formation of the active complex of aminoacyl-tRNA and EF-Tu.GTP.
通过分析315nm（由于T环中的2-硫代核糖胸苷残基）和295nm（由于tRNA的核心结构）处的圆二色性（CD）谱带，研究了嗜热栖热菌tRNA（1Ile）与嗜热栖热菌延伸因子Tu（EF-Tu）形成复合物时的构象变化。异亮氨酰-tRNA（1Ile）与EF-Tu.GTP形成三元复合物会增加这些CD谱带的强度，表明T环与D环之间的结合得到稳定，同时核心区域也发生了显著的构象变化。然而，EF-Tu.GTP与无电荷tRNA形成复合物时，核心区域的构象没有改变，而两个环的结合仍然稳定。另一方面，与EF-Tu.GDP的结合对异亮氨酰-tRNA或无电荷tRNA的构象没有明显影响。这些结果表明GTP的γ-磷酸基团和氨酰基在氨酰-tRNA与EF-Tu.GTP活性复合物形成中的重要性。
