Katunin V I, Kirillov S V
Mol Biol (Mosk). 1984 Nov-Dec;18(6):1486-96.
Phe-tRNAPhe+Y and N-acetyl-Phe-tRNAPhe+Y from yeast interact with prokaryotic 30S subunits and 70S ribosomes with slightly lower affinity than respective tRNA's of E. coli (decrease of standard free energy change of interaction less than 10%). The removal of Y-base from Phe-tRNAPhe+Y results in two orders of magnitude decrease of association constant of Phe-tRNAPh-Ye with P site of the 30S X poly(U) complex and one ordef of magnitude or more of that with A site. The same modification decreases the association constants of Phe-tRNAPhe-Y and N-acetyl-Phe-tRNAPhe-Y 60 and 15 times respectively with P site of the 70S X poly(U) complex. In the absence of poly(U) the affinity of N-acetyl-Phe-tRNAPhe-Y to P-site of 70S ribosome was 20-fold lower than that of native N-acetyl-Phe-tRNAPhe+Y. The sign of interaction enthalpy of N-acetyl-Phe-tRNAPhe+/-Y and Phe-tRNAPhe-Y changes below 6-7 degrees C exposing the hydrophobic part of P-site interactions. Similar removal of Y-base does not change both the enthalpy of interaction with P-site and magnesium concentration dependence.
来自酵母的苯丙氨酰 - tRNAphe + Y和N - 乙酰 - 苯丙氨酰 - tRNAphe + Y与原核30S亚基和70S核糖体相互作用，其亲和力略低于大肠杆菌相应的tRNA（相互作用的标准自由能变化降低小于10%）。从苯丙氨酰 - tRNAphe + Y上去除Y碱基会导致苯丙氨酰 - tRNAphe - Ye与30S X聚尿苷酸（poly(U)）复合物P位点的结合常数降低两个数量级，与A位点的结合常数降低一个或更多数量级。相同的修饰分别使苯丙氨酰 - tRNAphe - Y和N - 乙酰 - 苯丙氨酰 - tRNAphe - Y与70S X聚尿苷酸复合物P位点的结合常数降低60倍和15倍。在没有聚尿苷酸的情况下，N - 乙酰 - 苯丙氨酰 - tRNAphe - Y与70S核糖体P位点的亲和力比天然的N - 乙酰 -苯丙氨酰 - tRNAphe + Y低20倍。低于6 - 7摄氏度时，N - 乙酰 - 苯丙氨酰 - tRNAphe + / - Y和苯丙氨酰 - tRNAphe - Y相互作用焓的符号发生变化，暴露了P位点相互作用的疏水部分。类似地去除Y碱基既不改变与P位点相互作用的焓，也不改变对镁离子浓度的依赖性。
