Eckhardt H, Lührmann R
J Biol Chem. 1979 Nov 25;254(22):11185-8.
Hydrogen bonding between the 3' terminus of 16 S rRNA (... C-A-C-C-U-C-C-U-U-A-OH3) and complementary sequences within the initiator region of mRNA may be a crucial event in the specific initiation of protein biosynthesis (Shine, J., and Dalgarno, L. (1974) Proc. Natl. Acad. Sci. U. S. A. 71, 1342-1346; Steitz, J. A., and Jakes, K. (1975) Proc. Natl. Acad. Sci. U. S. A. 72, 4734-4738). Using equilibrium dialysis, we have studied the binding of G-A-dG-dG-U (which is complementary to the 3' end of 16 S rRNA and which has been synthesized enzymatically) to initiation factor-free Escherichia coli ribosomes. We have also investigated the effects of the pentanucleotide on initiation reactions in E. coli ribosomes. G-A-dG-dG-U has a specific binding site on the 30 S ribosome with an association constant of 2 x 10(6) M-1 at 0 degrees C. G-A-dG-dG-U inhibits the R17 mRNA-dependent binding of fMet-tRNA by about 70%, both with 70 S ribosomes and 30 S subunits. In contrast, the A-U-G-dependent initiation reaction and the poly(U)-dependent Phe-tRNA binding was not affected by the pentanucleotide with both ribosomal species.
16S rRNA的3'末端（...C-A-C-C-U-C-C-U-U-A-OH3）与mRNA起始区域内的互补序列之间的氢键可能是蛋白质生物合成特异性起始中的关键事件（Shine, J.和Dalgarno, L.（1974年）美国国家科学院院刊71, 1342 - 1346；Steitz, J. A.和Jakes, K.（1975年）美国国家科学院院刊72, 4734 - 4738）。我们使用平衡透析法研究了G-A-dG-dG-U（与16S rRNA的3'末端互补且已通过酶促合成）与不含起始因子的大肠杆菌核糖体的结合。我们还研究了该五核苷酸对大肠杆菌核糖体起始反应的影响。G-A-dG-dG-U在30S核糖体上有一个特异性结合位点，在0℃时结合常数为2×10⁶ M⁻¹。G-A-dG-dG-U在70S核糖体和30S亚基存在时，均能抑制fMet-tRNA与R17 mRNA的依赖性结合约70%。相比之下，该五核苷酸对两种核糖体的A-U-G依赖性起始反应和聚（U）依赖性苯丙氨酸-tRNA结合均无影响。
