Centre for Integrative Biology, Department of Integrated Structural Biology, Institute of Genetics and of Molecular and Cellular Biology, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche 7104, Institut National de la Santé de la Recherche Médicale U964, Université de Strasbourg, 67404 Illkirch, France.
Proc Natl Acad Sci U S A. 2013 Sep 24;110(39):15656-61. doi: 10.1073/pnas.1309578110. Epub 2013 Sep 12.
Translation initiation factor 2 (IF2) promotes 30S initiation complex (IC) formation and 50S subunit joining, which produces the 70S IC. The architecture of full-length IF2, determined by small angle X-ray diffraction and cryo electron microscopy, reveals a more extended conformation of IF2 in solution and on the ribosome than in the crystal. The N-terminal domain is only partially visible in the 30S IC, but in the 70S IC, it stabilizes interactions between IF2 and the L7/L12 stalk of the 50S, and on its deletion, proper N-formyl-methionyl(fMet)-tRNA(fMet) positioning and efficient transpeptidation are affected. Accordingly, fast kinetics and single-molecule fluorescence data indicate that the N terminus promotes 70S IC formation by stabilizing the productive sampling of the 50S subunit during 30S IC joining. Together, our data highlight the dynamics of IF2-dependent ribosomal subunit joining and the role played by the N terminus of IF2 in this process.
翻译起始因子 2（IF2）促进 30S 起始复合物（IC）的形成和 50S 亚基的结合，从而产生 70S IC。全长 IF2 的结构通过小角度 X 射线衍射和冷冻电子显微镜确定，与晶体相比，它揭示了 IF2 在溶液中和核糖体上的构象更为伸展。在 30S IC 中，N 端结构域仅部分可见，但在 70S IC 中，它稳定了 IF2 与 50S 的 L7/L12 柄之间的相互作用，并且在其缺失时，正确的 N-甲酰甲硫氨酸（fMet）-tRNA（fMet）定位和有效的转肽作用受到影响。因此，快速动力学和单分子荧光数据表明，N 端通过稳定 30S IC 结合过程中 50S 亚基的有效采样，促进了 70S IC 的形成。总之，我们的数据突出了 IF2 依赖性核糖体亚基结合的动力学以及 IF2 的 N 端在该过程中的作用。
