Shan Shu-ou, Herschlag Daniel
Department of Biochemistry, Stanford University, California 94305-5307, USA.
RNA. 2002 Jul;8(7):861-72. doi: 10.1017/s1355838202020216.
Conformational changes are often required for the biological function of RNA molecules. In the Tetrahymena group I ribozyme reaction, a conformational change has been suggested to occur upon binding of the oligonucleotide substrate (S) or the guanosine nucleophile (G), leading to stronger binding of the second substrate. Recent work showed that the two substrates are bridged by a metal ion that coordinates both the nonbridging reactive phosphoryl oxygen of S and the 2'-OH of G. These results suggest that the energy from the metal ion substrate interactions is used to drive the proposed conformational change. In this work, we provide an experimental test for this model. The results provide strong support for the proposed conformational change and for a central role of the bridging metal ion in this change. The results from this work, combined with previous data, allow construction of a two-state model that quantitatively accounts for all of the observations in this and previous-work. This model provides a conceptual and quantitative framework that will facilitate understanding and further probing of the energetic and structural features of this conformational change and its role in catalysis.
RNA分子的生物学功能通常需要构象变化。在嗜热四膜虫I组核酶反应中，有人提出在寡核苷酸底物（S）或鸟苷亲核试剂（G）结合时会发生构象变化，从而导致第二种底物的结合更强。最近的研究表明，两种底物由一个金属离子桥接，该金属离子同时配位S的非桥连反应性磷酰氧和G的2'-OH。这些结果表明，金属离子与底物相互作用产生的能量用于驱动所提出的构象变化。在这项工作中，我们对该模型进行了实验验证。结果为所提出的构象变化以及桥连金属离子在这一变化中的核心作用提供了有力支持。这项工作的结果与先前的数据相结合，使得构建一个双态模型成为可能，该模型能够定量解释这项工作以及先前工作中的所有观察结果。这个模型提供了一个概念性和定量的框架，将有助于理解和进一步探究这种构象变化的能量和结构特征及其在催化中的作用。
