MECHANISM AND KINETICS OF RNA FOLDING BY SAXS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 RNA通过折叠成特定的三维结构来执行许多生物功能。了解RNA是如何折叠的，对于了解核糖体等RNA-蛋白质复合体的组装、RNA对基因表达的调节以及RNA传感器和“核糖开关”的工程至关重要。 在反离子的存在下，RNA坍塌成致密的中间体，然后折叠成天然的三级结构。理论认为，不同崩溃机制之间的竞争沿着交替的折叠路径分割RNA种群，其中一些导致动力学捕获和错误折叠的中间产物。 RNA折叠中的一些重要问题包括(1)成核和塌陷的动力学机制，(2)阳离子和RNA序列如何决定初始塌陷转变的特异性，以及(3)结构在未折叠RNA集合中的分布。我们计划使用时间分辨小角X射线散射(SAXS)来解决这些问题，这些散射来自固氮弧菌的I组核酶。所提出的研究将为RNA三级结构的成核提供深入的认识，并为未折叠和折叠RNA中静电相互作用的理论模型提供实验测试。这项工作将包括固氮藻的野生型和突变体，并与更广泛研究的四膜虫内含子进行比较。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. RNAs perform many biological functions by folding into specific three-dimensional structures. Understanding how RNAs fold is crucial for understanding the assembly of RNA-protein complexes such as the ribosome, the regulation of gene expression by RNA, and the engineering of RNA sensors and "riboswitches". In the presence of counterions, RNAs collapse into compact intermediates, which subsequently fold into the native tertiary structure. Theory suggests that competition between different collapse mechanisms partitions the RNA population along alternate folding pathways, some of which lead to kinetically trapped and misfolded intermediates. Some of the important questions in RNA folding include (1) the kinetic mechanism of nucleation and collapse, (2) how cations and RNA sequence determine the specificity of the initial collapse transition, and (3) the distribution of structures in the ensemble of unfolded RNA. We plan to address these questions using time resolved small angle X-ray scattering (SAXS) on a group I ribozyme from the bacterium Azoarcus. The proposed studies will provide insight into the nucleation of RNA tertiary structure and provide experimental tests of theoretical models of electrostatic interactions in unfolded and folded RNAs. The work will include both wild type and mutants of Azoarcus and comparison to the more widely studied Tetrahymena intron.