STRUCTURAL BASIS OF RNA THERMOSTABILITY

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。 所有细菌的RNase P RNA都由两个独立的折叠结构域组成。在脂肪嗜热芽孢杆菌RNaseP RNA的晶体结构中，这些结构域相互竞争。这种并排包装被广泛认为是细菌P RNA能够适应的唯一天然结构。在这里，我们利用小角X射线散射、在线探测和分子模拟表明，来自枯草芽孢杆菌的P RNA，一个与嗜热脂肪芽孢杆菌相近的同源物，根据一价阳离子的存在，采用了两种全局不同的天然结构。在高离子条件下(E100 Mm)，由于催化结构域和特异性结构域的相对取向发生变化，结构紧凑20%。晶体结构很好地代表了这种结构。我们还为该结构在低离子条件下生成了一个分子模型，该结构与从SAXS测量获得的分子包络相匹配。使用互相关函数来量化晶体结构和模型与数据之间的一致性。我们的结果表明，多结构域RNA可以有不止一个稳定的天然结构。在P RNA的情况下，这些结构可能在RNaseP全酶(一种核糖核蛋白颗粒)的组装中很重要。

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. All bacterial RNase P RNAs are composed of two independently folding domains. These domains pack against each other in the crystal structure of the Bacillus stearothermophilus RNase P RNA. This side-by-side packing is widely assumed to be the only native structure bacterial P RNAs can adapt. Here we show using small-angle X-ray scattering, in-line probing and molecular modeling that the P RNA from Bacillus subtilis, a close homolog of B. stearothermophilus, adopts two globally distinct native structures depending on the presence of monovalent cations. The structure under high ionic conditions (e100 mM) is 20% more compact as a result of a change in the relative orientation of the catalytic and specificity domains. This structure is well represented by the crystal structure. We also generate a molecular model for the structure under low ionic conditions structures that matches the molecular envelop obtained from the SAXS measurements. The agreement between the crystal structure and the models with the data is quantified using a cross-correlation function. Our results indicate that multi-domain RNAs can have more than one stable native structure. In the case of P RNA, these structures may be important in the assembly of the RNase P holoenzyme, a ribonucleoprotein particle.