SOLUTION STRUCTURE OF THE SIGNAL RECOGNITION PARTICLE FROM T AQUATICUS: A 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。 信号识别颗粒(SRP)及其膜相关受体(SR)构成了一种进化保守的大分子核糖核蛋白复合体，催化新生分泌物和膜蛋白靶向蛋白转运器。SRP负责指导核糖体，核糖体目前正在将预定用于分泌或膜整合的蛋白质翻译到内质网或质膜。该受体负责将核糖体-新生蛋白-SRP复合体靶向到膜转位机制。SRP途径的组成和SRP依赖蛋白靶向的分子机制的基本步骤在所有三个生命王国中都是保守的。真细菌Thermus Aquaticus(Taq)的耐热信号识别颗粒是由长113个核苷酸(35 KDa)的SRP-RNA和受体亚基FtsY(33 KDal)和RNA与信号序列结合亚基FFH(48 KDa)两个蛋白质组成的核糖核酸-蛋白质复合体。此外，这两种蛋白都是结构上相关的GTP酶和依赖GTP的GTP酶激活蛋白(GAP)。核糖体-新生蛋白-SRP复合体与其受体的相互作用也依赖于GTP。SRP-SR复合体的GTP水解解离了这个复合体，允许新一轮的靶向。Taq-SRP的所有组分都是高表达和可溶的，并且已经通过凝胶过滤、动态光散射和分析超速离心法在均一性和稳定性方面进行了广泛的表征。SAXS的这项生物物理研究的目的是表征Taq-SRP及其亚组分在溶液中的形状和构象。由于分离的亚基的晶体结构是已知的，我们希望用SAXS技术构建结构未知的二元(FtsY/FFH)和三元(FtsY/FFH/SRP-RNA)配合物的低分辨率模型。

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. The signal recognition particle (SRP) and its membrane-associated receptor (SR) constitute an evolutionary conserved macromolecular ribonucleoproteic complex that catalyzes targeting of nascent secretory and membrane proteins to the protein translocation apparatus. The SRP is in charge of directing ribosomes which are currently translating proteins destined for either secretion or membrane integration to the endoplasmic reticulum or plasma membrane. The receptor is responsible for the targeting of the ribosome-nascent protein-SRP complex to the membrane translocation machinery. The components of the SRP pathway and the essential steps of the molecular mechanism of SRP-dependent protein targeting are conserved in all three kingdoms of life. The thermostable signal recognition particle from the eubacteria Thermus aquaticus (Taq) is a ribonucleic acid-protein complex composed of the SRP-RNA, which is 113 nucleotides long (35 kDa), and two proteins, the receptor subunit FtsY (33 kDal) and the RNA and signal sequence-binding subunit Ffh (48 kDa). In addition both proteins are structurally related GTPases and GTP-dependent GTPase-activating proteins (GAPs). The ribosome-nascent protein-SRP complex interaction with its receptor is also GTP dependent. GTP hydrolysis by the SRP-SR complex dissociates this complex, allowing a new round of targeting. All components of the Taq-SRP are overexpressed and soluble and have been extensively characterized by gel filtration, dynamic light scattering and analytical ultracentrifugation, in terms of homogeneity and stability. The aim of this biophysical study by SAXS is to charactize the shapes and the conformations of the Taq-SRP and its subcomponents in solution. Since the crystal structures of the isolated subunits are available, using SAXS techniques we wish to construct low-resolution models of the binary (FtsY/Ffh) and ternary (FtsY/Ffh/SRP-RNA) complexes whose structures are still unknown.