WIDE ANGLE SCATTERING OF PROTEIN SOLUTIONS FOR FOLD DETERMINATION

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。溶液中蛋白质的广角X射线散射（WAXS）提供了一系列其他方法无法获得的蛋白质结构分析能力。我们在BioCAT的实验旨在开发这些能力。我们目前正在进行三种研究途径：（i）基于WAXS模式的折叠分配：我们正在编制已知和未知折叠蛋白质的WAXS模式数据库，目标是将其用作无法结晶的蛋白质的折叠分配的基础。迄今为止，已经收集了100多种已知结构的蛋白质的WAXS数据。(ii)蛋白质-配体相互作用：WAXS提供了研究小分子配体结合诱导的蛋白质结构变化的能力。配体诱导的结构变化太大，无法容纳在晶格内，使得替代方法的发展至关重要。我们已经收集了10个蛋白质的存在和不存在的小分子配体的数据，并进行了详细的分析，这些系统中的5个诱导的结构变化。(iii)蛋白质呼吸：在比较WAXS模式从稀释的蛋白质溶液与那些从浓缩溶液中，我们发现了系统的差异，可以归因于结构的波动，在稀释溶液中更大。 正在对这些模式进行详细分析，以便从数量上衡量波动的规模。在浓缩溶液中抑制这些波动似乎是由于分子拥挤，一种促进细胞质中蛋白质稳定性的现象。

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. Wide-angle x-ray scattering from proteins in solution (WAXS) provides a set of capabilities for analysis of the structure of proteins not accessible by other methods. Our experiments at BioCAT are designed to develop those capabilities. We are currently pursuing three avenues of research: (i) Assignment of fold on the basis of WAXS patterns: We are compiling a database of WAXS patterns from proteins of known and unknown folds with the goal of using it as a basis for fold assignment for proteins that cannot be crystallized. WAXS data from over 100 proteins of known structure have been collected thusfar. (ii) Protein-ligand interactions: WAXS provides the capability of studying structural changes in proteins induced by binding of small molecule ligands. Ligand-induced structural changes are too large to be accommodated within a crystal lattice, making the development of alternative approaches critical. We have collected data on 10 proteins in the presence and absence of small molecule ligands, and carried out detailed analysis of the structural changes induced for 5 of these systems. (iii) Protein breathing: In comparing WAXS patterns from dilute protein solutions with those from concentrated solutions, we discovered systematic differences that could be attributed to structural fluctuations that are much greater in dilute solution. Detailed analysis of these patterns is being used to obtain a quantitative measure of the scale of the fluctuations. Suppression of these fluctuations in concentrated solution appears to be due to molecular crowding, a phenomena that promotes protein stability in the cell cytoplasm.