NUCLEOTIDE-DEPENDENT CONFORMATIONAL CHANGE IN ALPHA/BETA-TUBULIN & HSP90

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。α/β-微管蛋白和分子伴侣Hsp90在真核细胞的生命过程中具有重要的、不重叠的作用。这两种蛋白质都能结合和水解核苷三磷酸(微管蛋白为GTP，热休克蛋白90为ATP)，并采用多种构象作为其功能循环的一部分。阿加德实验室最近的结晶学结果为构象变化在这些蛋白质中的作用提供了新的见解。我们确定了与GTP结合的微管蛋白的结构。令人惊讶的是，我们观察到的构象基本上与密切相关的α/β-微管蛋白的GDP结合构象相同。我们的伽马微管蛋白的结构(结合生化数据)表明，微管蛋白中的构象转换在很大程度上与核苷酸状态无关。我们还确定了大肠杆菌Hsp90同源物的两种结构，HtpG，揭示了可能代表重要功能状态的截然不同的构象。小角X射线散射(SAXS)是最高分辨率的溶液技术，能够报告分子组装的构象状态，并提供了对这些蛋白质构象变化的独特结构洞察。特别是，研究这两种不同蛋白质的构象如何(或是否)对核苷酸状态做出反应，是形成对其功能有意义的机制理解的重要第一步。

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. alpha/beta-Tubulin and the molecular chaperone Hsp90 have essential, non-overlapping roles in the life of eukaryotic cells. Both proteins bind and hydrolyze nucleoside triphosphates (GTP for tubulin, ATP for HSP90), and adopt multiple conformations as part of their functional cycle. Recent crystallographic results from the Agard lab have provided new insights into the role of conformational change in these proteins. We determined the structure of gamma-tubulin bound to GTP. Surprisingly, the conformation we observed was essentially identical to what was thought to be the GDP-bound conformation of the closely related alpha/beta-tubulin. Our structure of gamma-tubulin (together with biochemical data) suggests that conformational switching in tubulins is largely independent of nucleotide state. We also determined two structures of the E. coli Hsp90 homolog, HtpG, revealing dramatically different conformations that likely represent important functional states. Small angle X-ray scattering (SAXS) is the highest resolution solution technique capable of reporting on the conformational state of molecular assemblies, and is providing unique structural insight into conformational changes in these proteins. In particular, studying how (or whether) the conformations of these two different proteins respond to nucleotide state is an essential first step in formulating a meaningful mechanistic understanding of their function.