FAST FOLDING EVENTS IN TPR PROTEINS

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。-螺旋蛋白质折叠的一个关键步骤是螺旋堆积：初级二级结构如何通过不同的和不同的堆积方式形成天然的三级结构，这种堆积方式不同于螺旋盘状的平行堆积和几乎垂直的血红蛋白堆积。其中一个重要的结构基序是四肽重复序列(TPR)，它存在于多种蛋白质中，调节蛋白质间的相互作用和多蛋白质复合体的组装。含有TPR的蛋白质参与多种生物学过程，如细胞周期调控、转录调控、线粒体和过氧化体蛋白运输、新生和蛋白质折叠等。对蛋白磷酸酶5的3个TPR结构域的X射线研究表明，TPR采用螺旋-转角-螺旋结构，相邻的TPR基序平行，形成反平行的螺旋。单个TPR基序中的两个？-螺旋具有约24度的堆积角度，形成右旋超螺旋形状。我们对TPR基序的兴趣不仅源于它们重要的生物学功能，还源于它们独特的分子结构和折叠特性。对TPR蛋白质折叠机制的研究将有助于更好地理解螺旋-螺旋相互作用以及具有不同堆积特征的β-螺旋蛋白质的折叠机制。对一个单独的TPR进行了初步的热力学和动力学研究，它还包含一个稳定的N-帽序列和一个C-末端的溶解螺旋，以提高其溶解性。圆二色谱实验表明，该TPR具有协同的双态热跃迁。激光诱导温度跳跃实验也观察到了双态折叠动力学。

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. One critical step in the ?-helical protein folding is helices packing: how the elementary secondary structures form the native tertiary structure through various and distinct packing styles, which differ from parallel packing in coiled-coils to almost perpendicular packing in hemoglobin. One of the specific structural motifs of interest is the tetratrico peptide repeat (TPR), which occurs in many classes of proteins, and mediates protein-protein interactions and the assembly of multiprotein complexes. Proteins containing TPRs are involved in many biological processes, such as cell cycle regulation, transcriptional control, mitochondrial and peroxisomal protein transport, neutogenesis and protein folding. The X-ray study of a domain with three TPRs from protein phosphatase 5 showed that TPR adopts helix-turn-helix structure, with adjacent TPR motifs in parallel fashion, resulting in a spiral of antiparallel ?-helices. The two ?-helices within a single TPR motif have a packing angle around 24 degree and form a right-handed superhelical shape. Our interest in the TPR motifs stems not only from their significant biological functions, but also from their unique molecular architecture and folding characteristics. The investigation of folding mechanisms of TPR proteins will provide better understanding of helix-helix interaction as well as folding mechanisms of ?-helical proteins with different packing features. Preliminary thermodynamic and kinetic study has been done on an individual TPR which also contains a stabilizing N-cap sequence and a solvating helix at C-teminal to enhance the solubility. CD experiments demonstrated this TPR has a cooperative two-state thermal transition. And two-state folding kinetics were also observed with the laser induced temperature jump experiments.