FAST FOLDING EVENTS IN TPR PROTEINS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。一个关键的步骤？螺旋蛋白折叠是螺旋排列：初级二级结构如何通过各种不同的排列方式形成原生三级结构，不同于螺旋状线圈中的平行排列和血红蛋白中的几乎垂直排列。我们感兴趣的一个特殊结构基序是四联肽重复序列（TPR），它存在于许多种类的蛋白质中，并介导蛋白质之间的相互作用和多蛋白复合物的组装。含有tpr的蛋白质参与许多生物过程，如细胞周期调节、转录控制、线粒体和过氧化物酶体蛋白质转运、神经发生和蛋白质折叠。对蛋白磷酸酶5的3个TPR结构域的x射线研究表明，TPR为螺旋-转-螺旋结构，相邻的TPR基序平行，形成反平行的螺旋结构。那两个？-单个TPR基序内的螺旋填充角约为24度，形成右旋超螺旋形状。我们对TPR基序的兴趣不仅源于其重要的生物学功能，还源于其独特的分子结构和折叠特性。对TPR蛋白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？-具有不同包装特征的螺旋蛋白。对单个TPR进行了初步的热力学和动力学研究，该TPR还含有稳定n帽序列和c端溶剂化螺旋以提高溶解度。CD实验表明，该TPR具有协同双态热转变。用激光诱导温度跳变实验观察了双态折叠动力学。

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.