人信号识别颗粒SRP68和SRP72复合物的结构与功能研究

The co-translational targeting or insertion of secretory and membrane proteins into the endoplasmic reticulum (ER) is a key biological process mediated by the signal recognition particle (SRP). Mammalian SRP can be divided into an Alu domain and an S domain. The two largest SRP proteins SRP68 and SRP72 are located in the S domain and are highly conserved in eukaryotes. These two proteins form a stable heterodimer and can bind to SRP RNA, which are essential for the proper functioning of eukaryotic SRP. However, only several fragmental structures of these two proteins are solved, the structural basis of how SRP68/72 exert complex biological functions remains a major challenge.. In this project, based on our preliminary results, we will determine several structures of human full-length SRP68 and SRP72, and their complexes with SRP RNA, to reveal the recognition and regulation mechanism of SRP by means of biochemistry, cell biology, molecular biology, structural biology studies. And we will perform many functional studies of SRP68/72 to uncover the effect of SRP72 and SRP68 mutations in human diseases. All these results might be of great significance to understand the function of the signal recognition particle, the molecular mechanism of co-translational targeting and to facilitate the diagnosis of diseases, furthermore to provide a direction for drug design against these related diseases.

膜蛋白和分泌蛋白靶向内质网的共翻译易位是一种非常重要的生物学过程，受信号识别颗粒(SRP)的严格调控。哺乳动物SRP复合物由Alu和S两个结构域组成。其中最大的两个蛋白亚基SRP68和SRP72位于S结构域，二者在不同物种中高度保守，在体内以异源二聚体形式存在并能与SRP RNA结合，这对SRP正常行使其生物学功能起着至关重要的作用。目前仅有SRP68和SRP72片段的结构信息，而它们发挥复杂生物学功能的结构基础尚不清楚。.在前期工作的基础上，本研究将通过生物化学、细胞生物学、分子生物学和结构生物学等技术方法，解析人全长SRP68/SRP72及其与RNA的复合物结构并进行多项功能研究，探讨它们之间的识别和调控机制，阐明突变体与人类多种癌症及其他相关疾病的关系。本项目将对研究信号识别颗粒复合物、蛋白质的翻译转运同步机制、相关疾病的诊断等具有重要的意义，并为抗疾病的药物分子设计指明方向。

膜蛋白和分泌蛋白靶向内质网的共翻译易位是一种非常重要的生物学过程，受信号识别颗粒(SRP)的严格调控。哺乳动物SRP复合物由Alu和S两个结构域组成。其中最大的两个蛋白亚基SRP68和SRP72位于S结构域，二者在不同物种中高度保守，在体内以异源二聚体形式存在并能与SRP RNA结合，这对SRP正常行使其生物学功能起着至关重要的作用。.本项目在SRP68/SRP72的结构与功能研究方面，取得一些重要的成果，培养高素质的研究生12人，毕业7名博士。标有本课题资助、以通信作者发表的SCI论文有12篇。发现SRP68蛋白C端23个氨基酸残基组成的短肽片段 (588-610) 与SRP72 N端 (1-163) 之间可通过形成疏水槽发生强相互作用。结构中所解析出来的SRP68短肽链是研究至今具有SRP72识别功能的最短片段。通过进一步结构分析、体内外生化功能研究以及定点突变实验, 发现癌症病人中SRP68和SRP72突变蛋白会明显减弱SRP68/72复合物的形成, 使SRP68和SRP72无法参与形成SRP大复合物, 进而影响SRP与内质网的结合, 最终使得SRP复合物丧失对蛋白质的内质网定位功能。本项目的研究结果为抗疾病肽类药物分子的设计和疾病诊断提供重要的结构信息。