Search for the Structural Basis of Biomacromolecular Fun

本课题组的主要研究兴趣是从结构生物学的角度研究控制生物过程的基本机制。我们利用核磁共振和其他各种生物物理和生化方法研究了包括核酸、酶和RNA-蛋白质-药物复合体在内的体系。我们目前的研究重点有以下几个方面。说唱项目。在人类基因组的14万多个基因中，大约有20%-30%编码完整的膜蛋白。这些蛋白质具有广泛的功能，从细胞信号的受体到离子和小分子的运输通道。最重要的是，膜蛋白代表了目前生产的所有药物中约60%的细胞靶标。低密度脂蛋白受体相关蛋白(LRP)是一种大的内源性受体，参与多种生物学途径，包括Wint途径，在脂蛋白代谢和参与凝血过程中的酶的分解代谢中发挥重要作用。LRP也是几种病毒和毒素进入细胞的通道。负责这类重要受体健康的蛋白质被称为受体相关蛋白(RAP)。在内质网中，RAP通过与新合成的受体相互作用，帮助其折叠，从而发挥分子伴侣的作用。同时，RAP作为一种拮抗剂，防止其他配体在分泌途径中过早地与受体结合，并将受体从内质网护送到高尔基体，在那里它与受体解离，然后再循环回内质网。本项目的目的是研究RAP的结构生物学及其与LRP的相互作用。该项目的第一阶段是确定蛋白质的溶液结构，并利用各种方法和工具揭示RAP生物学功能的结构基础。目前，我们正在完成第一阶段的研究。我们还计划研究RAP和LRP片段之间形成的复杂结构。L11和L11-rRNA-硫链霉菌工程。核糖体的高分辨X射线晶体结构，加上以往研究积累的知识，极大地加深了我们对这种蛋白质合成机制的结构和功能的了解。除了核糖体在蛋白质合成中的核心作用外，核糖体的生物发生和翻译控制也是重要的细胞过程。一些肿瘤抑制因子和原癌基因已经被发现或者影响成熟核糖体的形成，或者调节被称为翻译因子的蛋白质的活性。此外，几种核糖体蛋白还参与了抑制P53抑制因子Hdm2/MDM2和诱导P53活性以应对细胞压力的作用。这些结果揭示了在应激细胞环境下调节Hdm2/P53活性的新途径。核糖体蛋白的这些新发现的作用需要从一个新的角度来研究这些蛋白质，既包括核糖体蛋白合成，也包括它们潜在的调节作用。L11被认为在蛋白质合成的伸长和易位周期中起着重要作用，在这个过程中，EF-TU和EF-G在GTP和GDP阶段的活性都需要这两个因子与L11 N-末端结构域之间的协调运动。L11在50 S亚基的2.4分辨率X射线图谱中缺失，在50 S核糖体的低温电子显微镜密度图上，其两个结构域之间的取向与L11与rRNA形成的二元复合体中的取向相差约40度。因此，有必要对L11的结构及其作用有一个清楚的了解。该项目的目的是研究L11在游离和三元络合物形式下的动力学，以及硫链菌素抑制蛋白质合成的机制。

The general research interests of our group are to study fundamental mechanism that governs biological process from structural biology point of view. We study the systems that include nucleic acids, enzymes and RNA-protein-drug complexes using NMR and various other biophysical and biochemical methods. Our current research focuses are the following.1. RAP project. Of the more than 140,000 genes in the human genome, roughly 20-30% code for integral membrane proteins. These proteins have a vast array of functions ranging from receptors of cellular signals to channels for transporting ions and small molecules. Most importantly, membrane proteins represent the cellular targets for approximately 60% of all drugs currently manufactured. The low density lipoprotein receptor-related protein (LRP) is a large endocytic receptor that involved in several biological pathways, including Wint pathway, and plays prominent roles in lipoprotein metabolism and in the catabolism of proteinases involved in coagulation. LRP is also the cellular entry gateway for several viruses and toxins. The protein that is responsible for the well-being of this important class of the receptor is called the receptor associated protein (RAP). In the ER, RAP acts like a molecular chaperone by interacting with newly synthesized receptor to help it fold. In the meantime, RAP serves as an antagonist to prevent other ligands from binding to the receptors prematurely in the secretory pathway, and escorts the receptors from the ER to the Golgi where it dissociates from the receptors before recycling back to the ER. The aim of the project is to study the structure biology of RAP and its interaction with LRP. The first phase of the project is to determine the solution structure of the protein and is to reveal the structure basis for RAP's biological function using various methods and tools. At this point, we are completing the first phase study. We are also planning study the complex structure formed between RAP and the LRP fragment.2. L11 and L11-rRNA-thiostrepton project. High resolution X-ray crystal structures of ribosome together with the accumulative knowledge from previous investigation have tremendously enhanced our understanding the structure and the function of this protein synthesis machinery. In addition to its central role in protein synthesis, ribosome biogenesis and translation control are also essential cellular processe. Several tumor suppressors and proto-oncogenes have been found either to affect the formation of the mature ribosome or to regulate the activity of proteins known as translation factors. Furthermore, several ribosome proteins have been implicated in inactivating HDM2/MDM2, a p53 inhibitor and inducing p53 activity in response to cellular stress. The findings revealed a new pathway of regulating HDM2/p53 activity under stress cellular environment. These newly revealed roles for ribosome proteins necessitate a need to study these proteins from a fresh angle in the context of both ribosome protein synthesis as well as their potential regulatory roles. L11 is recognized to play an important role in the elongation and translocation cycle of protein synthesis, during which the activities of EF-TU and EF-G at both GTP and GDP stages require coordinated movement between the factors and the L11 N-terminal domain. L11 is absent from the 2.4 resolution X-ray map of 50 S subunit, and its orientation between the two domains in the cryo EM density map of 50 S ribosome is different by ca. 40 degrees from that in the binary complex formed between L11 and rRNA. Hence, there is a need for a clear understanding of the L11 structure and its role. The aim of the project is to study the dynamics of L11 in free and the ternary complex forms, and the mechanism of inhibition of protein synthesis by thiostrepton.