Structures, Dynamics, and Functions of Membrane Proteins

7.项目总结 膜蛋白是结构测定的重要靶点。人类体内四分之一的蛋白质 基因组是膜蛋白，而大多数药物靶点是膜蛋白。然而，两者 膜蛋白的结构测定和动力学表征因以下原因而滞后 技术困难主要源于蛋白质所处的磷脂环境；它是 高度不对称，含有疏水和亲水成分，并使蛋白质固定化。 因此，我们的首要目标是开发新的、更强大的方法来确定 膜蛋白的结构。这是揭示其功能基础的重要的第一步。 尽管使用溶液核磁共振、X射线结晶学和电子技术已经取得了相当大的进展 显微镜下，这是通过使用洗涤剂来扭曲结构的潜在代价 蛋白质样品的环境和低温温度。我们正在研究的蛋白质中没有一种 已经被结晶了。因此，我们寻求填补的技术差距是明确的。 研究计划的创新特征包括其科学广度，从分子生物学到 结构计算。几种较小的膜蛋白将用于方法开发，包括 HIV-1的VPU，丙型肝炎病毒的p7，以及细菌汞解毒的汞运输蛋白 系统。它们的双重目的是提出有趣的生化功能问题和作为 用于开发确定结构和描述较大的动力学的方法的易处理系统 膜蛋白，如我们G蛋白偶联受体(GPCRs)的主要靶点。 在研究计划结束时，我们希望能够描述趋化因子受体的功能。 这些研究将涉及单体蛋白质的结构和动力学，蛋白质-蛋白质相互作用， 以及蛋白质的构象变化。核磁共振的独特之处在于它能够表征全球和局部 蛋白质的动力学。因此，这些发现将是对x射线平行研究的高度补充。 结晶学和电子显微镜。此外，核磁共振能够描述结构、动力学和 生理条件下蛋白质在磷脂双层环境中的相互作用。

7. Project Summary Membrane proteins are important targets for structure determination. One quarter of the proteins in the human genome are membrane proteins, and the majority of drug targets are membrane proteins. However, both structure determination and dynamics characterization of membrane proteins have lagged because of technological difficulties resulting largely from the phospholipid environment in which the proteins reside; it is highly asymmetric with hydrophobic and hydrophilic components, and it immobilizes the proteins. Consequently, our overarching goal is to develop new and more powerful methods for determining the structures of membrane proteins. This is an essential first step in revealing the bases of their functions. Although considerable progress has been made using solution NMR, X-ray crystallography, and electron microscopy, this has been at the potential cost of distorting the structures through the use of detergent environments and cryogenic temperatures for the protein samples. None of the proteins that we are studying have been crystallized. Thus, the technology gap that we seek to fill is well defined. Innovative features of the research plan include its scientific breadth, which ranges from molecular biology to structure calculations. Several smaller membrane proteins will be used for methods development, including Vpu from HIV-1, p7 from HCV, and mercury transport proteins from the bacterial mercury detoxifications system. They serve the dual purposes of posing interesting biochemical functional questions and serving as tractable systems for developing methods of determining the structures and describing the dynamics of larger membrane proteins, such as our principal target of G-protein coupled receptors (GPCRs). At the conclusion of the research plan, we expect to be able to describe the functions of chemokine receptors. These studies will involve the structures and dynamics of the monomeric proteins, protein-protein interactions, and conformational changes in the proteins. NMR is unique in its ability to characterize global and local dynamics of proteins. Thus, the findings will be highly complementary to parallel studied by x-ray crystallography and electron microscopy. Moreover, NMR is capable of describing structure, dynamics, and interactions of the proteins in their phospholipid bilayer environment under physiological conditions.