Small K+ channels are model proteins for detecting basic interactions between membrane proteins and their surrounding bilayer with relevance for structure and function

小 K 通道是模型蛋白，用于检测膜蛋白及其周围双层之间与结构和功能相关的基本相互作用

• 批准号: 290743586
• 负责人: Professor Dr. Gerhard Thiel
• 金额: --
• 依托单位: Arbeitsgruppe Plant Membrane Biophysics
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/290743586?language=en
• 关键词: Small; K+; channels; model; proteins

Structure/function correlates of membrane proteins can only be fully understood with profound knowledge on the complex interplay between proteins with their lipid environment. In the last decade much work was devoted to understand the basic architecture of transmembrane domains (TMDs) and their embedding in lipid bilayers. A systematic research with simple synthetic one membrane spanning proteins has in this context provided many of the basic rules for the amino acid composition of a-helical TMDs. The goal of the present project is to extend this systematic approach and examine structure/function correlates of membrane proteins by entering a higher level of complexity, which includes a measurable function. Ideal tools for this endeavor are provided by small viral K+ channels with different TMDs. A subunit of these functional channel proteins is built from two TMDs, which are just long enough to span a membrane. From a bulk of experimental and structural work we already know essential properties of the TMDS of these channels, which are important for an anchoring of the proteins in the membrane. A successful realization of the project is further supported by experimental progress, which allows us to produce channel proteins by in vitro translation in so called nano-discs. From there they can be reconstituted in various types of lipid bilayers and their function recorded as single channel fluctuations. With this solid background we propose to systematically examine the functional properties of model channel proteins with different TMDs in lipid bilayers with distinct physic chemical flavors like variable bilayer thickness, different head groups and with or without cholesterol. This work will be complemented by structural work in which small and wide angle X-ray scattering methods are used to determine the effect of the channel proteins on the geometry of the lipid bilayer. High-resolution microscopy will be employed to examine the potential formation of channel clusters in different membranes. Taken together these complementary experiments will provide a solid data base for an understanding of structure and function relations of simple channel proteins in variable lipid environments. We will obtain detailed information on the influence of different membrane properties on K+ channel function including gating and unitary conductance. The data will further show how the two partners, e.g. the membrane and the protein, compensate mismatches in the length of TMDs with respect to bilayer thickness without compromising function. The fact that the general structure of the viral K+ channels is similar to the pore structure of complex channels opens the possibility to extrapolate data from this research to physiologically relevant K+ channels.

只有深入了解蛋白质与其脂质环境之间的复杂相互作用，才能充分理解膜蛋白的结构/功能相关性。在过去的十年中，大量的工作致力于了解跨膜结构域（TMD）的基本结构及其在脂质双层中的嵌入。在此背景下，一项对简单合成单跨膜蛋白的系统研究为α-螺旋TMD的氨基酸组成提供了许多基本规则。本项目的目标是扩展这种系统方法，并通过进入更高水平的复杂性（包括可测量的功能）来检查膜蛋白的结构/功能相关性。具有不同 TMD 的小型病毒 K+ 通道提供了实现这一目标的理想工具。这些功能性通道蛋白的一个亚基由两个 TMD 构建而成，这两个 TMD 的长度刚好足以跨越膜。从大量的实验和结构工作中，我们已经了解了这些通道的 TMDS 的基本特性，这对于蛋白质在膜中的锚定非常重要。该项目的成功实现得到了实验进展的进一步支持，这使我们能够通过所谓的纳米盘中的体外翻译来生产通道蛋白。从那里，它们可以在各种类型的脂质双层中重建，并将它们的功能记录为单通道波动。有了这个坚实的背景，我们建议系统地检查脂质双层中具有不同TMD的模型通道蛋白的功能特性，这些模型通道蛋白具有不同的物理化学风味，如可变的双层厚度、不同的头部基团以及有或没有胆固醇。这项工作将得到结构工作的补充，其中使用小角度和广角 X 射线散射方法来确定通道蛋白对脂质双层几何形状的影响。将采用高分辨率显微镜来检查不同膜中通道簇的潜在形成。总而言之，这些互补的实验将为理解可变脂质环境中简单通道蛋白的结构和功能关系提供坚实的数据库。我们将获得有关不同膜特性对 K+ 通道功能（包括门控和单一电导）影响的详细信息。数据将进一步显示这两个合作伙伴如何膜和蛋白质，补偿 TMD 长度与双层厚度的不匹配，而不影响功能。病毒 K+ 通道的一般结构与复杂通道的孔结构相似，这一事实为将本研究的数据外推到生理相关的 K+ 通道提供了可能性。