Correlations: Structure-Dynamics-Functions in Channels

描述（由申请人提供）：单通道和多通道电导测量，高分辨率固体核磁共振结构和动态表征，以及高水平的计算工作将导致结构-功能和动态-功能相关性。这些将极大地促进我们对离子通道电导、门控和阻塞机制以及许多功能细节的理解。先前通过该资助的支持导致了定义gramicidin A的功能机制，离子特异性和效率的新相关性，以及打开和关闭该通道的独特模型。对于甲型流感病毒的M2 H+通道也获得了初步的机制见解。全长M2蛋白的电生理和核磁共振研究表明，膜蛋白对其双层环境是多么敏感，以及这些结构是如何在水溶性蛋白中很少（如果有的话）观察到动态过程的。

DESCRIPTION (provided by applicant): Single and multi-channel conductance measurements, high resolution structural and dynamic characterization by solid-state NMR, and high level computational efforts will lead to structure-function and dynamic-function correlations. These will greatly facilitate our understanding of ion channel conductance, gating and blockage mechanisms, as well as numerous functional details. Previous support through this grant has led to novel correlations for defining functional mechanisms, ion specificity and efficiency in gramicidin A, as well as unique models for opening and closing this channel. Initial mechanistic insights have also been obtained for the M2 H+ channel from influenza A virus. Electrophysiological and NMR studies of the full length M2 protein have illustrated how sensitive membrane proteins are to their bilayer environment and how these structures can have dynamic processes rarely, if ever, observed in water soluble proteins. Here, we propose to characterize structure-dynamic-function correlations in the M2 H+ channel leading to mechanistic understandings. This protein is a proven drug target and it is the first H+ channel to be cloned and expressed. Several key features of this structure include the single transmembrane helix that can be kinked in the presence of a channel blocker, a histidine tetrad that appears to be responsible for H+ selectivity and acid gating, and a tryptophan tetrad that interacts with the histidines, at least in the closed state. High resolution backbone structure and dynamics, as a function of pH, will be obtained for this protein, as well as the pKas of the histidines under various conditions. These efforts will be guided by both modeling and functional characterizations of the protein. This work has broad implications for understanding how, in general, membrane proteins function and how ion specificity, conductance efficiency, gating and blockage can be achieved and characterized all in a lamellar phase lipid environment.