新型离子通道TehA突变体结构及其新颖门控机制的研究

Membrane proteins, embedded in the membrane, play important roles in diverse cellular functions. Recently, we determined a 1.2 ? resolution crystal structure of the bacterial TehA. Based on systematically analyses on the protein sequences, we discovered a family of novel anion channel, including the recent identified SLAC1. SLAC1 plays a central role in initiating stomatal closure in response to a wide range of environmental stress. This study shed new insight into the understanding of the SLAC1 function, based on the analysis of TehA structure. The current TehA structure snapshot a closed state of an ion channel, and the high resolution structural information revealed that the channel gate adopted a high energetic conformation. This finding, together with functional analysis, led to a novel gating mechanism for this family of novel anion channel, which needs further follow-up studies to confirm. In our preliminary study, we identified some interesting TehA mutants with possible open pore, as evidenced by their large conductance in the electrophysiological analysis on Xenopus oocyte. We plan to explore the novel gating mechanism through structural analysis on the open pore mutant of TehA. In addition, we aim to use TehA as a model to understand the different effect of detergent on the membrane protein crystallization and explore the possibility of using the bound Br- ion for phasing. The findings will be useful to understand the novel gating mechanism of a family of novel anion channel and shed light to the understanding the SLAC1 function.

膜蛋白是一类嵌在生物膜的蛋白质, 在各种各样生命活动中扮演了不同的角色，执行着重要的生物学功能。最近，我们解析了细菌膜蛋白TehA的1.2埃高分辨率的晶体结构，通过生物信息学分析发现了一类新型的离子通道，包括最近在植物中发现的响应胁迫应答过程中直接启动气孔关闭的SLAC1分子。该结构处于处于关闭状态的构象，但是高分辨率的结构细节揭示该离子通道的门处于不稳定的高能量状态，具有一种新颖的门控机制。我们在初步研究中发现了可能处于开放状态构象的突变体。本项目拟通过解析其突变体的晶体结构来进一步探索该类新型离子通道新颖的门控机制。此外，本项目还计划以TehA为模型蛋白，探索膜蛋白结晶的规律和卤素离子在膜蛋白相位求解中的应用，争取获得膜蛋白结构生物学研究方法上的突破。该项目的完成不仅能有助于深入认识新型膜蛋白离子通道的结构-功能，还将为理解在植物SLAC1分子作用机理提供重要信息。