Department of Life Sciences and the Zlotowski Center for Neurosciences, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva 84105, Israel.
J Mol Biol. 2010 Oct 22;403(2):167-73. doi: 10.1016/j.jmb.2010.08.041. Epub 2010 Sep 8.
Long-range coupling between distant functional elements of proteins may rely on allosteric communication trajectories lying along the protein structure, as described in the case of the Shaker voltage-activated potassium (Kv) channel model allosteric system. Communication between the distant Kv channel activation and slow inactivation pore gates was suggested to be mediated by a network of local pairwise and higher-order interactions among the functionally unique residues that constitute the allosteric trajectory. The mechanism by which conformational changes propagate along the Kv channel allosteric trajectory to achieve pore opening, however, remains unclear. Such conformational changes may propagate in either a concerted or a sequential manner during the reaction coordinate of channel opening. Residue-level structural information on the transition state of channel gating is required to discriminate between these possibilities. Here, we combine patch-clamp electrophysiology recordings of Kv channel gating and analysis using linear free-energy relations, focusing on a select set of residues spanning the allosteric trajectory of the Kv channel pore. We show that all allosteric trajectory residues tested exhibit an open-like conformation in the transition state of channel opening, implying that coupling interactions occur along the trajectory break in a concerted manner upon moving from the closed to the open state. Energetic coupling between the Kv channel gates thus occurs in a concerted fashion in both the spatial and the temporal dimensions, strengthening the notion that such trajectories correspond to pathways of mechanical deformation along which conformational changes propagate.
蛋白质中远距离功能元件之间的远程偶联可能依赖于沿着蛋白质结构的变构通讯轨迹,如 Shaker 电压激活钾 (Kv) 通道模型变构系统中所述。据推测,远距离 Kv 通道激活和缓慢失活孔门之间的通讯是通过构成变构轨迹的功能独特残基之间的局部成对和更高阶相互作用网络介导的。然而,构象变化沿着 Kv 通道变构轨迹传播以实现孔道开放的机制尚不清楚。在通道开放的反应坐标中,这种构象变化可能以协调或顺序的方式传播。需要关于通道门控的过渡态的残基水平结构信息来区分这些可能性。在这里,我们结合 Kv 通道门控的膜片钳电生理学记录和使用线性自由能关系的分析,重点研究跨越 Kv 通道孔变构轨迹的一组选定残基。我们表明,在通道打开的过渡状态下,所有测试的变构轨迹残基都表现出类似于开放的构象,这意味着在从关闭状态移动到开放状态时,沿着轨迹的耦合相互作用以协调的方式发生断裂。因此,Kv 通道门之间的能量耦合以协调的方式发生在空间和时间两个维度上,这加强了这样的轨迹对应于沿着构象变化传播的机械变形途径的观点。