Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia.
Biophys J. 2013 Dec 3;105(11):2461-73. doi: 10.1016/j.bpj.2013.09.058.
The slow delayed rectifier (I(KS)) channel is composed of KCNQ1 (pore-forming) and KCNE1 (auxiliary) subunits, and functions as a repolarization reserve in the human heart. Design of I(KS)-targeting anti-arrhythmic drugs requires detailed three-dimensional structures of the KCNQ1/KCNE1 complex, a task made possible by Kv channel crystal structures (templates for KCNQ1 homology-modeling) and KCNE1 NMR structures. Our goal was to build KCNQ1/KCNE1 models and extract mechanistic information about their interactions by molecular-dynamics simulations in an explicit lipid/solvent environment. We validated our models by confirming two sets of model-generated predictions that were independent from the spatial restraints used in model-building. Detailed analysis of the molecular-dynamics trajectories revealed previously unrecognized KCNQ1/KCNE1 interactions, whose relevance in I(KS) channel function was confirmed by voltage-clamp experiments. Our models and analyses suggest three mechanisms by which KCNE1 slows KCNQ1 activation: by promoting S6 bending at the Pro hinge that closes the activation gate; by promoting a downward movement of gating charge on S4; and by establishing a network of electrostatic interactions with KCNQ1 on the extracellular surface that stabilizes the channel in a pre-open activated state. Our data also suggest how KCNE1 may affect the KCNQ1 pore conductance.
缓慢延迟整流钾通道（I(KS)）由 KCNQ1（孔形成）和 KCNE1（辅助）亚基组成，作为人心肌复极化储备。靶向 I(KS)抗心律失常药物的设计需要 KCNQ1/KCNE1 复合物的详细三维结构，这一任务得益于 Kv 通道晶体结构（KCNQ1 同源建模模板）和 KCNE1 NMR 结构。我们的目标是构建 KCNQ1/KCNE1 模型，并通过在明确的脂质/溶剂环境中进行分子动力学模拟提取其相互作用的机制信息。我们通过确认两组与模型构建中使用的空间约束无关的模型生成预测来验证我们的模型。对分子动力学轨迹的详细分析揭示了以前未被识别的 KCNQ1/KCNE1 相互作用，这些相互作用在 I(KS)通道功能中的相关性通过电压钳实验得到了证实。我们的模型和分析表明，KCNE1 使 KCNQ1 激活减慢的三种机制：通过促进关闭激活门的 Pro 铰链处的 S6 弯曲；通过促进 S4 上门控电荷向下移动；并通过与细胞外表面上的 KCNQ1 建立静电相互作用网络，将通道稳定在预开放激活状态。我们的数据还表明 KCNE1 如何影响 KCNQ1 孔电导。
