Thermodynamics and Energetics of voltage-gated ion channels

离子通道是许多物理刺激的主要感受器，如电压、横向拉伸、渗透压等 和温度其中，温度传感和温度的基本生物物理原理- 依赖门控也许是最神秘的。尽管事实上，许多离子通道在电压- 门控离子通道（VGIC）超家族参与温度传感，许多高分辨率 结构现在是可用的，一个共同的结构基序或模块负责这个温度- 依赖性尚未确定。一种可能性是，温度敏感表型是由于 收敛演化和不同的离子通道已经以不同的方式变得对温度敏感。 根据这种思路，与化学信号不同，温度门控可能与化学信号无关。 因为它不受立体化学规则约束。该提案的目标是广泛地 探索离子通道中温度依赖性门控的机制，使用多管齐下的方法。在 具体目标1，我们将应用新开发的热力学工具和多维NMR 光谱学，以彻底表征生物物理机制的基础上提高温度- 在工程离子通道中的敏感门控。我们将测试的假设，状态依赖的变化， 侧链和脂酰基链的溶剂化可能是这些离子通道中温度依赖性的基础。在 具体目标2，我们将探索机电耦合的温度依赖性。这里的目标 是使用合理的设计方法来测试温度传感的替代机制。在这个范例中， 温度敏感性不是由于传感器本身，而是由于耦合的温度依赖性 电压传感器和孔门之间的相互作用。在具体目标3中，我们将探索 温度依赖性门控在一个生物化学易处理的原核通道。我们最近发现 MthK钾离子通道的钙依赖性门控具有高度的温度敏感性。我们 拟议中的研究将结合联合收割机量热法，电生理学和结构生物学与反向的力量 遗传学，以了解这些古离子温度依赖性的分子机制 渠道这三个具体目标将广泛地研究温度依赖性的机制， VGIC超家族通道的门控。我们希望这种多学科的方法将揭示 许多离子通道的温度依赖性的生物物理机制。

Ion channels are the primary sensors of many physical stimuli such as voltage, lateral stretch, osmolality and temperature. Of these, the fundamental biophysical principles of temperature-sensing and temperature- dependent gating are perhaps the most enigmatic. Despite the fact that many ion channels in the voltage- gated ion channel (VGIC) superfamily are involved in temperature sensing and that many high-resolution structures are now available, a common structural motif or module responsible for this temperature- dependence has not yet been identified. One possibility is that temperature-sensing phenotype is due to convergent evolution and different ion channels have become temperature-sensitive in different ways. According to this line of thinking, unlike a chemical signal, temperature gating may have less to do with a specific structural fold since it is not bound by rules of stereochemistry. The goal of this proposal is to broadly explore the mechanisms of temperature-dependent gating in ion channels using a multi-pronged approach. In specific aim 1, we will apply the newly developed thermodynamic tools and multi-dimensional NMR spectroscopy to thoroughly characterize the biophysical mechanisms that underlie enhanced temperature- sensitive gating in engineered ion channels. We will test the hypothesis that state-dependent change in solvation of side-chains and lipid acyl chains may underlie temperature-dependence in these ion channels. In the specific aim 2, we will explore the temperature-dependence of electromechanical coupling. The goal here is to use rational design approach to test an alternate mechanism of temperature sensing. In this paradigm, the temperature-sensitivity is not due to the sensor itself but due to temperature-dependence of coupling interactions between the voltage-sensor and pore gates. In specific aim 3, we will probe the mechanisms of temperature-dependent gating in a biochemically tractable prokaryotic channel. We have recently identified that the calcium-dependent gating of MthK potassium ion channel is highly temperature-sensitive. Our proposed studies will combine calorimetry, electrophysiology and structural biology with the power of reverse genetics to understand the molecular mechanisms that underlie temperature-dependence in these archeal ion channels. Taken together, the three specific aims will broadly study the mechanisms of temperature-dependent gating in channels of the VGIC superfamily. We expect that this multi-disciplinary approach will shed light on the biophysical mechanisms that underlie exquisite temperature-dependence in many ion channels.