Thermodynamics and Energetics of voltage-gated ion channels

离子通道是电压、侧向拉伸、渗透压等多种生理刺激的主要感受器 和温度。其中，温度传感和温度的基本生物物理原理- 依赖门控可能是最神秘的。尽管电压中的许多离子通道- 门控离子通道(VGIC)超家族涉及到温度传感和许多高分辨率 现在有了结构，一个常见的结构主题或模块负责这个温度- 依存性尚未确定。一种可能性是温度敏感表型是由于 收敛的进化和不同的离子通道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 特定的结构折叠，因为它不受立体化学规则的约束。这项提议的目标是广泛地 用多管齐下的方法探索离子通道中依赖温度的门控机制。在……里面 具体目标1，我们将应用最新开发的热力学工具和多维核磁共振 光谱学来彻底描述温度升高背后的生物物理机制- 工程离子通道中的灵敏门控。我们将检验这一假设，即状态依赖的变化在 侧链和脂酰链的溶剂化可能是这些离子通道的温度依赖性的基础。在……里面 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 是用合理的设计方法来测试一种替代的温度传感机制。在这个范例中， 温度敏感性不是由传感器本身引起的，而是由耦合的温度依赖性引起的 电压传感器和孔栅之间的相互作用。在具体目标3中，我们将探讨 生物化学上易处理的原核生物通道中的温度依赖门控。我们最近确认了 MthK钾离子通道的钙依赖门控是高度温度敏感的。我们的 拟议的研究将把量热学、电生理学和结构生物学与逆转的力量结合起来。 遗传学以了解这些原始离子中温度依赖的分子机制 频道。综上所述，这三个具体目标将广泛地研究温度依赖的机制 在VGIC超级家族的频道中选通。我们期望，这种多学科的方法将阐明 在许多离子通道中与温度密切相关的生物物理机制。

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.