Atomic resolution structures have provided significant insight into the gating and permeation mechanisms of various ion channels, including potassium channels. However, ion channels may also be regulated by numerous factors, including the physiochemical properties of the membrane in which they are embedded. For example, the matching of the bilayer’s hydrophobic region to the hydrophobic external surface of the ion channel is thought to minimize the energetic penalty needed to solvate hydrophobic residues or exposed lipid tails. To understand the molecular basis of such regulation by hydrophobic matching requires examining channels in the presence of the lipid membrane. Here we examine the role of hydrophobic matching in regulating the activity of the model potassium channel, KcsA. ⁸⁶Rb⁺ influx assays and single-channel recordings indicate that the non-inactivating E71A KcsA channel is most active in thin bilayers (<diC18:1PC). Bilayer thickness affects the open probability of KcsA and not its unitary conductance. Molecular dynamics simulations indicate that the bilayer can sufficiently modify its dimensions to accommodate KcsA channels without major perturbations in the protein helical packing within the nanosecond timescale. Based on experimental results and MD simulations, we present a model in which bilayer thickness influences the stability of the open and closed conformations of the intracellular gate of KcsA, with minimal impact on the stability of the selectivity filter of the non-inactivating mutant, E71A.

原子分辨结构为包括钾离子通道在内的各种离子通道的门控和渗透机理提供了重要的见识。但是，离子通道也可能受到多种因素的调节，包括嵌入它们的膜的物理化学特性。例如，认为双层的疏水区与离子通道的疏水外表面的匹配使溶剂化疏水残基或暴露的脂质尾部所需的能量损失最小。为了了解通过疏水性匹配进行调节的分子基础，需要在脂质膜存在的情况下检查通道。在这里，我们检查了疏水性匹配在调节模型钾通道KcsA活性中的作用。⁸⁶ Rb ⁺大量检测和单通道记录表明，非激活E71A KcsA通道在薄双层（<diC18：1PC）中最活跃。双层厚度影响KcsA的打开概率，而不影响其单位电导。分子动力学模拟表明，该双层可以在纳秒级时程内充分修改其尺寸以容纳KcsA通道，而不会在蛋白质螺旋堆积中产生重大干扰。基于实验结果和MD模拟，我们提出了一个模型，其中双层厚度影响KcsA细胞内门的打开和闭合构象的稳定性，而对非灭活突变体E71A的选择性过滤器的稳定性影响最小。