Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.
Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovation Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
Phys Chem Chem Phys. 2021 Jun 2;23(21):12045-12050. doi: 10.1039/d1cp00936b.
Potassium channels allow K+ to rapidly diffuse, while the selectivity filter (SF) actively blocks Na+. The presence of water in the SF during ion translocation remains under debate due to the experimental and computational challenges in characterizing the interactions between water, ions, and the SF. Our bottom-up approach has been applied to a system composed of a partial peptide of the SF (Ac-tyrosine-NHMe) with a metal ion and a single water molecule to probe these interactions. The IR photodissociation spectra of M+Ac-tyrosine-NHMe(H2O) (M = Na, K) combined with quantum chemical calculations revealed that the water molecule binding sites are ion-dependent. In addition, the ion-peptide distances are elongated significantly for the K+ complex in comparison to the Na+ complex by the addition of a single water molecule. This striking structural difference with the water molecule is discussed in relation to ion selectivity and translocation within the K+ channel.
钾通道允许 K+ 快速扩散，而选择性过滤器 (SF) 则主动阻止 Na+。由于在描述水、离子和 SF 之间相互作用方面存在实验和计算上的挑战，离子迁移过程中 SF 中是否存在水仍然存在争议。我们的自下而上方法已应用于由 SF 的部分肽（Ac-酪氨酸-NHMe）与金属离子和单个水分子组成的系统，以探测这些相互作用。M+Ac-酪氨酸-NHMe(H2O)（M = Na，K）的红外光解光谱与量子化学计算相结合，揭示了水分子的结合位点是离子依赖性的。此外，与 Na+ 配合物相比，通过添加单个水分子，K+ 配合物中的离子-肽距离显著延长。这种与水分子的显著结构差异与 K+ 通道内的离子选择性和转运有关。
