Cation-responsive cavity expansion of valinomycin revealed by cryogenic ion trap infrared spectroscopy
Cation-responsive cavity expansion of valinomycin revealed by cryogenic ion trap infrared spectroscopy
复制标题
低温离子阱红外光谱揭示缬氨霉素的阳离子响应空腔扩张
DOI：
10.1039/d2cp04570b
复制
发表时间：
2023
影响因子：
3.3
通讯作者：
Fujii Masaaki
中科院分区：
文献类型：
--
作者：
Hirata Keisuke;Sato Eiko;Lisy James M.;Ishiuchi Shun-Ichi;Fujii Masaaki
缬氨霉素（Valinomycin，VM）是一种天然的K+选择性离子载体，能将K+转运通过细胞膜。VM以C3对称的β-转角样骨架在其中心空腔中捕获K+。虽然VM-钠（Na+VM）复合物的结合亲和力相对于K+VM急剧降低，但VM对Rb+和Cs+具有相对高的亲和力。对较大离子的高亲和力，而不管离子大小，似乎与预期的最佳尺寸匹配模型相冲突，并提出了什么因素决定离子选择性的问题。红外光谱与支持计算的结合表明，VM可以通过其折叠的β-转角状骨架的伸长灵活地改变其空腔大小来容纳更大的Rb+和Cs+。对Rb+和Cs+的高亲和力可以归因于尺寸依赖的空腔膨胀。这些发现提供了一个新的视角，分子识别和选择性超越传统的大小匹配模型。
Valinomycin (VM) is a natural K+-selective ionophore that transports K+ through the cell membrane. VM captures K+ in its central cavity with a C3-symmetric β-turn-like backbone. Although the binding affinity is drastically decreased for the VM-sodium (Na+VM) complex with respect to K+VM, VM holds relatively high affinity to Rb+ and Cs+. The high affinity for larger ions irrespective of ionic size seems to conflict with the expected optimal size matching model and raises questions on what factors determine ion selectivity. A combination of infrared spectroscopy with supporting computational calculations reveals that VM can accommodate larger Rb+ and Cs+ by flexibly changing its cavity size with the elongation of its folded β-turn-like backbone. The high affinity to Rb+ and Cs+ can be ascribed to a size-dependent cavity expansion. These findings provide a new perspective on molecular recognition and selectivity beyond the conventional size matching model.