期刊
NATURE CHEMISTRY
卷 10, 期 8, 页码 813-820出版社
NATURE PORTFOLIO
DOI: 10.1038/s41557-018-0105-9
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资金
- German Research Foundation [FOR 2518]
- Scottish Universities' Physics Alliance
- BBSRC [BB/J013072/1]
- BBSRC [BB/J013072/1] Funding Source: UKRI
The seeming contradiction that K+ channels conduct K+ ions at maximal throughput rates while not permeating slightly smaller Na+ ions has perplexed scientists for decades. Although numerous models have addressed selective permeation in K(+ )channels, the combination of conduction efficiency and ion selectivity has not yet been linked through a unified functional model. Here, we investigate the mechanism of ion selectivity through atomistic simulations totalling more than 400 mu s in length, which include over 7,000 permeation events. Together with free-energy calculations, our simulations show that both rapid permeation of K+ and ion selectivity are ultimately based on a single principle: the direct knock-on of completely desolvated ions in the channels' selectivity filter. Herein, the strong interactions between multiple 'naked' ions in the four filter binding sites give rise to a natural exclusion of any competing ions. Our results are in excellent agreement with experimental selectivity data, measured ion interaction energies and recent two-dimensional infrared spectra of filter ion configurations.
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