ATR-FTIR Spectroscopy Revealing the Different Vibrational Modes of the Selectivity Filter Interacting with K+ and Na+ in the Open and Collapsed Conformations of the KcsA Potassiu

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• 作者：Yuji Furutani ; Hirofumi Shimizu ; Yusuke Asai ; Tetsuya Fukuda ; Shigetoshi Oiki ; Hideki Kandori
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2012
• 出版时间：December 20, 2012
• 年：2012
• 卷：3
• 期：24
• 页码：3806-3810
• 全文大小：337K
• 年卷期：v.3,no.24(December 20, 2012)
• ISSN：1948-7185

文摘

The potassium channel is highly selective for K⁺ over Na⁺, and the selectivity filter binds multiple dehydrated K⁺ ions upon permeation. Here, we applied attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy to extract ion-binding-induced signals of the KcsA potassium channel at neutral pH. Shifts in the peak of the amide-I signal towards lower vibrational frequencies were observed as K⁺ was replaced with Na⁺. These ion species-specific shifts deduced the selectivity filter as the source of the signal, which was supported by the spectra of a mutant for the selectivity filter (Y78F). The difference FTIR spectra between the solution containing various concentrations of K⁺ and that containing pure Na⁺ demonstrated two types of peak shifts of the amide-I vibration in response to the K⁺ concentration. These signals represent the binding of K⁺ ions to the different sites in the selectivity filter with different dissociation constants (K_D = 9 or 18 mM).

Keywords:

ion channels; KcsA; protein鈭抜on interaction; ion selectivity; FTIR