Accessibility of Cations to the Selectivity Filter of KcsA in the Inactivated State: An Equilibrium Binding Study

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Title: Accessibility of Cations to the Selectivity Filter of KcsA in the Inactivated State: An Equilibrium Binding Study
Authors: Giudici, A. Marcela | Renart, M. Lourdes | Díaz-García, Clara | Morales, Andrés | Poveda, José A. | González-Ros, José M.
Research Group/s: Fisiología de Membranas
Center, Department or Service: Universidad de Alicante. Departamento de Fisiología, Genética y Microbiología
Keywords: Potassium channels | C-type inactivation | Selectivity filter conformation | Protein thermal stability | Fluorescence | Ion-protein interactions
Knowledge Area: Fisiología
Issue Date: 5-Feb-2019
Publisher: MDPI
Citation: Giudici AM, Renart ML, Díaz-García C, Morales A, Poveda JA, González-Ros JM. Accessibility of Cations to the Selectivity Filter of KcsA in the Inactivated State: An Equilibrium Binding Study. International Journal of Molecular Sciences. 2019; 20(3):689. doi:10.3390/ijms20030689
Abstract: Cation binding under equilibrium conditions has been used as a tool to explore the accessibility of permeant and nonpermeant cations to the selectivity filter in three different inactivated models of the potassium channel KcsA. The results show that the stack of ion binding sites (S1 to S4) in the inactivated filter models remain accessible to cations as they are in the resting channel state. The inactivated state of the selectivity filter is therefore “resting-like” under such equilibrium conditions. Nonetheless, quantitative differences in the apparent KD’s of the binding processes reveal that the affinity for the binding of permeant cations to the inactivated channel models, mainly K+, decreases considerably with respect to the resting channel. This is likely to cause a loss of K+ from the inactivated filter and consequently, to promote nonconductive conformations. The most affected site by the affinity loss seems to be S4, which is interesting because S4 is the first site to accommodate K+ coming from the channel vestibule when K+ exits the cell. Moreover, binding of the nonpermeant species, Na+, is not substantially affected by inactivation, meaning that the inactivated channels are also less selective for permeant versus nonpermeant cations under equilibrium conditions.
Sponsor: This work was partly supported by the grant BFU2015-66612-P from the Spanish MINECO/FEDER, UE. CD-G acknowledges support from Medical Biochemistry and Biophysics Doctoral Programme (M2B-PhD) and FCT Portugal (SFRH/PD/BD/135154/2017).
ISSN: 1661-6596 (Print) | 1422-0067 (Online)
DOI: 10.3390/ijms20030689
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
Peer Review: si
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Appears in Collections:INV - Fisiología de Membranas - Artículos de Revistas

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