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Different roles for aspartates and glutamates for cation permeation in bacterial sodium channels

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Guardiani, Carlo, Fedorenko, Olena A., Khovanov, Igor A. and Roberts, Stephen K. (2019) Different roles for aspartates and glutamates for cation permeation in bacterial sodium channels. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1861 (2). pp. 495-503. doi:10.1016/j.bbamem.2018.11.011 ISSN 0005-2736.

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Official URL: http://dx.doi.org/10.1016/j.bbamem.2018.11.011

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Abstract

A key driving force for ion channel selectivity is represented by the negative charge of the Selectivity Filter carried by aspartate (D) and glutamate (E) residues. However, the structural effects and specific properties of D and E residues have not been extensively studied. In order to investigate this issue we studied the mutants of NaChBac channel with all possible combinations of D and E in the charged rings in position 191 and 192. Electrophysiological measurements showed significant Ca2+ currents only when position 191 was occupied by E. Equilibrium Molecular Dynamics simulations revealed the existence of two binding sites, corresponding to the charged rings and another one, more internal, at the level of L190. The simulations showed that the ion in the innermost site can interact with the residue in position 191 only when this is glutamate. Based on the MD simulations, we suggest that a D in position 191 leads to a high affinity Ca2+ block site resulting from a significant drop in the free energy of binding for an ion moving between the binding sites; in contrast, the free energy change is more gradual when an E residue occupies position 191, resulting in Ca2+ permeability. This scenario is consistent with the model of ion channel selectivity through stepwise changes in binding affinity proposed by Dang and McCleskey. Our study also highlights the importance of the structure of the selectivity filter which should contribute to the development of more detailed physical models for ion channel selectivity.

Item Type: Journal Article
Subjects: Q Science > QP Physiology
Divisions: Faculty of Science, Engineering and Medicine > Engineering > Engineering
Library of Congress Subject Headings (LCSH): Sodium channels, Calcium channels, Ion channels
Journal or Publication Title: Biochimica et Biophysica Acta (BBA) - Biomembranes
Publisher: Elsevier BV
ISSN: 0005-2736
Official Date: 1 February 2019
Dates:
DateEvent
1 February 2019Published
6 December 2018Available
30 November 2018Accepted
Volume: 1861
Number: 2
Page Range: pp. 495-503
DOI: 10.1016/j.bbamem.2018.11.011
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Open Access (Creative Commons)
Date of first compliant deposit: 12 December 2018
Date of first compliant Open Access: 12 December 2018
RIOXX Funder/Project Grant:
Project/Grant IDRIOXX Funder NameFunder ID
EP/M015831/1 [EPSRC] Engineering and Physical Sciences Research Councilhttp://dx.doi.org/10.13039/501100000266
EP/M016889/1[EPSRC] Engineering and Physical Sciences Research Councilhttp://dx.doi.org/10.13039/501100000266
EP/K000128/1[EPSRC] Engineering and Physical Sciences Research Councilhttp://dx.doi.org/10.13039/501100000266
UNSPECIFIEDUniversity of Warwickhttp://dx.doi.org/10.13039/501100000741

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