Contribution of Ion Binding Affinity to Ion Selectivity and Permeation in KcsA, a Model Potassium Channel

Biochemistry ◽  
2012 ◽  
Vol 51 (18) ◽  
pp. 3891-3900 ◽  
Author(s):  
M. L. Renart ◽  
E. Montoya ◽  
A. M. Fernández ◽  
M. L. Molina ◽  
J. A. Poveda ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Binding Affinity ◽  
Ion Selectivity ◽  
Ion Binding

Ion Binding Affinity in the Cavity of the KcsA Potassium Channel†

Biochemistry ◽  
2004 ◽  
Vol 43 (17) ◽  
pp. 4978-4982 ◽  
Author(s):  
Yufeng Zhou ◽  
Roderick MacKinnon
Keyword(s):  
Potassium Channel ◽  
Binding Affinity ◽  
Ion Binding ◽  
Kcsa Potassium Channel

scholarly journals Ion Interactions in the High-Affinity Binding Locus of a Voltage-Gated Ca2+ Channel

2000 ◽  
Vol 116 (4) ◽  
pp. 569-586 ◽  
Author(s):  
Robin K. Cloues ◽  
Susan M. Cibulsky ◽  
William A. Sather
Keyword(s):  
Binding Affinity ◽  
Single Channel ◽  
Ion Selectivity ◽  
Ion Pairs ◽  
Selectivity Filter ◽  
Ion Binding ◽  
Wild Type ◽  
Filter Function ◽  
Voltage Gated ◽  
Ca2 Channels

The selectivity filter of voltage-gated Ca2+ channels is in part composed of four Glu residues, termed the EEEE locus. Ion selectivity in Ca2+ channels is based on interactions between permeant ions and the EEEE locus: in a mixture of ions, all of which can pass through the pore when present alone, those ions that bind weakly are impermeant, those that bind more strongly are permeant, and those that bind more strongly yet act as pore blockers as a consequence of their low rate of unbinding from the EEEE locus. Thus, competition among ion species is a determining feature of selectivity filter function in Ca2+ channels. Previous work has shown that Asp and Ala substitutions in the EEEE locus reduce ion selectivity by weakening ion binding affinity. Here we describe for wild-type and EEEE locus mutants an analysis at the single channel level of competition between Cd2+, which binds very tightly within the EEEE locus, and Ba2+ or Li+, which bind less tightly and hence exhibit high flux rates: Cd2+ binds to the EEEE locus ∼104× more tightly than does Ba2+, and ∼108× more tightly than does Li+. For wild-type channels, Cd2+ entry into the EEEE locus was 400× faster when Li+ rather than Ba2+ was the current carrier, reflecting the large difference between Ba2+ and Li+ in affinity for the EEEE locus. For the substitution mutants, analysis of Cd2+ block kinetics shows that their weakened ion binding affinity can result from either a reduction in blocker on rate or an enhancement of blocker off rate. Which of these rate effects underlay weakened binding was not specified by the nature of the mutation (Asp vs. Ala), but was instead determined by the valence and affinity of the current-carrying ion (Ba2+ vs. Li+). The dependence of Cd2+ block kinetics upon properties of the current-carrying ion can be understood by considering the number of EEEE locus oxygen atoms available to interact with the different ion pairs.

scholarly journals Ion Selectivity in the KcsA Potassium Channel from the Perspective of the Ion Binding Site

2009 ◽  
Vol 96 (6) ◽  
pp. 2138-2145 ◽  
Author(s):  
Purushottam D. Dixit ◽  
Safir Merchant ◽  
D. Asthagiri
Keyword(s):  
Potassium Channel ◽  
Binding Site ◽  
Ion Selectivity ◽  
Ion Binding ◽  
Kcsa Potassium Channel

scholarly journals The Importance of Ion Binding for Potassium Channel Inactivation and Recovery

2010 ◽  
Vol 98 (3) ◽  
pp. 621a
Author(s):  
Albert C. Pan ◽  
Sudha Chakrapani ◽  
Vishwanath Jogini ◽  
Luis G. Cuello ◽  
Doris M. Cortes ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Ion Binding ◽  
Channel Inactivation

Ion Binding to KcsA: Implications in Ion Selectivity and Channel Gating

Biochemistry ◽  
2010 ◽  
Vol 49 (44) ◽  
pp. 9480-9487 ◽  
Author(s):  
M. L. Renart ◽  
I. Triano ◽  
J. A. Poveda ◽  
J. A. Encinar ◽  
A. M. Fernández ◽  
...  
Keyword(s):  
Ion Selectivity ◽  
Channel Gating ◽  
Ion Binding

scholarly journals Selective exclusion and selective binding both contribute to ion selectivity in KcsA, a model potassium channel

2017 ◽  
Vol 292 (37) ◽  
pp. 15552-15560 ◽  
Author(s):  
M. Lourdes Renart ◽  
Estefanía Montoya ◽  
A. Marcela Giudici ◽  
José A. Poveda ◽  
Asia M. Fernández ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Ion Selectivity ◽  
Selective Binding

scholarly journals A De Novo Mutation in the Sodium-Activated Potassium Channel KCNT2 Alters Ion Selectivity and Causes Epileptic Encephalopathy

Cell Reports ◽  
2017 ◽  
Vol 21 (4) ◽  
pp. 926-933 ◽  
Author(s):  
Sushmitha Gururaj ◽  
Elizabeth Emma Palmer ◽  
Garrett D. Sheehan ◽  
Tejaswi Kandula ◽  
Rebecca Macintosh ◽  
...  
Keyword(s):  
Potassium Channel ◽  
De Novo ◽  
Ion Selectivity ◽  
Epileptic Encephalopathy ◽  
De Novo Mutation
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