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  • The voltage-dependent gate in MthK potassium channels is located at the selectivity filter.

The voltage-dependent gate in MthK potassium channels is located at the selectivity filter.

Nature structural & molecular biology (2012-12-25)
David J Posson, Jason G McCoy, Crina M Nimigean
ABSTRACT

Understanding how ion channels open and close their pores is crucial for comprehending their physiological roles. We used intracellular quaternary ammonium blockers, electrophysiology and X-ray crystallography to locate the voltage-dependent gate in MthK potassium channels from Methanobacterium thermoautotrophicum. Blockers bind in an aqueous cavity between two putative gates: an intracellular gate and the selectivity filter. Thus, these blockers directly probe gate location--an intracellular gate will prevent binding when closed, whereas a selectivity filter gate will always allow binding. Kinetic analysis of tetrabutylammonium block of single MthK channels combined with X-ray crystallographic analysis of the pore with tetrabutyl antimony unequivocally determined that the voltage-dependent gate, like the C-type inactivation gate in eukaryotic channels, is located at the selectivity filter. State-dependent binding kinetics suggest that MthK inactivation leads to conformational changes within the cavity and intracellular pore entrance.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Tetrabutylammonium cyanide, technical, ≥80%
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Tetrabutylammonium hydroxide solution, technical, ~40% in H2O (~1.5 M)
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Tetrabutylammonium hydroxide solution, ~40% in water, suitable for ion chromatography
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Tetrabutylammonium hydroxide solution, 53.5-56.5% in H2O
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Tetrabutylammonium phosphate monobasic solution, 1.0 M in H2O
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Tetrabutylammonium hydroxide solution, 40 wt. % in H2O
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Tetrabutylammonium perchlorate, for electrochemical analysis, ≥99.0%
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Tetrabutylammonium azide
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Tetrabutylammonium iodide, ≥99.0% (AT)
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Tetrabutylammonium bromide solution, 50 wt. % in H2O
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Tetrabutylammonium bisulfate, suitable for ion pair chromatography, LiChropur, ≥99.0%
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