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High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels
Published on: January 27, 2013
KirBac1.1: it's an inward rectifying potassium channel
Wayland W L Cheng1, Decha Enkvetchakul, Colin G Nichols
1Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
The Journal of General Physiology
|February 11, 2009
Summary
This study successfully performed voltage clamp analysis on the prokaryotic KirBac1.1 channel, revealing its behavior as a bona fide inward rectifier potassium channel. These findings enable integrated structural and electrophysiological studies of Kir channels.
Area of Science:
- Biophysics
- Molecular Biology
- Structural Biology
Background:
- KirBac1.1 is a prokaryotic homolog of eukaryotic inward rectifier potassium (Kir) channels.
- Previous functional analysis of KirBac1.1 was limited, lacking voltage clamp data.
- Crystal structures of KirBac1.1 have been used for in silico modeling of eukaryotic Kir channels.
Purpose of the Study:
- To perform voltage clamp analysis on recombinant KirBac1.1 channels.
- To characterize the functional properties of KirBac1.1.
- To establish KirBac1.1 as a tractable model for integrated biophysical studies.
Main Methods:
- Expression of His-tagged KirBac1.1 in Escherichia coli.
- Voltage clamp recordings from excised membrane patches of giant liposomes.
- Site-directed mutagenesis (I138D) to assess ion selectivity and blocker sensitivity.
Main Results:
- KirBac1.1 exhibits K+ selectivity, insensitivity to spermine, and block by Ba2+, resembling weakly rectifying eukaryotic Kir channels.
- A pore-lining mutation (I138D) confers spermine sensitivity, mirroring eukaryotic Kir channel behavior.
- KirBac1.1 currents are inhibited by PIP2 and display multiple conductance states and variable gating kinetics at the single-channel level.
Conclusions:
- Voltage clamp analysis confirms KirBac1.1 functions as a bona fide Kir channel.
- KirBac1.1 serves as a valuable model for combined structural and electrophysiological investigations of Kir channels.
- This work bridges structural insights with functional electrophysiology for prokaryotic Kir channels.
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