KcsA - Prokaryotic pH-gated Potassium Channel

Family:
Prokaryotic Tetrameric Potassium Channels

Topology:
The channel protein contains two transmembrane helices (M1 and M2). The channel itself is a tetramer composed of four identical subunits so that the M2 helix faces the central pore, while the other M1 helix faces the lipid membrane.

History and function:
KcsA was the first potassium ion channel to be characterized using x-ray crystallography by Roderick MacKinnon and his colleagues in 1998. As one of the most studied ion channels to this day, KcsA is a template for research on K⁺ channel function. The KcsA channel is considered a model channel because its structure provides a framework for understanding K⁺ channel conduction, which has three parts: Potassium selectivity, channel gating by pH sensitivity, and voltage-gated channel inactivation.

Data and Applications

KcsA - Single Channel Recordings

Icon Orbit Orbit 16 and applications:
Data were kindly provided by Ionera.

Single channel currents of tetrameric potassium channel KcsA E71A recorded from 5 selected bilayers in parallel.
KcsA was expressed in vitro with its co-translational integration into liposoms containing asolectin lipids. The proteoliposomes were subsecuently fused with bilayer array containing POPE/POPG on the Orbit 16.
Conditions: Current traces were recorded in 20 mM MES pH 4.0 on the cis-side and 10 mM MOPS, pH 7.0 on the trans-side of the bilayer; containing 200 mM KCl symmetric solutions with membrane potential held at +150 mV.

KcsA - Bilayer Recordings

Vesicle Prep Pro data and applicatons:

The image shows a representative current trace recorded from a planar lipid bilayer in which purified KcsA channels were reconstituted (100 mM KCl, asymmetric pH; pH 4/pH 7). A ramp from -100 mV to +100 mV was used to evoke the single channel events.

Download: Application Note