Changes in single K+ channel behavior through the lipid phase transition

TL;DR

This study demonstrates that the activity of a K+ ion channel is directly affected by the phase state of the surrounding lipid bilayer, with properties changing notably during phase transitions.

Contribution

It provides experimental evidence linking lipid phase transitions to functional changes in ion channel activity, highlighting the influence of membrane physical properties.

Findings

Channel conductance varies with lipid phase

Open probability shows trend inversion at phase transition

Physical membrane properties modulate ion channel function

Abstract

We show that the activity of an ion channel is strictly related to the phase state of the lipid bilayer hosting the channel. By measuring unitary conductance, dwell times, and open probability of the K+ channel KcsA as a function of temperature in lipid bilayers composed of POPE and POPG in different relative proportions, we obtain that all those properties show a trend inversion when the bilayer is in the transition region between the liquid disordered and the solid ordered phase. These data suggest that the physical properties of the lipid bilayer influence ion channel activity likely via a fine tuning of its conformations. In a more general interpretative framework, we suggest that other parameters such as pH, ionic strength, and the action of amphiphilic drugs can affect the physical behavior of the lipid bilayer in a fashion similar to temperature changes resulting in functional changes of transmembrane proteins.