Science Topics - 83

Ion channels form the ion-conducting pores on the lipid bilayer of the cell membrane and govern ion transport across the membrane by opening and closing the gate. This gate is operated not only by various types of stimuli from inside and outside of the cell, but also by membrane lipids around the ion channels. However, how the lipids affect the activity of ion channels remained unclear. To unveil the molecular mechanism of the lipid effect on the channel activity, we have analyzed the single-channel current of the KcsA potassium channel in the artificial membranes having various lipid compositions. We revealed that the KcsA channel was highly active when the anionic phospholipids exist in the inner leaflet. We identified that a protruding helix from the pore structure was the “membrane lipid sensor” of the KcsA channel. Furthermore, in the anionic lipid membrane, the rolled configuration of the lipid sensor was shown to stabilize the active form of the KcsA channel. (Iwamoto and Oiki, Proc. Natl. Acad. Sci. U. S. A. 110:749-754, 2013)

Figure; KcsA channels sense inner membrane lipids through the “membrane lipid sensor”. In the anionic lipid membrane, the rolled configuration of the sensor stabilizes the active form of the KcsA channel.

Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui