| Modification Notes |
K+ channels are divided into three subclasses, reflecting the number of transmembrane segments (TMS), which are designated 6TMS, 4TMS, and 2TMS. Members of the 4TMS class contain two distinct pore regions, and include TWIK-1, TREK-1, TRAAK, TASK, TASK-2 and TASK-3. TRAAK is selectively expressed in the neuronal tissues of brain, spinal cord, and retina. TRAAK is activated by arachidonic acid, and other unsaturated fatty acids, but not by saturated fatty acids. TRAAK produces baseline K+ currents, which are strongly stimulated by mechanical stretch and insensitive to K+ channel blockers. |