Crystal structure of the human K2P TRAAK, a lipid- and mechano-sensitive K+ ion channel.

Science. 2012 Jan 27; 335(6067): 436-41
Brohawn SG, del Mrmol J, MacKinnon R

TRAAK channels, members of the two-pore domain K(+) (potassium ion) channel family K2P, are expressed roughly to one side in the nervous system as well as control the resting membrane potential. Their gating is sensitive to polyunsaturated greasy acids, mechanical deformation of the membrane, as well as temperature changes. Physiologically, these channels appear to control the noxious input threshold for temperature as well as pressure sensitivity in dorsal root ganglia neurons. We present the crystal structure of human TRAAK at the resolution of 3.8 angstroms. The channel comprises two protomers, each containing two distinct pore domains, that create the two-fold symmetric K(+) channel. The extracellular surface features the scrolled cap, 35 angstroms tall, that creates the bifurcated pore entryway as well as accounts for the insensitivity of two-pore domain K(+) channels to inhibitory toxins. Two diagonally opposed gate-forming middle helices form membrane-interacting structures that may underlie this channel's sensitivity to chemical as well as mechanical properties of the cell membrane.

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