Fig. 1: Subunit asymmetry in the TREK1 apo cryo-EM structure.
From: Membrane phospholipids control gating of the mechanosensitive potassium leak channel TREK1
a Cryo-EM density map of the apo state of the TREK1 channel and b a structural model of the channel, with the potassium ion selectivity filter (SF), extracellular cap domain, and four transmembrane domains labeled. c A superposition of the two apo TREK1 subunits, showing asymmetric positioning of TM4a (blue) relative to TM4b (purple), due to an 11° tilt in the distal portion of TM4. Transparent views of the TREK1 cryo-EM density map d side view and e bottom view, with density outside of the TREK1 map near the TM4b helix highlighted (pink). Magnified views (f), showing that this central density occludes the pore, sterically prevents TM4b from moving into the “up” state, and can be well modeled by a molecule of DDM (also shown in Supplementary Fig. 4). DDM density derived from the final unsharpened TREK1 apo map, visualized at a contour threshold of 0.0065 (g). Native mass spectrum of TREK1 dimer (20+ charge state is labeled), with deconvoluted spectrum (h), showing no evidence of phospholipid bound to TREK1.
