Fig. 4: Molecular details of the POPA lipids binding sites.
From: Membrane phospholipids control gating of the mechanosensitive potassium leak channel TREK1
The upper and lower POPA binding sites identified in the cryo-EM density map flank the TM4 helix (a). At the lower site (b, c), the well-resolved POPA headgroup sits in a groove between TM1 and TM4. A coulombic potential surface representation of the lower site (b) with a molecular representation shown in (c), demonstrates the strong electropositive nature of the lower binding site. At the upper site (d, e), the cryo-EM density for a lipid acyl tail can be seen inserting itself underneath TM4 to sit behind the selectivity filter pore helices. A molecular representation of this lipid binding site (e) shows that the lipid tail displaces the W275 residue from its outward-facing position in the TM4 down state (transparent) to an inward-facing orientation, bringing W275 close to the G137 residue.
