a, The structure of the TASK-1–BAY1000493 complex, viewed from the selectivity filter towards the vestibule, with the 2F o − F c map (blue) and the anomalous difference map at 3.3 Å (contoured at 3.5σ) collected at the Br edge (magenta). The two 50%-occupancy BAY1000493 molecules shown with carbons coloured teal or light blue, oxygens in red, nitrogens in dark blue, fluorines in cyan and bromines in maroon. b, The structure of the TASK-1–BAY2341237 complex, as for a, with the 2F o − F c map in blue. The BAY1000493 molecule (100% occupancy) is shown with carbons in green, chlorines in dark green and other atoms coloured as in a. c, The structure of TASK-1, with a 2F o − F c map shown in blue. There is some residual density below the selectivity filter, as is seen in many K 2P structures. d–f represent the same structures as in a–c, with the positive F o − F c difference density from omit maps (green) calculated with the inhibitors excluded. 2F o − F c and F o − F c maps are contoured at 1.0σ and 2.5σ, respectively. g, Superposition of the two complexes viewed from the membrane plane, with BAY1000493 in teal and BAY2341237 in green. The BAY1000493 complex is shown as a cartoon with side chains as sticks (gold and purple), and side chains from the BAY2341237 complex are shown in in red and blue. h, Schematic showing how the 50:50 distribution of BAY1000493 orientations occurs in crystals. i, Schematic showing how asymmetry could lead to 100% occupancy of one orientation in the case of BAY2341237. j, k, Interactions between TASK-1 and BAY1000493 (j) or BAY2341237 (k). Close contacts (less than 4.0 Å) between the protein and inhibitor atoms are shown as blue lines. For clarity, only the three closest contacts are shown if there were more than three contacts.