a) Bar graph shows the mean percentage EtOH response (activation or inhibition normalized to wild-type) for a Trp mutation in four different channels, GIRK2-L257W (n=9), GIRK4-L252W (n=8), IRK1-L245W (n=8) and GIRK2-PIP2-L257W (n=5). Only mutations in alcohol-binding pocket of wild-type GIRK channels affect the response to alcohol. b) Top, schematic of inward rectifier shows location of alcohol-binding pocket in cytoplasmic domains, two gates (G-loop and M2 transmembrane; black triangles) and pore-helix region (red ellipse). PIP2 is enriched in lower leaflet of bilayer (orange). Below, molecular surface representations of the alcohol pocket without (Leu), with MPD (Leu+MPD) and modeled with L257W (Trp), using the IRK1-MPD structure as a guide. c) Left, alignment of the putative closed state of GIRK1 chimeric channel (GIRK1-closed; green) (PDB:2QKS) with the IRK1-MPD structure (grey) (PDB:2GIX). Spaghetti structures show two adjacent cytoplasmic subunits (subunits D and A) and the hydrophobic alcohol pocket at the cytoplasmic subunit interface. Right, zoom shows alignment of the N-terminal domain, βD-βE and βL-βM ribbons from the IRK1-MPD (grey), GIRK1-open (orange) and GIRK1-closed (green) structures. IRK1-MPD aligns better with the putative open state of GIRK1. Note the significant displacement in the βL-βM beta ribbon element (arrow) and the side-chains of hydrophobic amino acids in the two structures. GIRK1-closed but not GIRK1-open has a collapsed alcohol-binding pocket, due to interaction and rotation of F46 (IRK1-F47), L246 (IRK1-L245) and F338 (IRK1-Y337). GIRK1-L333 in the βL-βM domain, implicated previously in Gββ gating of GIRK channels17-19, is shown for reference.