Figure 4: Cation-binding site in the central vestibule.
From: Structure of the Acid-sensing ion channel 1 in complex with the gating modifier Psalmotoxin 1
Ribbon representation of the PcTx1–ASIC1 complex with the sodium channel subunits in blue, yellow and red. (a) The complex structure in side view is sliced open at the front to provide a view inside the occluded, central vestibule highlighting some of its residues at the inner surface in stick representation. The location of the ion is indicated by the observed electron density (blue mesh) bound at position Glu417 right above Leu78 that shields the occluded vestibule from ion entrance at the extracellular vestibule. (b) Superposition and top view of the apo ASIC1 structure at 1.9 Å in white and the PcTx1 complex structure. The view reveals the electron density of the putative cation (blue mesh) bound at position Glu417 in the complex structure. In the apo ASIC1, the carboxylate groups of Glu417 are rotated to coordinate water molecules and form intrasubunit H-bonds with Glu80.
