Panel A shows a molecular structure with two views of a protein. The protein is depicted as a gray surface with one subunit removed for clarity. Sodium ions are shown traversing the transmembrane domain (TMD) from the intracellular side to the extracellular domain (ECD) vestibule. The ions are color-coded based on their position over time, with blue representing the initial position, green marking the exit from the TMD to the ECD, and red indicating the return across the TMD. Panel B is a line graph showing the current-voltage relationship for the cryo-electron microscopy ELIC5 with the ECD removed. The x-axis represents the applied potential in millivolts, ranging from minus 250 millivolts to 250 millivolts. The y-axis represents the current in picoamperes, ranging from minus 50 picoamperes to 50 picoamperes. The graph includes two lines: a blue dashed line for positive potentials with a conductance of 203 picosiemens and a red dashed line for negative potentials with a conductance of 178 picosiemens. The rectification ratio is 1.14, and the linear fit is forced to go through the origin.
The cryo-EM ELIC5 ECD limits sodium conductance. (A) Two examples of Na+ ions traversing the TMD from the intracellular side to the ECD vestibule, but unable to exit the ECD and traversing back across the TMD. Cryo-EM ELIC5 is shown as a gray surface with one subunit (closest to the viewer) removed for clarity. A single Na+ ion is shown in each panel with its position as a function of simulation time shown as a blue-green-red spectrum. The initial position of the Na+ ion on the intracellular side is shown as a large blue sphere. The time point when the Na+ ion exits the TMD to the ECD is marked by the large green sphere and the time point when the Na+ crosses back across the TMD is marked with a large red sphere. (B) I–V relationship for cryo-EM ELIC5 with the ECD removed (i.e., TMD-only construct) with the same coloring scheme as in Fig. 2 B. For B, the linear fit is forced to go through the origin.