The distances from sodium ions to the interacting residues and the snapshot of the local structure of sodium interaction sites. A, The distances from the resident sodium ions (top, Na2; bottom, Na3) to the residues D863/E865/E787/D818 in subunit 1. B, The snapshot of the local structure when two sodium ions resided in the D863/E865 pocket. C, The distances from the Na4 (top) and Na5 (bottom) to D863/E865/E787/D818 residues in subunit 1. D, The snapshot of the local structure D863/E865 pocket when four sodium ions are located in the site. E, The distances from the sodium ions (Na6 top and Na7 bottom) to the residues D863/E865/E787/D818 in subunit 4. F, The local structure of the D863/E865 pocket in subunit 4 with two resident sodium ions.