Fig. 4. The superimposed X-ray structures of Na⁺ (; 3C32) and Li⁺ (; 3C31) binding sites in the glutamate kainate receptor (GluR5). The Li⁺ structure is in purple with Li⁺ in turquoise and the Na⁺ structure is in green with Na⁺ in purple. The respective metal-binding residues are depicted as sticks with nitrogen in blue and oxygen in red. Distances from Asp100 to the cation are indicated.