Figure 3

Structural superposition of the Na⁺-binding sites of the F-type and V-type membrane ATPases. The structures are the same as in Fig. 2. Note the overlap between the Na⁺ ligands, as well as the non-ligating tyrosine (Tyr70B in I. tartaricus and Tyr68 in E. hirae) that is located beneath the Na⁺ ion and stabilizes the principal Glu ligand.