Fig. 4.

V_m also drives Na⁺ coupled amino acid symport. V_m drives Na⁺ that is stoichiometrically linked to an amino acid into the cell via a nutrient amino acid transporter (NAT, N). Although the membrane voltage is little changed, Na⁺ can recycle and amino acids can move into the cell as long as there is a sodium salt and an amino acid with affinity for the NAT in the outside bulk fluid. Although the energy for the symport process is ATP hydrolysis by the H⁺ V-ATPase there is no H⁺ involved in the symport per se, which is driven by the Na⁺ electrochemical potential difference