Fig. 10. Comparison of cation and amino-acid-associated net inward currents and transport occurring in Na⁺ medium by Xenopus oocytes injected with full-length cRNA from wild type (WT) and mutants of nutrient and neurotransmitter transporters. (A) In GAT1, WT Na⁺ and Cl^- activate the uptake of -aminobutyric acid (GABA) but not -amino acids, and a water channel is present. The transport is curtailed completely in the equivalent mutant Y140F. (B) In KAAT1, WT Na⁺ and Cl^- activate the uptake of leucine. The co-transport of the amino acids and ions is enhanced more than sevenfold in the mutant Y147F. (C) In CAATCH1 WT, there is no Cl^- activation and Na⁺ fluxes are thermodynamically uncoupled from the transport of proline and other neutral amino acids. In CAATCH1 Y147F mutant, methionine, but not proline, activates the Na⁺ channel (Stevens et al., 2002). AA, amino acid.