Fig. 2.

Substrate specificity of electrogenic transport in Af-Amt1. (A) Transient currents observed on the same sensor for ammonium (black), MA (red), DMA (gray), and the nonconducting ions sodium (blue) and potassium (green). (B) Background currents for all species in A were recorded on protein-free liposomes and were found to be negligible. (C) Bar graph of the peak currents for the conducted species (gray) and the respective background (yellow). Af-Amt1 shows distinct specificity for ammonium and MA. (D) Transients for 300 mM NH₄⁺ in the active solution at pH 7 (blue) and pH 5 (black) show a slight shift of the peak current, whereas a control (300 mM imidazolium, pH 5.0; green) is not conducted.