Fig. 5.

Ion selectivity of FocA. (A) Specific single-channel currents that changed directionality upon reversal of the applied holding potential were recorded for various monovalent anions. No currents derived from single-channel events were observed for any multivalent anion or any cation. (B) FocA showed high permeability for formate, but also for the highly similar hypophosphite, for chloride, and 70% permeability for nitrite. The high permeabilities observed for the organic acids acetate, lactate, and pyruvate match the product profile of mixed-acid fermentation.