Fig. 3.
Ion conductance through FocA and pH-dependent gating. (A) With varying, symmetric formate concentrations and a holding potential of 150 mV, the conductance of FocA increases with ion concentration. (B) Dependence of channel conductance on ion concentration for formate, acetate, lactate, pyruvate, and chloride. Formate, acetate, and lactate show near identical Gmax values of 26 pS, but differ in affinity, whereas pyruvate has the same affinity as formate, but only reaches a Gmax of 11 pS. (C) The permeability of FocA for formate anions shows specific, reversible gating at pH 5.7, in line with a switch of transport mode from passive channel to active importer (14, 18).