FIG. 3.

ΔpH measurement in ISO membrane vesicles of A. aceti IFO 3283. 9-AA fluorescence was measured with ISO membrane vesicles (101 μg of protein) prepared with 50 mM KPB (pH 6.0) as described in Materials and Methods. (A) The reaction was started by the addition of ISO vesicles to 50 mM KPB (pH 8.0), followed by the addition of 1 μM valinomycin (Val) and 0.1 μM nigericin (Nig) as indicated. (B) The reaction was started by the addition of lactate to the assay mixture containing ISO vesicles in 50 mM KPB (pH 6.0). (C) The quenching data (▪) obtained as shown in A by suspending the vesicles (pH 6.0) in 50 mM KPB buffer of pH 6.0, 6.5, 7.0, 7.5, and 8.0 were plotted against ΔpH, and lactate-dependent quenching data (□) without Val (+Lactate) or with Val (+Val) obtained in B were also plotted.