FIG. 3.
Maltose uptake by A. acidocaldarius cells (A) and maltose binding activity of MalEAa (B) in the presence of competing substrates. (A) Uptake was performed at 57°C, pH 3.6, and 3 μM [14C]maltose in the presence of the indicated sugars at a concentration of 1 mM each. Cells were preincubated for 2 min with nonlabeled sugars in minimal medium without a carbon source, and uptake was stopped after 1 min. (B) Binding assays were performed at 57°C, pH 3.6, and 5 μM [14C]maltose in the presence of the indicated sugars at a concentration of 1 mM each. MalEAa (5 μg) was preincubated for 1 min with nonlabeled sugars in buffer (pH 3.6), and the binding reaction was stopped after 1 min. Shaded bars, wild type MalEAa; black bars, recombinant MalEAa.