FIG. 4.

Competition with biotin-dextran for the binding domain of S. downei GtfI (GBD0) by unlabeled dextran T70, choline, and alternan. The concentration of biotinylated dextran was kept constant at 1 mM (a) or 100 μg/ml (b). The competitors choline or alternan were added after a 10-min preincubation with biotin-dextran and washed after a further 10-min incubation. Detection and washing steps were carried out as described in Materials and Methods. In panel b, the units for the ligands are micrograms per milliliter because the molecular weight distribution of the alternan is unknown.