Figure 3.

SDS/PAGE (UV-transilluminated) demonstrates that α-toxin heptamers form on human lymphocytes (lanes 1 and 2) and granulocytes (lanes 3 and 4). Cells were treated with 20 μg/ml S69C α-toxin labeled with fluorescein-maleimide (23) for 30 min at 37°C, washed, and solubilized in SDS at 95°C to dissociate heptamers (lanes 1 and 3) or solubilized in SDS at room temperature to preserve heptamers (lanes 2 and 4).