Apoptosis induced by the purified molecules grB and pfn is sensitive to dominant-negative dynamin. HeLa-DynWT or DN cells were treated to suppress (+tet) or induce (–tet) overexpression from the transfected dynamin cDNA. Cells were treated with the purified molecules grB (1 μg/mL) and sublytic pfn for 2 hours at 37° C. Caspase activation was assessed by labeling with M30 mAb, followed by flow cytometry. (A) The mean ± SD of 3 (WT) or 4 (DN) independent experiments is shown (*.01 < P < .05). (B) Representative flow cytometry data of untreated (mock) or grB- and pfn-treated cells.