VWF-CP activity of ADAMTS-13 mutants. Culture medium of HeLa cells expressing each mutant was incubated with purified VWF. (A) An aliquot of each reaction mixture was subjected to 5% SDS-PAGE under reducing conditions. The gel was stained with Coomassie Brilliant Blue R-250. (B) An aliquot of each reaction mixture was subjected to SDS–agarose gel electrophoresis. The multimeric patterns of VWF were visualized by Western blot analysis with an anti-VWF antibody.