Expression of ADAMTS-13 mutants. HeLa cells were transfected with plasmids encoding FLAG-tagged wild-type or mutant ADAMTS-13. The culture media and cell lysates were analyzed by Western blotting with an anti-FLAG M2 MoAb. (NC) Untransfected culture medium and cell lysate were used as negative controls. (A) Each culture medium sample was subjected to 10% SDS-PAGE under nonreducing conditions. (B) Each cell lysate sample was subjected to 10% SDS-PAGE under reducing conditions.