Digestion of the A1-A2-A3 domain fragments of VWF (rhuVWFA1-A2-A3) by rhuADAMTS13. WT and mutant VWF fragments were incubated with rhuADAMTS13 either under denaturing (+urea; top gel) or nondenaturing (– urea; bottom gel) conditions and visualized by SDS-PAGE and immunostaining (anti-HA antibody; numbers on the right side refer to a molecular weight marker). Although rhuVWFA1-A2-A3-WT is cleaved under denaturing conditions only, rhuVWFA1-A2-A3 harboring either the mutation G1505E, G1505R, G1609R, I1628T, G1629E, or G1631D is cleaved also under nondenaturing conditions as indicated by the appearance of smaller fragments.