Structures of VWF and fusion proteins for ADAMTS-13 substrate. The domain structure of human preproVWF is shown above the structures of recombinant fusion proteins designed in the present study. Amino acid residues of preproVWF are numbered from the initiating Met codon. The locations of 5 kinds of structural domains (A, B, C, D, and CK) are indicated. The mature VWF secreted from cells consists of 2050 residues (S764-K2813) from the D′ domain to the C-terminal CK domain. ADAMTS-13 cleaves the Y1605-M1606 peptidyl bond in the A2 domain (D1498-L1664). We made 5 different recombinant proteins flanked with GST- and H-tags: GST-D1459R1668-H (I), GST-E1554R1668-H (II), GST-D1587R1668-H (III), GST-D1596R1668-H (IV), and GST-D1596R1659-H (V).