In silico analysis of VWF SP cleavage. (A) Multiple sequence alignment showing the first 40 amino acids of VWF including the 22 residue SP (green bar). Conserved residues are in shaded boxes. The red dashed line marks the SPase cleavage site and the red residues in the human alignment mark the start of ex3del. Note the conservation of the ValLeuLeuAlaLeuAlaLeu hydrophobic motif, Cys prior to the cleavage site, Thr 3 residues prior to the cleavage site, and small residues such as Ala, Thr, and Gly after the cleavage site. (B) SP and cleavage site prediction output for WT VWF. (C) SP and cleavage site prediction output for ex3del VWF. The shaded red box indicates residues in exon 4.