Synthetic CUB-1 peptides block the cleavage of ULVWF under flow. (A) Each of the synthetic peptides (final concentration 200 μm) was incubated with PRP for 10 minutes at room temperature and the mixture was then perfused over the histamine-stimulated endothelial cells. All of the peptides corresponding to CUB sequences (CUB-1A to E) partially inhibited the cleavage of ULVWF strings, but the scrambled peptide CUB-1As did not. Two peptides corresponding to sequences in the catalytic domain (Met1 and Met2) also did not inhibit cleavage. (B) Inhibition of proteolysis by recombinant CUB-1 was dose-dependent with a maximal effect at 200 μM. The data are presented as mean ± SEM (Student t test, ^*P < .01 compared with untreated samples).