Figure 5.

TSP8 was not required to maintain the closed ADAMTS13 conformation but was essential for conformational activation by VWF D4-CK. The FRETS-VWF73 assay was used to determine the relative proteolytic activities of the C-terminal truncated ADAMTS13 variants WTΔCUB2 (A and B), WTΔCUB1-2 (C and D), WTΔTSP8 (E and F), and WTΔTSP8-CUB2 (G and H). The ability of VWF D4-CK (added at 1, 2, or 3 nm) to enhance the activities of these variants was also examined. In each panel the activities of WT and GoF ADAMTS13 are included for reference. Normalized raw data (A, C, E, and G) is representative of three independent experiments and relative proteolytic activities (B, D, F, and H) are presented as the mean ± S.D. (n = 3). *, p < 0.05; **, p < 0.01; ***, p < 0.005.