CUB1 binding to the spacer domain maintained the closed conformation of ADAMTS13.
A–C, the FRETS-VWF73 assay was used to determine the inhibitory effect of the CUB domain fragments (CUB1, CUB2, and CUB1-2) on the relative proteolytic activity of the truncated ADAMTS13 variant MDTCS (WT or GoF). In each panel the activities of WT and GoF ADAMTS13 are included for reference. Normalized results (A and B) are representative of three independent experiments, and relative proteolytic activities (C) are presented as the mean ± S.D. (n = 3). D, the same assay was also used to determine the proteolytic activity of C-terminal-truncated ADAMTS13 variants (ΔCUB2 and ΔCUB1-2). Results are presented as the mean ± S.D. (n = 3). *, p < 0.05; **, p < 0.01.