Autolytic sites in ADAMTS spacer domains. Amino acid sequence alignment (Clustal omega) of the Sp domain of human ADAMTS1 (Uniprot accession number: Q9UHI8, aa 725–749), ADAMTS4 (O75173, aa 686–837), ADAMTS5 (Q9UNA0, aa 732–874), ADAMTS7 (Q9UKP4, aa 698–809) 8 (Q9UP79, aa 690–831), and ADAMTS13 (Q76LX8, aa 556–685). Sequence identity of ADAMTS1, 4, 5, 7, and 13 were 58.8, 40.3, 34.1, 34.3, and 21.01%, respectively, compared with ADAMTS8. Beta strands and loops are indicated above the alignments in black and red, respectively. Conserved amino acids are colored according to their physicochemical properties (pink, positively charged; yellow, negatively charged; green, apolar; cyan, polar). Red arrows indicate autolytic cleavage sites identified in the present study as well as those reported in the literature (41, 42, 43).