Basic description
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ADAMTS proteases are secreted enzymes containing a prometalloprotease domain of the reprolysin type. The ADAMTS proteases function in processing of procollagens and von Willebrand factor as well as catabolism of aggrecan, versican and brevican. They have been demonstrated to have important roles in connective tissue organization, coagulation, inflammation, arthritis, angiogenesis and cell migration. ADAMTS9 is closest in homology to ADAMTS20, sharing 54% overall identity, and like ADAMTS20 ADAMTS9 gas a GON like domain at the carboxyterminal end. The GON domain at the carboxyterminal end is similar to the GON1 protein in C. elegans, mutations of which lead to defective gonadal development. ADAMTS9 is expressed in ovary and testis, but little is known about the role of ADAMTS9 in reproductive organs. ADAMTS9 is also expressed in the heart, placenta, lung, skeletal tissue, and pancreas, so the protein must have wider functions than just gonadal development. ADAMTS9, like ADAMTS20, has a total of 15 thrombospondin like domains. The first TS domain begins shortly after the catalytic and disintegrin domains. TS domains 2 to 6 follow a spacer domain, followed by linker domain 1, then TS domains 7 & 8, linker domain 2, and then TS domains 9 to 15. In other ADAMTS proteins the TS motifs are thought to bind to the ECM. The ADAMTS proteins contain at least one prohormone convertase cleavage site, although it appears that one site is used preferentially, and cleavage of the propeptide domain at this site generates active enzymes. For ADAMTS9, this site is the RRTKR sequence, and the mature ADAMTS9 has an aminoterminal sequence of FLSYPR. The catalytic site of ADAMTS9 is more like ADAMTS1, 14 and 15, with an HExxHVFNMxH sequence, perhaps giving these enzymes some shared specificity.
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