Abstract

SY01 ADAMTS13 structure and function Hall 3 09:30 14th July, 2003 Session Type: Symposium Subject area: Invited Speaker Session title: TTP/HUS Abstract: SY01 Authors: E. Sadler Howard Hughes Medical Institute, USA ADAMTS13 is a metalloprotease that circulates in the blood and cleaves von Willebrand factor (VWF) at a specific Tyr-Met bond in domain A2, which reduces the length of VWF multimers. Cleavage is accelerated by fluid shear stress or mild denaturants, suggesting that ADAMTS13 may preferentially act on VWF multimers that are under tensile stress, perhaps where platelets adhere to a growing thrombus. The importance of this reaction is indicated by the serious consequences of ADAMTS13 deficiency: congenital deficiency causes chronic relapsing thrombotic thrombocytopenic purpura (TTP), or Upshaw-Schulman Syndrome, and acquired deficiency due to inhibitory autoantibodies causes most cases of idiopathic TTP in adults. Although the physiological relevance of ADAMTS13 is clear, the biochemical basis for its function is not well understood. ADAMTS13 consists of 1427 amino acids that comprise a signal peptide, a short propeptide that terminates in a furin cleavage site, a metalloprotease domain, a disintegrin domain, a thrombospondin type 1 repeat (TS), a characteristic Cys-rich and spacer domain, 7 more TS repeats, and two CUB domains. This domain structure is conserved across vertebrata, including fish (D. rerio, T. rubripes, T. nigroviridis), birds (G. gallus), and mammals (H. sapiens, M. musculus, R. norvegicus). The number and diversity of the structural motifs found in ADAMTS13 suggest that its mechanism of action may be complex. The protease domain is similar to reprolysin-like snake venom metalloproteases, but modeling based on these crystallographic structures provides little insight into substrate recognition by ADAMTS13. By analogy to other proteins with similar domains, various motifs could bind VWF, cofactors, cell surfaces, or extracellular matrix. Studies with recombinant mutant ADAMTS13 indicate that normal function requires several domains besides the metalloprotease domain. Proteolytic activity toward VWF reportedly was impaired by missense mutations in the Cys-rich, spacer, TS#1, TS#5, TS#7, or CUB#1 domain. Furthermore, recombinant ADAMTS13 truncated after the metalloprotease, disintegrin, TS#1, or Cys-rich domain was inactive toward VWF; whereas ADAMTS13 truncated after the spacer domain or TS#8 was active. These data suggest that ADAMTS13 structural motifs C-terminal to its Cys-rich domain participate in the recognition and cleavage of VWF multimers. file:///E|/working/LAXMI-PRASAD/WileyML-3G/deepak/31-Jan/Monday/Abstract%20SY01.html (1 of 2) [1/31/2014 3:45:30 PM]