血管性血友病因子裂解酶(ADAMTS13)通过降解超大血管性血友病因子（VWF）抑制血小板聚集和微血管血栓的形成，维持正常的出凝血状态。ADAMTS13的缺陷导致致命性综合症-血栓性血小板减少性紫癜（TTP）。但是，ADAMTS13酶切VWF的分子学机制尚不明确。申请人发现ADAMTS13的半胱氨酸富集区（Cys-R）和间隔区（Spacer）结构域在识别、降解底物的过程中起着重要的作用。结合序列比对方法和晶体结构发现Cys-R和Spacer结构域中的EDGTLS和TEDRLPR氨基酸序列可能与底物的识别和结合有关，利用分子生物学技术对目标氨基酸进行突变后，在剪切力、蛋白变性的条件下观察其活性，揭示ADAMTS13酶切VWF的分子学机制。本研究的意义在于阐明Cys-R和Spacer结构域的生物学功能，为研究TTP的发病机制和治疗提供理论依据。

ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats-13) is a member of ADAMTS family. Proteolysis processing of von Willebrand factor (vWF) by ADAMTS13 metalloprotease is critical for maintaining normal hemostasis. An inability to cleave newly synthesized and released UL- vWF from endothelial cells and megakaryocytes due to deficiency of plasma ADAMTS13 activity leads to a potentially fatal thrombotic complication, thrombotic thrombocytopenic purpura (TTP). However, the molecular mechanisms underlying the vWF cleavage by ADAMTS13 under physiological condition are not clear. We have identified the important role of the Cys-rich and spacer domains, particularly the motif R659RYGEE664 in substrate recognition under fluid shear stress. However, the exact motifs or amino acid residues within these domains in substrate recognition are not fully understood. Sequence alignment and crystal structure of the Cys-rich and spacer domains of various ADAMTS members has allowed us to identify several more regions that appear to be critical for substrate recognition. Therefore, I propose to further define motifs or residues within the Cys-rich/spacer domain of ADAMTS13 that may be important for proteolytic cleavage of vWF by ADAMTS13 protease under physiological shear stress. The findings may help understanding of the molecular mechanisms of vWF proteolysis by ADAMTS13, and pathogenesis of TTP.