THE INTACT AND CLEAVED HUMAN ANTITHROMBIN III COMPLEX AS A MODEL FOR SERPIN-PROTEINASE INTERACTIONS
[ANT3_HUMAN] Defects in SERPINC1 are the cause of antithrombin III deficiency (AT3D) [MIM:613118]. AT3D is an important risk factor for hereditary thrombophilia, a hemostatic disorder characterized by a tendency to recurrent thrombosis. AT3D is classified into 4 types. Type I: characterized by a 50% decrease in antigenic and functional levels. Type II: has defects affecting the thrombin-binding domain. Type III: alteration of the heparin-binding domain. Plasma AT-III antigen levels are normal in type II and III. Type IV: consists of miscellaneous group of unclassifiable mutations. [:]                     [:]            
[ANT3_HUMAN] Most important serine protease inhibitor in plasma that regulates the blood coagulation cascade. AT-III inhibits thrombin, matriptase-3/TMPRSS7, as well as factors IXa, Xa and XIa. Its inhibitory activity is greatly enhanced in the presence of heparin.
Publication Abstract from PubMed
Antithrombin is a member of the serine proteinase inhibitor (serpin) family which contain a flexible reactive site loop that interacts with, and is cleaved by the target proteinase. In cleaved and latent serpins, the reactive site loop is inserted into a large central beta-sheet in the same molecule, whereas in ovalbumin, a nonfunctional serpin, the reactive site loop is completely exposed and in an alpha-helical conformation. However, in neither conformation can the reactive site loop bind to target proteinases. Here we report the structure of an intact and cleaved human antithrombin complex. The intact reactive site loop is in a novel conformation that seems well suited for interaction with proteinases such as thrombin and blood coagulation factor Xa.
The intact and cleaved human antithrombin III complex as a model for serpin-proteinase interactions.,Schreuder HA, de Boer B, Dijkema R, Mulders J, Theunissen HJ, Grootenhuis PD, Hol WG Nat Struct Biol. 1994 Jan;1(1):48-54. PMID:7656006
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.