Heparin is often identified as a proteoglycan, in which heparin or heparin sulfate associates with other proteins in a strong intrinsic affinity. It has also been found that HS chains are usually localized on the surface of cells and the complex with matrix proteins. This interesting discovery suggests that HS usually exists as an “immobile phase” attaching antithrombin and activates its function as an anticoagulant factor in the circulation system. In an anticoagulant process, antithrombin needs to bind to some coagulant proteases such as Factor Xa or thrombin and “neutralizes” their activity. There are several hypotheses to explain how the heparin chains activate this process. A simple model is that a long heparin chain could be a scaffold to improve the possibility of antithrombin contacting with other proteins. [1] Another direct model is that specific sulfate-containing heparin fragments (oligosaccharides) can allosterically enhance the binding affinity between antithrombin and thrombin or Factor Xa. We are going to describe the structural basis of the second model in the rest of contexts. [2]
Heparin Binding site on antithrombin
Green scene 1 will be a antithrombin specific site for binding heparin
Green scene 2 will be the complex with heparin
The mechanism of heparin regulating antithrombin thrombin interaction
Green scene 1 will be the interface between AT and thrombin
Green scene 2 will be the the interface structure plus heparin
This is a sample scene created with SAT to by Group, and another to make of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.
