Publikationsdatum:
2012-10-30
Beschreibung:
Antithrombin (AT) inhibits several blood coagulation proteases, including activated factor X (FXa), by forming stable complexes with these proteases. Herein, we demonstrate that AT forms a stable complex with zymogen factor X (FX). Sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and size-exclusion chromatography analyses showed that AT and FX formed an SDS-stable complex, which is distinct in apparent molecular mass from an FXa–AT complex, in the presence of heparin. Amino-terminal sequence analysis of the complex following SDS–PAGE under reducing conditions provided clear evidence that AT forms this complex with the heavy chain of FX, because two sequences, HGSPVDI (residues 1–7 of AT) and SVAQATS (residues 1–7 of the heavy chain of FX), were identified. Furthermore, sequence SLNPNRV, which corresponds to residues 394–400 of AT, was identified in the non-reduced FX–AT complex, indicating that FX cleaved the Arg393–Ser394 bond in a reactive centre loop of AT. Unfractionated heparin induced FX–AT complex formation more effectively than low-molecular weight heparin or AT-binding pentasaccharide, and appeared to promote complex formation mainly via a template effect. These data suggest that AT is capable of forming a stable complex with zymogen FX by acting as an inhibitor in the presence of heparin.
Print ISSN:
0021-924X
Digitale ISSN:
1756-2651
Thema:
Biologie
,
Chemie und Pharmazie
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