A cofactor for factor XI activation.

摘要

Factor XI,the precursor of factor XIa, dif-fers structurally in several important respects from the vitamin K-dependent (VKD) coagulation protease zymogens (the thrombin precursor prothrombin and factors VII, IX, and X).2 For example, factor XI lacks the Gla-domain through which the VKD proteins bind to phospholipid membranes. In addition, factor XIa does not appear to require a cofactor to mediate its primary hemostatic function, activation of factor IX. These properties reflect the different natural histories of factor XIa and the VKD proteases.