|Detection of Human Coagulation Factor X by Western Blot. Western blot shows lysates of HepG2 human hepatocellular carcinoma cell line. PVDF membrane was probed with 2 µg/mL of Goat Anti-Human Coagulation Factor X Antigen Affinity-purified Polyclonal Antibody (Catalog # AF1063) followed by HRP-conjugated Anti-Goat IgG Secondary Antibody (Catalog # HAF017). A specific band was detected for Coagulation Factor X at approximately 60 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.|
Factor X (Coagulation factor X; also Stuart factor) is a 74-76 kDa glycoprotein member of the peptidase S1 family of molecules. It is secreted by hepatocytes, and plays a key role in the coagulation cascade. Normally, Factor X circulates as a zymogen (or inactive form). Upon disruption of the vasculature, Factor X, and the circulating zymogen Factor V interact, and form what's called the prothrombinase complex on negatively-charged membrane phospholipids of platelets and endothelial cells. This complex converts prothrombin (Factor II) into thrombin, and thus initiates clot formation. Factor X (as a zymogen) is a disulfide-linked heterodimer. Its two chains are the result of intracellular processing of a 74-76 kDa single chain precursor. This creates a 55-57 kDa C-terminal heavy chain, and a 17-18 kDa N-terminal light chain. Prothrombinase complex formation results in the cleavage of the heavy chain, leading to the generation of a 45-46 kDa, prothrombin-cleaving active chain, and a soluble 10 kDa activation fragment. Cleavage is not the result of Factor V activity, but that of either Tissue Factor or Factor IXa, and the activities of there two enzymes are tightly regulated by the carbohydrates bound to the 10 kDa activation fragment. Mature human Factor X is synthesized as a 488 amino acid (aa) preproprecursor that contains a 31 aa signal sequence, a 9 aa prosegment (aa 32-40), a 139 aa light chain (aa 41-179), and a 306 aa heavy chain (aa 183-488). The light chain possesses a Gla domain that binds to Factor V (aa 41-85) plus two EGF-like motifs (aa 86-165), while the heavy chain contains the activation peptide sequence (aa 183-234) followed by a large peptidase S1 domain (aa 235-467). Over aa 24-488, human Factor X shares 77% aa sequence identity with mouse Factor X.