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Factor IX

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Title: Factor IX  
Author: World Heritage Encyclopedia
Language: English
Subject: Factor VIII, Coagulation, Tissue factor, Factor XI, Tissue plasminogen activator
Collection: Coagulation System, Ec 3.4.21, Peripheral Membrane Proteins, Zymogens
Publisher: World Heritage Encyclopedia

Factor IX

Coagulation factor IX
PDB rendering based on .
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols  ; FIX; HEMB; P19; PTC; THPH8
External IDs ChEMBL: GeneCards:
EC number
RNA expression pattern
Species Human Mouse
RefSeq (mRNA)
RefSeq (protein)
Location (UCSC)
PubMed search

Factor IX (or Christmas factor) (EC is one of the serine proteases of the coagulation system; it belongs to peptidase family S1. Deficiency of this protein causes hemophilia B. It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to hemophilia.[1]


  • Physiology 1
  • Domain architecture 2
  • Genetics 3
  • Role in disease 4
  • References 5
  • Further reading 6
  • External links 7


The blood coagulation and Protein C pathway.

Factor IX is produced as a zymogen, an inactive precursor. It is processed to remove the signal peptide, glycosylated and then cleaved by factor XIa (of the contact pathway) or factor VIIa (of the tissue factor pathway) to produce a two-chain form where the chains are linked by a disulfide bridge.[2][3] When activated into factor IXa, in the presence of Ca2+, membrane phospholipids, and a Factor VIII cofactor, it hydrolyses one arginine-isoleucine bond in factor X to form factor Xa.

Factor IX is inhibited by antithrombin.[2]

Factor IX expression increases with age in humans and mice. In mouse models mutations within the promoter region of factor IX have an age-dependent phenotype.[4]

Domain architecture

Factors VII, IX, and X all play key roles in blood coagulation and also share a common domain architecture.[5] The factor IX protein is composed of four protein domains: the Gla domain, two tandem copies of the EGF domain and a C-terminal trypsin-like peptidase domain which carries out the catalytic cleavage.

Human factor IX protein domain architecture, where each protein domain is represented by a coloured box

The N-terminal EGF domain has been shown to at least in part be responsible for binding tissue factor.[5] Wilkinson et al. conclude that residues 88 to 109 of the second EGF domain mediate binding to platelets and assembly of the factor X activating complex.[6]

The structures of all four domains have been solved. A structure of the two EGF domains and the trypsin-like domain was determined for the pig protein.[7] The structure of the Gla domain, which is responsible for Ca(II)-dependent phospholipid binding, was also determined by NMR.[8]

Several structures of 'super active' mutants have been solved,[9] which reveal the nature of factor IX activation by other proteins in the clotting cascade.


The gene for factor IX is located on the X chromosome (Xq27.1-q27.2) and is therefore X-linked recessive: mutations in this gene affect males much more frequently than females. It was first cloned in 1982 by Kotoku Kurachi and Earl Davie.[10]

Polly, a transgenic cloned Poll Dorset sheep carrying the gene for factor IX, was produced by Dr Ian Wilmut at the Roslin Institute in 1997.[11]

Role in disease

Deficiency of factor IX causes Christmas disease (hemophilia B).[1] Over 100 mutations of factor IX have been described; some cause no symptoms, but many lead to a significant bleeding disorder. The original Christmas disease mutation was identified by sequencing of Christmas' DNA, revealing a mutation which changed a cysteine to a serine.[12] Recombinant factor IX is used to treat Christmas disease, and is commercially available as BeneFIX[13] and Alprolix.[14] Some rare mutations of factor IX result in elevated clotting activity, and can result in clotting diseases, such as deep vein thrombosis.[15]

Factor IX deficiency is treated by injection of purified factor IX produced through cloning in various animal or animal cell vectors. Tranexamic acid may be of value in patients undergoing surgery who have inherited factor IX deficiency in order to reduce the perioperative risk of bleeding.[16]

A list of all the mutations in Factor IX is compiled and maintained at the Factor IX mutation database[17] maintained at the University College London.


  1. ^ a b Biggs R, Douglas AS, Macfarlane RG, Dacie JV, Pitney WR (Dec 1952). "Christmas disease: a condition previously mistaken for haemophilia". British Medical Journal 2 (4799): 1378–82.  
  2. ^ a b Di Scipio RG, Kurachi K, Davie EW (Jun 1978). "Activation of human factor IX (Christmas factor)". The Journal of Clinical Investigation 61 (6): 1528–38.  
  3. ^ Taran LD (Jul 1997). "Factor IX of the blood coagulation system: a review". Biochemistry. Biokhimii͡A 62 (7): 685–93.  
  4. ^ Boland EJ, Liu YC, Walter CA, Herbert DC, Weaker FJ, Odom MW, Jagadeeswaran P (Sep 1995). "Age-specific regulation of clotting factor IX gene expression in normal and transgenic mice". Blood 86 (6): 2198–205.  
  5. ^ a b Zhong D, Bajaj MS, Schmidt AE, Bajaj SP (Feb 2002). "The N-terminal epidermal growth factor-like domain in factor IX and factor X represents an important recognition motif for binding to tissue factor". The Journal of Biological Chemistry 277 (5): 3622–31.  
  6. ^ Wilkinson FH, Ahmad SS, Walsh PN (Feb 2002). "The factor IXa second epidermal growth factor (EGF2) domain mediates platelet binding and assembly of the factor X activating complex". The Journal of Biological Chemistry 277 (8): 5734–41.  
  7. ^ Brandstetter H, Bauer M, Huber R, Lollar P, Bode W (Oct 1995). "X-ray structure of clotting factor IXa: active site and module structure related to Xase activity and hemophilia B". Proceedings of the National Academy of Sciences of the United States of America 92 (21): 9796–800.  
  8. ^ Freedman SJ, Furie BC, Furie B, Baleja JD (Sep 1995). "Structure of the calcium ion-bound gamma-carboxyglutamic acid-rich domain of factor IX". Biochemistry 34 (38): 12126–37.  
  9. ^ Zögg T, Brandstetter H (Dec 2009). "Structural basis of the cofactor- and substrate-assisted activation of human coagulation factor IXa". Structure 17 (12): 1669–78.  
  10. ^ Kurachi K, Davie EW (Nov 1982). "Isolation and characterization of a cDNA coding for human factor IX". Proceedings of the National Academy of Sciences of the United States of America 79 (21): 6461–4.  
  11. ^ Nicholl D. (2002). An Introduction to Genetic Engineering Second Edition. Cambridge University Press. p. 257. 
  12. ^ Taylor SA, Duffin J, Cameron C, Teitel J, Garvey B, Lillicrap DP (Jan 1992). "Characterization of the original Christmas disease mutation (cysteine 206----serine): from clinical recognition to molecular pathogenesis". Thrombosis and Haemostasis 67 (1): 63–5.  
  13. ^ "Home: BeneFIX Coagulation Factor IX (Recombinant) Official Site". 
  14. ^ "Home: Alprolix [Coagulation Factor IX (Recombinant), Fc Fusion Protein] Official Site". 
  15. ^ Simioni P, Tormene D, Tognin G, Gavasso S, Bulato C, Iacobelli NP, Finn JD, Spiezia L, Radu C, Arruda VR (Oct 2009). "X-linked thrombophilia with a mutant factor IX (factor IX Padua)". The New England Journal of Medicine 361 (17): 1671–5.  
  16. ^ Rossi M, Jayaram R, Sayeed R (Sep 2011). "Do patients with haemophilia undergoing cardiac surgery have good surgical outcomes?". Interactive Cardiovascular and Thoracic Surgery 13 (3): 320–31.  
  17. ^ "Home: Factor IX Mutation Database". 

Further reading

  • Davie EW, Fujikawa K (1975). "Basic mechanisms in blood coagulation". Annual Review of Biochemistry 44: 799–829.  
  • Sommer SS (Jul 1992). "Assessing the underlying pattern of human germline mutations: lessons from the factor IX gene". FASEB Journal 6 (10): 2767–74.  
  • Lenting PJ, van Mourik JA, Mertens K (Dec 1998). "The life cycle of coagulation factor VIII in view of its structure and function". Blood 92 (11): 3983–96.  
  • Lowe GD (Dec 2001). "Factor IX and thrombosis". British Journal of Haematology 115 (3): 507–13.  
  • O'Connell NM (Jun 2003). "Factor XI deficiency--from molecular genetics to clinical management". Blood Coagulation & Fibrinolysis. 14 Suppl 1: S59–64.  
  • Du X (May 2007). "Signaling and regulation of the platelet glycoprotein Ib-IX-V complex". Current Opinion in Hematology 14 (3): 262–9.  

External links

  • GeneReviews/NCBI/NIH/UW entry on Hemophilia B
  • The MEROPS online database for peptidases and their inhibitors: S01.214
  • An X(-mas) Factor that gets our vote- QUite Interesting PDB Structure article at PDBe
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