factor IX

Coagulation factor IX (plasma thromboplastic component, Christmas disease, hemophilia B)
PDB rendering based on 1cfh.
Available structures
1cfh, 1cfi, 1edm, 1ixa, 1j34, 1j35, 1mgx, 1nl0, 1rfn
Identifiers
Symbols	F9; FIX; GLA domain; HEMB; MGC129641; MGC129642; PTC
External IDs	OMIM: 306900 MGI: 88384 HomoloGene: 106
Gene ontology Molecular function • coagulation factor IXa activity • calcium ion binding • peptidase activity Cellular component • extracellular region Biological process • proteolysis • blood coagulation
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	2158	14071
Ensembl	ENSG00000101981	ENSMUSG00000031138
UniProt	P00740	A0JLY3
RefSeq	NM_000133 (mRNA)	NM_007979 (mRNA)
	NP_000124 (protein)	NP_032005 (protein)
Location	Chr X: 138.44 - 138.47 Mb	Chr X: 56.35 - 56.38 Mb
PubMed search	[1]	[2]

Factor IX (or Christmas factor) is one of the serine proteases (EC 3.4.21.22) of the coagulation system; it belongs to peptidase family S1. Deficiency of this protein causes hemophilia B. It was discovered after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to hemophilia, in 1952.^[1]

Physiology

Factor IX is inactive unless activated by factor XIa (of the contact pathway) or factor VIIa (of the tissue factor pathway). 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.

Genetics

The gene for factor IX is located on the X chromosome (Xq27.1-q27.2). It was first cloned in 1982 by Kotoku Kurachi and Earl Davie.^[2]

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.^[3]

Role in disease

Deficiency of factor IX causes Christmas disease (hemophilia B). Over 100 mutations of factor IX have been described; some cause no symptoms, but many lead to a significant bleeding disorder.

Some rare mutations of factor IX result in elevated clotting activity, and can result in clotting diseases, such as deep vein thrombosis.^[4]

References

Further reading

v • d • e PDB Gallery 1cfh: STRUCTURE OF THE METAL-FREE GAMMA-CARBOXYGLUTAMIC ACID-RICH MEMBRANE BINDING REGION OF FACTOR IX BY TWO-DIMENSIONAL NMR SPECTROSCOPY   1cfi: NMR STRUCTURE OF CALCIUM ION-BOUND GAMMA-CARBOXY-GLUTAMIC ACID-RICH DOMAIN OF FACTOR IX   1edm: EPIDERMAL GROWTH FACTOR-LIKE DOMAIN FROM HUMAN FACTOR IX   1ixa: THE THREE-DIMENSIONAL STRUCTURE OF THE FIRST EGF-LIKE MODULE OF HUMAN FACTOR IX: COMPARISON WITH EGF AND TGF-A   1j34: Crystal Structure of Mg(II)-and Ca(II)-bound Gla Domain of Factor IX Complexed with Binding Protein   1j35: Crystal Structure of Ca(II)-bound Gla Domain of Factor IX Complexed with Binding Protein   1mgx: COAGULATION FACTOR, MG(II), NMR, 7 STRUCTURES (BACKBONE ATOMS ONLY)   1nl0: Crystal structure of human factor IX Gla domain in complex of an inhibitory antibody, 10C12   1rfn: HUMAN COAGULATION FACTOR IXA IN COMPLEX WITH P-AMINO BENZAMIDINE