factor ix factor ix factor ix (or christmas factor) (ec 3.4.21.22) is one of the serine proteases of the coagulation system; it belongs to peptidase family s1. deficiency of this protein causes haemophilia b. it was discovered in 1952 after a young boy named stephen christmas was found to be lacking this exact factor, leading to haemophilia. f9available structurespdbortholog search: pdbe rcsb list of pdb id codes1cfh, 1cfi, 1edm, 1ixa, 1mgx, 1nl0, 1rfn, 2wph, 2wpi, 2wpj, 2wpk, 2wpl, 2wpm, 3kcg, 3lc3, 3lc5, 4yzu, 4z0k, 4zae, 4wm0, 4wma, 4wmi, 4wmk, 4wn2, 4wnh, 5egm, 5jbc, 5jb9, 5jbb, 5jb8, 5jbaidentifiersaliasesf9, f9 p22, fix, hemb, p19, ptc, thph8, coagulation factor ix, blood coagulation factor ix, christmas factorexternal idsomim: 300746 mgi: 88384 homologene: 106 genecards: f9 gene location (human)chr.x chromosome (human)bandxq27.1start139,530,739 bpend139,563,459 bpgene location (mouse)chr.x chromosome (mouse)bandx a6|x 33.5 cmstart59,044,824 bpend59,076,119 bprna expression patternbgeehumanmouse (ortholog)top expressed inright lobe of liversecondary oocytepancreatic ductal cellkidneybloodhuman musculoskeletal systemmuscular systemmuscle organmuscle organkidneytop expressed inleft lobe of livergallbladdersexually immature organismthoracic diaphragmdentate gyruspiriform cortexjejunumentorhinal cortexhippocampus properbrown adipose tissuemore reference expression databiogpsmore reference expression datagene ontologymolecular function endopeptidase activity metal ion binding peptidase activity serine-type peptidase activity hydrolase activity calcium ion binding serine-type endopeptidase activity protein binding cellular component endoplasmic reticulum lumen plasma membrane golgi lumen extracellular exosome extracellular region extracellular space collagen-containing extracellular matrix biological process hemostasis blood coagulation, intrinsic pathway zymogen activation endoplasmic reticulum to golgi vesicle-mediated transport signal peptide processing blood coagulation, extrinsic pathway peptidyl-glutamic acid carboxylation proteolysis blood coagulation sources:amigo / quickgoorthologsspecieshumanmouseentrez215814071ensemblensg00000101981ensmusg00000031138uniprotp00740p16294refseq (mrna)nm_000133nm_001313913nm_007979nm_001305797refseq (protein)np_000124np_001300842np_001292726np_032005location (ucsc)chr x: 139.53 – 139.56 mbchr x: 59.04 – 59.08 mbpubmed searchwikidataview/edit humanview/edit mouse coagulation factor ix is on the world health organization's list of essential medicines. physiology 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. 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. 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. domain architecture factors vii, ix, and x all play key roles in blood coagulation and also share a common domain architecture. 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. 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. 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. the structure of the gla domain, which is responsible for ca(ii)-dependent phospholipid binding, was also determined by nmr. several structures of 'super active' mutants have been solved, which reveal the nature of factor ix activation by other proteins in the clotting cascade. genetics in human, the f9 gene is located on the x chromosome at position q27.1. 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. at least 534 disease-causing mutations in this gene have been discovered. the f9 gene was first cloned in 1982 by kotoku kurachi and earl davie. 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. role in disease