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{{PBB_Controls
{{Infobox_gene}}
| update_page = yes
'''Factor XI''' or '''plasma thromboplastin antecedent''' is the [[zymogen]] form of factor XIa, one of the [[enzyme]]s of the [[coagulation|coagulation cascade]]. Like many other coagulation factors, it is a [[serine protease]].  In humans, Factor XI is encoded by the ''F11'' [[gene]].<ref name="pmid3636155">{{cite journal | vauthors = Fujikawa K, Chung DW, Hendrickson LE, Davie EW | title = Amino acid sequence of human factor XI, a blood coagulation factor with four tandem repeats that are highly homologous with plasma prekallikrein | journal = Biochemistry | volume = 25 | issue = 9 | pages = 2417–24 | date = May 1986 | pmid = 3636155 | doi = 10.1021/bi00357a018 }}</ref><ref name="pmid2827746">{{cite journal | vauthors = Asakai R, Davie EW, Chung DW | title = Organization of the gene for human factor XI | journal = Biochemistry | volume = 26 | issue = 23 | pages = 7221–8 | date = Nov 1987 | pmid = 2827746 | doi = 10.1021/bi00397a004 }}</ref><ref name="pmid2612218">{{cite journal | vauthors = Kato A, Asakai R, Davie EW, Aoki N | title = Factor XI gene (F11) is located on the distal end of the long arm of human chromosome 4 | journal = Cytogenetics and Cell Genetics | volume = 52 | issue = 1-2 | pages = 77–8 | year = 1989 | pmid = 2612218 | doi = 10.1159/000132844 }}</ref><ref name="pmid1673289">{{cite journal | vauthors = Buetow KH, Shiang R, Yang P, Nakamura Y, Lathrop GM, White R, Wasmuth JJ, Wood S, Berdahl LD, Leysens NJ | title = A detailed multipoint map of human chromosome 4 provides evidence for linkage heterogeneity and position-specific recombination rates | journal = American Journal of Human Genetics | volume = 48 | issue = 5 | pages = 911–25 | date = May 1991 | pmid = 1673289 | pmc = 1683054 | doi =  }}</ref>
| require_manual_inspection = no
| update_protein_box = yes
| update_summary = no
| update_citations = yes
}}
{{GNF_Protein_box
| image = PBB_Protein_F11_image.jpg
  | image_source = [[Protein_Data_Bank|PDB]] rendering based on 1xx9.
| Name = Coagulation factor XI (plasma thromboplastin antecedent)
| HGNCid = 3529
| Symbol = F11
| AltSymbols =; FXI; MGC141891
| OMIM = 264900
| ECnumber =
| Homologene = 86654
| MGIid = 99481
| GeneAtlas_image1 = PBB_GE_F11_206610_s_at_tn.png
| Function = {{GNF_GO|id=GO:0003803 |text = coagulation factor IXa activity}} {{GNF_GO|id=GO:0003805 |text = coagulation factor XIa activity}} {{GNF_GO|id=GO:0008201 |text = heparin binding}} {{GNF_GO|id=GO:0008233 |text = peptidase activity}}  
| Component = {{GNF_GO|id=GO:0005576 |text = extracellular region}} {{GNF_GO|id=GO:0016020 |text = membrane}}
| Process = {{GNF_GO|id=GO:0006508 |text = proteolysis}} {{GNF_GO|id=GO:0007596 |text = blood coagulation}}  
| Orthologs = {{GNF_Ortholog_box
    | Hs_EntrezGene = 2160
    | Hs_Ensembl = ENSG00000088926
    | Hs_RefseqProtein = NP_062505
    | Hs_RefseqmRNA = NM_019559
    | Hs_GenLoc_db =
    | Hs_GenLoc_chr = 4
    | Hs_GenLoc_start = 187424272
    | Hs_GenLoc_end = 187446928
    | Hs_Uniprot = P03951
    | Mm_EntrezGene = 109821
    | Mm_Ensembl = ENSMUSG00000031645
    | Mm_RefseqmRNA = NM_028066
    | Mm_RefseqProtein = NP_082342
    | Mm_GenLoc_db =   
    | Mm_GenLoc_chr = 8
    | Mm_GenLoc_start = 46739987
    | Mm_GenLoc_end = 46760848
    | Mm_Uniprot = Q9DAT3
  }}
}}
{{SI}}
{{CMG}}
__NOTOC__


== Function ==


==Overview==
Factor XI (FXI) is produced by the [[liver]] and circulates as a [[protein dimer|homo-dimer]] in its inactive form.<ref name="pmid18441012">{{cite journal | vauthors = Wu W, Sinha D, Shikov S, Yip CK, Walz T, Billings PC, Lear JD, Walsh PN | title = Factor XI homodimer structure is essential for normal proteolytic activation by factor XIIa, thrombin, and factor XIa | journal = The Journal of Biological Chemistry | volume = 283 | issue = 27 | pages = 18655–64 | date = Jul 2008 | pmid = 18441012 | pmc = 2441546 | doi = 10.1074/jbc.M802275200 }}</ref> The plasma half-life of FXI is approximately 52 hours. The zymogen factor is activated into ''factor XIa'' by [[factor XII]]a (FXIIa), [[thrombin]], and FXIa itself; due to its activation by FXIIa, FXI is a member of the "contact pathway" (which includes [[high molecular weight kininogen|HMWK]], [[prekallikrein]], [[factor XII]], factor XI, and [[factor IX]]).<ref name="pmid11487044">{{cite journal | vauthors = Walsh PN | title = Roles of platelets and factor XI in the initiation of blood coagulation by thrombin | journal = Thrombosis and Haemostasis | volume = 86 | issue = 1 | pages = 75–82 | date = Jul 2001 | pmid = 11487044 | doi =  | url = http://www.schattauer.de/index.php?id=1268&pii=th01070007&no_cache=1 }}</ref>


'''Factor XI''' or '''plasma thromboplastin antecedent''' is one of the [[enzyme]]s of the [[coagulation|coagulation cascade]]. Like many other coagulation factors, it is a [[serine protease]].
Factor XIa activates factor IX by selectively cleaving [[arginine|arg]]-[[alanine|ala]] and [[arginine|arg]]-[[valine|val]] [[peptide bond]]s. Factor IXa, in turn, activates [[factor X]].
 
Inhibitors of factor XIa include [[protein Z-dependent protease inhibitor]] (ZPI, a member of the [[serine protease inhibitor]]/serpin class of proteins), which is independent of [[protein Z]] (its action on factor X, however, is protein Z-dependent, hence its name).


==Physiology==
== Structure ==
Factor XI (FXI) is produced by the [[liver]] and circulates as a homo-dimer in its inactive form. The plasma half-life of FXI is approximately 52 hours. The zymogen factor is activated into ''factor XIa'' by [[factor XII]]a (FXIIa), [[thrombin]], and it is also [[autocatalytic]], and FXI is a member of the "contact pathway" due to activation by FXIIa (with includes [[high molecular weight kininogen|HMWK]], [[prekallikrein]], [[factor XII]], factor XI and [[factor IX]]).


Factor XIa activates factor IX by selectively cleaving [[arginine|arg]]-[[alanine|ala]] and [[arginine|arg]]-[[valine|val]] [[peptide bond]]s. Factor IXa, in turn, activates [[factor X]].
Although synthesized as a single polypeptide chain, FXI circulates as a homodimer. Every chain has a relative molecular mass of approximately 80000. Typical plasma concentrations of FXI are 5 μg/mL, corresponding to a plasma concentration (of FXI dimers) of approximately 30 nM.
The FXI gene is 23kb in length, has 15 exons, and is found on chromosome 4q32-35.<ref name="pmid2827746"/><ref name="pmid2612218"/>
 
Factor XI consists of four [[PAN domain|apple domain]]s, that create a disk-like platform around the base of a fifth, catalytic [[serine protease]] domain.
One contains a binding site for [[thrombin]], another for [[high molecular weight kininogen]], a third one for [[factor IX]], [[heparin]] and [[glycoprotein Ib]] and the fourth is implicated in forming the factor XI homodimer, including a [[cysteine]] residue that creates a [[disulfide bond]].
 
In the homodimer, the apple domains create two disk-like platforms connected together at an angle, with the catalytic domains sticking out at each side of the dimer.


Inhibitors of factor XIa include [[protein Z-dependent protease inhibitor]] (ZPI, a member of the [[serine protease inhibitor]]/serpin class of proteins), which is independent of [[protein Z]] (its action on factor X, however, is protein Z-dependent, hence its name).
Activation by thrombin or [[factor XII]]a is achieved by cleavage of Arg369-Ile370 peptide bonds on both subunits of the dimer. This results in a partial detachment of the catalytic domain from the disk-like apple domains, still linked to the fourth domain with a disulfide bond, but now farther from the third domain.
This is thought that this exposes the factor IX binding site of the third apple domain, allowing factor XI's protease activity on it.
<ref>{{cite journal|vauthors=Emsley J, McEwan PA, Gailani D | title=Structure and function of factor XI | journal=Blood | date = Apr 2010 | volume= 115 | issue= 13 | pages= 2569–77 | pmid=20110423 | doi=10.1182/blood-2009-09-199182 | pmc=4828079}}</ref>


==Protein structure and molecular biology==
== Role in disease ==
Although synthesized as a single polypeptide chain, FXI circulates as a homo-dimer. Every chain has a relative molecular mass of approximately 80000. Typical plasma concentrations of FXI are 5 mg/l, corresponding to a plasma concentration (of FXI dimers) of approximately 30nM.
The FXI gene is 23kb in length, has 15 exons, and is found on chromosome 4q32-35.


==Role in disease==
Deficiency of factor XI causes the rare [[hemophilia C]]; this mainly occurs in [[Ashkenazi]] [[Jew]]s and is believed to affect approximately 8% of that population. Less commonly, hemophilia C can be found in Jews of Iraqi ancestry and in Israeli Arabs. The condition has been described in other populations at around 1% of cases. It is an [[autosomal recessive]] disorder. There is little spontaneous bleeding, but surgical procedures may cause excessive blood loss, and prophylaxis is required.<ref name="pmid8800510">{{cite journal | vauthors = Bolton-Maggs PH | title = Factor XI deficiency | journal = Baillière's Clinical Haematology | volume = 9 | issue = 2 | pages = 355–68 | date = Jun 1996 | pmid = 8800510 | doi = 10.1016/S0950-3536(96)80068-0 }}</ref>
Deficiency of factor XI causes the rare [[Haemophilia C]]; this mainly occurs in Ashkenazi Jews and is believed to affect approximately 8% of that population, of both sexes. The condition has been described in other populations at around 1% of cases. It is an [[autosomal recessive]] disorder. There is little spontaneous bleeding, but surgical procedures may cause excessive blood loss, and prophylaxis is required.


Low levels of factor XI also occur in many other disease states, including [[Noonan syndrome]].
Low levels of factor XI also occur in many other disease states, including [[Noonan syndrome]].
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High levels of factor XI have been implicated in [[thrombosis]], although it is uncertain what determines these levels and how serious the procoagulant state is.
High levels of factor XI have been implicated in [[thrombosis]], although it is uncertain what determines these levels and how serious the procoagulant state is.


==References==
== See also ==
{{reflist|2}}
*[[Contact activation pathway]] (also known as the ''intrinsic pathway'')
==Further reading==
*[[Tissue factor pathway]] (also known as the ''extrinsic pathway'')
{{refbegin | 2}}
 
{{PBB_Further_reading
== References ==
| citations =
{{reflist|33em}}
*{{cite journal | author=Gailani D, Zivelin A, Sinha D, Walsh PN |title=Do platelets synthesize factor XI? |journal=J. Thromb. Haemost. |volume=2 |issue= 10 |pages= 1709-12 |year= 2005 |pmid= 15456479 |doi= 10.1111/j.1538-7836.2004.00935.x }}
 
*{{cite journal | author=Dossenbach-Glaninger A, Hopmeier P |title=Coagulation factor XI: a database of mutations and polymorphisms associated with factor XI deficiency. |journal=Blood Coagul. Fibrinolysis |volume=16 |issue= 4 |pages= 231-8 |year= 2005 |pmid= 15870541 |doi= }}
== Further reading ==
*{{cite journal | author=Seligsohn U |title=Factor XI in haemostasis and thrombosis: past, present and future. |journal=Thromb. Haemost. |volume=98 |issue= 1 |pages= 84-9 |year= 2007 |pmid= 17597996 |doi= }}
{{refbegin|33em}}
*{{cite journal | author=Meijers JC, Davie EW, Chung DW |title=Expression of human blood coagulation factor XI: characterization of the defect in factor XI type III deficiency. |journal=Blood |volume=79 |issue= 6 |pages= 1435-40 |year= 1992 |pmid= 1547342 |doi=  }}
* {{cite journal | vauthors = Gailani D, Zivelin A, Sinha D, Walsh PN | title = Do platelets synthesize factor XI? | journal = Journal of Thrombosis and Haemostasis : JTH | volume = 2 | issue = 10 | pages = 1709–12 | year = 2005 | pmid = 15456479 | doi = 10.1111/j.1538-7836.2004.00935.x }}
*{{cite journal | author=Gailani D, Broze GJ |title=Factor XI activation in a revised model of blood coagulation. |journal=Science |volume=253 |issue= 5022 |pages= 909-12 |year= 1991 |pmid= 1652157 |doi= }}
* {{cite journal | vauthors = Dossenbach-Glaninger A, Hopmeier P | title = Coagulation factor XI: a database of mutations and polymorphisms associated with factor XI deficiency | journal = Blood Coagulation & Fibrinolysis : An International Journal in Haemostasis and Thrombosis | volume = 16 | issue = 4 | pages = 231–8  | date = Jun 2005 | pmid = 15870541 | doi = 10.1097/01.mbc.0000169214.62560.a5 }}
*{{cite journal | author=Buetow KH, Shiang R, Yang P, ''et al.'' |title=A detailed multipoint map of human chromosome 4 provides evidence for linkage heterogeneity and position-specific recombination rates. |journal=Am. J. Hum. Genet. |volume=48 |issue= 5 |pages= 911-25 |year= 1991 |pmid= 1673289 |doi=  }}
* {{cite journal | vauthors = Seligsohn U | title = Factor XI in haemostasis and thrombosis: past, present and future | journal = Thrombosis and Haemostasis | volume = 98 | issue = 1 | pages = 84–9  | date = Jul 2007 | pmid = 17597996 | doi = 10.1160/th07-04-0246 }}
*{{cite journal | author=Bodfish P, Warne D, Watkins C, ''et al.'' |title=Dinucleotide repeat polymorphism in the human coagulation factor XI gene, intron B (F11), detected using the polymerase chain reaction. |journal=Nucleic Acids Res. |volume=19 |issue= 24 |pages= 6979 |year= 1992 |pmid= 1762944 |doi= }}
* {{cite journal | vauthors = Meijers JC, Davie EW, Chung DW | title = Expression of human blood coagulation factor XI: characterization of the defect in factor XI type III deficiency | journal = Blood | volume = 79 | issue = 6 | pages = 1435–40  | date = Mar 1992 | pmid = 1547342 | doi =  }}
*{{cite journal | author=Clarkson K, Rosenfeld B, Fair J, ''et al.'' |title=Factor XI deficiency acquired by liver transplantation. |journal=Ann. Intern. Med. |volume=115 |issue= 11 |pages= 877-9 |year= 1991 |pmid= 1952475 |doi= }}
* {{cite journal | vauthors = Gailani D, Broze GJ | title = Factor XI activation in a revised model of blood coagulation | journal = Science | volume = 253 | issue = 5022 | pages = 909–12  | date = Aug 1991 | pmid = 1652157 | doi = 10.1126/science.1652157 }}
*{{cite journal | author=McMullen BA, Fujikawa K, Davie EW |title=Location of the disulfide bonds in human coagulation factor XI: the presence of tandem apple domains. |journal=Biochemistry |volume=30 |issue= 8 |pages= 2056-60 |year= 1991 |pmid= 1998667 |doi= }}
* {{cite journal | vauthors = Buetow KH, Shiang R, Yang P, Nakamura Y, Lathrop GM, White R, Wasmuth JJ, Wood S, Berdahl LD, Leysens NJ | title = A detailed multipoint map of human chromosome 4 provides evidence for linkage heterogeneity and position-specific recombination rates | journal = American Journal of Human Genetics | volume = 48 | issue = 5 | pages = 911–25  | date = May 1991 | pmid = 1673289 | pmc = 1683054 | doi =  }}
*{{cite journal | author=Naito K, Fujikawa K |title=Activation of human blood coagulation factor XI independent of factor XII. Factor XI is activated by thrombin and factor XIa in the presence of negatively charged surfaces. |journal=J. Biol. Chem. |volume=266 |issue= 12 |pages= 7353-8 |year= 1991 |pmid= 2019570 |doi=  }}
* {{cite journal | vauthors = Bodfish P, Warne D, Watkins C, Nyberg K, Spurr NK | title = Dinucleotide repeat polymorphism in the human coagulation factor XI gene, intron B (F11), detected using the polymerase chain reaction | journal = Nucleic Acids Research | volume = 19 | issue = 24 | pages = 6979 | year = 1992 | pmid = 1762944 | pmc = 329377 | doi = 10.1093/nar/19.24.6979-a }}
*{{cite journal | author=Asakai R, Chung DW, Davie EW, Seligsohn U |title=Factor XI deficiency in Ashkenazi Jews in Israel. |journal=N. Engl. J. Med. |volume=325 |issue= 3 |pages= 153-8 |year= 1991 |pmid= 2052060 |doi= }}
* {{cite journal | vauthors = Clarkson K, Rosenfeld B, Fair J, Klein A, Bell W | title = Factor XI deficiency acquired by liver transplantation | journal = Annals of Internal Medicine | volume = 115 | issue = 11 | pages = 877–9  | date = Dec 1991 | pmid = 1952475 | doi = 10.7326/0003-4819-115-11-877 }}
*{{cite journal | author=España F, Berrettini M, Griffin JH |title=Purification and characterization of plasma protein C inhibitor. |journal=Thromb. Res. |volume=55 |issue= 3 |pages= 369-84 |year= 1989 |pmid= 2551064 |doi= }}
* {{cite journal | vauthors = McMullen BA, Fujikawa K, Davie EW | title = Location of the disulfide bonds in human coagulation factor XI: the presence of tandem apple domains | journal = Biochemistry | volume = 30 | issue = 8 | pages = 2056–60  | date = Feb 1991 | pmid = 1998667 | doi = 10.1021/bi00222a008 }}
*{{cite journal | author=Asakai R, Chung DW, Ratnoff OD, Davie EW |title=Factor XI (plasma thromboplastin antecedent) deficiency in Ashkenazi Jews is a bleeding disorder that can result from three types of point mutations. |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=86 |issue= 20 |pages= 7667-71 |year= 1989 |pmid= 2813350 |doi= }}
* {{cite journal | vauthors = Naito K, Fujikawa K | title = Activation of human blood coagulation factor XI independent of factor XII. Factor XI is activated by thrombin and factor XIa in the presence of negatively charged surfaces | journal = The Journal of Biological Chemistry | volume = 266 | issue = 12 | pages = 7353–8  | date = Apr 1991 | pmid = 2019570 | doi =  }}
*{{cite journal | author=Asakai R, Davie EW, Chung DW |title=Organization of the gene for human factor XI. |journal=Biochemistry |volume=26 |issue= 23 |pages= 7221-8 |year= 1988 |pmid= 2827746 |doi= }}
* {{cite journal | vauthors = Asakai R, Chung DW, Davie EW, Seligsohn U | title = Factor XI deficiency in Ashkenazi Jews in Israel | journal = The New England Journal of Medicine | volume = 325 | issue = 3 | pages = 153–8  | date = Jul 1991 | pmid = 2052060 | doi = 10.1056/NEJM199107183250303 }}
*{{cite journal | author=Fujikawa K, Chung DW, Hendrickson LE, Davie EW |title=Amino acid sequence of human factor XI, a blood coagulation factor with four tandem repeats that are highly homologous with plasma prekallikrein. |journal=Biochemistry |volume=25 |issue= 9 |pages= 2417-24 |year= 1986 |pmid= 3636155 |doi= }}
* {{cite journal | vauthors = España F, Berrettini M, Griffin JH | title = Purification and characterization of plasma protein C inhibitor | journal = [[Thrombosis Research]] | volume = 55 | issue = 3 | pages = 369–84  | date = Aug 1989 | pmid = 2551064 | doi = 10.1016/0049-3848(89)90069-8 }}
*{{cite journal | author=Warn-Cramer BJ, Bajaj SP |title=Stoichiometry of binding of high molecular weight kininogen to factor XI/XIa. |journal=Biochem. Biophys. Res. Commun. |volume=133 |issue= 2 |pages= 417-22 |year= 1986 |pmid= 3936495 |doi= }}
* {{cite journal | vauthors = Asakai R, Chung DW, Ratnoff OD, Davie EW | title = Factor XI (plasma thromboplastin antecedent) deficiency in Ashkenazi Jews is a bleeding disorder that can result from three types of point mutations | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 86 | issue = 20 | pages = 7667–71  | date = Oct 1989 | pmid = 2813350 | pmc = 298131 | doi = 10.1073/pnas.86.20.7667 }}
*{{cite journal | author=Bouma BN, Vlooswijk RA, Griffin JH |title=Immunologic studies of human coagulation factor XI and its complex with high molecular weight kininogen. |journal=Blood |volume=62 |issue= 5 |pages= 1123-31 |year= 1983 |pmid= 6626744 |doi=  }}
* {{cite journal | vauthors = Asakai R, Davie EW, Chung DW | title = Organization of the gene for human factor XI | journal = Biochemistry | volume = 26 | issue = 23 | pages = 7221–8 | year = 1988 | pmid = 2827746 | doi = 10.1021/bi00397a004 }}
*{{cite journal | author=Tuszynski GP, Bevacqua SJ, Schmaier AH, ''et al.'' |title=Factor XI antigen and activity in human platelets. |journal=Blood |volume=59 |issue= 6 |pages= 1148-56 |year= 1982 |pmid= 7044446 |doi=  }}
* {{cite journal | vauthors = Fujikawa K, Chung DW, Hendrickson LE, Davie EW | title = Amino acid sequence of human factor XI, a blood coagulation factor with four tandem repeats that are highly homologous with plasma prekallikrein | journal = Biochemistry | volume = 25 | issue = 9 | pages = 2417–24  | date = May 1986 | pmid = 3636155 | doi = 10.1021/bi00357a018 }}
*{{cite journal | author=Imanaka Y, Lal K, Nishimura T, ''et al.'' |title=Identification of two novel mutations in non-Jewish factor XI deficiency. |journal=Br. J. Haematol. |volume=90 |issue= 4 |pages= 916-20 |year= 1995 |pmid= 7669672 |doi= }}
* {{cite journal | vauthors = Warn-Cramer BJ, Bajaj SP | title = Stoichiometry of binding of high molecular weight kininogen to factor XI/XIa | journal = Biochemical and Biophysical Research Communications | volume = 133 | issue = 2 | pages = 417–22 | year = 1986 | pmid = 3936495 | doi = 10.1016/0006-291X(85)90922-2 }}
*{{cite journal | author=Pugh RE, McVey JH, Tuddenham EG, Hancock JF |title=Six point mutations that cause factor XI deficiency. |journal=Blood |volume=85 |issue= 6 |pages= 1509-16 |year= 1995 |pmid= 7888672 |doi=  }}
* {{cite journal | vauthors = Bouma BN, Vlooswijk RA, Griffin JH | title = Immunologic studies of human coagulation factor XI and its complex with high molecular weight kininogen | journal = Blood | volume = 62 | issue = 5 | pages = 1123–31  | date = Nov 1983 | pmid = 6626744 | doi =  }}
}}
* {{cite journal | vauthors = Tuszynski GP, Bevacqua SJ, Schmaier AH, Colman RW, Walsh PN | title = Factor XI antigen and activity in human platelets | journal = Blood | volume = 59 | issue = 6 | pages = 1148–56  | date = Jun 1982 | pmid = 7044446 | doi =  }}
* {{cite journal | vauthors = Imanaka Y, Lal K, Nishimura T, Bolton-Maggs PH, Tuddenham EG, McVey JH | title = Identification of two novel mutations in non-Jewish factor XI deficiency | journal = British Journal of Haematology | volume = 90 | issue = 4 | pages = 916–20  | date = Aug 1995 | pmid = 7669672 | doi = 10.1111/j.1365-2141.1995.tb05215.x }}
* {{cite journal | vauthors = Pugh RE, McVey JH, Tuddenham EG, Hancock JF | title = Six point mutations that cause factor XI deficiency | journal = Blood | volume = 85 | issue = 6 | pages = 1509–16  | date = Mar 1995 | pmid = 7888672 | doi =  }}
* {{cite journal | vauthors = Riley PW, Cheng H, Samuel D, Roder H, Walsh PN | title = Dimer dissociation and unfolding mechanism of coagulation factor XI apple 4 domain: spectroscopic and mutational analysis | journal = Journal of Molecular Biology | volume = 367 | issue = 2 | pages = 558–73  | date = Mar 2007 | pmid = 17257616 | pmc = 1945241 | doi = 10.1016/j.jmb.2006.12.066 }}
* {{cite journal | vauthors = Samuel D, Cheng H, Riley PW, Canutescu AA, Nagaswami C, Weisel JW, Bu Z, Walsh PN, Roder H | title = Solution structure of the A4 domain of factor XI sheds light on the mechanism of zymogen activation | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 40 | pages = 15693–8  | date = Oct 2007 | pmid = 17884987 | pmc = 1987390 | doi = 10.1073/pnas.0703080104 }}
{{refend}}
{{refend}}
== External links ==
* The [[MEROPS]] online database for peptidases and their inhibitors: [http://merops.sanger.ac.uk/cgi-bin/merops.cgi?id=S01.213 S01.213]
{{PDB Gallery|geneid=2160}}


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Factor XI or plasma thromboplastin antecedent is the zymogen form of factor XIa, one of the enzymes of the coagulation cascade. Like many other coagulation factors, it is a serine protease. In humans, Factor XI is encoded by the F11 gene.[1][2][3][4]

Function

Factor XI (FXI) is produced by the liver and circulates as a homo-dimer in its inactive form.[5] The plasma half-life of FXI is approximately 52 hours. The zymogen factor is activated into factor XIa by factor XIIa (FXIIa), thrombin, and FXIa itself; due to its activation by FXIIa, FXI is a member of the "contact pathway" (which includes HMWK, prekallikrein, factor XII, factor XI, and factor IX).[6]

Factor XIa activates factor IX by selectively cleaving arg-ala and arg-val peptide bonds. Factor IXa, in turn, activates factor X.

Inhibitors of factor XIa include protein Z-dependent protease inhibitor (ZPI, a member of the serine protease inhibitor/serpin class of proteins), which is independent of protein Z (its action on factor X, however, is protein Z-dependent, hence its name).

Structure

Although synthesized as a single polypeptide chain, FXI circulates as a homodimer. Every chain has a relative molecular mass of approximately 80000. Typical plasma concentrations of FXI are 5 μg/mL, corresponding to a plasma concentration (of FXI dimers) of approximately 30 nM. The FXI gene is 23kb in length, has 15 exons, and is found on chromosome 4q32-35.[2][3]

Factor XI consists of four apple domains, that create a disk-like platform around the base of a fifth, catalytic serine protease domain. One contains a binding site for thrombin, another for high molecular weight kininogen, a third one for factor IX, heparin and glycoprotein Ib and the fourth is implicated in forming the factor XI homodimer, including a cysteine residue that creates a disulfide bond.

In the homodimer, the apple domains create two disk-like platforms connected together at an angle, with the catalytic domains sticking out at each side of the dimer.

Activation by thrombin or factor XIIa is achieved by cleavage of Arg369-Ile370 peptide bonds on both subunits of the dimer. This results in a partial detachment of the catalytic domain from the disk-like apple domains, still linked to the fourth domain with a disulfide bond, but now farther from the third domain. This is thought that this exposes the factor IX binding site of the third apple domain, allowing factor XI's protease activity on it. [7]

Role in disease

Deficiency of factor XI causes the rare hemophilia C; this mainly occurs in Ashkenazi Jews and is believed to affect approximately 8% of that population. Less commonly, hemophilia C can be found in Jews of Iraqi ancestry and in Israeli Arabs. The condition has been described in other populations at around 1% of cases. It is an autosomal recessive disorder. There is little spontaneous bleeding, but surgical procedures may cause excessive blood loss, and prophylaxis is required.[8]

Low levels of factor XI also occur in many other disease states, including Noonan syndrome.

High levels of factor XI have been implicated in thrombosis, although it is uncertain what determines these levels and how serious the procoagulant state is.

See also

References

  1. ↑ Fujikawa K, Chung DW, Hendrickson LE, Davie EW (May 1986). "Amino acid sequence of human factor XI, a blood coagulation factor with four tandem repeats that are highly homologous with plasma prekallikrein". Biochemistry. 25 (9): 2417–24. doi:10.1021/bi00357a018. PMID 3636155.
  2. ↑ 2.0 2.1 Asakai R, Davie EW, Chung DW (Nov 1987). "Organization of the gene for human factor XI". Biochemistry. 26 (23): 7221–8. doi:10.1021/bi00397a004. PMID 2827746.
  3. ↑ 3.0 3.1 Kato A, Asakai R, Davie EW, Aoki N (1989). "Factor XI gene (F11) is located on the distal end of the long arm of human chromosome 4". Cytogenetics and Cell Genetics. 52 (1–2): 77–8. doi:10.1159/000132844. PMID 2612218.
  4. ↑ Buetow KH, Shiang R, Yang P, Nakamura Y, Lathrop GM, White R, Wasmuth JJ, Wood S, Berdahl LD, Leysens NJ (May 1991). "A detailed multipoint map of human chromosome 4 provides evidence for linkage heterogeneity and position-specific recombination rates". American Journal of Human Genetics. 48 (5): 911–25. PMC 1683054. PMID 1673289.
  5. ↑ Wu W, Sinha D, Shikov S, Yip CK, Walz T, Billings PC, Lear JD, Walsh PN (Jul 2008). "Factor XI homodimer structure is essential for normal proteolytic activation by factor XIIa, thrombin, and factor XIa". The Journal of Biological Chemistry. 283 (27): 18655–64. doi:10.1074/jbc.M802275200. PMC 2441546. PMID 18441012.
  6. ↑ Walsh PN (Jul 2001). "Roles of platelets and factor XI in the initiation of blood coagulation by thrombin". Thrombosis and Haemostasis. 86 (1): 75–82. PMID 11487044.
  7. ↑ Emsley J, McEwan PA, Gailani D (Apr 2010). "Structure and function of factor XI". Blood. 115 (13): 2569–77. doi:10.1182/blood-2009-09-199182. PMC 4828079. PMID 20110423.
  8. ↑ Bolton-Maggs PH (Jun 1996). "Factor XI deficiency". Baillière's Clinical Haematology. 9 (2): 355–68. doi:10.1016/S0950-3536(96)80068-0. PMID 8800510.

Further reading

External links

  • The MEROPS online database for peptidases and their inhibitors: S01.213
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