Formulation	50%glycerol/water(v/v)
Storage	-20°C
Purity	>95%bySDS-PAGE
ActivityDetermination	Clottingassay
ShelfLife(properlystored)	12months

DomainStructureofFactorXI
ThedomainstructureofthefactorXImonomerisrepresented.TheareasidentifiedasR1throughR4correspondtofourtandemaminoacidsequencerepeatswhichultimatelycomprisetheheavychainoffactorXIa.DuringproteolyticactivationbyfactorXIIa,the"CATALYTICDOMAIN",whichcomprisesthelightchainoffactorXIa,iscleavedfromtheheavychainregion.TheheavyandlightchainsoffactorXIaremainassociatedthroughadisulfidebond.ThematurefactorXImoleculeisahomodimercomposedoftwoapparentlyidenticalmonomerswhichremainassociatedthroughdisulfidebonds.

SampleGelInformation:

Gel	Novex4-12%Bis-Tris
Load	HumanFactorXI,1µgperlane
Buffer	MOPS
Standard	SeeBluePlus2;Myosin(191kDa),PhosphorylaseB(97kDa),BSA(64kDa),GlutamicDehydrogenase(51kDa),AlcoholDehydrogenase(39kDa),CarbonicAnhydrase(28kDa),MyoglobinRed(19kDa),Lysozyme(14kDa)
SpecialNotes	Heavychainisadoubletduetothepresenceofupto50%betaform.Theconversionofalpha-Xatobeta-Xaoccursbyautocleavageofalpha-Xabyalpha-XaresultinginthelossofaCOOH-terminalpeptide.

Overview:

FactorXIisaplasmaglycoproteinwhichcirculatesinanon-covalentcomplexwithhighmolecularweightkininogen(1).Thematuremoleculeissynthesizedintheliverandisatwo-chainhomodimerwithamolecularweightofapproximately160,000(2,3).Itisestimatedthat5%ofthetotalmassisattributabletocarbohydrate(2).Thetwoidenticalmonomershavemolecularweightsof80,000,andarejoinedtogetherbydisulfidebonds.ThusbySDS-PAGEanalysis,factorXIappearsasasinglebandbothnon-reduced(Mr=160,000),andreduced(Mr=80,000).

FactorXIcirculatesasazymogenandrequiresproteolyticactivationtoacquireserineproteaseactivity.TheconversionoffactorXItofactorXIaiscatalyzedbyfactorXIIa,andresultsincleavageoftheArg369-Ile370bondineachmonomer(3).FactorXIaconsistsoftwoNH2-terminalderivedheavychains,andtwoCOOH-terminalderivedlightchains,allofwhichareheldtogetherbydisulfidebonds.FactorXIaparticipateswithintheintrinsicpathwayofcoagulationbycatalyzingtheconversionoffactorIXtofactorIXa.AbleedingdisordercalledplasmathromboplastinantecedentdeficiencyresultsfromalackoffactorXIprocoagulantactivity(4,5).ThevariablebleedingtendenciesobservedinfactorXIdeficientpatientsdonotcorrelatewitheitherfactorXIactivityorantigenlevels.ThislatterobservationmayberelatedtotheABIlityofthetissuefactor/factorVIIacomplextoalsoactivatefactorIXtoIXa.

Historically,factorXIhasbeendifficulttopurifyduetoitsrelativelylowconcentrationinplasma,anditssusceptibilitytoproteolysis(6).FactorXIispurifiedfromfreshfrozenplasmathatisstabilizedbyaddedinhibitors.TheplasmaisfirsttreatedwithBaCl2toremovethevitaminK-dependentproteins,andfactorXIisthenisolatedbyaffinitychromatography.AfinalchromatographysteponheparinsepharoseyieldsahomogeneouspreparationofintactfactorXI.Thefinishedproductissuppliedin50%(vol/vol)glycerol/H2Oandshouldbestoredat-20oC.

Properties:

Localization	Plasma;inassociationwithhighmolecularweightkininogen
Plasmaconcentration	2-7µg/ml(2,3,7,8)
Modeofaction	Zymogen;precursortotheserineproteasefactorXIa
Molecularweight	160,000(human)(2,3)
Extinctioncoefficient	E 1% 1cm,280nm =13.4(human)(2)
Isoelectricpoint	8.9-9.1
Structure	homodimerconsistingoftwoapparentlyidenticalsubunits(Mr~80,000)heldtogetherbydisulfidebonds.Monomerscontainfourtandemaminoacidrepeatsthatsharehomologywithplasmaprekallikrein(9).
Percentcarbohydrate	5%(human)(2)

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