| Formulation | 50%glycerol/water(v/v) |
| Storage | -20°C |
| Purity | >95%bySDS-PAGE |
| ActivityDetermination | Clottingassay |
| ShelfLife(properlystored) | 12months |
TheorganizationofthefactorXIIdomainstructurebasedonsequencehomologyisrepresented,where:EGF=epidermalgrowthfactor,TypeIandTypeII=domainshomologoustothosefoundinfibronectin,solidarrows=kallikreincleavagesitesthatforma-andβ-factorXIIa,dashedarrows=cleavagesleADIngtointermediateformsoffactorXIIa.
SampleGelInformation:
| Gel | Novex4-12%Bis-Tris |
|---|---|
| Load | HumanFactorXII,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:
FactorXII(XII)(HagemanFactor)isasinglechain(Mr=78,000)glycoproteinzymogenthatcirculatesinplasmaataconcentrationof40µg/ml(1-5).RecipricalactivationofXIItotheactiveserineproteasefactorXIIa(XIIa)bykallikreiniscentraltoinitiationoftheintrinsiccoagulationpathway.Surfaceboundα-XIIainturnactivatesfactorXItoXIa.Secondarycleavageofα-XIIabykallikreinyieldsβ-XIIa,whichcatalyzessolutionphaseactivationofkallikrein,factorVIIandtheclassicalcomplementcascade.
TheABIlityofavarietyofnegativelychargedsubstances,bothphysiologicalandnonphysiologicaltopromoteXIIactivationand,thus,initiationoftheintrinsicpathwayhasledtothepsuedonym"contactactivation".Bindingtoanionicsurfacesinducesaconformationalchange,makingtheXIIzymogenmoresusceptIBLetocleavagebyavarietyofproteases(6,7).ItisunlikelythatbindingtonegativelychargedsurfacesaloneissufficienttoactivateXII,sincehighlypurifiedpreparationsofXIIandplasmadeficientinprekallikreinandhighmolecularweightkininogendonotundergothis"autocatalysis"(8-11).
AsinglecleavagebykallikreinatR353-Val354ofXIIyieldsα-XIIa,a2chainprotease(Mr=80,000)heldtogetherbydisulfidebonds.TheCOOH-terminallightchain(Mr=28,000)containsthecatalytictriad(His-40,Asp-89,Ser-191),whiletheNH2-terminalheavychain(Mr=52,000)conatinstheanionicsurfacebindingportionofthemolecule.Asecondarycleavageofα-XIIabykallikreinoutsidethedisulfidebondyieldsβ-XIIa(XIIf,BHFa,HFf,hagemanfactorfragments)(Mr=28,000),whichnolongerbindsanionicsurfaces(12).β-XIIacanactivateprekallikrein,buthaslittleprocoagulantactivity(13,14).SeveralotherminorintermediateformsofXIIaareindicatedinthefigureabove.
InhibitorsofXIIaincludeC1-INH,α2-antiplasmin,α2-macroglobulinandantithrombinIII.Atphysiologicalconcentrations,therelativeeffectivenessoftheseinhibitorsis91:4.5:3:1.5,respectively(10,16-19).TheratioofC1-INHtoXIIhasbeenimplicatedinthe"coldactivation"offactorVIIandtheconversionofprorenintoreninonstorageofplasma(20,21).
HumanfactorXIIispreparedfromfreshfrozenplasmabyimmunoaffinitychromatographyandsuppliedin50%glycerolforstorageat-20oC.
Properties:
| Localization | Plasma | |||||
|---|---|---|---|---|---|---|
| Plasmaconcentration | 40µg/ml(3) | |||||
| Modeofaction | Zymogen;precursortotheserineproteasefactorXIIa;activatedbykallikrein/HMWK/anionicsurfacecomplextointitiatetheintrinsicpathway | |||||
| Molecularweight | 80,000(2) | |||||
| Extinctioncoefficient |
| |||||
| Isoelectricpoint | 6.8 | |||||
| Structure | singlechain(mr=80,000),organizedinto6domainsbasedonsequencehomology(5). | |||||
| Percentcarbohydrate | 17% |
