Description:
MULTIMERICSTRUCTUREOFVONWILLEBRANDFACTOR
Theformationofa1.8MDavonWillebrandfactor(vWF)multimerwithboundfactorVIIIisillustrated.EachvWFmonomer(Mr=260,000)containsafactorVIIIbindingsiteneartheNH2-terminalendofthemolecule.Themonomersarejoinedend-to-end(NH2toNH2andCOOHtoCOOH)bydisulfidebondstoformlargemultimers.ThematuremultimerscanbindonefactorVIIImoleculepermonomericsubunit.
PropertiesofvonWillebrandFactor
| Localization: | Plasmaandsubendothelium |
| Modeofaction: | facilitatesplateletplugformationbyformingabridgebetweenplateletglycoproteinIBandexposedcollageninthesubendothelium;alsobindsandtransportsfactorVIII |
| Molecularweight: | 260,000to>10,000,000 |
| Isoelectricpoint: | 5.7-5.9 |
| Extinctioncoefficient: | NotApplicable;concentrationdeterminedbytotalproteinassay. |
| Concentrationinplasma: | 10micrograms/mL |
| Structure: | multimericproteincomposedofidentical260,000molecularweightsubunits |
| Percentcarbohydrate: | approximately15% |
Formulation:
100mMGlycine,pH6.8
Purity:
>95%bySDS-PAGE
NOTtissue/cellculturegrade.Nottestedforendotoxin.
SampleGelInfo:
Gel:Novex4-12%Bis-Tris
Load:HumanvonWillebrandFactor,1µgperlane
Buffer:MOPS
Standard:SeeBluePlus2;Myosin(191kDa),PhosphorylaseB(97kDa),BSA(64kDa),GlutamicDehydrogenase(51kDa),AlcoholDehydrogenase(39kDa),CarbonicAnhydrase(28kDa),MyoglobinRed(19kDa),Lysozyme(14kDa)
Storage:
Storage
-80°C
ShelfLife(properlystored)
12months
Background:
OverviewofvonWillebrandFactor
VonWillebrandfactor(vWF)isamultimericplasmaglycoproteinthatisrequiredfornormalhemostaticplateletplugformation.Thematureplasmaproteiniscomposedofapparentlyidenticalsubunits(Mr=260,000)whichareheldtogetherbydisulfidebonds.ThecirculatingvWFmoleculerangesinsizefromdimers(Mr=520,000)toextremelylargemultimers(Mr>10,000,000).Duringnormalhemostasis,thelargermultimersofvWFareresponsIBLeforfacilitatingplateletplugformationbyformingabridgebetweenplateletglycoproteinIBandexposedcollageninthesubendothelium.EitheralackofvWFproteinorthepresenceofabnormalitieswhichresultindecreasedpolymerizationmaycausealossofBIOLOGicalactivitywhichischaracteristicofvonWillebrand’sdisease.
Inadditiontoitsroleinplateletplugformation,vWFisalsoresponsibleforthebindingandtransportoffactorVIII(antihemophilicfactor)inplasma.ItappearsthatthislattereventisresponsibleforboththestABIlityandeffectivedeliveryoffunctionalfactorVIII.StudiesindicatethatfactorVIIIbindstotheNH2-terminalportionofthematurevWFsubunitwithastoichiometryofonefactorVIIImoleculepervWFmonomer.
ThesinglechainvWFmonomercontainsalargenumberofcysteineresiduesatboththeNH2-terminalandCOOH-terminalends,whichareinvolvedinthemultimerformation.Carbohydrateanalysesindicatethatnearly15%ofthemassofvWFiscontributedbycarbohydrate.ItappearsthatthecarbohydrateservestoprotectvWFfromproteolysis,butisnotnecessaryforfunctionalactivityormultimerformation.
vWFispreparedfromcitratedhumanplasmausingacombinationoftheproceduresdescribedbyThorell,andLollar.AfactorVIIIfreevWFpreparation,furtherpurifiedtoensureremovaloffactorVIIIprocoagulantactivity,isalsoavailable.Thepreparationsare>95%pureasjudgedbySDS-PAGEunderreducingconditions,andconsistoflargemultimersasdeterminedbyelectrophoresisinSDS/agarosegels.Theproteinisshippedfrozenin0.025Msodiumcitrate,0.1Mglycine,0.1MNaCl,pH6.8,forstorageat-70°C.
