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1、ArchVirol(1988)103:3545VirologyArchives©bySpringer-Verlag1988StructuralproteinsofbovinecoronavirusstrainL9:effectsofthehostcellandtrypsintreatmentK.St.Cyr-Coats,J.Storz,K.A.Hussain,andK.L.SchnorrDepartmentofVeterinaryMicrobiologyandParasitology,SchoolofVeterinaryMedicine
2、,LouisianaStateUniversity,BatonRouge,Louisiana,U.S.A.AcceptedAugust12,1988Summary.Thepolypeptideprofileofthecell-adaptedstrainofbovinecorona-virus(MebusBCV-L9)isremarkablyaffectedbythehostcellandtrypsin.Wecomparedthestructuralproteinsofviruspurifiedfromdifferentcelllines
3、andfoundcell-dependentdifferencesinthevirusstructure.BCVwaspurifiedfromfourclonesofhumanrectaltumourcells(HRT-18):3F3,D2,3E3,and4B3.ThestructuralprofilesofBCVpropagatedinclones3E3and3F3wereiden-tical,consistingofproteinswithmolecularweightsof185,160,140,125,110,100,52,46
4、,37,31-34,and26-28kilodaltons(kd).BCVpurifiedfromcloneD2lackedthe100kdspecies,andclone4B3yieldedviruslackingthe46kdprotein.WecomparedthestructuresofBCVpropagatedinHRT-18cells[BCV(HRT-18)]andvirusraisedinbovinefetalspleencells[BCV(D2BFS)].Theconcentrationofthe185kdprotein
5、washigherinBCV(D2BFS),anditalsocontaineda200kdspecies.ProteinprofilesofinvitrotrypsintreatedanduntreatedBCV(HRT-18)differedonlyunderreducingconditions,suggestingthattrypsincleavagesitesarelocatedwithindisulfide-linkedregionsofaffectedproteins.PropagationofBCVinD2BFScells
6、inthepresenceoftrypsinresultedincleavageofthe185kdproteinandaconcommitantincreaseofthe100kdprotein.ActivationofthefusionfunctionprobablydependsonthiscleavageprocessbecausefusionofBCV-infectedD2BFScellsistrypsindependent.IntroductionProteolyticcleavageofinactiveprecursorp
7、olypeptidesofassembledvirionsintoanactiveformisnecessaryforinducingtheinfectivityofanumberofviruses.Notably,orthomyxovirusesandparamyxovirusesrequirecleavageofenvelopeproteinsforthevirusestobecomeinfectious.Processingoftheviralproteinsisaccomplishedeitherbycellularprotea
8、sesorbyexogenousproteasessuchastrypsin[2,3,7,9,10,11,18,19].Suchfindingsareemergingfor36K.St.Cyr-Coatse
