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1、J.gen.Virol.(1983),64,2577-2583.PrintedinGreatBritain2577Keywords:coronavirus/IBV/spikeproteinCoronavirusIBV:StructuralCharacterizationoftheSpikeProteinByDAVIDCAVANAGHDepartmentofMicrobiology,HoughtonPoultryResearchStation,Houghton,Huntingdon,PE172DA,U.K.(Accepted23Augus
2、t1983)SUMMARYThespikeprotein(S;surfaceprojection)ofavianinfectiousbronchitisvirus(IBV)strainM41comprisestwoglycopolypeptides,S1(mol.wt.90x103)and$2(mol.wt.84×103),inequimolarproportions.Theapparentmol.wt.ofSwascalculatedas354(+17)xt0sfollowingco-sedimentationwithcatalase
3、insucrosegradients.IncubationofradiolabelledIBVwithurearesultedintheremovalofmostS1,butnoneof$2,fromthevirusparticle.AsimilarresultwasobtainedusinglowconcentrationsofSDS,althoughsomenucleocapsid,butnotmatrix,proteinwasalsoreleased.2~SDSalonewasaseffectiveas2~SDSplus2~2-m
4、ercaptoethanolfortheseparationofS1and$2priortoSDS-polyacrylamidegelelectrophoresis.DithiothreitoldidnotremoveSfromvirionsbutdiddecreasethebuoyantdensityofthevirusfrom1.18g/mlto1.16g/ml,andchangedtheconfigurationofS.ItisconcludedthatIBVSproteinisanoligomercomprisingtwocop
5、iesofeachofS1and$2,althoughthepossibilitythattherearethreecopiesofeachglycopolypeptidecannotbediscounted.Sisattachedtothemembraneby$2,whileS1haslittleornocontactwiththemembraneandmayformthemajorpartofthebulbousendofS.InterpeptidedisulphidebondsdonotoccurinS,andtheassocia
6、tionofS1and$2isweak.INTRODUCTIONAvianinfectiousbronchitisvirus(IBV)causeseconomicallyimportantdiseaseinchickens,affectingbothrespiratoryandnon-respiratorytissues(Hofstad,1978).LikeothercoronavirusestheIBVvirusparticlecontainsthreemajorproteinstructures,thenucleocapsid(N)
7、,matrix(M)andthespike(surfaceprojectionorpeplomer)(S)proteins(forreferences,seeSiddelletal.,1982).Apolypeptideofabout50000mol.wt.(50K)formstheNprotein(Macnaughtonetal.,1977).TheMproteincomprisesapolypeptideof23Kwhichisheterogeneouslyglycosylated,themajorglycopolypeptideb
8、eingabout30K(Stemetal.,1982;Stern&Sefton,1982b;Cavanagh,1983a).TheSproteincomprisestwoglycopolypeptides