Disulfide BondsinFolding andTransport ofMouseHepatitis Coronavirus Glycoproteins

monoclonal antibody. Usingthisantibody inan immunofluorescence assay,we monitored thereducing effect ofDTTinsitu. DTTwas found toinitially affect onlytheSprotein present intheER; also, after longer treatment, theremaining signal alsogradually disappeared. Incontrast, folding and transport oftheM protein werenotinhibited byDTT.Underreducing conditions, M was transported efficiently tothetranssideoftheGolgicomplex, indicating thatcellular processessuchas ER-to-Golgi transport, 0-glycosylation, andGolgi retention were unaffected. InthepresenceofDTT,theM protein evenmovedatan increased ratetotheGolgi complex, whichisprobably because ofitsfailure tointeract withunfolded Sprotein. Theeffects ofinvivoreduction were reversible. WhenDTTwas removed frompulse-labeled cells, theSprotein folded posttranslationally andaberrantly; during itsoxidation, mostofSnow transiently aggregated intolarge