IDENTIFICATION OF THE MEMBRANE-PROTEIN OF PORCINE EPIDEMIC DIARRHEA VIRUS

Sequence information on the genome of porcine epidemic diarrhea virus (PEDV) has only recently been determined. In contrast, very little is known about the viral proteins. In the present report we have identifi ed the membrane glycoprotein (M) of PEDV by use of rabbit anti-peptide sera and transient expression of the cloned M gene in Vero cells and by expression in the baculovirus system. The native M protein of PEDV is incorporated into virions, is N-glycosylated, and migrates with a r elative mobility (Mr) of 27 k in polyacrylamide gels. In contrast, the M protein synthesized by recombinant baculoviruses migrates with a Mr of 23 k, that is, with identical mobility as the deglycosylated produ ct of PEDV. Thus, it appears that M protein specified by the recombina nt baculovirus is poorly, if at all, glycosylated. Using monoclonal an tibodies and rabbit antipeptide sera specific for the N and C termini of the M protein, we were able to show that a 19 k band detected in PE DV-infected cells but not in virions represented a fragment of M from which the C terminus had been cleaved off. Finally, by electron micros copy and immunogold labelling, the relative orientation of M within th e virion envelope was determined as NexoCcyt. In conclusion, all of th ese data strongly support the hypothesis that PEDV should be classifie d with the group I coronaviruses.