Characterization and isolation of structural polypeptides in haemagglutinating encephalomyelitis virus

Haemagglutinating encephalomyelitis virus (HEV), a member of the coronavirus family, was purified and analysed by SDS-polyacrylamide gel electrophoresis. It was shown to contain eight polypeptides, seven of which were glycosylated. They had apparent mol. wt. of 180,000 (GP 180), 130,0000 (GP 130), 120,000 (GP 120) 76,000 (GP 76), 64,000 (VP 64), 54,000 (GP 54), 32,000 (GP 32) and 31,000 (GP 31). Electrophoresis of virus samples dissociated under varying conditions showed that GP 54 and GP 120 could be interpreted as larger products of GP 31 and GP 32 and of GP 76, respectively. GP 76 also appeared as a dimer with a mol. wt. of 140,000 (GP 140) in the absence of beta-mercaptoethanol. Subviral particles, obtained by treatment with bromelain, banded at a slightly lower density than the intact virus and lacked surface projections. Analysis of these particles indicated that GP 180, GP 130 and GP 76 are associated with the virus projections. A small part of GP 31 and GP 32 also appeared to protrude from the lipid envelope since 20% of each molecule was sensitive to digestion. Two glycoproteins, GP 130 and GP 76, were solubilized with the detergent Triton X-100 and separated by rate zonal centrifugation. According to its activity-in indirect haemagglutination tests, GP 76 was considered to be a monovalent haemagglutinin subunit.