Rubella virus: structural and non-structural proteins

Rubella virus was rapidly concentrated and purified using polyethylene glycol 6000 as the precipitating agent. Electrophoresis in slab gels defined three structural proteins present in equimolar amounts, with mol. wt. of 59000 (E1), 43000 to 48000 (heterogeneous E2) and 34000 (core protein, C). E1 and E2 were glycosylated; different distributions of labelled carbohydrates within the broad band of E2 indicated that the slower migrating region was enriched in complex oligosaccharides. In infected cells, the counterparts to E1 and E2 were labelled with [3H]mannose and both migrated in gels as sharp bands, indicating that the heterogeneity observed in virion E2 was produced during virus maturation. After radioimmunoprecipitation of infected cell extracts with convalescent rubella serum, the intracellular equivalents of E1, E2 and C were readily defined in gels, as well as several putative non-structural proteins. Four of these were defined more clearly and without resort to immunoprecipitation by labelling with [35S]methionine during hypertonic treatment of infected cells at 24 h; their mol. wt. were 200 000, 150 000, 87 000 and 75 000. Pulse-chase experiments under these conditions showed that the largest ( ns200 ) was apparently cleaved to ns150 .