Immunochemical identification of rubella virus hemagglutinin

Purified rubella virus contains three major structural polypeptides whose apparent molecular weights are 62,000, a 47,000-54,000 complex, and 38,000 when analyzed by polyacrylamide gel electrophoresis. Both the 62,000 and 47,000-54,000 dalton polypeptides are glycosylated, but they vary in their relative [3H]glucosamine and [3H]mannose content. Limited-digest peptide maps confirm that each polypeptide is distinct and that the 47,000-54,000 dalton complex is a series of three glycopolypeptides with extensive similarities. Under nonreducing conditions, both the 62,000 dalton glycopolypeptide and the 47,000-54,000 dalton complex exist as monomers and also as disulfide-linked complexes. A complex of 105,000 daltons is a dimer of the 62,000 dalton glycopolypeptide and a second, at 95,000 daltons, is a mixed disulfide-bonded dimer of the 62,000 dalton glycopolypeptide and 47,000-54,000 dalton complex. The 38,000 dalton polypeptide migrated exclusively as a dimer of 78,000 daltons when unreduced. Two monoclonal antibodies which inhibit the hemagglutinin function of the virus were shown to be directed against the 62,000 dalton glycopolypeptide. This glycoprotein is therefore responsible at least in part for the hemagglutinin function of rubella virus.