Effects on the processing and antigenicity of linking the Pk epitope tag to the N or C terminus of the HN protein of the paramyxovirus, SV5

The mammalian cell expression vector pGEM-3zf(+) (in which expression is under control of the T7 promoter) was modified to facilitate the addition of a 14-amino acid epitope tag, termed Pk, to either the N or C terminus of recombinant proteins. The gene encoding the HN glycoprotein of the paramyxovirus, simian virus 5, was inserted into these modified vectors. The addition of the Pk tag to the N or C terminus did not prevent the glycosylation of the HN protein, its ability to oligomerise or its transport to the cell surface. In addition, the Pk-tagged HN glycoproteins reacted with a panel of monoclonal antibodies that recognise conformationally sensitive epitopes on the HN protein, suggesting that the presence of an additional 14-amino acid tag sequence at either N or C terminus of the HN protein had little effect on the folding and hence immunogenicity of the protein.