A comparison of the structural polypeptides of five strains of mumps virus

The polypeptide patterns of five strains of mumps virus have been compared under uniform electrophoresis conditions. These strains included the MJ and RW strains, recently isolated from human cerebrospinal fluid, the neuro-adapted Kilham strain and the chick embryo-adapted Enders and Jeryl Lynn strains. A similar pattern of polypeptides, featuring six common and virus-specific species, was obtained with purified virus grown in ovo, in chick embryo fibroblasts (CEF) or in Vero cells. These polypeptides have been designated VP₁ (mol. wt. 200 000), VP₂ (mol. wt. 80 000 or 75 000), VP₃ (mol. wt. 68 000), VP₄ (mol. wt. 58 000), VP₅ (mol. wt. 45 000), VP6 (mol. wt. 39 000). The virus glycoproteins were identified as VP₂ and VP₄; the nucleocapsid-associated proteins as VP₁, VP₃ and VP₅. Additional polypeptides occurring both in uninfected Vero cells and in uninfected CEFs appeared in polypeptide profiles of purified mumps virus preparations, and could not be designated virus-specific polypeptides. Although strain differences were minimal, we did observe an extra protein, nucleocapsid-associated, in patterns from the chick-adapted Enders strain of mumps virus and strain-dependent variability in the size of VP₂.