MUTATIONAL ANALYSIS OF THE PROTEOLYTIC CLEAVAGE SITE OF GLYCOPROTEIN-B (GB) OF MAREKS-DISEASE VIRUS

The Marek's disease virus (MDV) glycoprotein B (gB) precursor, gp100, is proteolytically cleaved into two disulfide-linked subunits, gp60 an d gp49. In the gB homologs of most other herpesviruses, a tetrapeptide , Arg-Xaa-Arg-Arg, is immediately upstream from the predicted cleavage site. We have investigated the specificity of the proteolytic cleavag e in gp100 by introducing mutations within its predicted cleavage site (Arg-Leu-Arg-Arg) and expressed these mutants in recombinant fowlpox virus (FPV). The results show that all three Arg residues at the predi cted cleavage site play an important role in the specific proteolytic cleavage of gp100. Furthermore, we demonstrated that the cleavage of g p100 is not necessary for transport of gB to the cell surface.