THE UL49.5 GENE OF PSEUDORABIES VIRUS CODES FOR AN O-GLYCOSYLATED STRUCTURAL PROTEIN OF THE VIRAL ENVELOPE

Sequence analysis of BamHI fragment 1 of the pseudorabies virus (PrV) genome identified a novel PrV gene located upstream of the UL50 gene e ncoding PrV dUTPase, The deduced protein product displayed homology to the product of the herpes simplex virus type 1 UL49.5 protein, The pr edicted PrV UL49.5 protein consists of 98 amino acids with a calculate d molecular mass of 10,155 Da, It contains putative signal peptide and transmembrane domains but lacks a consensus sequence for N glycosylat ion, PrV UL49.5 was expressed as a fusion protein with glutathione S-t ransferase in Escherichia coil, and a rabbit antiserum was generated, In Western blots (immunoblots) of purified virions, the antiserum dete cted a protein with an apparent molecular mass of 14 kDa. After fracti onation of the virions, the 14-kDa protein was detected in the envelop e fraction, Localization of the UL49.5 protein in the viral envelope w as confirmed by immunoelectron microscopy, The treatment of purified v irions with glycosidases led to a reduction of the apparent molecular mass in Western blots by approximately 2 kDa following digestion with neuraminidase and O-glycosidase, Our results demonstrate that the PrV UL49.5 protein is an O-glycosylated structural component of the viral envelope, It represents the 10th PrV glycoprotein described, According to the unified nomenclature for alphaherpesvirus glycoproteins, we pr opose to designate it glycoprotein N (gN).