IDENTIFICATION AND CHARACTERIZATION OF A NOVEL STRUCTURAL GLYCOPROTEIN IN PSEUDORABIES VIRUS, GL

Herpesvirus envelope glycoproteins play important roles in the interac tion between virions and target cells. In the alphaherpesvirus pseudor abies virus (PrV), seven glycoproteins that all constitute homologs of glycoproteins found in herpes simplex virus type 1 (HSV-1) have been characterized, including a homolog of HSV-1 glycoprotein H (gH). Since HSV-1 gH is found associated with another essential glycoprotein, gL, we analyzed whether PrV also encodes a gL homolog. DNA sequence analy sis of a corresponding part of the U-L region adjacent to the internal inverted repeat in PrV strains Kaplan and Becker revealed the presenc e of two open reading frames (ORF). Deduced proteins exhibited homolog y to uracil-DNA glycosylase encoded by HSV-1 ORF UL2 (54% identity) an d gL encoded by HSV-1 ORF UL1 (24% identity), respectively. To identif y the PrV UL1 protein, rabbit antisera were prepared against two synth etic oligopeptides that were predicted by computer analysis to encompa ss antigenic epitopes. Sera against both peptides reacted in Western b lots of purified virions with a 20-kDa protein. The specificity of the reaction was demonstrated by peptide competition. Since the PrV UL1 s equence did not reveal the presence of a consensus N-linked glycosylat ion site, concanavalin A affinity chromatography and enzymatic deglyco sylation of virion glycoproteins were used to ascertain that the PrV U L1 product is O glycosylated. Therefore, we designated this protein Pr V gL. Analysis of mutant PrV virions lacking gH showed that concomitan tly with the absence of gH, gL was also missing in purified virions. I n summary, we identified and characterized a novel structural PrV glyc oprotein, gL, which represents the eighth PrV glycoprotein described. In addition, we show that virion location of PrV gL is dependent on th e presence of PrV gH.