Identification and structure of the gene encoding gpII, a major glycoprotein of varicella-zoster virus

The genome of varicella-zoster virus (VZV) encodes three major families of glycoproteins (gpI, gpII, and gpIII). mRNA from VZV-infected cells was hybrid selected using a library of VZV recombinant plasmids and translated in vitro; polypeptide products were immunoprecipitated by polyclonal monospecific guinea pig antibodies to gpII. The mRNA encoding a 100-kD polypeptide precipitable by anti-gpII antibodies mapped to the HindIII D fragment near the center of the UL region. DNA sequence analysis of this region of the VZV genome revealed a 2.6-kbp open reading frame (ORF) potentially encoding a 98-kDa polypeptide possessing the characteristics of a glycoprotein. The 100-kDa polypeptide was specified by mRNA isolated by hybrid selection using a plasmid containing part of the 2.6-kbp ORF, and immunoprecipitation of this protein by anti-gpII antibodies and by convalescent zoster serum was blocked specifically by purified gpII. We conclude that the 2.6-kbp ORF encodes gpII. The imputed primary amino acid sequence of gpII shows a high degree of homology to that of herpes simplex virus type 1 (HSV-1) gB, a result consistent with the equivalent map locations of the respective genes in the HSV and VZV genomes and with the recently reported serological cross-reactivity of HSV-1 gB and VZV gpII. Unlike the mature gene products of gB, those of gpII have been described as a pair of glycoproteins with approximate molecular weights of 60 kDa in reducing gels, products of a single glycoprotein species with approximate mol mass of 125-140 kDa in nonreducing gels. Amino-terminal sequences of purified gpII were determined and compared to the imputed amino acid sequence. This comparison implies that the primary translational product is cleaved approximately into halves in vivo and suggests that mature gpII is a disulfide-linked heterodimer.