Comparison of the bovine herpesvirus 1 gI gene and the herpes simplex virus type 1 gB gene.

In a previous report, we localized the gene for a 130-kilodalton envelope glycoprotein (gI) of bovine herpesvirus 1 (BHV-1) to a 3.6-kilobase HpaI-KpnI restriction endonuclease fragment from the long unique region of the BHV-1 genome (map position 0.405 to 0.432) and showed that a herpes simplex virus 1 (HSV-1) glycoprotein B (gB) probe uniquely hybridized to this BHV-1 restriction fragment. Here we present the complete nucleotide sequence of the BHV-1 gI gene and the predicted 932-amino-acid sequence of the gI primary translation product. Comparison with the published nucleotide sequence of the HSV-1 (KOS) gB gene (D. J. Bzik, B. A. Fox, N. A. DeLuca, and S. Person, Virology 133:301-314, 1984) reveals a similarity of 56.3% at the nucleotide level and 45.9% at the amino acid level. Upstream of the proposed gI coding region are potential mRNA transcriptional promoter elements including a TATA box and multiple Sp1 binding sites (GC boxes). Downstream of the gI coding region are two sequence elements associated with mRNA cleavage and polyadenylation (AATAAA and a GT-rich region roughly 30 nucleotides further downstream). Like HSV-1 gB, the predicted gI amino acid sequence exhibits two broad hydrophobic regions likely to represent a transient amino-terminal signal sequence and a transmembrane anchor domain (near the carboxyl terminus). Additional features shared with gB include 6 potential N-linked glycosylation sites and 10 highly conserved cysteine residues in the gI extracellular domain. Two regions of nonsimilarity between gI and gB are a centrally located 22-amino-acid region of gI for which there is essentially no gB counterpart and the transient amino-terminal leaders which differ in both size and sequence. The hydrophobic signal sequence of the gI leader, unlike that of gB, is preceded by an unusually large region of predominantly hydrophilic amino acids. The unusual length of the gI leader may result from an overlap between that portion of the gI coding region and a potential upstream coding region.