Evolution of the herpes thymidine kinase: identification and comparison of the equine herpesvirus 1 thymidine kinase gene reveals similarity to a cell-encoded thymidylate kinase

Abstract

We have identified the equine herpesvirus 1 (EHV-1) thymidine kinase gene (TK) by DNA-mediated transformation and by DNA sequencing. Alignment of the amino acid sequence of the EHV-1 TK with the TKs from 3 other herpesviruses revealed regions of homology, some of which correspond to the previously identified substrate binding sites, while others have as yet, no assigned function. In particular, the strict conservation of an aspartate within the proposed nucleoside binding site suggests a role in ATP binding for this residue. Comparison of 5 herpes TKs with the thymidylate kinase of yeast revealed significant similarity which was strongest in those regions important to catalytic activity of the herpes TKs, and, therefore we propose that the herpes TK may be derived from a cellular thymidylate kinase. The implications for the evolution of enzyme activities within a pathway of nucleotide metabolism are discussed.

The Nucleotide Sequence of the Equine Herpesvirus 4 Thymidine Kinase Gene

“…4. Coalignment of the putative nucleotide-(a) and nucleoside-(b) binding sites of the predicted amino acid sequences of the TKs of EHV-4, EHV-1 (Robertson & Whalley, 1988), PRV (Kit, 1985a, b), BHV-I (Mittal & Field, 1989), BHV-2 (Sheppard & May, 1989), MarHV (Otsuka & Kit, 1984), HSV-1 (Wagner et al, 1981), HSV-2 (Kit et aL, 1983), VZV (Davison & Scott, 1986), EBV (Baer et al, 1984), HVS (Honess et al, 1989), MDV (Scott et al, 1989) and HVT (Scott et al, 1989). Residues conserved in all 13 herpesviruses are indicated below each alignment in upper case lettering.…”

“…The nucleotide sequences of the TK genes of a variety of herpesviruses, including EHV-1, have been reported (reviewed in Robertson & Whalley, 1988;Honess et al, 1989;Mittal & Field, 1989;Scott et aL, 1989). Here we report the nucleotide sequence of the EHV-4 TK gene and compare selected regions of the predicted amino acid sequence of its protein to those of other herpesvirus TK proteins.…”

“…The EHV-4 TK gene was expected to map at around 0.5 map units (m.u.) given the reported position of the EHV-1 TK gene (Robertson & Whalley, 1988) and evidence for collinearity of the long components of the EHV-1 and EHV-4 genomes (Cullinane et al, 1988). Southern blot analyses were performed in which recombinant plasmids containing EHV-4 BamHI fragments mapping between 0.39 and 0.62 m.u.…”

“…1). This probe contains the entire TK gene of EHV-1 and flanking sequence (Robertson & Whalley, 1988). Restriction digest products were electrophoresed through 0.75 % agarose and transferred to a GeneScreen membrane (New England Nuclear).…”

Glycoprotein 60 of equine herpesvirus type 1 is a homologue of herpes simplex virus glycoprotein D and plays a major role in penetration of cells

“…Therefore it is possible that the process of virus penetration is either a multi-step event or can proceed by independent mechanisms. For EHV-1, genes homologous to gB and gH have been sequenced (Robertson & Whalley, 1988;Whalley et al, 1989), and the products of these genes identified (Meredith et al, 1989;Bonass et al, 1990;L. A. Taylor, unpublished results).…”