Mapping and molecular characterization of a functional thymidine kinase from Amsacta moorei entomopoxvirus

A thymidine kinase (TK) gene from the entomopoxvirus of Amsacta moorei (AmEPV) has been identified, mapped, cloned, and sequenced. The AmEPV TK was shown to be biologically functional as cloning of the gene into a TK-derivative of the orthopoxvirus vaccinia creates a TK+ virus. The gene has been localized to a 1.5-kb EcoRI-Q DNA fragment which maps to the far left end of the viral genome. Sequence analysis reveals an open reading frame (ORF) of 182 amino acids potentially encoding a polypeptide of 21.2 kDa. Amino acid homology comparisons indicate that the gene is most closely related to the TKs of a variety of poxviruses (approximately 45%) and less so to the TKs of vertebrates (approximately 40%). The TK from African swine fever virus (ASF) showed the least homology (31.4%) to the AmEPV TK gene, suggesting that these two viruses are not closely related although ASF shares some biological features of poxviruses, and both ASF and AmEPV can replicate within arthropod hosts.