Substrate specificity of vaccinia virus thymidylate kinase

Recent concerns on the use of variola virus, the caus-ative agent of smallpox, as a biological weapon haveprompted new interest in the development of smallmolecule therapeutics [1]. Moreover, monkeypox, areemerging disease due to monkeypox virus infectionin humans, is spreading in Africa, indicating thatsmallpox, although eradicated by the World HealthOrganization vaccination campaign in the 1970s, couldagain become a serious threat. Smallpox is transmittedby person-to-person contact and through inhalationof virus-containing saliva droplets. It causes skinrash, respiratory and sometimes fatal hemorrhagic