Uracil-DNA glycosylase in the extreme thermophile Archaeoglobus fulgidus

Uracil-DNA glycosylase (UDG) is an essential enzyme for maintaining genomic integrity. Here we describe a UDG from the extreme thermophile Archaeoglob us fulgidus. The enzyme is a member of a new class of enzymes found in prok aryotes that is distinct from the UDG enzyme found in Escherichia coli, euk aryotes, and DNA-containing viruses. The A. fulgidus UDG: is extremely ther mostable, maintaining full activity after heating for 1.5 h at 95 degrees C . The protein is capable of removing uracil from double-stranded DNA contai ning either a U/A or U/G base pair as well as from single-stranded DNA. Thi s enzyme is product-inhibited by both uracil and apurinic/apyrimidinic site s. The A. fulgidus UDG has a high degree of similarity at the primary amino acid sequence level to the enzyme found in Thermotoga maritima, a thermoph ilic eubacteria, and suggests a conserved mechanism of UDG-initiated base e xcision repair in archaea and thermophilic eubacteria.