Uracil DNA glycosylase family 4, includes Thermotoga maritima TTUDGA, Bacillus phage SPO1 DNA polymerase, and similar proteins
Uracil DNA glycosylase family 4 includes Thermotoga maritima TTUDGA, a robust uracil DNA glycosylase that shares narrow substrate specificity and high catalytic efficiency with family 1, acting on double-stranded and single-stranded uracil-containing DNA. Members of this family possess four conserved cysteine residues required to coordinate the [4Fe-4S] iron-sulfur cluster. This family also includes the N-terminal domain of Bacillus phage SPO1 DNA polymerase. Bacteriophage SPO1 is one of a group of large, lytic, tailed bacteriophages of Bacillus subtilis, and contains hydroxymethyluracil (hmUra) in place of thymine in their DNA. It has been speculated that this UDG domain may help discriminate between hmUra containing SPO1 DNA and thymine-containing host DNA. Uracil-DNA glycosylases (UDGs) initiate repair of uracils in DNA. Uracil in DNA can arise as a result of mis-incorporation of dUMP residues by DNA polymerase or via deamination of cytosine. Uracil in DNA mispaired with guanine is one of the major pro-mutagenic events, causing G:C->A:T mutations. Thus, UDG is an essential enzyme for maintaining the integrity of genetic information. UDGs have been classified into various families on the basis of their substrate specificity, conserved motifs, and structural similarities. Although these families demonstrate different substrate specificities, often the function of one enzyme can be complemented by the other.
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