Thymine-DNA glycosylase, also known as TDG, belongs to the TDG/mug DNA glycosylase family. TDG is a nuclear protein which corrects G/T mismatches to G/C pairs by hydrolyzing the carbon-nitrogen bond between the sugar-phosphate backbone of the DNA and the mispaired thymin. TDG can also remove uracil and 5-bromouracil from mispairings with guanine. This enzyme plays a central role in cellular defense against genetic mutation caused by the spontaneous deamination of 5-methylcytosine and cytosine. Recombinant human TDG protein, fused to His-tag at N-terminus, was expressed in E.coli