Tyrosyl-DNA phosphodiesterase 1, also known as TDP1, is involved in repairing stalled topoisomerase I-DNA complexes by catalyzing the hydrolysis of the phosphodiester bond between the tyrosine residue of topoisomerase I and the 3-prime phosphate of DNA. This protein may also remove glycolate from single-stranded DNA containing 3-prime phosphoglycolate, suggesting a role in repair of free-radical mediated DNA double-strand breaks. Recombinant human TDP1, fused to His-tag at N-terminus, was expressed in E.coli.