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Catalytic domain, repeat 1, of Tyrosyl-DNA phosphodiesterase Catalytic domain, repeat 1, of Tyrosyl-DNA phosphodiesterase (Tdp1, EC 3.1.4.-), which exists in eukaryotes but not in prokaryotes. Tdp1 acts as an important DNA repair enzyme that removes stalled topoisomerase I-DNA complexes by catalyzing the hydrolysis of a phosphodiester bond between a tyrosine side chain and a DNA 3'-phosphate. It is a monomeric protein that contains two copies of a variant HKD motif (H-x-K-x(4)-D, where x represents any amino acid residue), which consists of the highly conserved histidine and lysine residues, but lacks the aspartate residue that is well conserved in other phospholipase D (PLD, EC 3.1.4.4) enzymes. Thus, this family represents a distinct class within the PLD superfamily. Like other PLD enzymes, Tdp1 may utilize a common two-step general acid/base catalytic mechanism, involving a DNA-enzyme intermediate to cleave phosphodiester bonds. A single active site involved in phosphatidyl group transfer would be formed by the two variant HKD motifs from the N- and C-terminal domains in a pseudodimeric way. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",