InterPro domain: IPR034157

This topoisomerase-primase (TOPRIM) nucleotidyl transferase/hydrolase domain is found in proteins of the type II family of DNA topoisomerases similar to Saccharomyces cerevisiae Topoisomerase II. TopoII enzymes cut both strands of the duplex DNA to remove (relax) both positive and negative supercoils in DNA. These enzymes covalently attach to the 5' ends of the cut DNA, separate the free ends of the cleaved strands, pass another region of the duplex through this gap, then rejoin the ends. These proteins also catenate/ decatenate duplex rings [ 1 ].

The TOPRIM domain has two conserved motifs, one of which centres at a conserved glutamate and the other one at two conserved aspartates (DxD). This glutamate and two aspartates, cluster together to form a highly acid surface patch. The conserved glutamate may act as a general base in strand joining and as a general acid in strand cleavage by topisomerases. The DXD motif may co-ordinate Mg ²⁺ , a cofactor required for full catalytic function [ 2 ].

1. Structure and function of type II DNA topoisomerases. Biochem. J. 303 ( Pt 3), 681-95
2. Toprim--a conserved catalytic domain in type IA and II topoisomerases, DnaG-type primases, OLD family nucleases and RecR proteins. Nucleic Acids Res. 26, 4205-13