TOPRIM_TopoIIB_SPO: topoisomerase-primase (TOPRIM) nucleotidyl transferase/hydrolase domain of the type found in the type IIB family of DNA topoisomerases and Spo11. This subgroup contains proteins similar to Sulfolobus shibatae topoisomerase VI (TopoVI) and Saccharomyces cerevisiae meiotic recombination factor: Spo11. Type II DNA topoisomerases catalyze the ATP-dependent transport of one DNA duplex through another, in the process generating transient double strand breaks via covalent attachments to both DNA strands at the 5' positions. TopoVI enzymes are heterotetramers found in archaea and plants. Spo11 plays a role in generating the double strand breaks that initiate homologous recombination during meiosis. S. shibatae TopoVI relaxes both positive and negative supercoils, and in addition has a strong decatenase activity. The TOPRIM domain has two conserved motifs, one of which centers at a conserved glutamate and the other one at two conserved aspartates (DxD. For topoisomerases the conserved glutamate is believed to act as a general base in strand joining and, as a general acid in strand cleavage. The DXD motif may co-ordinate Mg2+, a cofactor required for full catalytic function.
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