| Type: | Domain | Name: | DNA topoisomerase I, DNA binding, mixed alpha/beta motif, eukaryotic-type |
| Description: | DNA topoisomerases regulate the number of topological links between two DNA strands (i.e. change the number of superhelical turns) by catalysing transient single- or double-strand breaks, crossing the strands through one another, then resealing the breaks []. These enzymes have several functions: to remove DNA supercoils during transcription and DNA replication; for strand breakage during recombination; for chromosome condensation; and to disentangle intertwined DNA during mitosis [, ]. DNA topoisomerases are divided into two classes: type I enzymes (; topoisomerases I, III and V) break single-strand DNA, and type II enzymes (; topoisomerases II, IV and VI) break double-strand DNA [].Type I topoisomerases are ATP-independent enzymes (except for reverse gyrase), and can be subdivided according to their structure and reaction mechanisms: type IA (bacterial and archaeal topoisomerase I, topoisomerase III and reverse gyrase) and type IB (eukaryotic topoisomerase I and topoisomerase V). These enzymes are primarily responsible for relaxing positively and/or negatively supercoiled DNA, except for reverse gyrase, which can introduce positive supercoils into DNA. This entry represents a structural motif, consisting of a complex alpha/beta topology that forms the N-terminal DNA-binding domain of certain eukaryotic topoisomerase I (type IB) enzymes. To cleave the DNA backbone, these enzymes must make a transient phosphotyrosine bond. The N-terminal domain of human topoisomerase I is thought to coordinate the restriction of free strand rotation during the topoisomerisation step of catalysis. A conserved tryptophan residue may be important for the DNA-interaction ability of the N-terminal domain []. Human topoisomerase I has been shown to be inhibited by camptothecin (CPT), a plant alkaloid with antitumour activity. A binding mode for the anticancer drug camptothecin has been proposed on the basis of chemical and biochemical information combined with the three-dimensional structures of topoisomerase I-DNA complexes []. | Short Name: | TopoI_DNA-bd_mixed-a/b_euk |
| GO Term | Gene Name |
|---|---|
| GO:0003677 | IPR013030 |
| GO:0003917 | IPR013030 |
| GO:0006265 | IPR013030 |
| GO:0005694 | IPR013030 |
| GO Term | Gene Name |
|---|---|
| GO:0003677 | IPR013030 |
| GO:0003917 | IPR013030 |
| GO:0006265 | IPR013030 |
| GO:0005694 | IPR013030 |
| DB identifier | Type | Name |
|---|---|---|
| IPR008336 | Domain | DNA topoisomerase I, DNA binding, eukaryotic-type |
