InterPro : IPR001631

Name  DNA topoisomerase I Short Name  TopoI
Type  Family 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 family of DNA topoisomerase I enzymes includes both type IA enzymes from bacteria and type IB enzymes from eukaryotes and viruses.Human topoisomerase I has been shown to be inhibited by camptothecin (CPT), a plant alkaloid with antitumour activity []. The crystal structures of human topoisomerase I comprising the core and carboxyl-terminal domains in covalent and noncovalent complexes with 22-base pair DNA duplexes reveal an enzyme that "clamps" around essentially B-form DNA. The core domain and the first eight residues of the carboxyl-terminal domain of the enzyme, including the active-site nucleophile tyrosine-723, share significant structural similarity with the bacteriophage family of DNA integrases. 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 [].Vaccinia virus, a cytoplasmically-replicating poxvirus, encodes a type I DNA topoisomerase that is biochemically similar to eukaryotic-like DNA topoisomerases I, and which has been widely studied as a model topoisomerase. It is the smallest topoisomerase known and is unusual in that it is resistant to the potent chemotherapeutic agent camptothecin. The crystal structure of an amino-terminal fragment of vaccinia virus DNA topoisomerase I shows that the fragment forms a five-stranded, antiparallel beta-sheet with two short alpha-helices and connecting loops. Residues that are conserved between all eukaryotic-like type I topoisomerases are not clustered in particular regions of the structure [].

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

5 Contains

Id Name Short Name Type
IPR013500 DNA topoisomerase I, catalytic core, eukaryotic-type TopoI_cat_euk Domain
IPR011010 DNA breaking-rejoining enzyme, catalytic core DNA_brk_join_enz Domain
IPR014727 DNA topoisomerase I, catalytic core, alpha/beta subdomain TopoI_cat_a/b-sub_euk Domain
IPR014711 DNA topoisomerase I, catalytic core, alpha-helical subdomain, eukaryotic-type TopoI_cat_a-hlx-sub_euk Domain
IPR018521 DNA topoisomerase I, active site TopoI_AS Active_site

0 Found In

0 Parent Features

7 Publications

First Author Title Year Journal Volume Pages
Roca J The mechanisms of DNA topoisomerases. 1995 Trends Biochem Sci 20 156-60
Champoux JJ DNA topoisomerases: structure, function, and mechanism. 2001 Annu Rev Biochem 70 369-413
Gadelle D Phylogenomics of type II DNA topoisomerases. 2003 Bioessays 25 232-42
Wang JC Cellular roles of DNA topoisomerases: a molecular perspective. 2002 Nat Rev Mol Cell Biol 3 430-40
Tamura H Molecular cloning of a cDNA of a camptothecin-resistant human DNA topoisomerase I and identification of mutation sites. 1991 Nucleic Acids Res 19 69-75
Redinbo MR Crystal structures of human topoisomerase I in covalent and noncovalent complexes with DNA. 1998 Science 279 1504-13
Sharma A Crystal structure of the amino-terminal fragment of vaccinia virus DNA topoisomerase I at 1.6 A resolution. 1994 Structure 2 767-77

To cite PlanMine, please refer to the following publication:

Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)