InterPro : IPR005733

Name  DNA topoisomerase I, bacterial-type Short Name  TopoI_bac-type
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 twoclasses: 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 describes topoisomerase I from bacteria, which is more closely related to archaeal than to eukaryotic topoisomerase I []. Topoisomerase I is the major enzyme for relaxing negatively supercoiled DNA, and its presence is balanced by reverse gyrase, which can introduce negative supercoils. Prokaryotic topoisomerase I folds in an unusual way to give 4 distinct domains, enclosing a hole large enough to accommodate a double-stranded DNA segment. A tyrosine at the active site, which lies at the interface of 2 domains, is involved in transient breakage of a DNA strand, and the formation of a covalent protein-DNA intermediate through a 5'-phosphotyrosine linkage. The structure reveals a plausible mechanism by which this and related enzymes could catalyse the passage of one DNA strand through a transient break in another strand []. Topoisomerase I require Mg2+ as a cofactor for catalysis to take place.

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

5 Contains

Id Name Short Name Type
IPR013497 DNA topoisomerase, type IA, central Topo_IA_cen Domain
IPR013498 DNA topoisomerase, type IA, zn finger Topo_IA_Znf Domain
IPR003602 DNA topoisomerase, type IA, DNA-binding domain Topo_IA_DNA-bd_dom Domain
IPR003601 DNA topoisomerase, type IA, domain 2 Topo_IA_2 Domain
IPR013824 DNA topoisomerase, type IA, central region, subdomain 1 Topo_IA_cen_sub1 Domain

0 Found In

1 Parent Features

Id Name Short Name Type
IPR028612 DNA topoisomerase I, type IA Topoisom_1_IA Family

6 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
Perry K Structure of a complex between E. coli DNA topoisomerase I and single-stranded DNA. 2003 Structure 11 1349-58
Tse-Dinh YC Bacterial and archeal type I topoisomerases. 1998 Biochim Biophys Acta 1400 19-27

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)