Active Site

DNA topoisomerase I, active site (IPR018521)

Short name: TopoI_AS

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 [PMID: 7770916]. 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 [PMID: 12042765, PMID: 11395412]. DNA topoisomerases are divided into two classes: type I enzymes (EC:5.99.1.2; topoisomerases I, III and V) break single-strand DNA, and type II enzymes (EC:5.99.1.3; topoisomerases II, IV and VI) break double-strand DNA [PMID: 12596227].

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.

DNA topoisomerase I (EC:5.99.1.2) [PMID: 2560656, PMID: 7773745, PMID: 2542938, PMID: 7770916] is one of the two types of enzyme that catalyze the interconversion of topological DNA isomers. Type I topoisomerases act by catalyzing the transient breakage of DNA, one strand at a time, and the subsequent rejoining of the strands. When a eukaryotic type 1 topoisomerase breaks a DNA backbone bond, it simultaneously forms a protein-DNA link where the hydroxyl group of a tyrosine residue is joined to a 3'-phosphate on DNA, at one end of the enzyme-severed DNA strand. In eukaryotes and poxvirus topoisomerases I, there are a number of conserved residues in the region around the active site tyrosine [PMID: 2542938].

GO terms

Biological Process

GO:0006265 DNA topological change

Molecular Function

GO:0003677 DNA binding
GO:0003917 DNA topoisomerase type I activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns