Domain

DNA topoisomerase, type IA, domain 2 (IPR003601)

Short name: Topo_IA_2

Domain relationships

None.

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.

This entry describes domain 2 found in type IA topoisomerases, which may be an extension of the Toprim domain. The structures of bacterial topoisomerases I and III have been shown to consist of four domains that together form a toroidal structure with a central hole large enough to accommodate single- and double-stranded DNA. The N-terminal Toprim domain together with domain 3 forms the active site of the enzyme, while domains 2 and 4 form a single-strand DNA-binding groove [PMID: 14604525, PMID: 10574789]. The Toprim domain (IPR006171) forms a compact Rossmann fold that coordinates the Mg+2 ion [PMID: 9722641].

GO terms

Biological Process

GO:0006265 DNA topological change

Molecular Function

GO:0003677 DNA binding
GO:0003916 DNA topoisomerase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

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