DNA topoisomerase VI, subunit A (IPR004085)

Short name: TopoVI_A

Overlapping homologous superfamilies

Family relationships


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:; topoisomerases I, III and V) break single-strand DNA, and type II enzymes (EC:; topoisomerases II, IV and VI) break double-strand DNA [PMID: 12596227].

Type II topoisomerases are ATP-dependent enzymes, and can be subdivided according to their structure and reaction mechanisms: type IIA (topoisomerase II or gyrase, and topoisomerase IV) and type IIB (topoisomerase VI). These enzymes are responsible for relaxing supercoiled DNA as well as for introducing both negative and positive supercoils [PMID: 7980433].

This entry represents subunit A of topoisomerase VI, a type IIB topoisomerase found predominantly in archaea, but also in a few eukayotes, such as the plant Arabidopsis thaliana [PMID: 12618182]. This enzyme assembles as a heterotetramer, consisting of two A subunits required for DNA cleavage and two B subunits required for ATP hydrolysis. The B subunit is structurally similar to the ATPase domain of type IIA topoisomerases, but the A subunit is distinct, and instead shares homology with the Spo11 protein that mediates double-strand DNA breaks during meiotic recombination in eukaryotes [PMID: 10545127]. The core of subunit A is a dimer, with a deep groove in which the DNA molecule is thought to bind, with the monomers separating during DNA transport. Therefore, though related to type IIA topoisomerases, topoisomerase VI may have a distinctive mechanism of action.

GO terms

Biological Process

GO:0006265 DNA topological change

Molecular Function

GO:0003677 DNA binding
GO:0003918 DNA topoisomerase type II (ATP-hydrolyzing) activity

Cellular Component

GO:0005694 chromosome

Contributing signatures

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