TOP2c TopoisomeraseII
SMART ACC:	SM000433
Description:	Eukaryotic DNA topoisomerase II, GyrB, ParE
InterPro ACC:	IPR001241
InterPro abstract:	Type IIA topoisomerases together manage chromosome integrity and topology in cells. Topoisomerase II (called gyrase in bacteria) primarily introduces negative supercoils into DNA. In bacteria, topoisomerase II consists of two polypeptide subunits, gyrA and gyrB, which form a heterotetramer: (BA)2. In most eukaryotes, topoisomerase II consists of a single polypeptide, where the N- and C-terminal … expand Type IIA topoisomerases together manage chromosome integrity and topology in cells. Topoisomerase II (called gyrase in bacteria) primarily introduces negative supercoils into DNA. In bacteria, topoisomerase II consists of two polypeptide subunits, gyrA and gyrB, which form a heterotetramer: (BA)2. In most eukaryotes, topoisomerase II consists of a single polypeptide, where the N- and C-terminal regions correspond to gyrB and gyrA, respectively; this topoisomerase II forms a homodimer that is equivalent to the bacterial heterotetramer. There are four functional domains in topoisomerase II: domain 1 (N-terminal of gyrB) is an ATPase, domain 2 (C-terminal of gyrB) is responsible for subunit interactions (differs between eukaryotic and bacterial enzymes), domain 3 (N-terminal of gyrA) is responsible for the breaking-rejoining function through its capacity to form protein-DNA bridges, and domain 4 (C-terminal of gyrA) is able to non-specifically bind DNA [ PUBMED:8982450 ]. Topoisomerase IV primarily decatenates DNA and relaxes positive supercoils, which is important in bacteria, where the circular chromosome becomes catenated, or linked, during replication [ PUBMED:16023670 ]. Topoisomerase IV consists of two polypeptide subunits, parE and parC, where parC is homologous to gyrA and parE is homologous to gyrB. This entry represents DNA topoisomerase, type IIA. 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 [ PUBMED: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 [ PUBMED:12042765 PUBMED:11395412 ]. DNA topoisomerases are divided into two classes: type I enzymes ( EC:5.6.2.2 ; topoisomerases I, III and V) break single-strand DNA, and type II enzymes ( EC:5.6.2.2 ; topoisomerases II, IV and VI) break double-strand DNA [ PUBMED: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 [ PUBMED:7980433 ]. collapse
GO process:	DNA topological change (GO:0006265)
GO function:	DNA binding (GO:0003677), DNA topoisomerase type II (double strand cut, ATP-hydrolyzing) activity (GO:0003918), ATP binding (GO:0005524)
Family alignment:	View the Family alignment or the Alignment consensus sequence
There are 42 492 TOP2c domains in 42 492 proteins in SMART's NRDB database.

Taxonomic distribution of proteins containing TOP2c domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing TOP2c domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Relevant references for this domain

Primary literature for the TOP2c domain is listed below. Automatically-derived, secondary literature is also available.

Disease genes where sequence variants are found in this domain

UniRef sequences and OMIM curated human diseases associated with missense mutations within the TOP2c domain.

Protein	Description	Disease / phenotype
TOP2A_HUMAN		OMIM:126430 : TOPOISOMERASE, DNA, II, ALPHA; TOP2A

KEGG pathways involving proteins which contain this domain

This information is based on the mapping of SMART genomic protein database to KEGG orthologous groups. Percentages are related to the number of proteins containing a TOP2c domain which could be assigned to a KEGG orthologous group, and not all proteins containing TOP2c domains. Please note that proteins can be included in multiple pathways, ie. the numbers below will not add to 100%.

KEGG pathways

KEGG orthologous groups

3D structures in PDB containing this domain

Links to other resources describing this domain

Pfam	DNA_gyraseB_C
InterPro	IPR001241
PROSITE	TOPOISOMERASE_II