Type IIA DNA topoisomerase subunit A, alpha-helical domain superfamily (IPR013757)
Short name: Topo_IIA_A_a_sf
- DNA topoisomerase, type IIA, subunit A/C-terminal (IPR002205)
- DNA topoisomerase IV subunit A, Gram-positive (IPR005741)
- DNA topoisomerase IV, subunit A, Gram-negative (IPR005742)
- DNA gyrase, subunit A (IPR005743)
- DNA topoisomerase, type IIA-like domain superfamily (IPR013760)
Type IIA topoisomerases include the enzymes DNA gyrase, eukaryotic topoisomerase II (topo II), and bacterial topoisomerase IV (topo IV). 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 [PMID: 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 [PMID: 16023670]. Topoisomerase IV consists of two polypeptide subunits, parE and parC, where parC is homologous to gyrA and parE is homologous to gyrB.
This superfamily represents a mainly alpha helical subdomain of eukaryotic topoisomerase II domain 3, also found in subunit A (gyrA and parC) of bacterial gyrase and topoisomerase IV.
- G3DSA:1.10.268.10 (G3DSA:1.10.268.10)