TopoIIA_Trans_DNA_gyrase: Transducer domain, having a ribosomal S5 domain 2-like fold, of the type found in proteins of the type IIA family of DNA topoisomerases similar to the B subunits of E. coli DNA gyrase and E. coli Topoisomerase IV which are heterodimers composed of two subunits. The type IIA enzymes are the predominant form of topoisomerase and are found in some bacteriophages, viruses and archaea, and in all bacteria and eukaryotes. All type IIA topoisomerases are related to each other at amino acid sequence level, though their oligomeric organization sometimes differs. TopoIIA enzymes cut both strands of the duplex DNA to remove (relax) both positive and negative supercoils in DNA. These enzymes covalently attach to the 5' ends of the cut DNA, separate the free ends of the cleaved strands, pass another region of the duplex through this gap, then rejoin the ends. TopoIIA enzymes also catenate/ decatenate duplex rings. E.coli DNA gyrase is a heterodimer composed of two subunits. E. coli DNA gyrase B subunit is known to be important in nucleotide hydrolysis and the transduction of structural signals from ATP-binding site to the DNA breakage/reunion regions of the enzymes.
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