Identification of a unique domain essential for Escherichia coli DNA topoisomerase III‐catalysed decatenation of replication intermediates

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Abstract
A 17‐amino‐acid residue domain has been identified in Escherichia coli DNA topoisomerase III (Topo III) that is essential for Topo III‐mediated resolution of DNA replication intermediates in vitro. Deletion of this domain reduced Topo III‐catalysed resolution of DNA replication intermediates and decatenation of multiply linked plasmid DNA dimers by four orders of magnitude, whereas reducing Topo III‐catalysed relaxation of negatively supercoiled DNA substrates only 20‐fold. The presence of this domain has been detected in multiple plasmid‐encoded topoisomerases, raising the possibility that these enzymes may also be decatenases.