Bacillus cereus DNA topoisomerase I and IIIα: Purification, characterization and complementation of Escherichia coli TopoIII activity

Zhiyu Li, Hiroshi Hiasa, Russell DiGate

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

The Bacillus cereus genome possesses three type IA topoisomerase genes. These genes, encoding DNA topoisomerase I and IIIα (bcTopo I, bcTopo IIIα), have been cloned into T7 RNA polymerase-regulated plasmid expression vectors and the enzymes have been overexpressed, purified and characterized. The proteins exhibit similar biochemical activity to their Escherichia coli counterparts, DNA topoisomerase I and III (ecTopo I, ecTopo III). bcTopo I is capable of efficiently relaxing negatively supercoiled DNA in the presence of Mg2+ but does not possess an efficient DNA decatenation activity. bcTopo IIIα is an active topoisomerase that is capable of relaxing supercoiled DNA at a broad range of Mg2+ concentrations; however, its DNA relaxation activity is not as efficient as that of bcTopo I. In addition, bcTopo III is a potent DNA decatenase that resolves oriC-based plasmid replication intermediates in vitro. Interestingly, bcTopo I and bcTopo IIIα are both able to compensate for the loss of ecTopo III in E.coli cells that lack ecTopo I. In contrast, ecTopo I cannot substitute for ecTopo III under these conditions.

Original languageEnglish (US)
Pages (from-to)5415-5425
Number of pages11
JournalNucleic acids research
Volume33
Issue number17
DOIs
StatePublished - Nov 11 2005

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