The binding of DNA topoisomerase III (Tope III) to a single-stranded DNA substrate containing a strong cleavage site has been examined. The minimal substrate requirement for Tope III-catalyzed cleavage has been determined to consist of 7 bases: 6 bases 5' to the cleavage site and only 1 base 3' to the site. Nuclease P1 protection experiments indicate that the enzyme also binds to its substrate asymmetrically, protecting ~ 12 bases 5' to the cleavage site and only 2 bases 3' to the cleavage site, A catalytically inactive mutant of Tope III shows the same protection pattern as the active polypeptide, indicating that Tope III is a site-specific binding protein as well as a topoisomerase. Consistent with this view, an oligonucleotide containing a cleavage site is a more effective inhibitor and is bound more efficiently by Tope III than an oligonucleotide without a cleavage site.
CITATION STYLE
Zhang, H. L., Malpure, S., & DiGate, R. J. (1995). Escherichia coli DNA topoisomerase III is a site-specific DNA binding protein that binds asymmetrically to its cleavage site. Journal of Biological Chemistry, 270(40), 23700–23705. https://doi.org/10.1074/jbc.270.40.23700
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