We have purified to apparent homogeneity a type II DNA topoisomerase from Xenopus laevis oocyte nuclei (germinal vesicles, or GV). The most pure preparations contain a single polypeptide of 175,000 daltons as determined by SDS-gel electrophoresis. The enzyme changes the linking number of DNA circles in steps of two and reversibly knots or catenates DNA rings. No gyrase activity is detectable and ATP is required.
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| http://dx.doi.org/10.1002/j.1460-2075.1983.tb01585.x | DOI Listing |
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