Reverse gyrase—a topoisomerase which introduces positive superhelical turns into DNA

Abstract
An enzymatic activity which converts closed circular DNA into a positively supercoiled form is present in cellular extracts of Sulfolobus, an acidothermophilic archaebacterium. This novel enzyme is a type II DNA topoisomerase and is active only at temperatures > 55.degree. C in the presence of ATP and Mg2+.
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