Evidence for the presence of topoisomerase like activity in mitochondria of Saccharomyces cerevisiae.

During studies on the enzymology of DNA replication in mitochondria of Saccharomyces cerevisiae, a topoisomerase like activity was detected for the first time. Crude extracts of mitoplast were found to show enzyme activities which could both catenate and relax supercoiled plasmid DNA. Chromatography of the mitoplast lysate on a phosphocellulose column, using Tris-HCl (pH 7.5) buffer containing 0.6 M NaCl as eluent, was found to yield a topoisomerase like activity capable of relaxing supercoiled plasmid DNA (Fraction 1). This fraction was not dependent on ATP for its activity. The other fraction eluting at 1M NaCl showed predominantly catenating activity, which was found to be ATP dependent.