Characterization of mitochondrial DNA topoisomerase I fromNeurospora crassa |
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Authors: | J Turňa A Pudzisová M Osuský L' Supeková T Kuchta |
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Institution: | 1. Department of Molecular Biology Faculty of Science, Comenius University, 842 15, Bratislava, Slovakia 2. Department of Biochemistry, Faculty of, Science, Comenius University, 842 15, Bratislava, Slovakia
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Abstract: | DNA topoisomeraseI isolated from the lower eukaryoteNeurospora crassa mitochondria was characterized. Molar mass of the enzyme in the native state is 120 kDa and 60–65 kDa when denatured. The pH optimum of the enzyme is 7.8 and the KCl optimum concentration is 40 mmol/L. This topoisomerase is independent of ATP and Mg2+. N-Ethylmaleimide, 4-chloromercuribenzoate, SDS, guanidinium chloride, polyethylene glycol, heparin and ethidium bromide inhibit its activity, while novobiocin, nalidixic acid, Triton X-100 and chloroquine do not. Polyamines, and histone, H1 stimulate the topoisomerase activity. We classify this DNA topoisomerase as typeI and eukaryotic. Conversion of the topoisomerase to a nonspecific endonuclease at increased temperature is proposed. |
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