Purification and characterization of a novel ATP-independent type I DNA topoisomerase from a marine methylotroph |
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Authors: | Kwack Man Sup Park Jung Eun Park Jong Kun Lee Jung Sup |
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Affiliation: | Department of Biotechnology and Research Center for Proteineous Materials, Chosun University, Gwangju 501-759, Republic of Korea. |
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Abstract: | DNA topoisomerase is involved in DNA repair and replication. In this study, a novel ATP-independent 30-kDa type I DNA topoisomerase was purified and characterized from a marine methylotroph, Methylophaga sp. strain 3. The purified enzyme composed of a single polypeptide was active over a broad range of temperature and pH. The enzyme was able to relax only negatively supercoiled DNA. Mg(2+) was required for its relaxation activity, while ATP gave no effect. The enzyme was clearly inhibited by camptothecin, ethidium bromide, and single-stranded DNA, but not by nalidixic acid and etoposide. Interestingly, the purified enzyme showed Mn(2+)-activated endonuclease activity on supercoiled DNA. The N-terminal sequence of the purified enzyme showed no homology with those of other type I enzymes. These results suggest that the purified enzyme is an ATP-independent type I DNA topoisomerase that has, for the first time, been characterized from a marine methylotroph. |
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Keywords: | Marine methylotroph Type I DNA topoisomerase Supercoiled DNA relaxation |
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