Kwack MS, Park JE, Park JK, Lee JS. Purification and characterization of a novel ATP-independent type I DNA topoisomerase from a marine methylotroph.
Arch Biochem Biophys 2005;
437:168-77. [PMID:
15850556 DOI:
10.1016/j.abb.2005.03.014]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Revised: 03/12/2005] [Accepted: 03/14/2005] [Indexed: 10/25/2022]
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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