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Studies On Type I And Type Ii Dna Topoisomerases From Mammalian Mitochondria, Jia-Hwei Lin

Theses and Dissertations in Biomedical Sciences

Mammalian mitochondria contain a unique DNA topoisomerase I with characteristics of both nuclear and bacterial type I DNA topoisomerases. This enzyme, purified from bovine liver, requires cations as cofactors and possesses optimal activity at pH 7.0, 37°C and either 150 mM K+ or Na+ ions. Similar to nuclear enzymes and different from the bacterial enzyme, divalent ions such as Ca²⁺ or Mg²⁺ will stimulate but are not essential for the enzymatic activity.

Like the nuclear DNA topoisomerase I, the mitochondrial enzyme is capable of relaxing both negatively and positively supercoiled DNA. The relaxation of negatively supercoiled DNA is …