Characterization of mitochondrial DNA topoisomerase I from Neurospora crassa.
DNA topoisomerase I isolated from the lower eukaryote Neurospora 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 type I and eukaryotic. Conversion of the topoisomerase to a nonspecific endonuclease at increased temperature is proposed.
Department of Molecular Biology, Faculty of Science, Comenius University, Bratislava, Slovakia.
J
J
Turna
A
A
Pudzisová
M
M
Osuský
L
L
Supeková
T
T
Kuchta
D000255:Adenosine Triphosphate / Q000494:pharmacology; D004264:DNA Topoisomerases, Type I / Q000737:chemistry / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D006657:Histones / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology; D008970:Molecular Weight; D009492:Neurospora crassa / Q000201:enzymology*; D009994:Osmolar Concentration; D011073:Polyamines / Q000494:pharmacology; D013696:Temperature; D059004:Topoisomerase I Inhibitors
D006657:Histones; D011073:Polyamines; D059004:Topoisomerase I Inhibitors; D000255:Adenosine Triphosphate; D004264:DNA Topoisomerases, Type I; D008274:Magnesium; D005033:Ethylmaleimide