K. Sakurai et al., A ROLE OF IRON IN LAMBDA-DNA STRAND BREAKS IN THE REACTION SYSTEM OF ALLOXAN WITH REDUCED GLUTATHIONE - IRON(III) BINDING TO THE DNA, Biological & pharmaceutical bulletin, 17(2), 1994, pp. 227-231
lambda DNA strand breaks were easily induced in a reaction system invo
lving alloxan dth reduced glutathione (GSH) in the presence of FeCl3 i
n a HEPES-NaOH buffer, pH 7.4. Increasing concentrations of FeCl3, in
the reaction system caused DNA strand breaks in a concentration-depend
ent fashion, suggesting that iron is required to induce the DNA strand
breaks. Catalase, scavengers of hydroxyl radicals (HO.) and iron-chel
ators almost completely inhibited the DNA strand breaks, but superoxid
e dismutase (SOD) did not do so, suggesting that the HO., formed by a
Fenton-type reaction, was the species responsible for the DNA strand b
reaks. The addition of FeCl3, to the solution containing DNA caused th
e formation of a DNA-Fe(III) complex, in which Fe(III) was reduced by
an alloxan radical (HA) but not by a superoxide radical. Only when apo
transferrin was added to the reaction mixtures before the addition of
FeCl3, were both the DNA strand breaks and the reduction of Fe(III) st
rongly inhibited. These results suggest that the Fe(III) bound to DNA
catalyzes the DNA strand breaks which may be caused by the generation
of site-specific HO. via an HA.-dependent Fenton-type reaction.