STRAND BREAKS IN DNA INDUCED BY A THIOL/FE(III)/O2 MIXED-FUNCTION OXIDASE SYSTEM AND ITS PROTECTION BY A YEAST ANTIOXIDANT PROTEIN

Strand breaks can be produced in pBluescript plasmid DNA and calf thymus DNA by a mixed-function oxidase (MFO) system comprised of Fe3+, O2, and dithiothreitol as an electron donor. Superoxide dismutase does not block this damage whereas a 27-KDa yeast antioxidant protein specifically inhibits strand breaks in DNA induced by the dithiothreitol MFO system. In contrast, this protein does not inhibit strand breaks in DNA induced by an ascorbate MFO system although catalase inhibits damage in DNA caused by both MFO systems. Based on the specificity of this protein, we propose that the antioxidant protein functions as a sulfur radical scavenger. © 1993 Academic Press, Inc.