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Media type:
E-Article
Title:
Exonuclease III Recognizes Urea Residues in Oxidized DNA
Contributor:
Kow, Yoke Wah;
Wallace, Susan S.
imprint:
National Academy of Sciences of the United States of America, 1985
Published in:Proceedings of the National Academy of Sciences of the United States of America
Language:
English
ISSN:
0027-8424
Origination:
Footnote:
Description:
<p>Escherichia coli exonuclease III was found to be associated with an activity that recognizes urea residues in DNA but not thymine glycol residues from which the urea residues were prepared. This activity was not due to a contaminating activity such as endonuclease III since urea-containing DNA was a competitive inhibitor of exonuclease III when apurinic DNA was used as a substrate and vice versa. The apparent kinetic constants for both the substrate and inhibitor were determined. Like its apurinic activity, exonuclease III activity against urea residues was endonucleolytic, nicking on the 5<sup>′</sup>side of the damage and having an optimal Mg<sup>2+</sup>concentration between 2 and 10 mM. Also, the enzyme recognized alkali-stable damages produced in DNA by H<sub>2</sub>O<sub>2</sub>in vitro. We suggest that it may be this activity of exonuclease III that accounts for its biological role in vivo.</p>