Exonuclease III and the catalase hydroperoxidase II in Escherichia coli are both regulated by the katF gene product.

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Abstract
The levels of both exonuclease II (exo III, product of xthA) and hydroperoxidase II (HP-II, product of katE) activity in Escherichia coli were influenced by a functional katF gene. The katF gene product is also necessary for synthesis of HP-II. Mutations in either katF or xthA, but not katE, result in sensitivity, to H2O2 and near-UV (300-400 nm) radiation. Exo III, encoded by the xthA locus, recognizes and removes nucleoside 5''-monophosphates near apurinic and apyrimidinic sites in damaged DNA. Extracts of katF mutant strains had little detectable exo III activity. When a katF+ plasmid was introduced into the katF mutant, exo III activity exceeded wild-type levels. We propose that the katF gene is a trans-acting positive regulator of exo III and HP-II enzymes, both of which are involved in cellular recovery from oxidative damage.