Abstract
In Salmonella typhimurium, a single enzyme catalyzes both the acetyl CoAdependent Oacetylation of hydroxylamines (a key step in the activation of mutagenic nitroaromatic compounds and related aromatic and heterocyclic amines) and the Nacetylation of aromatic amines. S. typhimurium Ames test mutants lacking this activity are highly resistant to the genotoxic effects of nitro compounds. However, such mutants have not yet been obtained in Escherichia coli. We used a PCRbased method to engineer a null mutation (deletion) of the nhoA gene encoding the enzyme in E. coli and we transduced this mutation into a lacZ strain background suitable for use in mutation assays. In E. coli, as in S. typhimurium, nhoA mutants show marked resistance to nitro compound mutagenicity. The new strains provide a clean background for expression of recombinant Nacetyltransferases.
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