title: Isolation and preliminary characterization of Escherichia coli mutants deficient in exonuclease VII.
abstract: Strains of Escherichia coli containing reduced levels of exonuclease VII activity due to mutations in the xseB gene have been isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Seven mutants of independent origin deficient in exonuclease VII activity were obtained. Four of these contained defects in xseA, a locus which has been previously identified, and three others contained mutations in a gene distinct from xseA, which we have designated xseB. Genetic mapping studies place the xseB locus between proC and dnaZ. Exonuclease VII purified from KLC835 (xseA+ xseB3) is more heat labile than enzyme purified from the parent strain PA610 (xse+), showing that xseB is a structural gene for exonuclease VII. The isolation of lambda transducing phage carrying xseA is also described.
mesh_terms: D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005090:Exodeoxyribonucleases / Q000235:genetics* / Q000378:metabolism; D005796:Genes; D005798:Genes, Bacterial; D005838:Genotype; D009154:Mutation; D014161:Transduction, Genetic
chemical_list: D005090:Exodeoxyribonucleases; C026870:exodeoxyribonuclease VII