Escherichia coli mutants deficient in exonuclease VII.

摘要: Mutants of Escherichia coli having reduced levels exonuclease VII activity have been isolated by a mass screening procedure. Nine mutants, five which are known to be independent origin, were obtained and designated xse. The defects in these strains lie at two or more loci. One loci, xseA, lies the interval between purG purC; it is 93 97% co-transducible with guaA. order genes this region purG-xseA guaA,B-purC. available data do not allow xseA ordered respect guaA,B. Exonuclease purified from E. KLC3 xseA3 heat labile than parent, PA610 xse+. Therefore, structural gene for VII. show increased sensitivity nalidixic acid an abnormally high frequency recombination (hyper-Rec phenotype) as measured procedure Konrad Lehlman (1974). hyper-Rec character approximately one-half that polAex1 mutant defective 5' leads 3' hydrolytic deoxyribonucleic polymerase I. double mutant, xseA7, twice alone. xseA- slightly sensitive ultraviolet irradiation parent strain. Bacteriophages T7, fd, lambdared grow normally strains.