title: Genetic recombination in Escherichia coli: the role of exonuclease I.
abstract: The indirect suppression of recB(-) and recB(-)recC(-) mutations by the sbcB(-) allele is caused by the loss of a nuclease active on denatured DNA. Results from enzyme purifications and studies with a specific antiserum demonstrate that the activity present in sbcB(+) strains, and lost in sbcB(-) strains, is exonuclease I. It is likely that sbcB is the structural gene for exonuclease I. The loss of exonuclease I activity restores the recombination proficiency of Escherichia coli cells that has been lost by mutations in the recB and/or recC genes. This indicates that in the absence of the recB-recC-determined enzyme, exonuclease I prevents recombination. Hypothetical pathways illustrating this conclusion are presented.
mesh_terms: D000483:Alleles; D004247:DNA; D003851:Deoxyribonucleases / Q000302:isolation & purification / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology*; D005796:Genes; D007106:Immune Sera / Q000494:pharmacology; D009154:Mutation; D011995:Recombination, Genetic; D014161:Transduction, Genetic
chemical_list: D007106:Immune Sera; D004247:DNA; D003851:Deoxyribonucleases