Studies on the DNA photoreactivating enzyme from Escherichia coli: I. Transduction of the phr gene by bacteriophage lambda

Abstract

Isolation and characterization of the photoreactivating enzyme, which repairs UV-irradiated DNA by using visible or near ultraviolet light to monomerize pyrimidine dimers, have been impeded principally by the low cellular content of the enzyme. We have greatly increased the photoreactivating enzyme activity in E. coli through use of a transducing phage carrying the phr gene. We constructed a transducing phage, λcI857S7dg D → J, and have shown that after induction of an E. coli strain lysogenic for this phage there is approximately 2000 times as much photoreactivating enzyme activity in cell free extracts as is found with the parental strain. These results, as well as those on the capacity for photoreactivation of colony-forming ability of strains with deletions of known extent, indicate that phr lies between gal and attλ.