Recombination-Promoting Activity of the Bacteriophage Rap Protein in Escherichia coli K-12

The rap gene of bacteriophage was placed in the chromosome of an Escherichia coli K-12 strain in which the recBCD gene cluster had previously been replaced by the red genes and in which the recG gene had been deleted. Recombination between linear double-stranded DNA molecules and the chromosome was tested in variants of the recG red rap strain bearing mutations in genes known to affect recombination in other cellular pathways. The linear DNA was a 4-kb fragment containing the cat gene, with flanking lac sequences, released from an infecting phage chromosome by restriction enzyme cleavage in the cell. Replacement of wild-type lacZ with lacZ::cat was monitored by measuring the production of Lac-deficient chloramphenicolresistant bacterial progeny. The results of these experiments indicated that the rap gene could functionally substitute for the E. coli ruvC gene in Red-mediated recombination.