What makes the bacteriophage λ Red system useful for genetic engineering: molecular mechanism and biological function

Abstract

Recent studies have generated interest in the use of the homologous recombination system of bacteriophage λ for genetic engineering. The system, called Red, consists primarily of three proteins: λ exonuclease, which processively digests the 5′-ended strand of a dsDNA end; β protein, which binds to ssDNA and promotes strand annealing; and γ protein, which binds to the bacterial RecBCD enzyme and inhibits its activities. These proteins induce a ‘hyper-rec’ state in Escherichia coli and other bacteria, in which recombination events between DNA species with as little as 40 bp of shared sequence occur at high frequency. Red-mediated recombination in the hyper-rec bacterium proceeds via a number of different pathways, and with the involvement of different sets of bacterial proteins, depending in part on the nature of the recombining DNA species. The role of high-frequency double-strand break repair/recombination in the life cycle of the lambdoid phages is discussed.