Role of Exonuclease and β Protein of Phage λ in Genetic Recombination, V. Recombination of λ DNA in Vitro

Abstract

The sequential action of lambda exonuclease and polynucleotide ligase upon redundant joint molecules is sufficient to produce intact polynucleotide chains and heat-stable, biologically active molecules of lambda DNA, whereas the action of ligase alone is insufficient. These results (a) confirm the previously described mechanism of single-strand assimilation, including a subsidiary mechanism by which the further action of lambda exonuclease is arrested when a redundant strand is completely assimilated, and (b) represent a simulation of the steps in genetic recombination that follow the formation of biparental complexes (synapsis). lambda exonuclease is postulated to catalyze a concerted reaction that includes exposure of complementary sequences, formation of heteroduplex regions, and elimination of redundant branches.