DNA synaptase: an enzyme that fuses DNA molecules at a region of homology.

This paper describes an enzyme from Escherichia coli, and its purification to apparent homogeneity. The protein, which we call "DNA synaptase" and which may be representative of a class of enzymes, fuses double-stranded DNA molecules at a region of homology. In addition, the purified enzyme is able to catalyze the association of single-stranded DNA with homologous duplex DNA. The genome fusion reaction catalyzed by the purified enzyme occurs in the presence of Mg2+, spermidine, and 2-mercaptoethanol and does not require a high-energy cofactor. By bringing two genomes together at a region of homology, DNA synaptase has a property expected for an enzyme that participates in an early step in genetic recombination. However, the synaptase can be recovered from Rec A- cells, and thus it is not yet possible to determine whether this enzyme plays a role in physiological recombination or in another cellular process that involves genome fusion, such as the recombinational repair of damaged DNA.