Exchanging partners: recombination in E. coli.

Examination of the many proteins involved in recombination in Escherichia coli has provided detailed information concerning how homologous DNA is paired and exchanged between different molecules. Recent studies have begun to resolve long-standing issues, such as how a DNA helicase with rampant nuclease activity is able to promote the initiation of recombination, how the four-stranded intermediate arising from DNA strand exchange is migrated and resolved and how ancillary proteins assist RecA protein-mediated activities. In addition, the identification of eukaryotic homologues of RecA protein, similar both in structure and in function, shows that at least some of the fundamental steps of recombination have been conserved in all organisms. This finding holds promise that the development of in vitro systems for recombination by eukaryotic proteins lies in the not-too-distant future.