DNA conformation induced by the bacteriophage T4 UvsX protein appears identical to the conformation induced by the Escherichia coli RecA protein.

The study of homologous genetic recombination has been dominated by the RecA protein of Escherichia coli, which is involved in DNA recombination and repair, as well as phage induction, in vivo. The active form of the RecA protein is a helical filament formed on DNA in the presence of ATP, and within this filament, the DNA is extensively stretched to about 5.1 A rise per base-pair and untwisted to about 19 base-pairs per turn. The bacteriophage T4 UvsX protein is only weakly homologous to RecA, but it has very similar ATP-dependent DNA binding and strand-exchange activities. We can now show that the UvsX protein forms helical filaments that are very similar to those made by RecA, and induces the same extended DNA conformation within these filaments that is induced by RecA. This implies that the unusual conformation of DNA in the RecA filament may be a universal structure in homologous recombination.