Interchangeable parts of the Escherichia coli recombination machinery

In Escherichia coli, at least two groups of proteins, or "recombination machines," can operate independently on broken DNA to produce a X-terminated single-stranded DNA filament coated with RecA protein and ready for synapsis with intact homologous DNA. Recent analyses of mutants lacking one or more of the activities required for presynaptic filament formation by one recombination machine demonstrate that parts of the two normally separate machines can interchange to initiate homologous recombination.