Co-ordination of multiple DNA molecules in RecA fiber evidenced by linear dichroism spectroscopy.

Polarized light spectroscopy has been used to study the interaction of RecA protein with DNA. Several different DNA complexes have been identified and characterized with respect to stoichiometries, base orientation and nuclease accessibility. By using spectroscopically distinguishable DNAs, we determined the number of DNA molecules co-ordinated by the RecA fiber in each of these complexes, and established their base pairing abilities. Based on these observations, we discuss the molecular mechanism of the RecA-mediated strand exchange reaction.