Use of ion exchange chromatography for the study of RecA‐DNA interaction

Abstract
In vitro binding or RecA protein to double-stranded DNA (dsDNA) was studied using ion-exchange liquid chromatography. The method allowed quantification of both free DNA and free protein. The results unambiguously showed a binding stoichiometry or 3 base pairs per RecA monomer. The binding exhibited cooperativity, and the stoichiometry suggested that RecA does not form complexes with two molecules or dsDNA. More than 90% of RecA molecules in the sample were active for DNA binding.