An interaction between the Escherichia coli RecF and RecR proteins dependent on ATP and double-stranded DNA.

The DNA binding and ATPase activities of RecF protein are modulated by RecR protein. Stoichiometric amounts of RecF protein bind to double-stranded (ds) DNA (about 1 RecF monomer/4-6 base pairs) in the presence of adenosine 5'-O-(3-thio)triphosphate (ATP gamma S), forming a homogeneous protein coating on the DNA. Little or no cooperativity is evident in the binding process. In the presence of ATP, RecF binding to dsDNA is much weaker, and no RecF protein coating forms. Instead, small numbers of RecF protomers are interspersed randomly along the DNA. RecR protein does not bind appreciably to the dsDNA under these same conditions. However, a protein coating, similar to that which was observed with RecF protein alone in the presence of ATP gamma S, was produced when both RecF and RecR proteins were incubated with dsDNA in the presence of ATP. An interaction between RecF and RecR enables both proteins to bind tightly to the dsDNA in an approximately 1:1 molar ratio. We also report a weak ATP hydrolytic activity of RecF which is stimulated by RecR.