ATP hydrolysis and DNA binding by the Escherichia coli RecF protein

The Escherichia coli RecF protein possesses a weak ATP hydrolytic activity. ATP hydrolysis leads to RecF dissociation from double-stranded (ds)DNA, Th e RecF protein is subject to precipitation and an accompanying inactivation in vitro when not bound to DNA. A mutant RecF protein that can bind but ca nnot hydrolyze ATP (RecF K36R) does not readily dissociate from dsDNA in th e presence of ATP. This is in contrast to the limited dsDNA binding observe d for wild-type RecF protein in the presence of ATP but is similar to dsDNA binding by wild-type RecF binding in the presence of the nonhydrolyzable A TP analog, adenosine 5'-O-(3-thio)triphosphate (ATPyS). In addition, wild-t ype RecF protein binds tightly to dsDNA in the presence of ATP at low pH wh ere its ATPase activity is blocked. A transfer of RecF protein from labeled to unlabeled dsDNA is observed in the presence of ATP but not ATP gamma S. The transfer is slowed considerably when the RecR protein is also present. In competition experiments, RecF protein appears to bind at random locatio ns on dsDNA and exhibits no special affinity for single strand/double stran d junctions when bound to gapped DNA. Possible roles for the ATPase activit y of RecF in the regulation of recombinational DNA repair are discussed.