Can catalyze the hydrolysis of ATP in the presence of single-stranded DNA, the ATP-dependent uptake of single-stranded DNA by duplex DNA, and the ATP-dependent hybridization of homologous single-stranded DNAs. It interacts with LexA causing its activation and leading to its autocatalytic cleavage (By similarity). This protein undergoes a protein self splicing that involves a post-translational excision of the intervening region (intein) followed by peptide ligation. Belongs to the RecA family.