Binds the consensus sequence 5'-TGTTC-N(4)-GAACA-3'; some genes have a tandem consensus sequence, at high concentrations their binding is cooperative (PubMed:27489856). Binds to the promoters of a number of genes, including dinB, imuA, lexA, recA, recQ, splB and uvrA (PubMed:27489856). Represses a number of genes involved in the response to DNA damage (SOS response) (By similarity). In the presence of single-stranded DNA, RecA interacts with LexA causing an autocatalytic cleavage which disrupts the DNA-binding part of LexA, leading to derepression of the SOS regulon and eventually DNA repair (By similarity). Hydrolysis of Ala-|-Gly bond in repressor LexA. Homodimer. Belongs to the peptidase S24 family.