LexA repressor (IPR006200)

Short name: LexA

Family relationships


This group of proteins are serine peptidases belong to MEROPS peptidase S24 (LexA family, clan SF). The family contains the LexA proteins. LexA represses around 20 genes of the cellular SOS response to DNA damage in Escherichia coli [PMID: 7845208]. Damage to cellular DNA results in inactivation of LexA, allowing transcription of the genes involved in DNA repair. In E. coli, this derepression of the DNA repair system is mediated by RecA, which binds to LexA upon interaction with single-stranded DNA. This results in inactivation of LexA by proteolytic self cleavage, disrupting the DNA-binding capabilities of LexA.

LexA consists of around 200 amino acids, of which the first 90 form the DNA-binding domain. The remaining residues form the protease domain, Ser-119 and Lys-156 being the active residues. The crystal structures of the wild type and several mutant forms of LexA reveal two distinct conformations: one compatible with cleavage, and the other in which the cleavage site is approximately 20 A from the catalytic centre. It is suggested that recA activates the self-cleavage of LexA and related proteins through selective stabilisation of the cleavable conformation [PMID: 11551506].

GO terms

Biological Process

GO:0006508 proteolysis

Molecular Function

GO:0004252 serine-type endopeptidase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.