IUBMB Enzyme Nomenclature


Accepted name: repressor LexA

Reaction: Hydrolysis of Ala84Gly bond in repressor LexA

Other names: LexA repressor

Comments: RecA protein and single-stranded DNA are required for activity, which is attributed to a Ser/Lys dyad [2]. The LexA protein represses the SOS regulon, which regulates the genes involved in DNA repair. In the presence of single-stranded DNA, the RecA protein interacts with repressor LexA, causing it to undergo an autocatalytic cleavage which disrupts the DNA-binding part of the repressor, and inactivates it. The consequent derepression of the SOS regulon leads to DNA repair. This peptidase activity of LexA was previously attributed to the RecA protein (formerly EC Type example of peptidase family S24

Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number: 84721-00-6


1. Horii, T., Ogawa, T. and Ogawa, H. Nucleotide sequence of the LexA gene of E. coli. Cell 23 (1981) 689-697. [PMID: 7013987]

2. Slilaty, S.N. and Little, J.W. Lysine-156 and serine-119 are required for LexA repressor cleavage: a possible mechanism. Proc. Natl. Acad. Sci. USA 84 (1987) 3987-3991. [PMID: 3108885]

3. Kim, B. and Little, J.W. LexA and λ CI repressors as enzymes: specific cleavage in an intermolecular reaction. Cell 73 (1993) 1165-1173. [PMID: 8513500]

4. Little, J.W., Kim, B., Roland, K.L., Smith, M.H., Lin, L.-L. and Slilaty, S.N. Cleavage of LexA repressor. Methods Enzymol. 244 (1994) 266-284. [PMID: 7845214]

[EC created 1995]

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