LexA repressor
| LexA DNA binding domain | |||||||||
|---|---|---|---|---|---|---|---|---|---|
lexa s119a mutant | |||||||||
| Identifiers | |||||||||
| Symbol | LexA_DNA_bind | ||||||||
| Pfam | PF01726 | ||||||||
| Pfam clan | CL0123 | ||||||||
| InterPro | IPR006199 | ||||||||
| SCOP2 | 1leb / SCOPe / SUPFAM | ||||||||
| |||||||||
The LexA repressor or LexA (Locus for X-ray sensitivity A) is a transcriptional repressor (EC 3.4.21.88) that represses SOS response genes coding primarily for error-prone DNA polymerases, DNA repair enzymes and cell division inhibitors. LexA forms de facto a two-component regulatory system with RecA, which senses DNA damage at stalled replication forks, forming monofilaments and acquiring an active conformation capable of binding to LexA and causing LexA to cleave itself, in a process called autoproteolysis.
LexA polypeptides contains a two domains: a DNA-binding domain and a dimerization domain. The dimerization domain binds to other LexA polypeptides to form dumbbell shaped dimers. The DNA-binding domain is a variant form of the helix-turn-helix DNA binding motif, and is usually located at the N-terminus of the protein. This domain is bound to an SOS box upstream of SOS response genes until DNA damage stimulates autoproteolysis.