LexA repressor

The LexA repressor or LexA (Locus for X-ray sensitivity A) is a transcriptional <a href="/facts/Repressor/qGBBQwqS">repressor</a> (<a href="/facts/Enzyme_Commission_number/Y5GNLRKX">EC</a> <a href="https://enzyme.expasy.org/EC/3.4.21.88">3.4.21.88</a>) that represses <a href="/facts/SOS_response/LFrC6t6N">SOS response</a> genes coding primarily for error-prone <a href="/facts/DNA_polymerase/xtNLncBu">DNA polymerases</a>, <a href="/facts/DNA_repair/hsURuYYq">DNA repair</a> <a href="/facts/Enzyme/DSI1Fh7y">enzymes</a> and <a href="/facts/Cell_division/n5MrunWj">cell division</a> inhibitors. LexA forms de facto a <a href="/facts/Two-component_regulatory_system/VP6hvFTe">two-component regulatory system</a> with <a href="/facts/RecA/MPHuQLK9">RecA</a>, 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 <a href="/facts/Proteolysis/GtQdv6J7">autoproteolysis</a>.
LexA polypeptides contains a two domains: a <a href="/facts/DNA-binding_domain/x2vlHUKl">DNA-binding domain</a> and a <a href="/facts/Protein_dimer/c8LwFJPG">dimerization</a> domain. The dimerization domain binds to other LexA polypeptides to form dumbbell shaped dimers. The DNA-binding domain is a variant form of the <a href="/facts/Helix-turn-helix/a2qHSHUL">helix-turn-helix</a> DNA binding <a href="/facts/Protein_motif/g8EBDBGW">motif</a>, and is usually located at the <a href="/facts/N-terminus/yKYpuaBJ">N-terminus</a> of the protein. This domain is bound to an <a href="/facts/SOS_box/grmJ9xCb">SOS box</a> upstream of SOS response genes until DNA damage stimulates autoproteolysis.

LexA repressor open-in-new

LexA repressor