Ligand-binding domain of a transcription repressor, FucR, which functions as a molecular sensor of L-fucose availability
Ligand-binding domain of a transcription repressor, FucR, which functions as a molecular sensor of L-fucose availability. FcuR acts as an inducer of fucRRIAK and as a corepressor of another locus that regulates production of fucosylated glycans. FcuR and its close homologs in this group are a member of the LacI-GalR family repressors that are composed of two functional domains: an N-terminal HTH (helix-turn-helix) domain, which is responsible for the DNA-binding specificity, and a C-terminal ligand-binding domain, which is homologous to the sugar-binding domain of ABC-type transport systems that contain the type I periplasmic binding protein-like fold. As also observed in the periplasmic binding proteins, the C-terminal domain of the bacterial transcription repressor undergoes a conformational change upon ligand binding which in turn changes the DNA binding affinity of the repressor.