MarR family transcription factors

Figure 1. Representative MarR homologs and their mode of gene regulation. (A) Structure of MTH313 (3BPX), a MarR homolog of unknown function from Methanobacterium thermoautotrophicum, in complex with the ligand salicylate (shown in magenta). One monomer is shown in gray, the other is colored from amino to carboxyl terminus (blue to red). Note the asymmetrical ligand binding; only ligand binding at the primary site (at the right) is associated with protein conformational changes and is therefore considered physiologically relevant. (B) Structure of Deinococcus radiodurans HucR (2FBK). Each monomer is shown in light and dark blue. HucR includes an amino-terminal extension conserved among a subset of MarR homologs (shown in orange) that is not seen in other reported MarR protein structures. DNA recognition helices are colored green and residues required for binding of the ligand urate are shown in magenta. (C) Structure of Staphylococcus epidermidis TcaR (3KP5) in complex with kanamycin (shown in magenta). Note that the symmetry-related site is unoccupied. Each monomer is shown in light and dark blue, with the DNA recognition helices in green. (D) Structure of oxidized OhrR from Xanthomonas campestris (2PFB). Each monomer is shown in light and dark blue with oxidized cysteines in orange. (E) Typical organization of genomic locus comprising gene encoding MarR homolog. Genes are depicted as blue arrows. The intergenic region between divergently encoded genes contains cognate DNA site(s). (F) In the absence of ligand, the MarR homolog (green symbol) binds the intergenic region, repressing expression of both genes. In the presence of ligand, DNA binding is attenuated and genes are expressed. MarR family transcription factors