title: Structure of the transcriptional regulator LmrR and its mechanism of multidrug recognition.
abstract: LmrR is a PadR-related transcriptional repressor that regulates the production of LmrCD, a major multidrug ABC transporter in Lactococcus lactis. Transcriptional regulation is presumed to follow a drug-sensitive induction mechanism involving the direct binding of transporter ligands to LmrR. Here, we present crystal structures of LmrR in an apo state and in two drug-bound states complexed with Hoechst 33342 and daunomycin. LmrR shows a common topology containing a typical beta-winged helix-turn-helix domain with an additional C-terminal helix involved in dimerization. Its dimeric organization is highly unusual with a flat-shaped hydrophobic pore at the dimer centre serving as a multidrug-binding site. The drugs bind in a similar manner with their aromatic rings sandwiched in between the indole groups of two dimer-related tryptophan residues. Multidrug recognition is facilitated by conformational plasticity and the absence of drug-specific hydrogen bonds. Combined analyses using site-directed mutagenesis, fluorescence-based drug binding and protein-DNA gel shift assays reveal an allosteric coupling between the multidrug- and DNA-binding sites of LmrR that most likely has a function in the induction mechanism.
authors.affiliation: Department of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
authors.forename: Pramod Kumar
authors.initials: PK
authors.lastname: Madoori
authors.forename: Herfita
authors.initials: H
authors.lastname: Agustiandari
authors.forename: Arnold J M
authors.initials: AJ
authors.lastname: Driessen
authors.forename: Andy-Mark W H
authors.initials: AM
authors.lastname: Thunnissen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001562:Benzimidazoles / Q000737:chemistry*; D003630:Daunorubicin / Q000737:chemistry*; D019281:Dimerization; D019077:Helix-Turn-Helix Motifs; D006860:Hydrogen Bonding; D013294:Lactococcus lactis / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D001562:Benzimidazoles; C017807:bisbenzimide ethoxide trihydrochloride; D003630:Daunorubicin