Multidrug-Binding Transcription Factor QacR Binds the Bivalent Aromatic Diamidines DB75 and DB359 in Multiple PositionsBrooks, B.E., Piro, K.M., Brennan, R.G.
(2007) J.Am.Chem.Soc. 129: 8389-8395
- PubMed: 17567017
- DOI: 10.1021/ja072576v
- Primary Citation of Related Structures:
- PubMed Abstract:
Staphylococcus aureus QacR is a multidrug-binding transcription repressor. Crystal structures of multiple QacR-drug complexes reveal that these toxins bind in a large pocket, which is composed of smaller overlapping "minipockets". Stacking, van der W ...
Staphylococcus aureus QacR is a multidrug-binding transcription repressor. Crystal structures of multiple QacR-drug complexes reveal that these toxins bind in a large pocket, which is composed of smaller overlapping "minipockets". Stacking, van der Waals, and ionic interactions are common features of binding, whereas hydrogen bonds are limited. Pentamidine, a bivalent aromatic diamidine, interacts with QacR differently as one positively charged benzamidine moiety is neutralized by the dipoles of side-chain and peptide backbone oxygens rather than a formal negative charge from proximal acidic residues. To understand the binding mechanisms of other bivalent benzamidines, we determined the crystal structures of the QacR-DB75 and QacR-DB359 complexes and measured their binding affinities. Although these rigid aromatic diamidines bind with low-micromolar affinities, they do not use single, discrete binding modes. Such promiscuous binding underscores the intrinsic chemical redundancy of the QacR multidrug-binding pocket. Chemical redundancy is likely a hallmark of all multidrug-binding pockets, yet it is utilized by only a subset of drugs, which, for QacR, so far appears to be limited to chemically rigid, bivalent compounds.
Department of Biochemistry and Molecular Biology, University of Texas MD Anderson Cancer Center, Unit 1000, Houston, TX 77030, USA.