Structural insight into DNA recognition by bacterial transcriptional regulators of the SorC DeoR family

The SorC DeoR family is a large family of bacterial transcription regulators that are involved in the control of carbohydrate metabolism and quorum sensing. To understand the structural basis of DNA recognition, structural studies of two functionally characterized SorC DeoR family members from Bacillus subtilis were performed the deoxyribonucleoside regulator bsDeoR and the central glycolytic genes regulator bsCggR. Each selected protein represents one of the subgroups that are recognized within the family. Crystal structures were determined of the N terminal DNA binding domains of bsDeoR and bsCggR in complex with DNA duplexes representing the minimal operator sequence at resolutions of 2.3 and 2.1 amp; 8197; , respectively. While bsDeoRDBD contains a homeodomain like HTH type domain, bsCggRDBD contains a winged helix turn helix type motif. Both proteins form C2 symmetric dimers that recognize two consecutive major grooves, and the protein DNA interactions have been analyzed in detail. The crystal structures were used to model the interactions of the proteins with the full DNA operators, and a common mode of DNA recognition is proposed that is most likely to be shared by other members of the SorC DeoR famil

Structure of the effector binding domain of the arabinose repressor AraR from Bacillus subtilis

In Bacillus subtilis, the arabinose repressor AraR negatively controls the expression of genes in the metabolic pathway of arabinose-containing polysaccharides. The protein is composed of two domains of different phylogenetic origin and function: an N-terminal DNA-binding domain belonging to the GntR family and a C-terminal effector-binding domain that shows similarity to members of the GalR/LacI family. The crystal structure of the C-terminal effector-binding domain of AraR in complex with the effector l-arabinose has been determined at 2.2 Å resolution. The l-arabinose binding affinity was characterized by isothermal titration calorimetry and differential scanning fluorimetry; the K (d) value was 8.4 ± 0.4 µM. The effect of l-arabinose on the protein oligomeric state was investigated in solution and detailed analysis of the crystal identified a dimer organization which is distinctive from that of other members of the GalR/LacI family