The GbsR Family of Transcriptional Regulators: Functional Characterization of the OpuAR Repressor.

摘要: Accumulation of compatible solutes is a common stress response microorganisms challenged by high osmolarity; it can be achieved either through synthesis or import. These processes have been intensively studied in Bacillus subtilis, where systems for the production proline and glycine betaine identified, which five transporters osmostress protectants (Opu) characterized. Glycine relies on import choline via substrate-restricted OpuB system promiscuous OpuC transporter its subsequent oxidation GbsAB enzymes. Transcription opuB gbsAB operons under control MarR-type regulator GbsR, acts as an intracellular choline-responsive repressor. Modeling studies using X-ray structure Mj223 protein from Methanocaldococcus jannaschii template suggest that GbsR homo-dimer with N-terminal DNA-reading head C-terminal dimerization domain; flexible linker connects these two domains. In vicinity region, aromatic cage predicted inducer-binding site, whose envisioned architecture resembles present substrate-binding proteins ABC transporters. We used bioinformatics to assess phylogenomics GbsR-type found they are widely distributed among Bacteria Archaea. Alignments analysis genetic context corresponding structural genes allowed their assignment into four sub-groups. one sub-groups proteins, gbsR-type associated OpuA-, OpuB-, OpuC-type uptake systems. focus here named OpuAR us, expression opuA-type gene clusters. Using such marine bacterium infantis, we show repressor opuA transcription, several (e.g., choline, betaine, betaine) serve inducers. Site-directed mutagenesis rational improvement putative site respect affinity binding. Collectively, our data characterize GbsR-/OpuAR-type extended sub-group within MarR-superfamily transcriptional regulators identify novel type substrate-inducible protectants.