LVIS553 transcriptional regulator specifically recognizes novobiocin as an effector molecule

In this study we aimed to identify small molecules with high affinity involved in the allosteric regulation of LVIS553, a MarR member from Lactobacillus brevis ATCC367. Using high throughput screening, novobiocin was found to specifically bind LVIS553 with a K(D) = 33.8 +/- 2.9 microM consistent with a biologically relevant ligand. Structure guided site-directed mutagenesis identified Lys(9) as a key residue in novobiocin recognition. The results found in vitro were correlated in vivo. An increased tolerance to the antibiotic was observed when LVIS553 and the downstream putative transport protein LVIS552 were either expressed in a low copy plasmid in L. brevis or as a single copy chromosomal insertion in Bacillus subtilis. We provide evidence that LVIS553 is involved in the specific regulation of a new mechanism of tolerance to novobiocin.