CodY regulates expression of the Bacillus subtilis extracellular proteases Vpr and Mpr

Abstract

CodY is a global transcriptional regulator in low-G+C Gram-positive bacteria that is responsive to GTP and branched-chain amino acids. By interacting with its two cofactors, it is able to sense the nutritional and energetic status of the cell and respond by regulating expression of adaptive genetic programs. In Bacillus subtilis, more than 200 genes, including those for peptide transporters, intracellular proteolytic enzymes, and amino acid degradative pathways, are controlled by CodY. In this study, we demonstrated that expression of two extracellular proteases, Vpr and Mpr, is negatively controlled by CodY. By gel mobility shift and DNase I footprinting assays, we showed that CodY binds to the regulatory regions of both genes, in the vicinity of their transcription start points. The mpr gene is also characterized by the presence of a second, higher-affinity CodY-binding site located at the beginning of its coding sequence. Using strains carrying vpr- or mpr-lacZ transcriptional fusions in which CodY-binding sites were mutated, we demonstrated that repression of both protease genes is due to the direct effect by CodY and that the mpr internal site is required for regulation. The vpr promoter is a rare example of a sigma H-dependent promoter that is regulated by CodY. In a codY null mutant, Vpr became one of the more abundant proteins of the B. subtilis exoproteome.

Importance: CodY is a global transcriptional regulator of metabolism and virulence in low-G+C Gram-positive bacteria. In B. subtilis, more than 200 genes, including those for peptide transporters, intracellular proteolytic enzymes, and amino acid degradative pathways, are controlled by CodY. However, no role for B. subtilis CodY in regulating expression of extracellular proteases has been established to date. In this work, we demonstrate that by binding to the regulatory regions of the corresponding genes, B. subtilis CodY negatively controls expression of Vpr and Mpr, two extracellular proteases. Thus, in B. subtilis, CodY can now be seen to regulate the entire protein utilization pathway.