Role of the transcriptional activator RocR in the arginine‐degradation pathway of Bacillus subtilis

Abstract

SummaryIn Bacillus subtilis, genes involved in arginine and ornithine catabolism constitute two operons, rocABC and rocDEF. Inducible expression of these two operons is SigL-dependent and requires the transcriptional activator RocR. RocR is a member of the NtrC/ NifA family of regulators. To study the molecular mechanisms leading to the activation of RocR, we constructed a series of mutants affected in various steps of arginine catabolism. Results obtained using these mutants strongly suggest that the true inducer is ornithine or citrulline. Constitutive mutants of rocR containing either missense mutations, frameshift mutations resulting from deletions, or in-frame deletions leading to the synthesis of N-terminal truncated RocR polypeptides were obtained. Analysis of these mutants indicates that the N-terminal part of RocR is an intramolecular repressor domain. AhrC is a second positive regulatory protein of the rocABC and rocDEF operons. Two missense mutations modifying the Nterminal domain of RocR led to high constitutive expression of the Roc regulon in the absence of AhrC. Constitutive RocR proteins still require the presence of UAS1 and therefore probably bending of the DNA region located between the UAS1 and the promoter, suggesting that AhrC is not involved in DNA bending which facilitates interaction between RocR and 54 -RNA polymerase. We suggest that the positive role of AhrC involves protein-protein interaction with RocR.

Cyclic Di-AMP Homeostasis in Bacillus subtilis

“…Based on this finding, it is tempting to speculate that the N-terminal helices are involved in the control of the activity of the DAC domain and thus in the sporespecific synthesis of c-di-AMP. Similarly, inhibitory protein domains have been found in the B. subtilis transcription factor RocR and the alternative factor 54 (51,52). Future studies will focus on the distinct molecular mechanisms controlling the c-di-AMP levels in B. subtilis.…”

Comprehensive Absolute Quantification of the Cytosolic Proteome of Bacillus subtilis by Data Independent, Parallel Fragmentation in Liquid Chromatography/Mass Spectrometry (LC/MSE)

“…Indeed, in the presence of arginine, the transcription factor AhrC is known (a) to repress the expression of genes coding for arginine synthesis and (b) to induce the degradation of arginine. In addition, genes for arginine degradation are transcribed from a L -dependent promoter and activated by RocR (38). Considering only these regulations, arginine synthesis should be repressed.…”

Carbon Catabolite Control of the Metabolic Network inBacillus subtilis

“…Moreover, the sigL gene encoding a 54 -type factor of B. subtilis L involved in nitrogen metabolism 104) is a direct target of CcpA. 64) The L regulon contains the levanase operon, levDEFG-sacC, involved in fructose and levan metabolism, 59,104) three rocABC, rocDEF, and rocG operons associated with arginine catabolism, [107][108][109] an acoABCL operon encoding the acetoin dehydrogenase complex, 51,110) and the seven-cistronic bkd operons 111) encoding enzymes involved in leucine and valine degradation. Of these, acoABCL, levDEFG-sacC, and rocG have been experimentally proven to carry the respective cre sequences.…”

“…131) This protein also represses sr1, 132) which encodes a small non-coding regulatory RNA that inhibits the translation of ahrC encoding a transcriptional regulator that activates the rocABC and rocDEF operons for arginine catabolism and represses the gene cluster for arginine biosynthesis. 108,[133][134][135] CcpN is active when cells are growing on a glycolytic substrate, even if the medium also contains a gluconeogenic substrate. 127) CcpN is inhibited on interaction with YqfL, which is active during gluconeogenesis, and pckA and gapB as well as sr1 are derepressed.…”