Regulation of the putative bglPH operon for aryl-beta-glucoside utilization in Bacillus subtilis

Abstract

The expression of the putative operon bglPH of Bacillus subtilis was studied by using bglP'-lacZ transcriptional fusions. The bglP gene encodes an aryl-beta-glucoside-specific enzyme II of the phosphoenolpyruvate sugar:phosphotransferase system, whereas the bglH gene product functions as a phospho-beta-glucosidase. Expression of bglPH is regulated by at least two different mechanisms: (i) carbon catabolite repression and (ii) induction via an antitermination mechanism. Distinct deletions of the promoter region were created to determine cis-acting sites for regulation. An operatorlike structure partially overlapping the -35 box of the promoter of bglP appears to be the catabolite-responsive element of this operon. The motif is similar to that of amyO and shows no mismatches with respect to the consensus sequence established as the target of carbon catabolite repression in B. subtilis. Catabolite repression is abolished in both ccpA and ptsH1 mutants. The target of the induction by the substrate, salicin or arbutin, is a transcriptional terminator located downstream from the promoter of bglP. This structure is very similar to that of transcriptional terminators which regulate the induction of the B. subtilis sacB gene, the sacPA operon, and the Escherichia coli bgl operon. The licT gene product, a member of the BglG-SacY family of antitermination proteins, is essential for the induction process. Expression of bglP is under the negative control of its own gene product. The general proteins of the phosphoenolpyruvate-dependent phosphotransferase system are required for bglP expression. Furthermore, the region upstream from bglP, which reveals a high AT content, exerts a negative regulatory effect on bglP expression.

Antitermination of transcription of catabolic operons

“…LicT is also positively regulated by the general components of the PTS and it is possible that LicT is active as a dimer and that phosphorylation by the PTS enhances dimerization. The finding that an increased number of LicT copies overcomes the dependence of bglP expression on the PTS supports this model (Krü ger and Hecker, 1995). There is some cross-talk between LicT and the other antiterminator proteins of the bgl-sac family.…”

“…LicT also causes antitermination at a RAT-terminator sequence in the leader of the bglPH operon (Krü ger and Hecker, 1995;Le Coq et al, 1995). bglP encodes EII bgl , a ␤-glucoside-specific enzyme of the PTS, and bglH encodes a phospho-␤-glucosidase.…”

Carbon Catabolite Control of the Metabolic Network inBacillus subtilis

“…75) Thus HPr-mutants (ptsH1) are partially or completely relieved from CCR of several catabolic genes. 15,26,59,76,77) Most enzymes that are relieved from CCR in a ccpA mutant are also relieved from CCR in a ptsH1 mutant, implying that P-Ser-HPr and CcpA are involved in the same CCR mechanism and that they possibly interact with each other. This coincides with the fact that CcpA is a protein synthesized constitutively irrespective of the presence or absence of a preferred carbon source, 14) suggesting that CcpA requires a corepressor, which might be P-Ser-HPr, to exert catabolite repression.…”

“…The operons involved in the catabolism of secondary carbon sources are as follows (the carbon sources in parentheses): gntRKPZ (gluconate), 16,35,36) xylAB (xylose), 9) iolABCDEFGHIJ (myo-inositol), 40,41,102) trePAR (trehalose), 25,47,103) galKT (galactose), 25) glpFK (glycerol), 33) glvARC (6-P--glucoside), 34) bglPH ( -glucoside), 26,27) yjlBCD-uxaC-yjmBCD-uxuA-yjmFexuTR-uxaBA (hexuronate), 25,48) xynPB ( -xyloside), 65) yxjC-scoAE-bdh ( -hydroxybutyrate), 25,49) ara-ABDLMNPQ-abfA (arabinose) 24,52,53) and abnA xsa (arabinose), 50) kdgRKAT (hexuronate), 25,42) and kduID (galacturonate). 43) The yxkF-msmX operon probably involved in the transport of unknown sugars has been found to be under CcpA-mediated CCR.…”

Transcription–repair coupling factor is involved in carbon catabolite repression of the Bacillus subtilis hut and gnt operons

“…Loss-of-function mutations in the B. subtilis ccpA gene relieve CCR of all of the genes known to contain a functional cre (Henkin et al, 1991;Fujita and Miwa, 1994;Grundy et al, 1994;Dahl and Hillen, 1995;Krü ger and Hecker, 1995;Martin-Verstraete et al, 1995;Bryan et al, 1996). The CcpA protein is a member of the LacI/GalR family of regulatory proteins (Henkin et al, 1991;Weickert and Adhya, 1992).…”