Induction of levansucrase in Bacillus subtilis: an antitermination mechanism negatively controlled by the phosphotransferase system

Abstract

The target of the induction by sucrose of the levansucrase gene is a transcription terminator (sacRt) located upstream from the coding sequence, sacB. The two-gene locus sacX-sacY (formerly sacS) and the ptsI gene were previously shown to be involved in this induction. ptsI encodes enzyme I of the phosphoenolpyruvate-dependent phosphotransferase system. SacX is strongly homologous to sucrose-specific phosphotransferase system-dependent permeases. SacY is a positive regulator of sacB. Here we show that SacY is probably an antiterminator interacting directly with sacRt, since in Escherichia coli the presence of the sacY gene stimulates the expression of a reporter gene fused downstream from sacRt. Missense mutations affecting sacY were sequenced, and the sacB regulation was studied in isogenic strains carrying these mutations or in vitro-generated mutations affecting sacX, sacY, or ptsI. The phenotype of double mutants suggests a model in which SacX might be a sucrose sensor that would be phosphorylated by the phosphotransferase system and, in this state, could inhibit the SacY antiterminator. Exogenous sucrose, or a mutation inactivating the phosphotransferase system, would dephosphorylate SacX and allow antitermination at sacRt.

Transcripts of the genes sacB, amyE, sacC and csn expressed in Bacillus subtilis under the control of the 5′ untranslated sacR region display different stabilities that can be modulated

“…4). These transcripts were of the expected lengths (about 2200, 2400, 1100 and 1650 nt, for amyE, sacC, csn and sacB, respectively), in agreement with the previously determined site of transcription initiation in the sacR leader sequence (Shimotsu & Henner, 1986) and generated by transcriptional antitermination at the terminator structure present in sacR (Crutz et al, 1990). A short additional transcript which hybridized only with the 5h sacR probe was observed in the case of sacC (Fig.…”

BglR protein, which belongs to the BglG family of transcriptional antiterminators, is involved in beta-glucoside utilization in Lactococcus lactis

“…The bglR-encoded protein is homologous to regulatory proteins of the BglG family. All previously described members of this family control the utilization of sugars (1,13,15,16,36,39,40). Disruption of bglR revealed that its product is required for maximal growth on arbutin and salicin as sole carbon sources.…”

“…These systems include the control of the Bacillus subtilis levansucrase sacB gene by SacY (7,13), of the B. subtilis sacPA operon by SacT (6,14,39), of B. subtilis 13-glucan utilization by licT (40), of Lactobacillus casei lactose utilization (1), and of the Erwinia chrysanthemi P-glucoside phosphotransferase gene arbF by ArbG (15).…”

Carbon Catabolite Control of the Metabolic Network inBacillus subtilis

“…These proteins (SacY, SacT, LicT, and GlcT) positively control the genes involved in the metabolism of carbohydrates that are taken up by the PTS; SacY and T are involved in sucrose metabolism, LicT in the metabolism of oligo--glucoside and aryl--glucoside, and GlcT in glucose assimilation. SacY and T [140][141][142] are antiterminators of the sacB (encoding levansucrase)-levB (endolevanase)-yveA, sacX (IIBC SacX )-sacY, and sacP (IIBC SacP )-sacA (sucrose-6-P hydrolase)-ywdA operons, whereas LicT 27,143) is an antiterminator of the licS gene (endo-1,3-1,4--glucanase) and the bglP (IIBCA Bgl )-bglH (6-P--glucosidase)-yxiE operon, and GlcT 144,145) is that of the ptsG (IICBA Glc )-ptsH (HPr)-ptsI (EI) operon. In the presence of the cognate PTS-sugars that activate these antiterminators, they bind to a conserved motif called the ribonucleic antiterminator (RAT), which is present in the untranslated leader-mRNAs of their target genes.…”