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J Stülke

Publications and source records attributed to J Stülke.

25 records · Page 2Linked to original sources
PubMed1995

Two different mechanisms mediate catabolite repression of the Bacillus subtilis levanase operon.

There are two levels of control of the expression of the levanase operon in Bacillus subtilis: induction by fructose, which involves a positive regulator, LevR, and the fructose phosphotransferase system encoded by this operon (lev-PTS), and a global regulation, catabolite repression. The LevR activator interacts with its target, the upstream activating sequence (UAS), to stimulate the transcription of the E sigma L complex bound at the "-12, -24" promoter. Levanase operon expression in the presence of glucose was tested in strains carrying a ccpA gene disruption or a ptsH1 mutation in which Ser-46 of HPr is replaced by Ala. In a levR+ inducible genetic background, the expression of the levanase operon was partially resistant to catabolite repression in both mutants, indicating that the CcpA repressor and the HPr-SerP protein are involved in the glucose control of this operon. In addition, a cis-acting catabolite-responsive element (CRE) of the levanase operon was identified and investigated by site-directed mutagenesis. The CRE sequence TGAAAACGCTT(a)ACA is located between positions -50 and -36 from the transcriptional start site, between the UAS and the -12, -24 promoter. However, in a background constitutive for levanase, neither HPr, CcpA, nor CRE is involved in glucose repression, suggesting the existence of a different pathway of glucose regulation. Using truncated LevR proteins, we showed that this CcpA-independent pathway required the presence of the domain of LevR (amino acids 411 to 689) homologous to the BglG family of bacterial antiterminators.

Bacillus subtilis↗
PubMed1995

The HPr protein of the phosphotransferase system links induction and catabolite repression of the Bacillus subtilis levanase operon.

The LevR protein is the activator of expression of the levanase operon of Bacillus subtilis. The promoter of this operon is recognized by RNA polymerase containing the sigma 54-like factor sigma L. One domain of the LevR protein is homologous to activators of the NtrC family, and another resembles antiterminator proteins of the BglG family. It has been proposed that the domain which is similar to antiterminators is a target of phosphoenolpyruvate:sugar phosphotransferase system (PTS)-dependent regulation of LevR activity. We show that the LevR protein is not only negatively regulated by the fructose-specific enzyme IIA/B of the phosphotransferase system encoded by the levanase operon (lev-PTS) but also positively controlled by the histidine-containing phosphocarrier protein (HPr) of the PTS. This second type of control of LevR activity depends on phosphoenolpyruvate-dependent phosphorylation of HPr histidine 15, as demonstrated with point mutations in the ptsH gene encoding HPr. In vitro phosphorylation of partially purified LevR was obtained in the presence of phosphoenolpyruvate, enzyme I, and HPr. The dependence of truncated LevR polypeptides on stimulation by HPr indicated that the domain homologous to antiterminators is the target of HPr-dependent regulation of LevR activity. This domain appears to be duplicated in the LevR protein. The first antiterminator-like domain seems to be the target of enzyme I and HPr-dependent phosphorylation and the site of LevR activation, whereas the carboxy-terminal antiterminator-like domain could be the target for negative regulation by the lev-PTS.

Amino Acid Sequence↗
PubMed1995

New beta-glucoside (bgl) genes in Bacillus subtilis: the bglP gene product has both transport and regulatory functions similar to those of BglF, its Escherichia coli homolog.

The Bacillus subtilis sacY and sacT genes encode antiterminator proteins, similar to the Escherichia coli bglG gene product and required for transcription of sucrose metabolism genes. A Tn10 insertion into bglP (formerly sytA) has been previously identified as restoring sucrose utilization to a strain with deletions of both sacY and sacT. The nucleotide sequence of bglP showed a high degree of homology with the E. coli bglF gene (BglF is a beta-glucoside permease of the phosphotransferase system and also acts as a negative regulator of the BglG antiterminator). Complementation studies of an E. coli strain with a deletion of the bgl operon showed that BglP was a functional beta-glucoside permease. In B. subtilis, bglP complemented in trans both the bglP::Tn10 original insertion and a phenotypically similar bglP deletion. Disruption of licT abolished the suppressor phenotype in a bglP mutant. LicT is a recently identified third B. subtilis antiterminator of the BglG/SacY family. These observations indicated that BglP was also a negative regulator of LicT. Both LicT and BglP seem to be involved in the induction by beta-glucosides of an operon containing at least two genes, bglP itself and bglH, encoding a phospho-beta-glucosidase. Other beta-glucoside genes homologous to bglP and bglH have been recently described in B. subtilis. Thus, B. subtilis possesses several sets of beta-glucoside genes, like E. coli, but these genes do not appear to be cryptic.

Amino Acid Sequence↗
PubMed1994

Regulation of xylanolytic enzymes in Bacillus subtilis.

The synthesis of the xylanolytic enzymes beta-xylanase and beta-xylosidase of Bacillus subtilis was studied. In contrast to many catabolic extracellular enzymes, beta-xylanase was synthesized constitutively during exponential growth and was not repressed by glucose. beta-Xylosidase synthesis was induced 100-fold by xylose and repressed 100-fold by glucose. Carbon catabolite repression was abolished in a ccpA mutant. Titration experiments using a multicopy operator sequence responsible for carbon catabolite repression indicated that the gene encoding beta-xylosidase is part of the same carbon catabolite repression regulon as the amyE and bgIS genes.

Bacillus subtilis↗
PubMed1993

Catabolite repression of beta-glucanase synthesis in Bacillus subtilis.

beta-Glucanase synthesis in Bacillus subtilis was repressed by glucose and other substrates of glycolysis. Experiments with different pts mutants showed that the phosphoenolpyruvate: sugar phosphotransferase system is not involved in carbon catabolite repression of beta-glucanase synthesis. Carbon catabolite repression of beta-glucanase synthesis was completely abolished in a ccpA mutant. An operator structure similar to those upstream of amyE and the xyl operon was found and was shown by site-directed mutagenesis to be the target for carbon catabolite repression of beta-glucanase synthesis. The presence of this operator on a multi-copy plasmid resulted in a reduced repression of both beta-glucanase and alpha-amylase synthesis. It seems likely that the gene encoding these enzymes are part of one regulon with respect to catabolite repression.

Bacillus subtilis↗
PubMed1990

Detection of a 2 mu derivative yeast plasmid with altered properties.

The Saccharomyces cerevisiae (Sacch. cerevisiae) strain RXII, like many others, harbours plasmid DNAs. and one category of them is homologous to the 2 mu plasmid of yeast. DNA-DNA hybridization experiments indicated altered structures of this species as regards the number and distribution of the restriction sites. The efforts made to clone either the whole plasmid in pBR328 or its fragments in pBR322 vectors remained unsuccessful, since deleted plasmids were isolated without insert DNA, and even the loss of vector sequences was observed. The data suggest, that the 2 mu derivative plasmid in strain RXII represent an unique category of this extrachromosomal genetic element.

Autoradiography↗