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PubMed2004

Anaerobiosis and low specific growth rates enhance hemolysin BL production by Bacillus cereus F4430/73.

Bacillus cereus F4430/73 produced the highest levels of hemolysin BL (HBL) when grown under anaerobiosis in MOD medium. Anaerobic cells grown in a chemostat at low specific growth rate (0.1-0.2 h(-1)) expressed up to sevenfold more HBL than did cells held at a faster growth rate. At 0.2 h(-1), the presence of 90 mM glucose resulted in inhibition of HBL production. Glucose was found to repress HBL induction at the mRNA level, indicating the potential involvement of catabolite repression in the regulation of HBL. Based on these data, it is suggested that growth rate could be an effector of catabolite regulation of HBL.

Anaerobiosis↗
PubMed2001

Characterization of glucose-repression-resistant mutants of Bacillus subtilis: identification of the glcR gene.

In Bacillus subtilis, carbon catabolite repression (CCR) is mediated by the pleiotropic repressor CcpA and by ATP-dependent phosphorylation of the HPr protein of the phosphotransferase system (PTS). In this study, we attempted to identify novel genes that are involved in the signal transduction pathway that ultimately results in CCR in the presence of repressing carbon sources such as glucose. Seven mutants resistant to glucose repression of the levanase operon were isolated and characterized. All mutations were trans-acting and pleiotropic as determined by analyzing CCR of beta-xylosidase and of the sacPA and bglPH operon. Moreover, all mutations specifically affected repression exerted by glucose but not by other sugars. The mutations were mapped to three different loci on the genetic map, ptsG, glcR, and pgi. These three genes encode proteins involved in glucose metabolism. A novel repressor gene, glcR (ywpI), defined by two mutations, was studied in more detail. The glcR mutants exhibit loss of glucose repression of catabolic operons, a deficiency in glucose transport, and absence of expression of the ptsG gene. The mutant GlcR proteins act as super-repressors of ptsG expression.

Bacillus subtilis↗
PubMed1983

Partial purification and characterization of succinyl-CoA synthetase from Saccharomyces cerevisiae.

Succinyl-CoA synthetase from Saccharomyces cerevisiae was partially purified (20-fold) with a yield of 44%. The Michaelis-Menten constants were determined: Km (succinate) = 17 mM; Km (ATP) = 0.13 mM; Km (CoA) = 0.03 mM. The succinyl-CoA synthetase has a molecular weight of about 80000 dalton (as determined by polyacrylamide gradient gel electrophoresis). The pH optimum is at 6.0. During fermentation the activity of succinyl-CoA synthetase is lower than in aerobically grown yeast cells. The presence of succinyl-CoA synthetase in fermenting yeasts may be regarded as an indication for the oxidative formation of succinate. In fermenting yeast cells succinyl-CoA synthetase is repressed by glucose if ammonium sulphate serves as nitrogen source. This catabolite repression is not observed with disaccharides or when amino acids are used as nitrogen source.

Adenosine Triphosphate↗
PubMed2002

Quantification of the influence of HPrSer46P on CcpA-cre interaction.

Carbon catabolite repression (CCR) of the Bacillus megateriumxyl operon is dependent on the catabolite responsive element cre, the catabolite control protein (CcpA) and the histidine-containing phosphocarrier protein phosphorylated at the serine 46 residue (HPrSer46P). The latter is formed in the presence of glucose and mediates CCR via CcpA. We present evidence for the presence of HPrSer46P in a ternary complex with CcpA and cre. We also demonstrate increased stability of this complex compared to the CcpA-cre complex by electrophoretic mobility shift analysis (EMSA). This stabilization by HPrSer46P is the same for the xyl cre and an improved cre. Thus, HPrSer46P is a co-repressor for CcpA. In addition, surface plasmon resonance (SPR) experiments yielded binding constants of CcpA and the CcpA-HPrSer46P complex with cre. HPrSer46P stimulated CcpA binding to cre 50-fold. The binding constant is 4.9(+/- 0.5) x 10(6) M(-1). Non-phosphorylated HPr did not affect the complex formation between CcpA and cre. Previously proposed effects by glucose-6-phosphate, fructose-1,6-diphosphate and NADP on CcpA-cre or CcpA-HPrSer46P-cre formation were not found in EMSA and SPR experiments.

Amino Acid Substitution↗
PubMed2001

The Escherichia coli glucose transporter enzyme IICB(Glc) recruits the global repressor Mlc.

In addition to effecting the catalysis of sugar uptake, the bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes. Exposure of cells to glucose can result in repression or induction of gene expression. While the mechanism for carbon catabolite repression by glucose was well documented, that for glucose induction was not clearly understood in Escherichia coli. Recently, glucose induction of several E.coli genes has been shown to be mediated by the global repressor Mlc. Here, we elucidate a general mechanism for glucose induction of gene expression in E.coli, revealing a novel type of regulatory circuit for gene expression mediated by the phosphorylation state-dependent interaction of a membrane-bound protein with a repressor. The dephospho-form of enzyme IICB(Glc), but not its phospho-form, interacts directly with Mlc and induces transcription of Mlc-regulated genes by displacing Mlc from its target sequences. Therefore, the glucose induction of Mlc-regulated genes is caused by dephosphorylation of the membrane-bound transporter enzyme IICB(Glc), which directly recruits Mlc to derepress its regulon.

Bacterial Proteins↗
PubMed1996

G1n3p is capable of binding to UAS(NTR) elements and activating transcription in Saccharomyces cerevisiae.

When readily used nitrogen sources are available, the expression of genes encoding proteins needed to transport and metabolize poorly used nitrogen sources is repressed to low levels; this physiological response has been designated nitrogen catabolite repression (NCR). The cis-acting upstream activation sequence (UAS) element UAS(NTR) mediates Gln3p-dependent, NCR-sensitive transcription and consists of two separated dodecanucleotides, each containing the core sequence GATAA. Gln3p, produced in Escherichia coli and hence free of all other yeast proteins, specifically binds to wild-type UAS(NTR) sequences and DNA fragments derived from a variety of NCR-sensitive promoters (GDH2, CAR11 DAL3, PUT1, UGA4, and GLN1). A LexA-Gln3 fusion protein supported transcriptional activation when bound to one or more LexAp binding sites upstream of a minimal CYC1-derived promoter devoid of UAS elements. LexAp-Gln3p activation of transcription was largely independent of the nitrogen source used for growth. These data argue that Gln3p is capable of direct UAS(NTR) binding and participates in transcriptional activation of NCR-sensitive genes.

Base Sequence↗
PubMed1977

Some biochemical effects of 4-deoxy-4-fluoro-D-glucose on Escherichia coli.

The uptake of 4-deoxy-4-fluoro-D-glucose (4FG), without subsequent catabolism, by resting cells of Escherichia coli (ATCC 11775) is 0.06 mg/mg dry weight. In frozen-thawed cells of this organism, 4FG is a substrate for the phosphoenolpyruvate phosphotransferase system with a rate of phosphorylation twice that found for the isomeric 3-deoxy-3-fluoro-D-glucose. 4FG is not a carbon source for growth of this organism and it inhibits the extent of growth of cells in the presence of glucose. The inhibition of growth of E. coli K12 on lactose by 4FG is also observed and this is considered to be consistent with the fact that 4FG is an uncompetitive inhibitor of beta-galactosidase (EC 3.2.1.23) activity and that 4FG or 4-deoxy-4-fluoro-D-glucose-6 phosphate repress beta-galactosidase synthesis. These results support the view that catabolite repression may be produced by compounds which are not necessarily metabolised further than hexose-6-phosphates.

Cell Division↗
PubMed1995

Cloning, structural organization and regulation of expression of the Penicillium chrysogenum paf gene encoding an abundantly secreted protein with antifungal activity.

An abundantly secreted, highly basic 12-kDa protein (PAF) was purified from the culture medium of Penicillium chrysogenum (Pc). Based on the N-terminal amino acid (aa) sequence of the protein, an oligodeoxyribonucleotide probe was derived and used for amplification of the encoding cDNA by PCR. This cDNA fragment encodes a Cys-rich preproprotein of 92 aa which appears to be processed to a mature product of 55 aa. The deduced aa sequence of the preproprotein reveals 42.6% identity to an antifungal protein (AFP) of Aspergillus giganteus. Agar diffusion tests confirmed that the Pc protein exhibits antifungal activity. In order to investigate the promoter region and the structural organization of the paf gene, a genomic 6-kb fragment was isolated and partially sequenced. Comparison of the nucleotide sequence of the genomic fragment and the cDNA clone revealed the presence of a coding region of 279 bp which is interrupted by two introns of 76 and 68 bp in length. In the promoter region, a typical TATA box, a motif resembling the fungal carbon catabolite repression element, as well as several putative GATA factor binding motifs, were found. Northern blot analysis indicated that the regulation of paf expression occurs at the level of mRNA transcription and is under control of carbon catabolite and nitrogen metabolite repression regulatory circuits.

Amino Acid Sequence↗
PubMed1984

Isolation and characterization of a pleiotropic glucose repression resistant mutant of Saccharomyces cerevisiae.

A new mutation has been described which confers resistance to catabolite repression in Saccharomyces cerevisiae. The mutant allele, termed grr-1 for glucose repression-resistant, is characterized by insensitivity to glucose repression for the cytoplasmic enzymes invertase, maltase, and galactokinase, as well as the mitochondrial enzyme cytochrome c oxidase. Hexokinase levels in grr-1 mutants are approximately 3-fold higher than the corresponding activity of the parental strain. Although the grr-1 allele is expressed phenotypically similarly to the hex-1 (hxk-2) and hex-2 mutations described by Entian et al. (1977) and Zimmermann and Scheel (1977) respectively, we have shown genetically and physiologically that grr-1 represents a new class of mutation.

Alleles↗
PubMed1966

Role of the galactose pathway in the regulation of beta-galactosidase.

Paigen, Kenneth (Roswell Park Memorial Institute, Buffalo, N.Y.). Role of the galactose pathway in the regulation of beta-galactosidase. J. Bacteriol. 92:1394-1403. 1966.-Galactose and its metabolites, galactose-1-phosphate, uridine diphosphogalactose, and uridine diphosphoglucose, as well as metabolites derived from uridine diphosphoglucose, were tested for their role in the regulation of beta-galactosidase. In cultures of wild-type Escherichia coli strains K-12 and B, exogenous galactose was no more effective as a repressor than were other carbon sources. Exogenous galactose also did not repress beta-galactosidase when added to mutants which can accumulate intracellular galactose or galactose-1-phosphate, indicating that these compounds do not repress. In such strains, repression of beta-galactosidase formation did occur if galactose was added in the presence of another metabolizable carbon source. This repression is presumably a consequence of the growth inhibition which follows the accumulation of these compounds, and the general catabolite repression which develops during growth inhibition. Exogenous galactose did repress beta-galactosidase in a mutant which accumulates uridine diphosphogalactose. This appears to result from a combination of several factors. These include a general inhibition of protein synthesis through depletion of the uridine triphosphate pool, catabolite inhibition as a consequence of growth inhibition, as well as a specific inhibition of beta-galactosidase formation. Glucose repression of beta-galactosidase was normal in a mutant strain blocked in the formation of uridine diphosphoglucose from uridine triphosphate and glucose-1-phosphate, indicating that neither uridine diphosphoglucose nor any compound uniquely derived from it functions as the hypothetical catabolite repressor. It is concluded that at least two separate mechanisms exist for the endogenous repression of beta-galactosidase in E. coli. One is exerted by uridine diphosphogalactose or its metabolic product; the other, by the generalized catabolite repressor which is still formed in strains unable to make uridine diphosphogalactose or uridine diphosphoglucose.

Enzyme Repression↗
PubMed1994

The Aspergillus nidulans CREA protein mediates glucose repression of the ethanol regulon at various levels through competition with the ALCR-specific transactivator.

Carbon catabolite repression in Aspergillus nidulans is mediated by a negative-acting protein coded by the creA gene. We have investigated how CREA controls the expression of the ethanol regulon genes. CREA is a major component of the control of this regulon. Its presence in the cell results in a permanent, albeit partial, repression of the alc genes under all physiological growth conditions, even when the fungus is grown on carbon sources considered to be non-repressing. A crucial step in the control processes is the repression of the positive-acting specific regulatory gene alcR, by the binding of CREA on its cognate target sites on the alcR promoter. The removal of one of these targets, URSA, results in a 50% derepression of the alcR gene. Furthermore, the presence of this sequence contributes directly to the low alcR expression under nonrepressing conditions and reduces alcR promoter function by at least 100-fold. CREA acts both on the regulatory gene alcR and directly on the two structural genes alcA and aldA, as glucose repression of the latter genes occurs in strains where alcR transcription is driven by a strong constitutive and derepressed promoter. In vivo and in vitro competition experiments show that CREA acts by competing directly with the binding of the ALCR activator for the same region of the alcR promoter, a region which encompasses overlapping targets for both regulatory proteins. These data are consistent with a model in which the activating and repressing regulatory proteins compete to regulate expression of the ethanol regulon genes.

Alcohol Dehydrogenase↗
PubMed1999

Heat-induced expression and chemically induced expression of the Escherichia coli stress protein HtpG are affected by the growth environment.

Differences in expression of the Escherichia coli stress protein HtpG were found following exposure of exponentially growing cells to heat or chemical shock when cells were grown under different environmental conditions. With an htpG::lacZ reporter system, htpG expression increased in cells grown in a complex medium (Luria-Bertani [LB] broth) following a temperature shock at 45 degrees C. In contrast, no HtpG overexpression was detected in cells grown in a glucose minimal medium, despite a decrease in the growth rate. Similarly, in pyruvate-grown cells there was no heat shock induction of HtpG expression, eliminating the possibility that repression of HtpG in glucose-grown E. coli was due to catabolite repression. When 5 mM phenol was used as a chemical stress agent for cells growing in LB broth, expression of HtpG increased. However, when LB-grown cells were subjected to stress with 10 mM phenol and when both 5 and 10 mM phenol were added to glucose-grown cultures, repression of htpG expression was observed. 2-Chlorophenol stress resulted in overexpression of HtpG when cells were grown in complex medium but repression of HtpG synthesis when cells were grown in glucose. No induction of htpG expression was seen with 2, 4-dichlorophenol in cells grown with either complex medium or glucose. The results suggest that, when a large pool of amino acids and proteins is available, as in complex medium, a much stronger stress response is observed. In contrast, when cells are grown in a simple glucose mineral medium, htpG expression either is unaffected or is even repressed by imposition of a stress condition. The results demonstrate the importance of considering differences in growth environment in order to better understand the nature of the response to an imposed stress condition.

Bacterial Proteins↗
PubMed1992

SRN1, a yeast gene involved in RNA processing, is identical to HEX2/REG1, a negative regulator in glucose repression.

The yeast RNA1 gene encodes a cytosolic protein that affects pre-tRNA splicing, pre-rRNA processing, the production of mRNA, and the export of RNA from the nucleus to the cytosol. In an attempt to understand how the RNA1 protein affects such a diverse set of processes, we sought second-site suppressors of a mutation, rna1-1, of the RNA1 locus. Mutations in a single complementation group were obtained. These lesions proved to be in the same gene, SRN1, identified previously in a search for second-site suppressors of mutations that affect the removal of intervening sequences from pre-mRNAs. The SRN1 gene was mapped, cloned, and sequenced. DNA sequence analysis and the phenotype of disruption mutations showed that, surprisingly, SRN1 is identical to HEX2/REG1, a gene that negatively regulates glucose-repressible genes. Interestingly, SRN1 is not a negative regulator of RNA1 at the transcriptional, translational, or protein stability level. However, SRN1 does regulate the level of two newly discovered antigens, p43 and p70, one of which is not glucose repressible. These studies for the first time link RNA processing and carbon catabolite repression.

Amino Acid Sequence↗
PubMed2004

Expression of the promoter for the maltogenic amylase gene in Bacillus subtilis 168.

An additional amylase, besides the typical alpha-amylase, was detected for the first time in the cytoplasm of B. subtilis SUH4-2, an isolate from Korean soil. The corresponding gene (bbmA) encoded a maltogenic amylase (MAase) and its sequence was almost identical to the yvdF gene of B. subtilis 168, whose function was unknown. Southern blot analysis using bbmA as the probe indicated that this gene was ubiquitous among various B. subtilis strains. In an effort to understand the physiological function of the bbmA gene in B. subtilis, the expression pattern of the gene was monitored by measuring the beta-galactosidase activity produced from the bbmA promoter fused to the amino terminus of the lacZ structural gene, which was then integrated into the amyE locus on the B. subtilis 168 chromosome. The promoter was induced during the mid-log phase and fully expressed at the early stationary phase in defined media containing beta-cyclodextrin (beta-CD), maltose, or starch. On the other hand, it was kept repressed in the presence of glucose, fructose, sucrose, or glycerol, suggesting that catabolite repression might be involved in the expression of the gene. Production of the beta-CD hydrolyzing activity was impaired by the spo0A mutation in B. subtilis 168, indicating the involvement of an additional regulatory system exerting control on the promoter. Inactivation of yvdF resulted in a significant decrease of the beta-CD hydrolyzing activity, if not all. This result implied the presence of an additional enzyme(s) that is capable of hydrolyzing beta-CD in B. subtilis 168. Based on the results, MAase encoded by bbmA is likely to be involved in maltose and beta-CD utilization when other sugars, which are readily usable as an energy source, are not available during the stationary phase.

Amino Acid Sequence↗
PubMed1976

Cis-dominant regulatory mutations affecting the formation of glucose-repressible alcohol dehydrogenase (ADHII) in Saccharomyces cerevisiae.

The formation of ADHII in Saccharomyces cerevisiae is regulated by carbon catabolite repression. There are two genes involved in the formation of ADHII: ADR2, the structural gene as identified by electrophoretic variants and ADR1, possibly a regulatory gene. A new genetic element involved in the regulation of ADHII was identified by three allelic mutants insensitive to strong glucose repression. They were called ADR3c (wild type designation ADR3) and found to be tightly linked to the structural gene, ADR2. The alcohol dehydrogenase found in ADR3c mutants could not be distinguished electrophoretically from the ADHII of the glucose-sensitive wild type, ADR3. Dominance relations between ADR3c and ADR3 were established in diploids heterozygous for ADR3 and the two alleles of ADR2 (ADR2-S: slow ADHII, ADR2-F: fast ADHII). During growth on 10% glucose, an ADR3c adr2-F/ADR3 ADR2-Sheterozygous diploid formed only the fast ADHII variant wheras an ADR3c ADR2-S/ADR3 ADR2-F heterozygote produced only the slow form. This was taken as evidence of the cis-dominance of all ADR3c alleles. The cis-effect of ADR3c was also demonstrated in glucose-derepressed diploids. The ADR3c mutations do not only cause glucose-insensitive ADHII frmation, but also reduce the activity of the adjacent structural gene during derepression. Thus ADR3c alleles were considered to be controlling site mutations. No pleiotropic effects were observed on the formation of enzymes related to the function of ADHII. An adr1 ADR2 ADR3 single mutant did not form ADHII. In contrast to this, an adr1 ADR2 ADR3c double mutant formed ADHII at a similar level as double mutant formed ADHII at a similar level as an ADR1 ADR2 ADR3c mutant. This showed that ADR3c was epistatic over adr1 (previously suggested as a positive regulatory gene). From this it was concluded that ADR1 is the fact a positive regulatory gene the function of which is required for the expression of the structural gene for ADHII, ADR2. ADR3 is the controlling site for the structural gene ADR2. Mutations at this site, ADR3c, alleviate the requirement for the ADR2 gene product. Adr3c is discussed as a promotor or operator site.

Alcohol Oxidoreductases↗
PubMed1988

Sequence and organization of pobA, the gene coding for p-hydroxybenzoate hydroxylase, an inducible enzyme from Pseudomonas aeruginosa.

The only recognized gene for the metabolism of p-hydroxybenzoate in Pseudomonads (pobA) has been isolated from Pseudomonas aeruginosa to provide the DNA for mutagenesis studies of the protein product, p-hydroxybenzoate hydroxylase. Since pobA is induced by p-hydroxybenzoate to produce large amounts of enzyme, its regulation in P. aeruginosa is significant. The nucleotide sequence of pobA is presented with the derived amino acid (aa) sequence, which has only two substitutions compared to the amino acid sequence obtained from the enzyme from P. fluorescens. The derived amino acid sequence predicts that the enzyme is a single polypeptide of 394 aa residues and contains one molecule of FAD. The complete structure of the protein from P. aeruginosa can be derived by analogy from the published structure of the protein from P. fluorescens. Transcription mapping was used to determine that there is one site for the initiation of mRNA synthesis in P. aeruginosa. The presence of a putative operator in the sequence suggests primary regulation by a repressor protein which binds p-hydroxybenzoate. The ribosome-binding site permits translation of the gene in Escherichia coli at levels comparable to its production in P. aeruginosa, but it produces no detectable product in E. coli under the influence of its own promoter sequence. The promoter does not conform to the common consensus sequence of E. coli promoters. The results have identified an apparent novel promoter for P. aeruginosa, which may reflect the presence of a sigma factor required for pobA induction. Repression of expression by glucose suggests a binding site in the sequence for catabolite repression.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1997

Contacts between Bacillus subtilis catabolite regulatory protein CcpA and amyO target site.

Catabolite control protein A (CcpA) is a global regulatory protein involved in catabolite repression and glucose activation in Gram-positive bacteria. cis -Acting DNA sequences, catabolite response elements ( cre s), involved in this regulatory system contain a 14 base pair (bp) region of dyad symmetry. CcpA, a repressor of the Lac I family, has been shown to bind specifically to cre s. To better understand cre recognition by CcpA, we have focused on the interaction between CcpA and the amyE cre , called amyO, which is located at the transcription start site of the alpha-amylase gene. DNA-protein complexes were probed with dimethylsulfate (DMS) and N -ethylnitrosourea (EtNU) to identify guanines and phosphates that participate in complex formation. Interaction between amyO and CcpA visualized through methylation protection and interference showed that CcpA contacts guanine residues at the outer bounds of amyO with higher affinity than near the dyad axis. From ethylation interference studies, it was found that CcpA contacts three phosphate groups at each end of amyO, and one or two phosphate groups near the dyad axis. Exonuclease III protection revealed that CcpA protects a 26 bp region centered around the dyad axis of amyO. The isolated N-terminal fragment still specifically bound to the sequence resembling the half sites of the amyO sequence. Considering these findings and the helical structure of B-DNA, our results suggest that each of the two monomers of the CcpA molecule contact the major groove in each half of the region of dyad symmetry and that the contacts are on the same face of the DNA helix, which is typical of bacterial repressor-operator interactions. However, the absence of strong contacts near the dyad axis by CcpA is in contrast to the situation with the gal repressor, another member of the Lac I family of repressors.

Bacillus subtilis↗
PubMed1990

Exoprotease Activity of Two Marine Bacteria during Starvation.

Exoprotease activity during 120 h of total energy and nutrient starvation was examined in two marine bacteria, Vibrio sp. strain S14 and Pseudomonas sp. strain S9. The activity was determined by spectrophotometric measurement of the rate of release of soluble color from an insoluble azure dye derivative of hide powder (hide powder azure). Starved cells of both strains (5 h for S14, and 4 or 24 h for S9) showed greater extracellular proteolytic activity than at the onset of starvation. The exoprotease activity of cells starved for longer periods of time then decreased, but was found to be present at significant levels throughout the starvation period studied (120 h). The accumulation of exoprotease activity in the bulk phase during starvation indicated that both strains constitutively excreted extracellular proteases. As deduced from experiments with chloramphenicol, de novo protein synthesis during starvation was required for the production and/or release of the exoproteases into the surrounding environment. The degradation of hide powder azure allowed an immediate increase in respiration rate, also by long-term-starved cells. This suggests that metabolic systems are primed to respond to the availability of substrates, allowing the cells to recover rapidly. The regulation of exoprotease activity was also studied and found to be different in the two strains. Casamino Acids repressed exoprotease activity in Pseudomonas sp. strain S9, whereas a mechanism similar to catabolite repression was found for Vibrio sp. strain S14 in that glucose repressed activity and cyclic AMP reversed this effect. The exoproteases appeared to be metalloproteinases because the addition of EDTA to cell-free starvation supernatants from both strains significantly inhibited the activity of the proteases.

Journal Article↗