Biomedical subjects

M Hecker

Publications and source records attributed to M Hecker.

At least 127 records · Page 7Linked to original sources

PubMed1996

General and oxidative stress responses in Bacillus subtilis: cloning, expression, and mutation of the alkyl hydroperoxide reductase operon.

The AhpC subunit of the Bacillus subtilis alkyl hydroperoxide reductase was identified as a general stress protein induced in response to heat or salt stress or after entry of the organism into the stationary phase. The ahp operon, encoding the two subunits AhpC and AhpF, was cloned and localized between the gntRKPZ operon and the bglA locus. Two-dimensional gel analyses revealed an especially strong induction of AhpC and AhpF in cells subjected to oxidative stress. Transcriptional studies showed a 3- to 4-fold induction of ahp mRNA after heat or salt stress or starvation for glucose and a 20-fold induction by oxidative stress, thus confirming the protein induction data for AhpC and AhpF. Stress induction occurred at a sigmaA-dependent promoter that overlaps with operator sites similar to the per box. Compared with the wild type, the ahpC mutant was resistant to hydrogen peroxide because of the derepression of the peroxide regulon (N. Bsat, L. Chen, and J. D. Helmann, J. Bacteriol. 178:6579-6586, 1996) but more sensitive to cumene hydroperoxide (CHP) during exponential growth. In contrast, stationary-phase wild-type and ahpC mutant cells displayed complete resistance to treatment with 1 mM CHP. Moreover, a sigmaB mutant was found to be extremely sensitive to CHP during vegetative growth and in stationary phase, which indicates that sigmaB-dependent general stress proteins are involved in the protection of cells against oxidative stress.

Amino Acid Sequence↗

PubMed1996

LicT, a Bacillus subtilis transcriptional antiterminator protein of the BglG family.

Gene licS of Bacillus subtilis encodes an excreted Beta-1,3-1,4-endoglucanase necessary for lichenan utilization. Upstream of licS we found a gene (termed licT) together with its promoter which encodes a transcriptional antiterminator of the BglG family. Genes licT and licS are separated by a palindromic sequence (lic-t) reminiscent of transcriptional terminators recognized by the antiterminator proteins of the BglG family. The LicT protein can prevent termination at terminator lic-t and also at terminator t2 of the Escherichia coli bgl operon and BglG prevents termination at lic-t. The role of LicT in licS regulation by preventing termination at its terminator lic-t appears to be limited since expression of licS is inducible only two- to threefold. This limited regulation is mainly due to a high basal level of licS expression which can in part be attributed to the presence of a second promoter preceding licS and located downstream of lic-t. However, disruption of gene licT leads not only to loss of inducibility of licS but also to loss of growth on lichenan or on its degradation products, indicating its stringent role in beta-glucan utilization.

Amino Acid Sequence↗

PubMed1996

Transcriptional analysis of bglPH expression in Bacillus subtilis: evidence for two distinct pathways mediating carbon catabolite repression.

In Bacillus subtilis, aryl-beta-glucosides such as salicin and arbutin are catabolized by the gene products of bglP and bglH, encoding an enzyme II of the phosphoenolpyruvate sugar-phosphotransferase system and a phospho-beta-glucosidase, respectively. These two genes are transcribed from a single promoter. The presence of a transcript of about 4,000 nucleotides detected by Northern (RNA) blot analysis indicates that bglP and bglH are part of an operon. However, this transcript is only present when cells are grown in the presence of the inducing substrate, salicin. In the absence of the inducer, a transcript of about 110 nucleotides can be detected, suggesting that transcription terminates downstream of the promoter at a stable termination structure. Initiation of transcription is abolished in the presence of rapidly metabolized carbon sources. Catabolite repression of bglPH expression involves the trans-acting factors CcpA and HPr. In a ccpA mutant, transcription initiation is relieved from glucose repression. Furthermore, we report a catabolite responsive element-CcpA-independent form of catabolite repression requiring the ribonucleic antiterminator-terminator region, which is the target of antitermination, and the wild-type HPr protein of the phosphotransferase system. Evidence that the antitermination protein LicT is a crucial element for this type of regulation is provided.

Bacillus subtilis↗

PubMed1996

Intracellular pH and tyrosine phosphorylation but not calcium determine shear stress-induced nitric oxide production in native endothelial cells.

Signalling pathways determining the shear stress-induced production of NO from endothelial cells in situ were investigated using a bioassay system in which shear stress was increased by inducing vasoconstriction in an endothelium-intact donor segment (rabbit iliac artery) while maintaining a constant luminal perfusion rate. Shear stress-induced NO production, as assessed by changes in the tone of a preconstricted endothelium-denuded detector ring, was biphasic and consisted of an initial transient (20- to 25-minute) Ca(2+)-dependent phase followed by a Ca(2+)-independent plateau phase, which was maintained as long as the donor segment remained constricted. Stretching the donor segments to their in vivo length abolished the initial phase without affecting the plateau phase of NO release. Inhibition of the Na(+)-H+ exchanger using HOE 694 elicited an intracellular acidification which attenuated shear stress-induced NO production. The specific protein kinase C inhibitor, Ro 31-8220, was without effect, whereas the unspecific inhibitors, staurosporine and calphostin C, abolished the shear stress-induced production of NO. Erbstatin A, a tyrosine kinase inhibitor, attenuated the shear stress-induced tyrosine phosphorylation of specific cellular proteins and abrogated the associated NO production. In summary, these data indicate that shear stress activates the NO synthase at basal levels of [Ca2+]i via a mechanotransduction cascade that involves tyrosine phosphorylation and can be modulated by changes in pHi. The apparent fundamental alteration of the endothelial NO synthase under shear stress that renders its maintained activation independent of an increase in [Ca2+]i is probably the consequence of a change in the enzyme microenvironment.

Animals↗

PubMed1995

sigma B-dependent regulation of gsiB in response to multiple stimuli in Bacillus subtilis.

The expression of the gsiB gene of Bacillus subtilis in response to a wide variety of stress conditions was analysed, and the results provide evidence that gsiB is subject to a sigma B-dependent regulation. Primer extension experiments established identical start points for gsiB transcription during growth and after the induction by heat shock, salt or ethanol stress, and glucose limitation. The sequence upstream of the transcription start point shows great similarity to the sequences of sigma B-dependent promoters of B. subtilis. sigma B was absolutely required for the increase in gsiB mRNA level and in the synthesis rate of GsiB in response to various stimuli. Measurements of the ATP pool indicated that changes in the level of ATP might be one of the signals that regulate the activity of sigma B in B. subtilis.

Adenosine Triphosphate↗

PubMed1995

Characterization of the stable L-arginine-derived relaxing factor released from cytokine-stimulated vascular smooth muscle cells as an NG-hydroxyl-L-arginine-nitric oxide adduct.

The nature of an L-arginine-derived relaxing factor released from vascular smooth muscle cells cultured on microcarrier beads and stimulated for 20 h with interleukin 1 beta was investigated. Unlike the unstable relaxation elicited by authentic nitric oxide (NO) in a cascade superfusion bioassay system, the effluate from vascular smooth muscle cells induced a stable relaxation that was susceptible to inhibition by oxyhemoglobin. Three putative endogenous NO carriers mimicked this stable relaxing effect: S-nitroso-L-cysteine, low molecular weight dinitrosyl-iron complexes (DNICs), and the adduct of NG-hydroxy-L-arginine (HOArg) with NO. Inactivation of S-nitroso-L-cysteine by Hg2+ ions or trapping of DNICs with agarose-bound bovine serum albumin abolished their relaxing effects, whereas that of the vascular smooth muscle cell effluate remained unaffected. In addition, neither S-nitrosothiols nor DNICs were detectable in the effluate from these cells, as judged by UV and electron spin resonance (ESR) spectroscopy. The HOArg-NO adduct was instantaneously generated upon reaction of HOArg with authentic NO under bioassay conditions. Its pharmacological profile was indistinguishable from that of the vascular smooth muscle cell effluate, as judged by comparative bioassay with different vascular and nonvascular smooth muscle preparations. Moreover, up to 100 nM HOArg was detected in the effluate from interleukin 1 beta-stimulated vascular smooth muscle cells, suggesting that sufficient amounts of HOArg are released from these cells to spontaneously generate the HOArg-NO adduct. This intercellular NO carrier probably accounts for the stable L-arginine-derived relaxing factor released from cytokine-stimulated vascular smooth muscle cells and also from other NO-producing cells, such as macrophages and neutrophils.

Acetylcholine↗

PubMed1995

Increase in serum NG-hydroxy-L-arginine in rats treated with bacterial lipopolysaccharide.

Aortic rings isolated from rats 4 h after an injection i.p. of 30 mg/kg Escherichia coli lipopolysaccharide showed a marked hyporeactivity to noradrenaline. This effect was paralleled by an increase in the level of nitrite/nitrate in the serum of lipopolysaccharide-treated rats, indicative of an enhanced nitric oxide (NO) synthase activity. Most important, however, the serum concentration of the NO synthase intermediate, NG-hydroxy-L-arginine, was also markedly elevated from 3.7 to 15.8 microM. Circulating NG-hydroxy-L-arginine may thus represent a sensitive and specific marker of NO synthase activity in vivo.

Amino Acid Oxidoreductases↗

PubMed1995

Inhibition of arginase by NG-hydroxy-L-arginine in alveolar macrophages: implications for the utilization of L-arginine for nitric oxide synthesis.

The hypothesis was investigated that the nitric oxide (NO) synthase intermediate, NG-hydroxy-L-arginine (HOArg), is an arginase inhibitor in rabbit or rat alveolar macrophages. Exogenously applied HOArg strongly inhibited the arginase activity present in these cells (IC50 > or = 15 microM), and attenuated L-[3H]arginine transport (IC50 > or = 500 microM) in rabbit alveolar macrophages. Moreover, up to 37 microM HOArg were detected in the conditioned medium, but not in the lysate, of rat alveolar macrophages exposed to bacterial lipopolysaccharide for 18 h. HOArg may thus be a potent endogenous arginase inhibitor in these cells which increases the availability of L-arginine for NO biosynthesis.

Amino Acid Oxidoreductases↗

PubMed1995

Kinin-mediated activation of endothelial no formation: possible role during myocardial ischemia.

Endothelial cells produce a variety of factors involved in the control of vascular tone, platelet activation and cell growth, one of the most important being nitric oxide (NO). Although continuously produced in response to fluid shear stress, the release of NO from these cells can be enhanced further by humoral stimuli, such as bradykinin. This is the result of a chain of complex intracellular events involving changes in Ca2+, pH and protein phosphorylation. Endothelial cells are also capable of synthesizing bradykinin from an endogenous source, the release of which is markedly enhanced under hypoxic conditions. The finding that ACE inhibitors promote the local accumulation of the peptide and increase its efficacy at the receptor level may partly explain the potent anti-ischemic and cardioprotective effects of these drugs.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1995

Volatile and intravenous anesthetics selectively attenuate the release of endothelium-derived hyperpolarizing factor elicited by bradykinin in the coronary microcirculation.

In addition to nitric oxide (NO) and prostacyclin (PGI2) another endothelium-derived factor, which hyperpolarizes vascular smooth muscle cell via activation of K+ channels, contributes to the vasorelaxant effect of bradykinin in different vascular beds. Preliminary findings suggest that this endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilatation is attenuated by both volatile and intravenous anesthetics. Since EDHF may play an important role in the coronary microcirculation, we investigated the effects of isoflurane (2 vol.% equivalent to approximately 250 microM), etomidate (30 and 100 microM), phenobarbital (100 microM) and thiopental (30 and 100 microM) on the EDHF-mediated dilator response to bradykinin and on the endothelium-independent dilatation evoked by sodium nitroprusside (SNP) in the isolated saline-perfused rat heart (Langendorff preparation). None of the anesthetics tested affected the dilator response to bradykinin or SNP under basal conditions. However, following inhibition of NO and PGI2 formation with NG-nitro-L-arginine (100 microM) and diclofenac (1 microM) respectively, isoflurane, etomidate and thiopental, but not phenobarbital, significantly attenuated the NO/PGI2-independent, i.e. EDHF-mediated dilator response to bradykinin, while the vasorelaxant effect of SNP remained unaffected. Isoflurane, etomidate and thiopental, but not phenobarbital, display cytochrome P450-inhibiting properties, suggesting that these anesthetics impair the cytochrome P450-dependent synthesis of EDHF in the coronary microcirculation.

Analysis of Variance↗

PubMed1995

Characterization of furoxans as a new class of tolerance-resistant nitrovasodilators.

The vasodilator effects of C92-4609 (4-hydroxymethyl-furoxan-3-carboxamide, CAS 1609), C92-4678(4-phenyl-furoxan-3-carboxylic acid (pyridyl-3-yl-methyl)-amide), C92-4679 (3-phenyl-furoxan-4-carboxylic acid (pyridyl-3-yl-methyl)-amide) and C93-4759 (3-hydroxymethyl-furoxan-4-carboxamide) were studied in the isolated rabbit femoral artery and jugular vein. All furoxans were potent vasodilators in the femoral artery (EC50 0.1-50 microM), while they were less potent in the jugular vein by at least one order of magnitude. Apart from C92-4679, the vasodilatory potency of the furoxans correlated well with their nitric oxide (NO)-releasing capacity which was estimated both by stimulation of purified soluble guanylyl cyclase activity and electron spin resonance spectroscopy with a trapping agent for NO. The hypothesis that furoxans stimulate soluble guanylyl cyclase in the smooth muscle by spontaneously releasing NO was supported by the marked attenuation of their vasodilator effect in the presence of oxyhaemoglobin (10 microM) or following treatment with methylene blue (30 microM). In contrast to earlier findings, NO release from these furoxans was not thiol-dependent, as demonstrated for C92-4609, the relaxant effect of which in the femoral artery was not altered in the presence of N-acetyl-L-cysteine (1 mM). Moreover the KCa+ channel inhibitor, tetrabutylammonium (3 mM), but not the KATP+ channel inhibitor, glibenclamide (3 microM), significantly attenuated the dilator response to C92-4679 in the femoral artery. Pretreatment of these segments with the cytochrome P450 inhibitor, SKF525a (30 microM), also reduced the C92-4679-induced relaxation in this vascular bed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Escherichia coli K12 relA strains as safe hosts for expression of recombinant DNA.

Most Escherichia coli K12 strains survive for a relatively long time outside the laboratory. Under the same conditions the isoallelic E. coli K12 relA mutants die faster because they lack the stringent response. The killing rate is increased by using a plasmid-encoded suicide system consisting of the phage T7 lysozyme gene driven by the E. coli alkaline phosphatase gene promoter (phoA). Cells containing this system were rapidly and effectively killed as soon as phosphate was made limiting. The combination of the chromosomal relA mutation and a conditional suicide system of this type provides an effective means of biological containment for recombinant E. coli strains.

Alkaline Phosphatase↗

PubMed1995

Inhalation anesthetics inhibit the release of endothelium-derived hyperpolarizing factor in the rabbit carotid artery.

BACKGROUND: Inhalation anesthetics may interfere with the synthesis or action of endothelium-derived vasoactive factors. We investigated the effects of desflurane, enflurane, halothane, isoflurane, and sevoflurane on the release of nitric oxide and endothelium-derived hyperpolarizing factor (EDHF) in the isolated endothelium-intact carotid artery of the rabbit. METHODS: Isolated segments of the carotid artery were suspended in Krebs-Henseleit solution (37 degrees C) and preconstricted with phenylephrine (1 microM). Relaxations caused by acetylcholine (ACh) (0.03-10 microM) or sodium nitroprusside (0.01-10 microM) were compared in the presence or absence of the nitric oxide synthase inhibitor NG-nitro-L-arginine (0.1 mM) in segments exposed to desflurane (8%), enflurane (2-4%), halothane (2-3.5%), isoflurane (2-4%), or sevoflurane (2%) as well as in NG-nitro-L- arginine-treated segments exposed to enflurane (2%) in combination with the KCa(+)-channel blocker tetrabutylammonium (0.3 mM) or the cytochrome P450 inhibitor clotrimazole (3 microM). RESULTS: Desflurane, enflurane, and sevoflurane selectively inhibited the ACh-induced release of EDHF. Halothane and isoflurane also weakly affected the nitric oxide-mediated relaxant response to ACh. The inhibitory effect of these two anesthetics on EDHF release was concentration-dependent. Relaxations induced by sodium nitroprusside were not inhibited by any of the anesthetics tested. Three structurally unrelated cytochrome P450 inhibitors clotrimazole (0.1 mM), metyrapone (1 mM), and SKF525a (proadifen, 0.1 mM) abolished the EDHF-mediated relaxation elicited by ACh. The pharmacologic profile of the inhibitory effect of enflurane on the release of EDHF closely resembled that of clotrimazole but not that of tetrabutylammonium. Moreover, all anesthetics inhibited the cytochrome P450-catalyzed O-dealkylation of 7-ethoxycoumarin by rabbit liver microsomes in a concentration-dependent manner. CONCLUSIONS: Inhalation anesthetics significantly attenuate the EDHF-mediated relaxant response to ACh in the rabbit carotid artery. This effect appears to be attributable to inhibition of the cytochrome P450-dependent synthesis of EDHF by the endothelium.

Acetylcholine↗

PubMed1995

Inhibition by N-acetyl-5-hydroxytryptamine of nitric oxide synthase expression in cultured cells and in the anaesthetized rat.

1. Induction of the calcium-independent isoform of nitric oxide (NO) synthase (iNOS) in various cell types has been implicated in the circulatory failure in experimental models of septic shock. Tetrahydrobiopterin (BH4) appears to be an essential co-factor for NO formation and therefore an inhibition of its biosynthesis represents a feasible therapeutic target. We have investigated the effects of an inhibitor of BH4 synthesis, N-acetyl-5-hydroxytryptamine (N-acetylserotonin, NAS), on the expression of iNOS in cultured macrophages and smooth muscle cells in vitro, and on the hypotensive response to bacterial lipopolysaccharide (LPS) in the anaesthetized rat in vivo. 2. NAS (0.01-5 mM) caused a concentration-dependent inhibition of the accumulation of nitrite in the conditioned medium of LPS/interferon-gamma (IFN gamma)-stimulated RAW 264.7 macrophages and interleukin-1 beta (IL-1 beta)-activated vascular smooth muscle cells (VSMC). This effect was paralleled by a similar decrease in the iNOS protein content of these cells, as determined by immunoblot analysis. 3. Pretreatment of RAW 264.7 macrophages with the BH4 precursor, dihydrobiopterin (BH2, 0.1 mM) did not restore nitrite formation in the presence of NAS (1 mM). 4. Intravenous administration of NAS (1 mg kg-1 min-1 for 30 min) in anaesthetized rats significantly reduced the fall in mean arterial blood pressure, restored the pressor response to noradrenaline (1 micrograms kg-1), and ameliorated the increase in plasma nitrite following exposure to LPS (10 mg kg-1). 5. NAS pretreatment also attenuated iNOS activity in lung homogenates, as determined by the conversion of radiolabelled L-arginine to L-citrulline, and partially restored the constrictor effect of noradrenaline in aortic rings isolated from LPS-treated rats. Moreover, NAS significantly reduced the rise in the plasma concentration of tumour necrosis factor alpha (TNFalpha) in response to LPS.6. These findings suggest that NAS inhibits the expression rather than the activity of iNOS in cultured macrophages and smooth muscle cells. This effect of NAS appears to be independent of the availability of BH4, but may be related to an attenuation of the release of TNFalpha following LPS administration, as shown in the anaesthetized rat. This mechanism may also account for the beneficial haemodynamic effect of NAS in our experimental model of endotoxaemia.

Anesthesia↗

PubMed1995

Selective inhibition by barbiturates of the synthesis of endothelium-derived hyperpolarizing factor in the rabbit carotid artery.

1. Several lines of evidence suggest that both volatile and intravenous anaesthetics may interfere with the synthesis and release of endothelium-derived vasoactive factors. We have investigated the effects of three different barbiturates on the release of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in phenylephrine (1 microM)-preconstricted, endothelium-intact ring segments of the rabbit carotid artery. The segments were pretreated with the cyclo-oxygenase inhibitor, diclofenac (1 microM), to prevent the formation of vasoactive prostanoids, such as prostacyclin (PGI2). 2. Acetylcholine (ACh) elicited a concentration-dependent relaxation (EC50 0.15 microM) in control segments which was not significantly different from the relaxant responses of segments pretreated with methohexitone (0.03-0.3 mM), phenobarbitone (0.1-0.3 mM) or thiopentone (0.1-0.3 mM). 3. Inhibition of NO synthesis with NG-nitro-L-arginine (0.1 mM) significantly reduced the maximum relaxant response to ACh from 96 to 40%. This NO/PGI2-independent relaxation appeared to be mediated by the release of EDHF, since it was strongly diminished in the presence of the K+Ca inhibitors, tetrabutylammonium (1-3 mM) and charybdotoxin (10 nM), following preconstriction with potassium calcium (40 mM) or removal of the endothelium. Thiopentone or methohexitone markedly attenuated the EDHF-mediated relaxant response to ACh, while phenobarbitone had no effect. The endothelium-independent relaxation elicited by sodium nitroprusside (0.01-10 microM), on the other hand, was only marginally affected by these anaesthetics. 4. The cytochrome P450 inhibitor, clotrimazole (3-100 microM), mimicked the inhibitory effect of thiopentone and methohexitone on the NO/PGI2-independent relaxant response to ACh. Moreover the cytochrome P450-catalyzed O-dealkylation of 7-ethoxycoumarin by rabbit liver microsomes was inhibited in the presence of thiopentone or methohexitone (0.3-1 mM), while phenobarbitone was without effect.5. These findings suggest that thiopentone and methohexitone selectively attenuate the EDHF-mediated relaxant response to ACh in the rabbit carotid artery, presumably by interfering with its synthesis from arachidonic acid via the cytochrome P450 epoxygenase pathway.

Acetylcholine↗

PubMed1995

A gene at 333 degrees on the Bacillus subtilis chromosome encodes the newly identified sigma B-dependent general stress protein GspA.

In Bacillus subtilis, general stress proteins (Gsps) are induced in response to different stresses (heat, salt, or ethanol) or after nutrient starvation. The majority of the genes for the Gsps are organized in a very large stationary-phase or stress regulon which is controlled by alternative sigma factor sigma B. The most striking spots on Coomassie-stained two-dimensional gels belong to GsiB and GspA, which are synthesized at extremely high levels in response to different stresses. Therefore, we determined the N-terminal protein sequence of GspA, which exhibited total identity to a hypothetical 33.5-kDa protein of B. subtilis encoded by open reading frame 2 (ipa-12d) in the sacY-tyrS1 intergenic region. The GspA-encoding gene gspA and the upstream and downstream regions were cloned with the aid of the PCR technique. By primer extension experiments, one sigma B-dependent promoter immediately upstream of the coding region was identified. A putative factor-independent terminator closely followed the coding region. By Northern (RNA) blot analysis, a 0.95-kb transcript was detected which indicates a monocistronic transcriptional unit. The gspA mRNA was strongly induced by different stimuli like heat or salt stress and starvation for glucose. Analysis of RNA isolated from a sigma B deletion mutant revealed that the transcription of gspA is sigma B dependent. Insertional inactivation of the B. subtilis chromosomal gspA gene confirmed that the gspA gene is not essential for either vegetative growth or growth under the influence of different stresses. In gspA mutant cells, the level of flagellin was increased severalfold over that in wild-type cells.

Amino Acid Sequence↗

PubMed1995

Separate mechanisms activate sigma B of Bacillus subtilis in response to environmental and metabolic stresses.

sigma B is a secondary sigma factor that controls the general stress response of Bacillus subtilis. sigma B-dependent transcription is induced by the activation of sigma B itself, a process that involves release of sigma B from an inhibitory complex with its primary regulator, RsbW. sigma B becomes available to RNA polymerase when RsbW forms a complex with an additional regulatory protein (RsbV) and, because of this, fails to bind sigma B. Using Western blot (immunoblot) analyses, reporter gene fusion assays, and measurements of nucleotide pool sizes, we provide evidence for two independent processes that promote the binding of RsbW to RsbV. The first occurs during carbon limitation or entry into stationary phase. Activation of sigma B under these circumstances correlates with a drop in the intracellular levels of ATP and may be a direct consequence of ATP levels on RsbW's binding preference. The second activation process relies on the product of a third regulatory gene, rsbU. RsbU is dispensable for sigma B activation during carbon limitation or stationary phase but is needed for activation of sigma B in response to any of a number of different environmental insults (ethanol treatment, salt or acid shock, etc.). RsbU, or a process dependent on it, alters RsbW binding without regard for intracellular levels of ATP. In at least some instances, the effects of multiple inducing stimuli are additive. The data are consistent with RsbW being a regulator at which distinct signals from separate effectors can be integrated to modulate sigma B activity.

Adaptation, Physiological↗

PubMed1995

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

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.

Arbutin↗