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At least 19 recordsLinked to original sources
PubMed1977

[The alpha-methylglucoside transport in Escherichia coli K12 cells].

The transport of alpha-methylglucoside (MG) in the wild type cells of Escherichia coli K12 and the isogenic mutant strains, defective in the activity of phosphoenolpyruvate: sugar phosphotransferase system components was studied. It was shown that the enzyme IIB' in the absence of enzyme I and HPr is able to transport MG into the cells by a "facilitated" diffusion mechanism. Compounds which dissipate the energy of membrane protone potential such as NaN3, carbonylcyanide-m-chlorophenylhydrasone, dicyclohexylcarbodiimide, enhance the utilization of MG by the wild-type cells. However, the cells retaining intact enzyme IIB' but deficient in the phospho approximately HPr-generating system, were not sensitive to the action of poisons. The cells possessing the intact phospho HPr-generating system and inactive enzyme IIB' are also unaffected by the poisons. It seems that these results do not confirm the hypothesis of the direct delta mu H+ involvement in the regulation of transmembrane phosphorylation. The hypothesis is postulated that the energy metabolism inhibitors influence the phosphatase activity of factor III of the phosphotransferase system. The present data are well explained by this hypothesis.

Biological Transport↗
PubMed1976

Effects of colicins K and E1 on the glucose phosphotransferase system.

1. Glycerol-grown cells of Escherichia coli and its mutant uncA, treated with colicin E1 or K, exhibited a several-fold higher level of alpha-methylglucoside uptake than untreated cells. This stimulation was independent of the carbon source present during the uptake test. In a mutant strain that has elevated levels of alpha-methylglucoside accumulation the addition of colicin E1 or carbonylcyanide m-chlorophenylhydrazone (CCCP) did not further enhance the uptake. 2. Colicins K and E1 decreased the apparent Km for alpha-methylglucoside uptake significantly and increased the V about twofold. The exit of the glucoside was severely inhibited by the colicins. 3. In the presence of colicins, alpha-methylglucoside is still accumulated via the phosphoenolpyruvate-phosphotransferase system since no accumulation or phosphorylation occurs in an enzyme I mutant. The colicins increased the relative intracellular concentration of phosphorylated alpha-methylglucoside, possibly by inhibiting the dephosphorylation reaction, and caused an excretion of this compound. 4. The results are interpreted as indicating that energization of the membrane has an inhibitory effect on the phosphotransferase system. Possible modes of action are discussed.

Biological Transport↗
PubMed1977

Effect of the petite mutation on maltose and alpha-methylgucoside fermentation inSaccharomyces cerevisiae.

Several hundred petite mutants were isolated from yeast strains of different genotype to examine the effect of the petite mutation on maltose and alpha-methylglucoside fermentation. In most cases petite mutants isolated retain the ability to ferment maltose and alpha-methylglucoside, although at a slower rate. In one strain (1403-7A), however, the ability to ferment alpha-methylglucoside is completely lost in all petite mutants isolated from this strain. It is suggested that mitochondrial factors may be involved in the utilization of alpha-methylglucoside in strain 1403-7A.

Erythromycin↗
PubMed1978

Significance of the inactivation of transport in thermal death of Escherichia coli.

Cells of Escherichia coli ML308-225, harvested from the exponential phase, were heated in 50 mM potassium phosphate, and the loss in viability and inability to transport lactose, proline, and alpha-methylglucoside was compared. After cells were heated at 48 degrees C for 15 min, there was a 16% loss in viability and a similarly small reduction in the steady-state accumulation of lactose at 25 degrees C. The initial rates of lactose and proline transport were severely inhibited by heating at either 48 or 50 degrees C, but substantial recovery occurred within 5 to 7 min at 25 degrees C. Heating at 50 degrees C for 15 min caused an 86% loss in viability, but only a 53% decrease in the steady-state accumulation of lactose and only a 24% reduction in the initial rate of alpha-methylglucoside uptake. Twice as much alpha-methylglucoside was accumulated at 50 degrees C as at 25 degrees C. Although alpha-methylglucoside phosphate leaked from the cells at 50 degrees C, the concentration retained within the cells was about 500 times that externally, when only about 14% of the cells were viable. Overall, these results indicate that cells made nonviable by heating at 50 degrees C still have significant membrane integrity.

Biological Transport, Active↗
PubMed1976

Involvement of the glucose enzymes II of the sugar phosphotransferase system in the regulation of adenylate cyclase by glucose in Escherichia coli.

The nature of the interaction of glucose with toluene-treated cells of Escherichia coli leading to inhibition of adenylate cyclase was examined by the use of analogues. Those analogues with variations of the substituents about carbon atoms 1 or 2 (e.g. alpha-methylglucoside or 2-deoxyglucose) are inhibitory, and they are also substrates of the phosphoenolpyruvate-dependent sugar phosphotransferase system. Analogues with changes in other parts of the molecule (e.g. 3-O-methylglucose or galactose), L-glucose and several disaccharides and pentoses, do not inhibit adenylate cyclase and are not substrates of the phosphotransferase system. This correlation suggests some functional relationship between the adenylate cyclase and phosphotransferase systems. Further studies were done with mutants defective in glucose enzymes II of the phosphotransferase system (designated GPT and MPT); these two activities are measured by phosphorylation of alpha-methyl-glucoside and 2-deoxyglucose, respectively. The wild-type parent phosphorylates both analogues, and both inhibit adenylate cyclase. In the GPT- mutant, alpha-methylglucoside does not inhibit adenylate cyclase and is not phosphorylated, while 2-deoxyglucose is inhibitory and phosphorylated. In the GPT- MPT- double mutant, adenylate cyclase activity is present, but neither alpha-methylglucoside nor 2-deoxyglucose inhibits adenylate cyclase, and neither sugar is phosphorylated. These studies demonstrate that glucose inhibition of adenylate cyclase in toluene-treated cells requires an interaction of this sugar with either the GPT or mpt enzyme II of the phosphotransferase system.

Adenylyl Cyclases↗
PubMed1978

Insulin action on Escherichia coli. Regulation of the adenylate cyclase and phosphotransferase enzymes.

Insulin on Escherichia coli was studied using wild type E. coli B/r and K12 strains and a number of phosphoenolpyruvate phosphotransferase mutants. In vivo, the effects of insulin on the differential rate of tryptophanase synthesis, the rate of alpha-methylglucoside uptake and the rate of growth on glucose were determined in E. coli B/r. In vitro, the effect of insulin on the adenylate cyclase and the phosphotransferase activities was determined using toluenized cell preparations of E. coli B/r, E. coli K12 and phosphotransferase mutant strains. The specificity of insulin action on E. coli was determined using glucagon, vasopressin and somatropin as well as insulin antisera. Results show the specific action of insulin on E. coli, inhibiting tryptophanase induction and adenylate cyclase activity, while stimulating growth on glucose and uptake and phosphorylation of alpha-methylglucoside.

Adenylyl Cyclases↗
PubMed1979

A kinetic study of the interactions between amino acids and monosaccharides at the intestinal brush-border membrane.

1. The influx of amino acids into guinea-pig intestinal rings in vitro is inhibited by monosaccharides, and that of monosaccharides by amino acids. Two hypotheses have been proposed to account for these heterologous interactions. According to the first, the cis hypothesis, there is an allosteric interaction between substrates binding to separate but related sites at the outer face of the brush-border membrane matrix. In contrast, the trans hypothesis envisages the interaction to result from a partial dissipation of the electrochemical sodium gradient due to the cotransport of each substrate with sodium ions. 2. In an attempt to distinguish between the merits of the two hypotheses, we examined the kinetics of the inhibition of phenylalanine influx by two sugars of widely different affinities, galactose and beta-methylglucoside. Since beta-methylglucoside carries more sodium into the cell than galactose, the trans hypothesis would predict it to be the stronger inhibitor, but in fact the opposite result is found. 3. Equations were developed to describe the inhibitions in accordance with the cis hypothesis. The satisfactory agreement between experimental observations and theoretical predictions provides support for the applicability of the model. Further implications of the polyfunctional carrier model are discussed.

Allosteric Regulation↗
PubMed1975

Altered hexose transport and salt sensitivity in cyclic adenosine 3',5'-monophosphate-deficient Escherichia coli.

A cyclic adenosine 3',5'-monophosphate (cAMP)-deficient mutant strain of Escherichia coli K-12 was studied to determine the effect this cyclic nucleotide has on the overall growth and metabolism of this organism. Deficient cells were found to be more susceptible to growth inhibition by salts than were their cAMP-sufficient counterparts. The deficient cells transported alpha-methylglucoside by passive diffusion, whereas the parental cells or mutant cells grown in the presence of exogenous cAMP were able to take up alpha-methylglucoside by the normal active transport process. When viewed together with earlier studies conducted on cAMP-deficient cells, these findings support the view that cAMP plays a key role in regulating the construction and operation of the E. coli membrane system.

Ammonium Chloride↗
PubMed1977

The absorption of protons with alpha-methyl glucoside and alpha-thioethyl glucoside by the yeast N.C.Y.C. 240. Evidence against the phosphorylation hypothesis.

1. When yeast N.C.Y.C. 240 was grown with maltose in a complex medium based on yeast extract and peptone, washed cell preparations fermented alpha-methyl glucoside much more slowly than maltose. 2. The yeast absorbed alpha-methyl[14C]glucoside from a 10mM solution in the presence of antimycin and iodoacetamide, producing [14C]glucose, which accumulated outside the cells. The yeast itself contained hexose phosphates, trehalose, alpha-methyl glucoside and other products labelled with 14C, but no alpha-methyl glucoside phosphate. 3. About 1 equiv. of protons was absorbed with each equivalent of alpha-methylglucoside, and 1 equiv. of K+ ions left the yeast. 4. alpha-Thioethyl glucoside was also absorbed along with protons. Studies by g.l.c. showed that the yeast concentrated the compound without metabolizing it. 5. The presence of trehalose, sucrose, maltose, L-sorbose, glucose or alpha-phenyl glucoside in each case immediately stimulated proton uptake, whereas fructose, 3-O-methylglucose and 2-deoxyglucose failed to do so. 6. The observations support the conclusion that alpha-thioethyl glucoside, alpha-methyl glucoside and maltose are substrates of one or more proton symports, whereas they seem inconsistent with the notion that the absorption of alpha-methyl glucoside involves the phosphorylation of the carbohydrate [Van Stevenick (1970) Biochim. Biophys. Acta 203, 376-384].

Carbohydrate Metabolism↗
PubMed1976

Grouping antigens of four Lactobacillus species and their characteristics.

Antigenic analyses of Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus brevis and Lactobacillus buchneri were carried out by double immunodiffusion in agar. Antigens were extracted from whole cells and cell wall preparations with cold trichloroacetic acid. Most strains of the four species possessed antigen 9 in their cell walls. Another antigen, antigen 10, was found in the cell walls of all the strains of L. brevis and L. buchneri, and in some strains of L. lactis, but not in L. bulgaricus. Fractionation of the antigens was attempted using the cell wall extracts of L. lactis L-10 with only antigen 9 and of L. brevis X-1 with both antigens 9 and 10. The partially purified fractions of antigen 9 and of the complex of antigens 9 and 10 were obtained by zone electrophoresis. However, antigen 10 from the complex could not be separated by the same method or gel filtration on Sephadex G-100 since the two antigens 9 and 10 of the complex always behaved together. The fraction of antigen 9 consisted almost entirely of glycerol and glucose as sugar components, the molar ratio being 2: 1. The complex of antigens 9 and 10 also consisted of the same sugars, and the molar ratio of glycerol: glucose was 4: 1. Inhibition tests indicated that the immunodominant component of antigen 9 was a-methylglucoside (glucose), and most probably the determinant is a glycosylated glycerol teichoic acid. It was considered that the determinant of antigen 10 is a glycerol teichoic acid although glucosamine and galactosamine inhibited effectively the reaction between antigen 10 and its antibody.

Antigens, Bacterial↗
PubMed1977

Regulation of staphylococcal enterotoxin B.

The effect of glucose and the glucose analogues 2-deoxyglucose and alpha-methyl-glucoside on the synthesis and regulation of staphylococcal enterotoxin B was examined. The attenuating effect of glucose on staphylococcal enterotoxin B synthesis was observed. However, when this effect was examined with analogues of glucose, contradictory responses were seen. alpha-Methylglucoside had a slight stimulatory effect on enterotoxin production and other extracellular proteins, whereas 2-deoxyglucose markedly inhibited enterotoxin production. beta-hemolysin and staphylococcal nuclease were also inhibited by 2-deoxy glucose but the synthesis of nuclease could be rescued by the addition of glucose to 2-deoxyglucose-containing cultures. Enterotoxin and beta-hemolysin synthesis were not subject to glucose rescue. The cells used in this study were permeable to cyclic 3',5'-adenosine monophosphate, but the addition of this compound did not reverse glucose repression or 2-deoxyglucose inhibition of enterotoxin B synthesis. We conclude from these data that the regulation of enterotoxin is not under catabolite control as previously reported.

Cyclic AMP↗
PubMed1977

Control of ribosome synthesis in Escherichia coli: analysis of an energy source shift-down.

The rate of ribosome synthesis and accumulation in Escherichia coli during the transition after an energy source shift-down was analyzed. The shift was imposed on cultures of stringent and relaxed strains growing in glucose minimal medium by the addition of the glucose analogue alpha-methylglucoside. In the stringent strain, ribosome synthesis was almost instantaneously reduced after the shift, whereas the relaxed strain exhibited a more gradual response. The rate of messenger ribonucleic acid (mRNA) synthesis was affected similarly, though to a smaller extent. A comparison of the rates of synthesis and accumulation of ribosomal RNA (rRNA) and ribosomal proteins showed that far more ribosomal components were synthesized after the shift than were accumulated, indicating that a substantial part of the rRNA made after the shift was unstable. A new method was used to measure relative rates of rRNA synthesis and to estimate the transcription time for the rRNA operon under different conditions. In steady states of growth with growth rates ranging from 0.75 to 2.3 doublings/h, as well as during the transition after a shift-down, the transcription time of the rRNA operon was constant. The rate of synthesis of rRNA correlated during this transition - in contrast to the rate of accumulation (M. T. Hansen et al., J. Bacteriol. 122: 585-591, 1975) - with the ppGpp pool in the same way as has been observed during partial amino acid starvation.

Bacterial Proteins↗
PubMed1979

Amino acid and sugar transport in Escherichia coli (ColIb) during abortive infection by bacteriophage T5.

T5 bacteriophage cannot replicate in Escherichia coli containing the colicinogenic factor ColIb. We show that active transport of proline and glutamine begins to decline at about 10 min after infection, the same time at which macromolecular synthesis stops during abortive infection. Uptake of alpha-methylglucoside is stimulated, however, and this change is evident even by 5 min after infection. These changes in membrane function do not occur during infections that are productive because of mutations on the plasmid or phage. The results suggest that the abortive infection is caused by membrane depolarization.

Amino Acids↗
PubMed1977

The electrochemical proton gradient and phenylalanine transport in Escherichia coli irradiated with near-ultraviolet light.

Irradiation of Escherichia coli with near-ultraviolet (near-UV) light diminished the electrochemical proton gradient and the accumulation of L-phenylalanine. Inhibitors known to collapse the proton gradient and the comparison of two techniques measuring the electrical potential substantiated the estimates made. At several fluences (doses), a linear relationship was observed between the phenylalanine gradient and the combined electrical and chemical potentials (the electrochemical proton gradient), suggesting a close coupling between them. However, additional effects of near-UV light on the phenylalanine permease were not discounted. The combined potentials provided sufficient energy for the observed accumulation of phenylalanine, assuming a proton to amino acid cotransport ratio of 1. An increase in membrane permeability did not contribute to the loss of phenylalanine transport, as shown by an increase in the rate and extent of alpha-methylglucoside uptake.

Amino Acids↗
PubMed1977

The effect of proflavine on pyruvate kinase I of Escherichia coli B.

Proflavine (PF) inhibited glucose use in sensitive but not resistant Escherichia coli B. Glucose transport (as measured by alpha-methylglucoside accumulation) was only partly inhibited by PF concentration that completely blocked glucose use. Fructose 1,6-diphosphate-(FDP)-regulated pyruvate kinase (PK1) (EC 2.7.1.40), the only glycolytic enzyme affected by PF, was completely inhibited by a dye concentration of 0.8 mM. The inhibition curve for PF was sigmoidal, suggesting that PF was acting as an allosteric inhibitor. PF increased the K 1/2 for phosphoenolpyruvate (PEP) and lowered the V; however, it had no effect on the Hill number for PEP. PF inhibition was partially reversed by FDP but not by cyclic AMP, AMP, ATP, fuctose 6-phosphate, or dithiothreitol. Studies with a variety of acridines indicated that those substituted at the 3-position are the most effective inhibitors and also that hydrophobic interactions may be involved in PF inhibition of PK I. PK I for E. coli B/Pr was also strongly inhibited by PF, indicating that PF resistance does not lie at the level of this enzyme. Ribose-5-phosphate-regulated pyruvate kinase (EC 2.7.1.40) was much less sensitive that PK I to the inhibitory effects of PF. A role for PF as a molecular probe for PK I has been proposed.

Acridines↗
PubMed1977

[Catabolyte inhibition of lactate transport in Escherichia coli].

E. coli cells growing on the medium containing glucose and lactate do not utilize lactate. One reason of preferential utilization of glucose is catabolite inhibition of lactate transport. It is necessary for glucose to penetrate into the cell to inhibit lactate transport. Besides glucose the inhibition of the lactate transport is also caused by fructose and by non-metabolized analogue of glucose--alpha-methylglucoside.

Biological Transport↗