The bacterial phosphoenolpyruvate: sugar phosphotransferase system

Transport of D-beta-hydroxybutyrate across rat liver mitochondrial membranes

1. D-beta-hydroxybutyrate, a major ketone body, is produced or converted in mitochondria from various animal tissues. 2. It is an easy permeate anion of the inner mitochondrial membrane. However, its translocation is not a passive diffusion process since it is inhibited by pyruvate transport inhibitors like alpha-cyanocinnamate and derivatives. 3. This carrier mediated process is associated with proton movements. Besides, dicarboxylate anions strongly inhibit the penetration into mitochondria. 4. This is in agreement with the existence of a second transport process related to the dicarboxylate carrier.

Cloning and DNA sequence analysis of the wild-type and mutant cyclic AMP receptor protein genes from Salmonella typhimurium

The crp gene from Salmonella typhimurium, as well as two mutant adenylate cyclase regulation genes designated crpacr-3 and crpacr-4, were cloned into the EcoRI site of plasmid pUC8. Initially cloned on 5.6-kilobase fragments isolated from EcoRI digests of chromosomal DNA, these genes were further subcloned into the BamHI-EcoRI site of plasmid pBR322. When tested, Escherichia coli crp deletion strains harboring the clones regained their ability to pleiotropically ferment catabolite-repressible sugars. Also, the crpacr-containing strains displayed sensitivity to exogenous cyclic AMP (cAMP) when grown on eosin-methylene blue medium with xylose as the carbon source. The proteins encoded by the S. typhimurium wild-type and mutant crp genes were found to have similar molecular weights when compared with the wild-type cAMP receptor protein (CRP) from E. coli. DNA sequence analysis of the wild-type crp gene showed only a three-nucleotide difference from the E. coli sequence, suggesting little divergence of the crp gene between these organisms. The crpacr sequences, however, each contained single nucleotide changes resulting in amino acid substitutions at position 130 of the CRP. Based on the site at which these substitutions occur, the crpacr mutations are believed to affect CRP-cAMP interactions.

The phosphoenolpyruvate-dependent fructose-specific phosphotransferase system in Rhodopseudomonas sphaeroides. Energetics of the phosphoryl group transfer from phosphoenolpyruvate to fructose

Energy coupling to fructose transport in Rhodopseudomonas sphaeroides is achieved by phosphorylation of the membrane-spanning fructose-specific carrier protein, EFruII. The phosphoryl group of phosphoenolpyruvate is transferred to EFruII via the cytoplasmic component SF (soluble factor). The standard free enthalpy of hydrolysis of the two phosphorylated proteins has been estimated from isotope exchange measurements in chemical equilibrium. The delta G degrees for SF-P is -60.5 kJ/mol. The standard free enthalpy for hydrolysis of EII-P is -37.9 kJ/mol, but -45.2 kJ/mol when SF is still complexed to it, as in the overall reaction. Therefore the standard free enthalpy of hydrolysis of SF X EII-P is 70% of the standard free enthalpy of hydrolysis of P-enolpyruvate. The measurements reveal two regulation sites in the system. First, the phosphorylation of SF is inhibited by pyruvate when the concentration ratio of pyruvate/P-enolpyruvate becomes too high. Second, a low concentration of internal fructose prevents the phosphorylation of the carrier by the internal fructose-1-P pool when the concentration of the latter becomes too high or the phosphorylation rate by P-enolpyruvate too slow. Furthermore comparison of the isotope exchange and the overall phosphotransferase reaction kinetics leads to the conclusion that binding of fructose to the carrier is a slow step relative to the phosphoryl group transfer from EFruII to fructose.

Phosphoenolpyruvate-sugar phosphotransferase transport system of Streptococcus mutans: purification of HPr and enzyme I and determination of their intracellular concentrations by rocket immunoelectrophoresis

Enzyme I and HPr, the general proteins of the phosphoenolpyruvate-sugar phosphotransferase system, play a pivotal role in the control of sugar utilization in gram-negative and gram-positive bacteria. To determine whether growth conditions could modify the rate of biosynthesis of these proteins in Streptococcus mutans, we first purified to homogeneity enzyme I and HPr from S. mutans ATCC 27352. Using specific antibodies obtained against these proteins, we determined by rocket electrophoresis the intracellular levels of enzyme I and HPr in cells of S. mutans 27352 grown under various batch culture conditions and in a number of glucose-grown cells of other strains of S. mutans. HPr was purified by the procedure reported by Gauthier et al. (L. Gauthier, D. Mayrand, and C. Vadeboncoeur, J. Bacteriol. 160:755-763, 1984) and displayed a single band with a molecular weight of 6,650 when analyzed by sodium dodecyl sulfate-urea gel electrophoresis. Enzyme I was purified by DEAE-cellulose chromatography, affinity chromatography on an anti-Streptococcus salivarius column, and preparative electrophoresis. The protein migrated as a single band in native and denaturating gel electrophoresis. The subunit molecular weight of enzyme I determined by electrophoresis under denaturating conditions was 68,000. In gel filtration chromatography at 4 degrees C, the enzyme migrated as a 135,000- to 160,000-molecular-weight species, suggesting that enzyme I is a dimer. In double immunodiffusion experiments, antibodies against HPr reacted with several oral streptococci, Streptococcus lactis, Streptococcus faecium, and Lactobacillus casei, but not with Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Antibodies against enzyme I of S. mutans 27352 cross-reacted with enzyme I from all the other oral streptococci tested. No cross-reaction was observed with other gram-positive and gram-negative bacteria. The levels of enzyme I and HPr determined by rocket electrophoresis in S. mutans 27352 varied at the most by twofold, depending on the growth conditions. Glucose-grown cells of other S. mutans strains contained levels of enzyme I and HPr which were similar to those found in S. mutans 27352.

The functional significance of glucose dehydrogenase in Klebsiella aerogenes

In order to assess the functional significance of the quinoprotein glucose dehydrogenase recently found to be present in K+ -limited Klebsiella aerogenes, a broad study was made of the influence of specific environmental conditions on the cellular content of this enzyme. Whereas high activities were manifest in cells from glucose containing chemostat cultures that were either potassium- or phosphate-limited, only low activities were apparent in cells from similar cultures that were either glucose-, sulphate- or ammonia-limited. With these latter two cultures, a marked increase in glucose dehydrogenase activity was observed when 2,4-dinitrophenol (1 mM end concentration) was added to the growth medium. These results suggested that the synthesis of glucose dehydrogenase is not regulated by the level of glucose in the growth medium, but possibly by conditions that imposed an energetic stress upon the cells. This conclusion was further supported by a subsequent finding that K+ -limited cells that were growing on glycerol also synthesized substantial amounts of glucose dehydrogenase. The enzyme was found to be membrane associated, and preliminary evidence has been obtained that it is located on the periplasmic side of the cytoplasmic membrane and functionally linked to the respiratory chain. This structural and functional orientation is consistent with glucose dehydrogenase serving as a low impedance energy generating system.

Influence of transport energization on the growth yield of Escherichia coli

The growth yields of Escherichia coli on glucose, lactose, galactose, maltose, maltotriose, and maltohexaose were estimated under anaerobic conditions in the absence of electron acceptors. The yields on these substrates exhibited significant differences when measured in carbon-limited chemostats at similar growth rates and compared in terms of grams (dry weight) of cells produced per mole of hexose utilized. Maltohexaose was the most efficiently utilized substrate, and galactose was the least efficiently utilized under these conditions. All these sugars were known to be metabolized to glucose 6-phosphate and produced the same pattern of fermentation products. The differences in growth yields were ascribed to differences in energy costs for transport and phosphorylation of these sugars. A formalized treatment of these factors in determining growth yields was established and used to obtain values for the cost of transport and hence the energy-coupling stoichiometries for the transport of substrates via proton symport and binding-protein-dependent mechanisms in vivo. By this approach, the proton-lactose stoichiometry was found to be 1.1 to 1.8 H+ per lactose, equivalent to approximately 0.5 ATP used per lactose transported. The cost of transporting maltose via a binding-protein-dependent mechanism was considerably higher, being over 1 to 1.2 ATP per maltose or maltodextrin transported. The formalized treatment also permitted estimation of the net ATP yield from the metabolism of these sugars; it was calculated that the growth yield data were consistent with the production of 2.8 to 3.2 ATP in the metabolism of glucose 6-phosphate to fermentation products.

Cloning and location of the dgsA gene of Escherichia coli

The dgsA locus of Escherichia coli was isolated on plasmids obtained from the library of L. Clarke and J. Carbon (Cell 9:91-99, 1976). Restriction fragment analysis and further subcloning demonstrated that the gene is located at kilobase 425 on the Bouché physical map of the terminus region (J. P. Bouché, J. Mol. Biol., 154:1-20, 1982). This corresponds to 35.2 min on the Bachmann genetic map (B. J. Bachmann, Microbiol. Rev. 47:180-230, 1983).

Gene fusions to the ptsM/pel locus of Escherichia coli

We have constructed gene fusions between ptsM/pel and lacZ. These fusions affect both phenotypes assigned to the ptsM/pel locus (at 40 min), namely, no growth on mannose or glucosamine and inhibition of the penetration of bacteriophage lambda DNA, as well as that of other lambdoid phages such as Hy-2. Since the lacZ gene fusions are insertion mutations that abolish target gene function by disrupting the linear contiguity of the gene, it would appear that ptsM and pel are either the same gene or two genes within the same operon. Several size classes of these ptsM/pel-lacZ fusions have been isolated and the corresponding hybrid proteins are associated with the cytoplasmic membrane of Escherichia coli. This is consistent with the proposal that ptsM/pel codes for Enzyme II of the phosphotransferase transport system (PTS) specific for mannose, glucosamine, fructose and glucose. However, we have also identified Tn10 insertion mutations that confer a Man- phenotype but have no effect on the Pel phenotype. Complementation analysis indicates that the Tn10 insertions and the lacZ gene fusions are in different genes. Both of these genes are involved in mannose uptake. This suggests that the locus at 40 min can be subdivided into two genes whose products are required for mannose uptake and that only one of these is involved in the penetration of lambda DNA.

Lactose metabolism in Streptococcus lactis: studies with a mutant lacking glucokinase and mannose-phosphotransferase activities

A mutant of Streptococcus lactis 133 has been isolated that lacks both glucokinase and phosphoenolpyruvate-dependent mannose-phosphotransferase (mannose-PTS) activities. The double mutant S. lactis 133 mannose-PTSd GK- is unable to utilize either exogenously supplied or intracellularly generated glucose for growth. Fluorographic analyses of metabolites formed during the metabolism of [14C]lactose labeled specifically in the glucose or galactosyl moiety established that the cells were unable to phosphorylate intracellular glucose. However, cells of S. lactis 133 mannose-PTSd GK- readily metabolized intracellular glucose 6-phosphate, and the growth rates and cell yield of the mutant and parental strains on sucrose were the same. During growth on lactose, S. lactis 133 mannose-PTSd GK- fermented only the galactose moiety of the disaccharide, and 1 mol of glucose was generated per mol of lactose consumed. For an equivalent concentration of lactose, the cell yield of the mutant was 50% that of the wild type. The specific rate of lactose utilization by growing cells of S. lactis 133 mannose-PTSd GK- was ca. 50% greater than that of the wild type, but the cell doubling times were 70 and 47 min, respectively. High-resolution 31P nuclear magnetic resonance studies of lactose transport by starved cells of S. lactis 133 and S. lactis 133 mannose-PTSd GK- showed that the latter cells contained elevated lactose-PTS activity. Throughout exponential growth on lactose, the mutant maintained an intracellular steady-state glucose concentration of 100 mM. We conclude from our data that phosphorylation of glucose by S. lactis 133 can be mediated by only two mechanisms: (i) via ATP-dependent glucokinase, and (ii) by the phosphoenolpyruvate-dependent mannose-PTS system.

Intracellular phosphorylation of glucose analogs via the phosphoenolpyruvate: mannose-phosphotransferase system in Streptococcus lactis

The bacterial phosphoenolpyruvate:sugar-phosphotransferase system (PTS) mediates the vectorial translocation and concomitant phosphorylation of sugars. The question arises of whether the PTS can also mediate the phosphorylation of intracellular sugars. To investigate this possibility in Streptococcus lactis 133, lactose derivatives have been prepared containing 14C-labeled 2-deoxy-glucose (2DG), 2-deoxy-2-fluoro-D-glucose (2FG), or alpha-methylglucoside as the aglycon substituent of the disaccharide. Two of the compounds, beta-O-D-galactopyranosyl-(1,4')-2'-deoxy-D-glucopyranose (2'D-lactose) and beta-O-D-galactopyranosyl-(1,4')-2'-deoxy-2'-fluoro-D-glucopyranose (2'F-lactose), were high-affinity substrates of the lactose-PTS. After translocation, the radiolabeled 2'F-lactose 6-phosphate (2'F-lactose-6P) and 2'D-lactose-6P derivatives were hydrolyzed by P-beta-galactoside-galactohydrolase to galactose-6P and either [14C]2FG or [14C]2DG, respectively. Thereafter, the glucose analogs appeared in the medium, but the rates of sugar exit from mannose-PTS-defective mutants were greater than those determined in the parent strain. Unexpectedly, the results of kinetic studies and quantitative analyses of intracellular products in S. lactis 133 showed that initially (and before exit) the glucose analogs existed primarily in phosphorylated form. Furthermore, the production of intracellular [14C]2FG-6P and [14C]2DG-6P (during uptake of the lactose analogs) continued when the possibility for reentry of [14C]2FG and 2DG was precluded by addition of mannose-PTS inhibitors (N-acetylglucosamine or N-acetylmannosamine) to the medium. By contrast, (i) only [14C]2DG, [14C]2FG, and trace amounts of [14C]2FG-6P were found in cells of a mannose-PTS-defective mutant, and (ii) only [14C]2FG and [14C]2DG were present in cells of a double mutant lacking both mannose-PTS and glucokinase activities. We conclude from these data that the mannose-PTS can effect the intracellular phosphorylation of glucose and its analogs in S. lactis 133.

Identification of the phosphocarrier protein enzyme IIIgut: essential component of the glucitol phosphotransferase system in Salmonella typhimurium

The phosphoenolpyruvate-dependent phosphorylation of glucitol has been shown to require four distinct proteins in Salmonella typhimurium: two general energy-coupling proteins, enzyme I and HPr, and two glucitol-specific proteins, enzyme IIgut and enzyme IIIgut. The enzyme IIgut was solubilized from the membrane and purified about 100-fold, free of the other protein constituents of the phosphotransferase system. Enzyme IIIgut was found in both the soluble and the membrane fractions. The soluble enzyme IIIgut was purified to near homogeneity by gel filtration, hydroxylapatite chromatography, and hydrophobic chromatography on butylagarose. It was sensitive to parital inactivation by trypsin and N-ethylmaleimide, but was stable at 80 degrees C. The protein had an approximate molecular weight of 15,000. It was phosphorylated in the presence of phosphoenolpyruvate, enzyme I, and HPr, and this phosphoprotein was dephosphorylated in the presence of enzyme IIgut and glucitol. Antibodies were raised against enzyme IIIgut. Enzyme IIIglc and enzyme IIIgut exhibited no enzymatic or immunological cross-reactivity. Enzyme IIgut, enzyme IIIgut, and glucitol phosphate dehydrogenase activities were specifically induced by growth in the presence of glucitol. These results serve to characterize the glucitol-specific proteins of the phosphotransferase system in S. typhimurium.

Analysis of the ptsH-ptsI-crr region in Escherichia coli K-12: nucleotide sequence of the ptsH gene

The nucleotide sequence of an Escherichia coli DNA segment containing the ptsH gene and the first 162 nucleotides of the ptsI gene encoding, respectively, Hpr and enzyme I of the phosphoenolpyruvate-dependent glycose phosphotransferase system (PTS), was determined. The ptsH promoter was localized using the S1 mapping technique. A nucleotide sequence very similar to the consensus binding site for cAMP receptor protein was found in the -35 region of the ptsH promoter. The ptsH gene is transcribed in the same direction as the ptsI gene and the crr gene (encoding enzyme IIIGlc of the PTS). Analysis of the nucleotide sequence substantiates the notion that the ptsH-ptsI-crr genes constitute a polycistronic operon.

The indirect nature of interaction of glucose transport with the system transporting galactosides

The membrane transport systems for galactosides and glucose derivatives interact in enteric microorganisms. Stop-flow experiments with a double wavelength spectrophotometer and a flow-through cuvette (designed to minimize light-scattering effects) were used to measure the speed of interaction in Escherichia coli. The in vivo hydrolysis of ortho-nitrophenol-beta-D-galactopyranoside was measured by comparing the light transmitted by cell suspensions at 420 nm with that at 500 nm. Measurements at the latter wavelength corrected for residual scattering effects. The stop-flow experiment allowed the study of the early kinetics of transport and hydrolysis. It was found with strain ML308 that there was a significant lag in the achievement of steady-state inhibition by glucose and its derivative methyl-alpha-D-glucopyranoside (alpha MG). This strain constitutively produces high levels of permease and beta-galactosidase. The absorbancy increases at 420 nm are limited by transport because the beta-galactosidase is present inside the cells in excess. From earlier results, it was not surprising that inhibition is delayed with low concentrations of the glucose compounds, but the new double wavelength technique showed no kinetic component of rapid inhibition. This result therefore excludes competition for some membrane-bound component and is consistent with the production of the dephosphorylated form of the soluble Enzyme IIIglu that binds and inhibits the permease system in the membrane.

Phosphorylation in vivo and in vitro of the arginine-ornithine periplasmic transport protein of Escherichia coli

The arginine-ornithine periplasmic binding protein, an essential component of the arginine-ornithine transport system of Escherichia coli, was isolated in a phosphorylated form and in a non-phosphorylated form from the periplasmic fluid, after incubation of intact cells with (32P)orthophosphate under conditions similar to those used for arginine transport studies. The binding protein could also be labeled with 32Pi by incubation in vitro of the periplasmic fluid with [gamma-32P]ATP, or by incubation in vitro of the purified binding protein with radioactive ATP, Mg2+ and a phosphokinase enzyme released by osmotic-shock treatment. The two forms of the protein were separated by DEAE-Sephacel chromatography. By several different criteria, which included binding studies, analyses of the amino acid composition of the two forms of the protein, analysis by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and testing for other components of the periplasmic space with affinities for inorganic phosphate, it was concluded that the 32P-labeled protein corresponds to a phosphorylated form of the arginine-ornithine-binding protein. The phosphorylation reaction required Mg2+ and a phosphokinase from the periplasmic fluid. The dissociation constant of the phosphorylated protein for arginine was 5.0 microM (dissociation constant of the unmodified protein equals 0.1 microM), suggesting that the chemically modified protein is the active form of the molecule which releases the ligand for its translocation through the cytoplasmic membrane. The pH-stability profile of the phosphoprotein has a 'U'-shape characteristic of acyl phosphates. Reaction of the phosphorylated binding protein with hydroxylamine at pH 5.4, also released Pi from the phosphoprotein. These properties suggest that the phosphoryl group of the phosphoprotein is linked covalently to a carboxyl function of the protein. This information indicates that ATP is a direct energy donor for the active transport of arginine and ornithine in E. coli, and a step of phosphorylation of the arginine-ornithine-binding protein appears to be involved in the utilization of the phosphate bond energy by the arginine-ornithine transport system.

Isolation of a novel protein involved in the transport of fructose by an inducible phosphoenolpyruvate fructose phosphotransferase system in Streptococcus mutans

Fructose transport in Streptococcus mutans LG-1 is mediated by at least two distinct phosphoenolpyruvate fructose phosphotransferase systems. One system is constitutive and consists of membrane components enzyme II as well as enzyme I and heat-stable protein. The other system is inducible and requires, in addition to enzyme I and heat-stable protein, a soluble substrate-specific protein for catalytic activity. This protein factor, designated IIIfru, was purified by DEAE-cellulose chromatography, hydroxylapatite chromatography, molecular sieving on Sephadex G-75, and preparative electrophoresis. The purified preparation showed only one protein band, with a molecular weight of 12,600, on sodium dodecyl sulfate-urea-polyacrylamide gel electrophoresis, on gel electrophoresis with the discontinuous buffer Tris-glycine, and after electrofocusing in gel (pI congruent to 3.7). The molecular weight of the native protein determined by gel filtration at 4 degrees C was 51,000. Immunodiffusion experiments performed with immunoglobulins prepared against the purified IIIfru from S. mutans LG-1 suggested that other S. mutans strains possessed a IIIfru. No precipitin bands, however, were detected with extracts from S. salivarius, S. sanguis, S. lactis, S. faecalis, Staphylococcus aureus, Bacillus subtilis, Lactobacillus casei, and Escherichia coli.

Proton suicide: general method for direct selection of sugar transport- and fermentation-defective mutants

We devised a positive selection procedure for bacterial mutants incapable of producing acid from sugars by fermentation. The method relied on the production of elemental bromine from a mixture of bromide and bromate under acidic conditions. When wild-type Escherichia coli cells were plated on media containing a fermentable sugar and an equimolar mixture of bromide and bromate, most of the cells were killed but a variety of mutants unable to produce acid from the sugar survived. Among these mutants were those defective in (i) sugar uptake, (ii) the glycolytic pathway, and (iii) the excretion. There were also novel mutants with some presumed regulatory defects affecting fermentation.

Lactose transport in Streptococcus mutans: isolation and characterization of factor IIIlac, a specific protein component of the phosphoenolpyruvate-lactose phosphotransferase system

The transport of lactose in Streptococcus mutans is mediated via an inducible phosphoenolpyruvate-lactose phosphotransferase system. This system requires for catalytic activity a membrane fraction (enzyme II), two general proteins called enzyme I and HPr, and a soluble specific protein termed factor IIIlac. This protein factor was purified from S. mutans ATCC 27352 by chromatographies on DEAE-cellulose, hydroxylapatite, Ultrogel AcA 34, and phosphocellulose. The purified protein migrated as a single band with a molecular weight of 10,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and urea. The molecular weight calculated from the amino acid composition was 10,541. Gel filtration of the native protein gave a molecular weight of 41,500. Its isoelectric point was ca. 4.70. A specific antiserum was prepared against purified factor IIIlac. Immunodiffusion experiments revealed that only cellular extracts from lactose-grown cells contained factor IIIlac. A cross-reaction was observed with all of the S. mutans strains tested as well as with Streptococcus sanguis 10556, Streptococcus lactis 11454, and Staphylococcus aureus 6538. No precipitin band was observed with extracts of Streptococcus salivarius, Streptococcus faecalis, Lactobacillus casei, and Bacillus subtilis.

Phosphoenolpyruvate-dependent phosphorylation site in enzyme IIIglc of the Escherichia coli phosphotransferase system

Enzyme-IIIglc is part of the glucose phosphotransferase system of Escherichia coli and Salmonella typhimurium and is phosphorylated by phosphoenolpyruvate in a reaction requiring enzyme I (phosphoenolpyruvate-protein phosphotransferase), and the histidine-containing phospho-carrier protein HPr. In this paper we report the isolation of IIIglc from E. coli and the characterization of the active center. Alkaline hydrolysis of [32P]P-IIIglc and chromatography of the hydrolysate suggested that the phosphoryl group is bound to a histidyl residue in P-IIIglc of S. typhimurium. Here we present 1H-NMR measurements of IIIglc and P-IIIglc from E. coli which further substantiate that the phosphoryl group in P-IIIglc is linked to the N-3 position of a histidyl residue. After phosphorylation of IIIglc with [32P]Phosphoenolpyruvate, enzyme I and HPr, the phosphorylated protein was cleaved with either alkaline protease from Streptomyces griseus or subtilisin from Bacillus subtilis. According to amino acid analysis both proteases produced the same peptide carrying the phosphoryl group. The amino acid sequence of this peptide was found to be Val-His-Phe-Gly-Ile-Asp. The lower electrophoretic mobility of P-IIIglc on dodecylsulfate/polyacrylamide gels and its stronger binding to the hydrophobic matrix of a reversed-phase column compared to unphosphorylated protein may indicate a structural change following phosphoenolpyruvate-dependent phosphorylation.

Role of IIIGlc of the phosphoenolpyruvate-glucose phosphotransferase system in inducer exclusion in Escherichia coli

The phosphoenolpyruvate-D-glucose phosphotransferase system of Enterobacteriaceae is thought to regulate the synthesis and activity of a number of catabolite uptake systems, including those for maltose, lactose, and glycerol, via the phosphorylation state of one of its components, IIIGlc. We have investigated the proposal by Kornberg and co-workers (FEBS Lett. 117(Suppl.):K28-K36, 1980) that not IIIGlc, but an unknown protein, the product of the iex gene, is responsible for the exclusion of the above-mentioned compounds from the cell. The iex mutant HK738 of Escherichia coli contains normal amounts of IIIGlc as measured by specific antibodies, in contrast to crr mutants that lack IIIGlc. The IIIGlc of the iex strain functions normally in glucose and methyl alpha-glucoside transport, and the specific activity in in vitro phosphorylation is approximately 60% of that of the parent. The IIIGlc activity of the iex strain is, however, heat labile, in contrast to the parental IIIGlc, suggesting that the mutant contains an altered IIIGlc. This is supported by the observation that IIIGlc from the iex strain cannot bind to the lactose carrier. Thus it cannot inhibit the carrier, and this explains why the uptake of non-phosphotransferase system compounds in an iex strain is resistant to phosphotransferase system sugars. The introduction of a plasmid containing a wild-type crr+ allele into the iex strain restores the iex phenotype to that of the iex+ parent. The IIIGlc produced from the plasmid in the iex strain is heat stable and binds normally to the lactose carrier. These results lead to the conclusion that the iex mutation is most likely allelic with crr and results in an altered, temperature-sensitive IIIGlc that is still able to function D-glucose and methyl alpha-glucoside uptake and phosphorylation and in the activation of adenylate cyclase, but is unable to bind to and inhibit the lactose carrier.

Properties of ATP-dependent protein kinase from Streptococcus pyogenes that phosphorylates a seryl residue in HPr, a phosphocarrier protein of the phosphotransferase system

Transport of sugars across the cytoplasmic membranes of gram-positive bacteria appears to be regulated by the action of a metabolite-activated, ATP-dependent protein kinase that phosphorylates a seryl residue in the phosphocarrier protein of the phosphotransferase system, HPr. We have developed a quantitative assay for measuring the activity of this enzyme from Streptococcus pyogenes. The product of the in vitro protein kinase-catalyzed reaction was shown to be phosphoseryl-HPr by several independent criteria (rates of hydrolysis in the presence of various agents, detection of serine-phosphate in acid hydrolysates, immunological assay, and electrophoretic migration rates). HPrs isolated from four different gram-positive bacteria (S. pyogenes, Streptococcus faecalis, Staphylococcus aureus, and Bacillus subtilis) were shown to be phosphorylated by the kinase from S. pyogenes. In contrast, Escherichia coli HPr was not a substrate of this enzyme. The soluble kinase released from the particulate fraction of the cells with high salt in the presence of a protease inhibitor was shown to have an approximate molecular weight of 60,000 as estimated by gel filtration. Its activity was dependent on divalent cations, with Mg2+ and Mn2+ being most active. EDTA, Pi, and high concentrations of salt were strongly inhibitory. The enzyme was optimally active at pH 7.0, exhibited high affinity for its substrates, and was dependent on the presence of one of several metabolites. Of these compounds, fructose 1-6-diphosphate was most active, with gluconate 6-phosphate, 2-phosphoglycerate, 2,3-diphosphoglycerate, phosphoenolpyruvate, and pyruvate exhibiting moderate to low stimulatory activities. Other compounds tested, including a variety of sugar phosphates, pyridine nucleotides, and other metabolites were without effect. The ATP-dependent phosphorylation of HPr on the seryl residue was strongly inhibited by phosphoenolpyruvate-dependent phosphorylation of the active histidyl residue of this protein. Treatment of the kinase with diethyl pyrocarbonate strongly inhibited the ATP-dependent phosphorylation activity, although the sulfhydryl reagents N-ethylmaleimide, p-chloromercuribenzoate, and iodoacetate were without effect. These results serve to characterize the HPr (serine) kinase, which apparently regulates the rates of carbohydrate transport in streptococcal cells via the phosphotransferase system. A primary role of this kinase in the control of cellular inducer levels and carbohydrate metabolic rates is proposed.

Purification and properties of D-mannitol-1-phosphate dehydrogenase and D-glucitol-6-phosphate dehydrogenase from Escherichia coli

D-Mannitol-1-phosphate dehydrogenase (EC 1.1.1.17) and D-glucitol-6-phosphate dehydrogenase (EC 1.1.1.140) were purified to apparent homogeneity in good yields from Escherichia coli. The amino acid compositions, N-terminal amino acid sequences, sensitivities to chemical reagents, and catalytic properties of the two enzymes were determined. Both enzymes showed absolute specificities for their substrates. The subunit molecular weights of mannitol-1-phosphate and glucitol-6-phosphate dehydrogenases were 40,000 and 26,000, respectively; the apparent molecular weights of the native proteins, determined by gel filtration, were 40,000 and 117,000, respectively. It is therefore concluded that whereas mannitol-1-phosphate dehydrogenase is a monomer, glucitol-6-phosphate dehydrogenase is probably a tetramer. These two proteins differed in several fundamental respects.

Genetic studies of the phs locus of Escherichia coli, a mutation causing pleiotropic lesions in metabolism and pH homeostasis

In Escherichia coli a pleiotropic mutation, phs, has been reported to affect Na+-linked metabolic functions and pH homeostasis. The phs mutation was previously mapped by its proximity to a met marker, presumed to be metB at 89 min. We have shown that a second mutation to auxotrophy, cymX, which is satisfied by either methionine or cysteine, is closely linked to phs. The cymX and phs lesions map close to trkB and rpsL at 73.5 min and we postulate that they are alleles of cysG and crp, respectively. The basis of the pH sensitivity of DZ3 is discussed in the light of this new information.

Preliminary crystallographic data for a monoclonal Fab fragment specific for HPr of the phosphoenolpyruvate: sugar phosphotransferase system of Escherichia coli

Crystals for Fab fragments from a monoclonal antibody to HPr of the phosphoenopyruvate:sugar phosphotransferase system of Escherichia coli have been obtained from 14% polyethylene glycol 6000, 5 mM-Tris X HCl, 50 mM-sodium phosphate and 0.2 M-sodium chloride at pH 8.0. The space group is P2(1) with a = 110.85 A, b = 66.18 A, c = 67.21 A, beta = 113.0 degrees and Z = 4. The crystals exhibit the forms [100], [011] and [011] and the solvent content is 47%.

Transformation of Streptococcus sanguis Challis with Streptococcus lactis plasmid DNA

Streptococcus lactis plasmid DNA, which is required for the fermentation of lactose (plasmid pLM2001), and a potential streptococcal cloning vector plasmid (pDB101) which confers resistance to erythromycin were evaluated by transformation into Streptococcus sanguis Challis. Plasmid pLM2001 transformed lactose-negative (Lac-) mutants of S. sanguis with high efficiency and was capable of conferring lactose-metabolizing ability to a mutant deficient in Enzyme IIlac, Factor IIIlac, and phospho-beta-galactosidase of the lactose phosphoenolpyruvate-phosphotransferase system. Plasmid pDB101 was capable of high-efficiency transformation of S. sanguis to antibiotic resistance, and the plasmid could be readily isolated from transformed strains. However, when 20 pLM2001 Lac+ transformants were analyzed by a variety of techniques for the presence of plasmids, none could be detected. In addition, attempts to cure the Lac+ transformants by treatment with acriflavin were unsuccessful. Polyacrylamide gel electrophoresis was used to demonstrate that the transformants had acquired a phospho-beta-galactosidase characteristic of that normally produced by S. lactis and not S. sanguis. It is proposed that the genes required for lactose fermentation may have become stabilized in the transformants due to their integration into the host chromosome. The efficient transformation into and expression of pLM2001 and pDB101 genes in S. sanguis provides a model system which could allow the development of a system for cloning genes from dairy starter cultures into S. sanguis to examine factors affecting their expression and regulation.

Sidedness of native membrane vesicles of Escherichia coli and orientation of the reconstituted lactose: H+ carrier

The orientation of the lactose:H+ carrier of Escherichia coli in various preparations of native and reconstituted vesicles is determined with two impermeant, macromolecular probes: antibodies directed against the C-terminal decapeptide of the carrier and carboxypeptidase A (EC 3.4.17.1). Two methods are employed. Method I is based upon the digestion of all accessible and, therefore, presumably external, C termini of the carrier with carboxypeptidase A and detection of the remaining, internal C termini with 125I-labelled anti-(C-terminus) antibody after electrophoresis of the carrier in the presence of sodium dodecyl sulfate and transfer to nitrocellulose filters. Method II is based upon the binding of 125I-labelled anti-(C-terminus) antibody to the external C termini of the carrier in vesicles and the subsequent isolation of bound antibody by centrifugation. The labelled antibodies are calibrated using a preparation of inside-out vesicles prepared by high-pressure lysis of strain T206. The carrier content is determined by substrate binding. Because the C terminus of the carrier is known to reside on the cytoplasmic side of the membrane, these methods can also be used to determine the sidedness of various preparations of membrane vesicles. Spheroplasts are confirmed to contain carrier molecules of a single orientation, corresponding to that in right-side-out vesicles. In contrast, in purified cytoplasmic membrane vesicles and in crude membrane preparations obtained by sonication or by high-pressure lysis, 96% of the C termini are accessible to carboxypeptidase A, even after repeated sonication. This implies that nearly all carrier molecules in these preparations possess an orientation opposite to that in the cell or in right-side-out vesicles. In proteoliposomes containing carrier reconstituted or purified and reconstituted by two different methods, only 48% of the carrier molecules are oriented in the same way as in the cell. Subjecting such proteoliposomes to cycles of freezing and thawing or to sonication results in a reshuffling of carrier molecules between the inside-out and right-side-out populations while maintaining 41% in the right-side-out orientation. Digestion of the C terminus of the carrier with carboxypeptidase A does not alter either galactoside binding or countertransport. Thus carrier molecules of the inside-out orientation cannot be selectively inactivated. Additionally, an antiserum directed against the purified carrier is demonstrated to contain nearly exclusively anti-(C-terminus) antibodies, which can, in principle, be used in Method I.(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of streptococcal mutants presumed to be defective in sugar catabolism

The tetrazolium method for detection of bacterial mutants defective in sugar catabolism was modified for use with streptococci. The critical factors were (i) the concentration of tetrazolium, which must be titrated to determine the optimum concentration for each species or even strain, and (ii) anaerobic incubation of tetrazolium-containing agar plates. When used with standard mutagenesis protocols, this method yielded lactose-negative mutants of nine streptococcal strains representing six species. A collection of lactose-negative mutants of streptococcus, sanguis Challis was characterized and contained phospho-beta-galactosidase, lactose phosphotransferase, and general phosphotransferase mutants.

Isoelectrophoretic separation and the detection of soluble proteins containing acid-labile phosphate: use of the phosphoenolpyruvate:sugar phosphotransferase system as a model system for N1-P-histidine- and N3-P-histidine-containing proteins

Procedures have been developed for the detection of acid-labile phosphorylations of proteins. The phosphoproteins were separated by native isoelectric focusing while maintaining the gel at about 0 degree C, and denaturing urea-Nonidet isoelectric focusing gels were adapted to run at -10 degrees C. The proteins of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS), HPr, which contains 1-P-histidine, and factor IIIglc and enzyme I, which contain 3-P-histidine when they are phosphorylated, were used to develop the conditions. Autoradiography of [32P]-labeled phosphoproteins was carried out on frozen gels which had not been acid fixed in order to avoid hydrolysis of the phosphohistidines . The frozen gels were subsequently fixed and stained, and reautoradiography revealed whether the phosphoproteins were acid stable or labile. In addition to the known proteins of the PTS, at least one other protein whose phosphorylation was dependent on enzyme I and HPr was found in Salmonella typhimurium and Escherichia coli [E.B. Waygood , and R.L. Mattoo (1983) Canad . J. Biochem. Cell Biol. 61, 150-153]. Initial experiments with rat tissues have demonstrated acid-labile phosphorylations in proteins which were either [gamma-32P]ATP or [32P]phosphoenolpyruvate dependent. The interconversion of phosphoenolpyruvate and ATP in crude extracts of bacterial cells was examined, and appropriate controls were found. Protein phosphorylation dependent upon phosphoenolpyruvate was much greater in S. typhimurium and E. coli than the corresponding ATP-dependent phosphorylation, while the opposite was found for rat tissues.

Interaction between IIIGlc of the phosphoenolpyruvate:sugar phosphotransferase system and glycerol kinase of Salmonella typhimurium

Purified IIIGlc of the phosphoenolpyruvate:sugar phosphotransferase system of Salmonella typhimurium inhibits glycerol kinase. Phosphorylation of IIIGlc via phosphoenolpyruvate, enzyme I, and HPr abolishes this inhibition. The glycerol facilitator is not inhibited by IIIGlc. It is proposed that regulation of glycerol metabolism by the phosphoenolpyruvate:sugar phosphotransferase system is at the level of glycerol kinase.

Metabolic alterations mediated by 2-ketobutyrate in Escherichia coli K12

We have previously proposed that 2-ketobutyrate is an alarmone in Escherichia coli. Circumstantial evidence suggested that the target of 2-ketobutyrate was the phosphoenol pyruvate: glycose phosphotransferase system (PTS). We demonstrate here that the phosphorylated metabolites of the glycolytic pathway experience a dramatic downshift upon addition of 2-ketobutyrate (or its analogues). In particular, fructose-1,6-diphosphate, glucose-6-phosphate, fructose-6-phosphate and acetyl-CoA concentrations drop by a factor of 10, 3, 4, and 5 respectively. This result is consistent with (i) an inhibition of the PTS by 2-ketobutyrate, (ii) a control of metabolism by fructose-1,6-diphosphate. Since fructose-1,6-diphosphate is an activator of phosphoenol pyruvate carboxylase and of pyruvate kinase, the concentration of their common substrate, phosphoenol pyruvate, does not decrease in parallel.

Interactions in vivo between IIIGlc of the phosphoenolpyruvate:sugar phosphotransferase system and the glycerol and maltose uptake systems of Salmonella typhimurium

Our previous studies indicated that the ability of phosphoenolpyruvate:sugar phosphotransferase system (PTS) substrates to inhibit the uptake of glycerol or maltose in Salmonella typhimurium is dependent on the relative cellular content of the PTS-sensitive uptake system and of the PTS protein IIIGlc. Our present study confirms and extends those observations. The maltose and glycerol uptake systems are rendered (wholly or partially) insensitive to PTS inhibition by the presence of a second PTS-sensitive uptake system (respectively that for glycerol or maltose) and its substrate. Both the second PTS-sensitive uptake system and its substrate were needed for this protective effect. Galactose and the galactose permease (a PTS-insensitive transport system) did not have any effect on PTS-mediated inhibition of the maltose uptake system. The protective effect of the second PTS-sensitive uptake system and its substrate is counteracted by increasing the cellular levels of IIIGlc. Overproduction of IIIGlc in crr-plasmid-containing strains renders the glycerol and maltose uptake systems hypersensitive to inhibition by PTS substrates. We interpret our results on the basis of a stoichiometric interaction between IIIGlc and a PTS-sensitive uptake system, in which the IIIGlc--transport-system complex is inactive. Competition between two PTS-sensitive transport systems for formation of inactive complex with IIIGlc lowers the free intracellular concentration of IIIGlc resulting in a mutual protective effect against inhibition by IIIGlc.

Transport and metabolism of trehalose in Escherichia coli and Salmonella typhimurium

The metabolism of trehalose in wild type cells of Escherichia coli and Salmonella typhimurium has been investigated. Intact cells of Escherichia coli (grown on trehalose) accumulated [14C]-trehalose as [14C]-trehalose 6-phosphate. Toluene-treated cells catalyzed the synthesis of the [14C]-sugar phosphate from [14C]-trehalose and phosphoenolpyruvate; ATP did not serve as phosphoryl donor. Trehalose 6-phosphate could subsequently be hydrolyzed by trehalose 6-phosphate hydrolase, an enzyme which catalyzes the hydrolysis of the disaccharide phosphate into glucose and glucose 6-phosphate. Both Escherichia coli and Salmonella typhimurium induced this enzyme when they grew on trehalose. These findings suggest that trehalose is transported in these bacteria by an inducible phosphoenolpyruvate:trehalose phosphotransferase system. The presence of a constitutive trehalase was also detected.

Properties of a Streptococcus lactis strain that ferments lactose slowly

Streptococcus lactis 7962, which ferments lactose slowly, has a lactose phosphoenolpyruvate-dependent phosphotransferase system and low phospho-beta-galactosidase activity, in addition to high beta-galactosidase activity. Lactose 6'-phosphate accumulated to a high concentration (greater than 100 mM) in cells growing on lactose. In contrast, lactic streptococci, which ferment lactose rapidly and use only the lactose-phosphotransferase system for uptake, contained high phospho-beta-galactosidase activity and low concentrations (0.9 to 1.6 mM) of lactose 6'-phosphate. It is concluded that rate-limiting phospho-beta-galactosidase activity is primarily responsible for defective lactose metabolism in S. lactis 7962.

L-Sorbose metabolism in Klebsiella pneumoniae and Sor+ derivatives of Escherichia coli K-12 and chemotaxis toward sorbose

L-Sorbose degradation in Klebsiella pneumoniae was shown to follow the pathway L-sorbose leads to L-sorbose-1-phosphate leads to D-glucitol-6-phosphate leads to D-fructose-6-phosphate. Transport and phosphorylation of L-sorbose was catalyzed by membrane-bound enzyme IIsor of the phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system, specific for and regulated by this ketose and different from all other enzymes II described thus far. Two soluble enzymes, an L-sorbose-1-phosphate reductase and a D-glucitol-6-phosphate dehydrogenase, were involved in the conversion of L-sorbose-1-phosphate to D-fructose-6-phosphate. This dehydrogenase was temperature sensitive, preventing growth of wild-type strains of K. pneumoniae at temperatures above 35 degrees C in the presence of L-sorbose. The enzyme was distinct from a second D-glucitol-6-phosphate dehydrogenase involved in the metabolism of D-glucitol. The sor genes were transferred from the chromosome of nonmotile strains of K. pneumoniae by means of a new R'sor+ plasmid to motile strains of Escherichia coli K-12. Such derivatives not only showed the temperature-sensitive Sor+ phenotype characteristic for K. pneumoniae or Sor+ wild-type strains of E. coli, but also reacted positively to sorbose in chemotaxis tests.

Cell volume change of Escherichia coli under stringent control. Apparent increase of K+ in rel- cells

With several pairs of rel+ and rel- strains of Escherichia coli, the effects of amino acid starvation on the intracellular concentration of K+ and the rate of uptake of 42K+ were investigated. In the early phase of the experiments, the intracellular concentration of K+ was estimated by the conventional method in which the cell volume per A660 value of the culture was assumed to be constant, being not influenced by the variation of growth condition and strain. Apparently, the K+ concentration of rel+ cells was kept almost constant, while that of rel- cells increased about 1.5-fold 2 h after the exposure to amino acid starvation. Unexpectedly, however, the above assumption was found not to be valid in the present study. The cell volume per A660 changed only slightly in CP78 (rel+) cells, while it increased markedly in CP79 (rel-) cells after the exposure to amino acid starvation. Reestimation of the K+ concentrations based on the estimated respective values of cell volumes per A660 revealed no significant difference between both strains. After all, the above apparent phenomenon was found to be due to the fact that the increase in cell volume of the rel+ cells was arrested upon amino acid starvation whereas that in the rel- cells was not. The 42K+ uptake by the rel+ cells was depressed upon amino acid starvation, whereas that by the rel- cells increased. Some regulatory mechanism was suggested to operate in both strains to keep their K+ concentrations constant. When intracellular concentration of a metabolite is to be determined, importance of measurement of cell volume under the respective conditions, without assuming the constancy of the cell volume per A660 of the culture, was pointed out.

Kinetic characterization and regulation of phosphoenolpyruvate-dependent methyl alpha-D-glucopyranoside transport by Salmonella typhimurium membrane vesicles

Membrane vesicles from Salmonella typhimurium SB3507 were used to study the kinetics of methyl alpha-D-glucopyranoside (MeGlc) transport by the phosphoenolpyruvate: glycose phosphotransferase system (PTS). During the first minute of phosphoenolpyruvate-dependent MeGlc transport, two distinct rates were observed; an initial rapid rate, V1 (Vmax, 7.4-8.4 nmol X mg-1 X min-1; Km, 8.2-11.2 X 10(-6)M), followed by a second slower rate, V2 (Vmax, 4-4.6 nmol X mg-1 X min-1; Km, 3.4-6.4 X 10(-6) M). The change in rate occurred when the intravesicular MeGlc phosphate concentration was 0.2 mM or less, depending on the external MeGlc concentration. The rate-limiting component in MeGlc transport was found to be enzyme II-BGlc, not phosphoenolpyruvate uptake or the PTS proteins enzyme I, HPr, and IIIGlc. The change from V1 to V2 thus suggests that the PTS is regulated in intact vesicles. However, this regulation was completely relieved by permeabilizing the vesicles with toluene. That is, the toluene-treated vesicles showed only V1 for MeGlc phosphorylation. Evidence was obtained to show that pyruvate and its metabolic products generated by the vesicles exerted no effect on the rate of MeGlc transport. Furthermore, the result from a dual-label experiment excluded exchange transphosphorylation as the mechanism for regulating MeGlc transport by the vesicles. Possible mechanisms for regulation of the PTS are discussed.

Experimental evolution of a novel pathway for glycerol dissimilation in Escherichia coli

Wild-type Escherichia coli utilizes glycerol aerobically through an inducible pathway mediated by an ATP-dependent kinase and a glycerol 3-phosphate dehydrogenase which is a flavoprotein. A mutant, strain ECL424, employing a novel pathway for glycerol utilization was isolated. The novel pathway is mediated by an NAD-linked dehydrogenase and a dihydroxyacetone specific enzyme II of the phosphoenolpyruvate phosphotransferase system. This study describes the selection from strain ECL424, a derivative which grows more rapidly on glycerol. The derivative, strain ECL428, produces twice the parental levels of both the dehydrogenase and the enzyme II during growth on glycerol. The function of the dehydrogenase in wild-type cells is unknown, although hydroxyacetone (acetol), 3-hydroxy-2-butanone (acetoin), and 1-amino-2-propanone are gratuitous inducers. The induction can be prevented by glucose whose effect can be cancelled by external cyclic AMP. The effects of hydroxyacetone, glucose, and cyclic AMP are attenuated in the two mutants in which the dehydrogenase is produced at high basal levels. The dihydroxyacetone specific enzyme II is inducible by the substrate in both wild-type and mutant strains and serves for growth on the triose.

Regulatory interactions among the cya, crp and pts gene products in Salmonella typhimurium

A well-characterized set of pts deletion mutants of Salmonella typhimurium were used to re-evaluate the purported role of the PTS in the inducer exclusion process and in regulation cAMP synthesis. During the course of these studies a class of secondary mutations was isolated which suppress the inhibition of cAMP synthesis caused by pts mutations. These suppressor mutations were traced to the crp locus and tentatively designated as acr (adenylate cyclase regulation) mutations. A new model is proposed in which CRP rather than adenylate cyclase is believed to be the central regulatory element in the catabolite repression phenomenon.