SEARCH · PubMed Health

Results for “Melibiose”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1992

Primary structure and characteristics of the melibiose carrier of Klebsiella pneumoniae.

The melB gene coding for the melibiose carrier of Klebsiella pneumoniae was cloned and sequenced. There were two potential translation initiation sites. It was predicted that the melibiose carrier consists of 471 (or 467) amino acid residues. Seventy-eight percent of the 471 amino acids were identical to the Escherichia coli melibiose carrier. Sugar transport characteristics were studied using an E. coli mel- mutant expressing cloned K. pneumoniae melB gene. Accumulation of melibiose via the K. pneumoniae melibiose carrier was not stimulated by adding NaCl or LiCl which stimulates melibiose accumulation via the E. coli melibiose carrier. Lactose was accumulated only in the presence of LiCl. TMG (methyl-1-thio-beta-D-galactopyranoside) was accumulated in the absence of added NaCl or LiCl. The accumulation was stimulated by LiCl but not by NaCl. Rapid H+ uptake was observed when melibiose or TMG was added to cell suspensions. These results suggest that the preferred cation couplings via K. pneumoniae melibiose carrier are H(+)-melibiose, Li(+)-lactose, and H+/Li(+)-TMG. This coupling spectrum is quite different from that of the E. coli melibiose carrier. It is of special interest that the K. pneumoniae melibiose carrier seems to be lacking the ability to recognize Na+ which is a preferred coupling cation of the E. coli melibiose carrier for all known sugar substrates. Further investigation of these two carriers may give us insight into the Na+ recognition site.

Amino Acid Sequence↗

PubMed1992

Melibiose transport system in Lactobacillus plantarum.

Lactobacillus plantarum ATCC 8014 grew on melibiose at 30 C, but not at 37 C, although it grew on galactose or lactose at either temperature. ATCC 8014 grown on lactose at 30 or 37 C accumulated melibiose slowly, suggesting that melibiose may partly be transported by a lactose transport system. A lactose-negative mutant, NTG 21, derived from ATCC 8014 was isolated. The mutant was totally deficient in lactose transport, but retained normal melibiose transport activity. In NTG 21, the melibiose transport activity was induced by melibiose at 30 C, but not at 37 C. The transport activity itself was found to be stable for at least 3 hr at 37 C, suggesting that the induction process in the cytoplasm rather than the inducer entrance is temperature-sensitive in the organism. The organism also failed to form alpha-galactosidase at 37 C when grown on melibiose. The enzyme synthesis, however, was induced by galactose in NTG 21 (and also by lactose in ATCC 8014) even at 37 C, indicating that the induction of the enzyme is essentially not temperature-sensitive. In NTG 21, melibiose transport system and alpha-galactosidase were induced by galactose, melibiose and o-nitrophenyl-alpha-D-galactopyranoside when the strain was grown at 30 C. Raffinose induced melibiose transport system only a little, while it was a good inducer for alpha-galactosidase. Inhibition studies revealed that galactose may be a weak substrate of the melibiose transport system; no inhibition was demonstrated with lactose and raffinose.

Biological Transport↗

PubMed1978

Cation-sugar cotransport in the melibiose transport system of Escherichia coli.

The entry of Na+ or H+ into cells of Escherichia coli via the melibiose transport system was stimulated by the addition of certain galactosides. The principal cell used in these studies (W3133) was a lactose transport negative strain of E. coli possessing an inducible melibiose transport system. Such cells were grown in the presence of melibiose, washed, and incubated in the presence of 25 microM Na+. The addition of thiomethylgalactoside (TMG) resulted in a fall in Na+ concentration in the incubation medium. No TMG-stimulated Na+ movement was observed in uninduced cells. In an alpha-galactosidase negative derivative of W3133 (RA11) a sugar-stimulated Na+ uptake was observed in melibiose-induced cells on the addition of melibiose, thiodigalactoside, methyl-alpha-galactoside, methyl-beta-galactoside, and galactose, but not lactose. It was inferred from these studies that the substrates of the melibiose system enter the cell on the melibiose carrier associated with the simultaneous entry of Na+ when this cation is present in the incubation medium. Extracellular pH was measured in unbuffered suspensions of induced cells in order to study proton movement across the membrane of cells exposed to different galactosides. In the absence of external Na+ or Li+ the addition of melibiose or methyl-alpha-galactoside resulted in marked alkalinization of the external medium (consistent with H+-sugar cotransport). On the other hand TMG, thiodigalactoside, and methyl-beta-galactoside gave no proton movement under these conditions. When Na+ was present, the addition of TMG or melibiose resulted in acidification of the medium. This observation is consistent with the view that the entry of Na+ with TMG or melibiose carries into the cell a positive charge (Na+) which provides the driving force for the diffusion of protons out of the cell. It is concluded that the melibiose carrier recognition of cations differs with different substrates.

Biological Transport↗

PubMed1978

Effect of lithium ion on melibiose transport in Escherichia coli.

Both Li+ and Na+ stimulated the uptake of thiomethylgalactoside by the melibiose transport system of Escherichia coli. On the other hand, Li+ inhibited the growht of cells on melibiose as a sole source of carbon. This inhibition was specific for melibiose, and Li+ had no effect on growth of cells on glucose, galactose, lactose, or glycerol. The effect of the cation on melibiose transport was investigated in a mutant which cannot utilize glucose. After entry into this cell, melibiose is cleaved into glucose and galactose by alpha-galactosidase, and the resulting glucose is excreted. Since the entry step was found to be rate-limiting, glucose production could be taken as a measure of melibose transport. Li+ inhibited the transport of melibiose, but not the induction of the melibiose operon nor the activity of alpha-galactosidase. Li+ was found to inhibit the entry of p-nitrophenyl-alpha-D-galactoside, but not p-nitrophenyl-beta-D-galactoside entry. Thus, the cation specificity for the melibiose membrane carrier varies different transport substrates.

Biological Transport, Active↗

PubMed1992

Resistance of the melibiose carrier to inhibition by the phosphotransferase system due to substitutions of amino acid residues in the carrier of Salmonella typhimurium.

The melibiose carrier of Salmonella typhimurium is under the control of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS). We isolated mutants of the melibiose carrier that showed resistance to inhibition via the PTS. Growth of the mutants on melibiose was not inhibited by 2-deoxyglucose, a non-metabolizable substrate of the PTS, although growth of the parent strain was inhibited. Transport activity of the melibiose carrier in the mutants was fairly resistant to inhibition by 2-deoxyglucose, although the activity in the parent was sensitive to inhibition. We cloned the mutated melB gene that encodes the melibiose carrier, determined the nucleotide sequences, and identified replaced nucleotides. The mutations resulted in substitutions of Asp-438 with Tyr, Arg-441 with Ser, or Ile-445 with Asn. All of these residues are in the COOH-terminal region of the carrier. The secondary structure of this region is predicted to be an alpha-helix, and the mutated residues were on the same side of the helix. This region showed sequence similarity to a region of the MalK protein, in which substitution of amino acid residues also resulted in PTS-resistant mutants. Thus the COOH-terminal portion of the melibiose carrier is important for the interaction of dephosphorylated IIIGlc, which is an entity causing reversible inactivation of the carrier.

Amino Acid Sequence↗

PubMed1992

Preferential utilization of glucose over melibiose, and vice versa, in a pts mutant of Salmonella typhimurium.

Preferential utilization of glucose and melibiose was investigated in wild type cells and in pts mutant (ptsI-leaky) cells of Salmonella typhimurium. A typical diauxic growth and preferential utilization of glucose over melibiose were observed in wild type cells when these two sugars were added as carbon source. Similar results were obtained with a pts mutant (SB1476) although utilization of glucose was slow. When cyclic adenosine 3',5'-monophosphate (cAMP) was added to the culture medium to release the catabolite repression, preferential utilization of glucose was still observed in wild type cells. With glucose-induced mutant cells, preferential utilization of glucose was observed in the presence of cAMP. Gradual utilization of melibiose took place when glucose concentration in the medium decreased. Surprisingly, preferential utilization of melibiose over glucose was observed with melibiose-induced and glucose-uninduced mutant cells in the presence of cAMP.

Cell Division↗

PubMed1992

Asp-51 and Asp-120 are important for the transport function of the Escherichia coli melibiose carrier.

Asp-51 and Asp-120 of the Escherichia coli melibiose carrier on plasmid pKKMB were separately replaced by amber codons and transformed into eight amber suppressor strains, producing eight amino acid substitutions for each site. Glu-51 and Glu-120 were the only replacements in the carrier that allowed the cells to ferment melibiose and that showed transport of melibiose against a concentration gradient. Revertants to Glu-51 and Glu-120 show less activity than the wild type. The Asp-51 position is more crucial for Na(+)-stimulated melibiose accumulation than is the Asp-120 site.

Base Sequence↗

PubMed1992

Transfer of genes for utilization of starch (sta2) and melibiose (mel) to industrial strains of Saccharomyces cerevisiae by single-chromosome transfer, using a kar1 mutant as vector.

A method has been developed for the transfer of genes from other yeast strains and species to industrial yeast strains, using a haploid, kar1-1 mutant strain of Saccharomyces cerevisiae as a vector. The sta2 gene, conferring the ability to metabolize starch was transferred from an auxotrophic haploid strain of S. cerevisiae (S. diastaticus) and the melibiose-metabolism (mel) gene(s), from S. kluyveri, to the kar1-1 mutant [K5-5A; (alpha ade2 his4 can1 gal) by normal mating and protoplast fusion. From this strain, the genes were transferred to baker's yeast and brewing yeast strains, which did not utilize starch, and to baker's yeast strains, which did not utilize melibiose, by protoplast fusion, spore-cell pairing, or rare-mating. Strains that utilized starch or melibiose were obtained by all three methods. Pulsed-field gel electrophoresis preparations showed little change in the mobility of the chromosomes of the hybrids. The most probable explanation for the results obtained is that single chromosomes were transferred, first, from the donor strains to the kar1-1 haploid mutant strain, and then from the kar1-1 vector to the recipient industrial strain of S. cerevisiae. The transfer of the genes is probably accomplished through formation of disomic strains and then, in the case of the hybrids that metabolize starch, by integration of the sta2 gene into the genome of the industrial yeast strains.

Chromosomes, Fungal↗

PubMedDate not supplied

[Arabinose, melibiose and xylose oxidation and fermentation in "Serratia" (author's transl)].

The oxidative and fermentative metabolisms of D(+)raffinose, D(-)arabinose, L(+)arabinose, D(+)melibiose and D(+)xylose were compared in 181 strains belonging to the genus Serratia, including collection strains and clinical isolates from various sources. At 30 degrees C, raffinose was neither fermented nor oxidized by S. marcescens, but was fermented by S. liquefaciens and S. rubidaea. D(-)arabinose was oxidized by all strains. L(+)arabinose, melibiose and xylose were fermented by all S. liquefaciens and S. rubidaea, while they were oxidized by most S. marcescens. Two strains of the latter species, however, were able to ferment xylose. The use of Hugh and Leifson's oxidation-fermentation medium containing melibiose or L(+)arabinose can help to differentiate S. rubidaea from pigmented strains of S. marcescens and to differentiate S. liquefaciens from unpigmented strains of S. marcescens.

Arabinose↗

PubMed1992

Cloning and sequencing of the melB gene encoding the melibiose permease of Salmonella typhimurium LT2.

The nucleotide sequence of the melB gene coding for the Na+ (Li+)/melibiose symporter of Salmonella typhimurium LT2 was determined, and its amino acid sequence was deduced. It consists of 1428 bp, corresponding to a protein of 476 amino acid residues (calculated molecular weight 52,800). The amino acid sequence is homologous to that of the melibiose permease of Escherichia coli K12, with 85% identical residues. All, except one, of the amino acid residues that have been reported to be important for cation or substrate recognition in the melibiose permease of E. coli are conserved in the melibiose permease of S. typhimurium. In addition, part of the sequence resembles the lactose permease of Streptococcus thermophilus, the animal glucose transporter (GLUT1), the plasmid-coded raffinose permease (RafB), and the NADH-ubiquinone oxidoreductase chain 4 (Nuo4) of Aspergillus amstelodami.

Amino Acid Sequence↗

PubMed1992

Membrane topology of the melibiose carrier of Escherichia coli.

The minimum structural information necessary to formulate and assess mechanistic models of integral membrane protein function is that of membrane topology. This paper characterizes the topological structure of the melibiose carrier of Escherichia coli based on constraints provided by genetic fusions to the compartment-specific reporter protein alkaline phosphatase. Twenty-eight unique chimeras exhibiting either low alkaline phosphatase activity (cytoplasmic location of the fusion joint) or high alkaline phosphatase activity (periplasmic location of the fusion joint) were characterized and used in conjunction with Goldman-Engelman-Steitz hydropathy analysis to model topological structure. The melibiose carrier is predicted to have a cytoplasmic amino terminus, two sets of six transmembrane domains separated by an unusually large cytoplasmic loop ("six-loop-six" arrangement), and a 45-residue cytoplasmic carboxyl tail. Remarkably, the identical six-loop-six arrangement is predicted from the hydrophobicity plots of the H(+)-coupled lactose, arabinose, xylose, and citrate cotransporters of E. coli, the glucose transporter from rat brain, the family of glucose transporters isolated from various human tissues and cell lines, and the human, mouse, and hamster multidrug resistance transporters (Henderson, P.J.F. (1990) Res. Microbiol. 141, 316-328; Maloney, P.C. (1990) Res. Microbiol. 141, 374-383). Such a broad degree of conservation (or convergence) suggests a distinct structural and/or mechanistic advantage associated with the six-loop-six motif. The nature of this advantage is as yet unknown.

Alkaline Phosphatase↗

PubMed1978

Role of Na+ and Li+ in thiomethylgalactoside transport by the melibiose transport system of Escherichia coli.

Thiomethyl-beta-galactoside (TMG) accumulation via the melibiose transport system was studied in lactose transport-negative strains of Escherichia coli. TMG uptake by either intact cells or membrane vesicles was markedly stimulated by Na+ or Li+ between pH 5.5 and 8. The Km for uptake of TMG was approximately 0.2 mM at an external Na+ concentration of 5 mM (pH 7). The alpha-galactosides, melibiose, methyl-alpha-galactoside, and o-nitrophenyl-alpha-galactoside had a high affinity for this system whereas lactose, maltose and glucose had none. Evidence is presented for Li+-TMG or Na+-TMG cotransport.

Biological Transport, Active↗

PubMed1992

Melibiose permease of Escherichia coli: mutation of histidine-94 alters expression and stability rather than catalytic activity.

Previous studies utilizing site-directed mutagenesis [Pourcher et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 468-472] indicate that out of seven histidinyl residues in the melibiose (mel) permease of Escherichia coli, only His94 is important. The role of His94 has now been investigated by replacing the residue with Asn, Gln, or Arg. Cells expressing mel permease with Asn94 or Gln94 retain 30% or 20% of wild-type activity, respectively, and surprisingly, immunological assays demonstrate that diminished transport activity is due to a proportional reduction in the amount of permease in the membrane. Moreover, kinetic analyses of transport and ligand binding studies with right-side-out membrane vesicles indicate that both substrate recognition and turnover (kcat) are comparable in the mutant permeases and the wild-type. Mel permease with Arg in place of His94 also binds ligand and catalyzes sugar accumulation, but only when the cells are grown at 30 degrees C, and evidence is presented that Arg94 permease is inactivated at 37 degrees C. Finally, labeling studies demonstrate that expression and/or insertion of the permease, but not degradation, is strongly dependent on the amino acid present at position 94 and temperature. The findings indicate that an imidazole group at position 94 is required for proper insertion and stability of mel permease, but not for transport activity per se. Since replacement of the other six histidinyl residues in mel permease with Arg has little or no effect on transport activity, it is concluded that histidinyl residues do not play a direct role in the mechanism of this secondary transport protein.

Base Sequence↗

PubMed1976

Genetic co-regulation of galactose and melibiose utilization in Saccharomyces.

The gal3 mutation of Saccharomyces, which is associated with an impairment in the utilization of galactose, has been shown to be pleiotropic, causing similar impairments in the utilization of melibiose and maltose. Milibiose utilization and alpha-galactosidase production are directly controlled by the galactose regulatory elements i, c, and GAL4. The fermentation of maltose and the induction of alpha-glucosidase are regulated independently of the i, c, GAL4 system. The production of alpha-galactosidase and galactose-1-phosphate uridyl transferase is coordinate in galactokinaseless strains. Galactose serves as a nonmetabolized, gratuitous inducer of alpha-galactosidase in strains lacking the genes for one or more of the Leloir pathway enzymes.

Alleles↗

PubMed1978

Permease-specific mutations in Salmonella typhimurium and Escherichia coli that release the glycerol, maltose, melibiose, and lactose transport systems from regulation by the phosphoenolpyruvate:sugar phosphotransferase system.

Several carbohydrate permease systems in Salmonella typhimurium and Escherichia coli are sensitive to regulation by the phosphoenolpyruvate:sugar phosphotransferase system. Mutant Salmonella strains were isolated in which individual transport systems had been rendered insensitive to regulation by sugar substrates of the phosphotransferase system. In one such strain, glycerol uptake was insensitive to regulation; in another, the maltose transport system was resistant to inhibition; and in a third, the regulatory mutation specifically rendered the melibiose permease insensitive to regulation. An analogous mutation in E. coli abolished inhibition of the transport of beta-galactosides via the lactose permease system. The mutations were mapped near the genes which code for the affected transport proteins. The regulatory mutations rendered utilization of the particular carbohydrates resistant to inhibition and synthesis of the corresponding catabolic enzymes partially insensitive to repressive control by sugar substrates of the phosphotransferase system. Studies of repression of beta-galactosidase synthesis in E. coli were conducted with both lactose and isopropyl beta-thiogalactoside as exogenous sources of inducer. Employing high concentrations of isopropyl beta-thiogalactoside, repression of beta-galactosidase synthesis was not altered by the lactose-specific transport regulation-resistant mutation. By contrast, the more severe repression observed with lactose as the exogenous source of inducer was partially abolished by this regulatory mutation. The results support the conclusions that several transport systems, including the lactose permease system, are subject to allosteric regulation and that inhibition of inducer uptake is a primary cause of the repression of catabolic enzyme synthesis.

Biological Transport↗

PubMed1977

Yersinia enterocolitica: biochemical, serological, and gas-liquid chromatographic characterization of rhamnose-, raffinose-, melibiose-, and citrate-utilizing strains.

Thirteen atypical Yersinia enterocolitica isolates, all fermenting rhamnose, raffinose, and melibiose and utilizing sodium citrate within 24 to 48 h at 22 degrees C (Y.e.rh+), were examined biochemically-serologically, and by gas-liquid chromatography. These data, as well as cultural, biochemical, and antibiotic susceptibility data gathered from two previous studies involving (i) these same atypical Y.e.rh+ isolates, (ii) Y. enterocolitica serotypes O:1 through O:15 (rhamnose, raffinose, and citrate negative [Y.e.rh-]), (iii) Y. enterocolitica serotype O:16 (rhamnose positive but raffinose and citrate negative), and (iv) Yersinia pseudotuberculosis serogroups I through V were statistically compared. Both preand postabsorption agglutination studies demonstrated the serological distinctiveness of Y.e.rh+ from Y.e.rh- and Y. pseudotuberculosis. At the same time, three immunological groups among the 13 Y.e.rh+ strains were seen; 8 corresponded to Y. enterocolitica serotype O:17; 1 to Y. enterocolitica serotype O:16; and the remaining four were nontypable in antisera against known Y. enterocolitica antigen types. Each of the three Yersinia groups tested chromatographically produced acetic and lactic acids. Both Y.e.rh- and Y.e.rh+ formed propionic acid, but only Y.e.rh+ produced detectable amounts of succinic acid. Based on 49 variables, statistical analysis of the three Yersinia groups studied placed each of the Y.e.rh+ strains in a homogeneous group separate from both Y.e.rh- and Y. pseudotuberculosis. These data, coupled with deoxyribonucleic acid homology studies of Brenner and co-workers (D. J. Brenner, A. G. Steigerwalt, D. F. Falcao, R. E. Weaver, and G. R. Fanning, Int. J. Syst. Bacteriol. 26:180-194, 1976), support the distinctiveness of Y.e.rh+ from typical Y. enterocolitica and Y. pseudotuberculosis.

Chromatography, Gas↗

PubMed1977

A xanthine-negative, melibiose-positive species of Streptomyces.

The organism VH/CN-71 which had been isolated from a growth in a cat and described initially as an "unusual strain of Nocardia" is a streptomycete. This organism can also produce acid from melibiose although it is unable to decompose xanthine. Its sporophores are short, hooked, curved, or open-looped with extended spirals. Present data suggest that VH/CN-71 may belong to the "flavus" series of Streptomyces.

Animals↗

PubMed1976

Sugar transport. 2nducer exclusion and regulation of the melibiose, maltose, glycerol, and lactose transport systems by the phosphoenolpyruvate:sugar phosphotransferase system.

The bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) can repress the synthesis of certain catabolic enzyme systems in Salmonelly typhimurium and Escherichia coli. The present studies are concerned with an explanation of PTS-mediated repression by studying induction of the catabolic systems required for utilization of the non-PTS sugars glycerol, maltose, melibiose, and lactose. Repression of synthesis of these enzyme systems by various concentrations of PTS sugars was studied in wild type cells, in pts mutants, and in pts crr double mutants described in the accompanying reports (Saier, M. H., Jr., Simoni, R. D., and Roseman, S (1976) J. Biol. Chem. 251, 6584-6597: Saier, M. H., Jr., and Roseman, S. (1976) J. Biol. Chem., 6598-6605). The extent of repression was found to correlate with the degree of inhibition of uptake of the inducing non-PTS sugars. In both uninduced cells and cells fully induced for the respective transport system listed above, PTS sugars inhibited these transport systems. With both induced and uninduced cell types pts mutants were much more sensitive than wild type cells, while pts crr double mutants were completely resistant to the effects of the PTS sugars. Kinetic studies with the fully induced cells indicated that inhibition of transport by PTS sugars was reversible, that it affected the Vmax rather than the Km of entry, and that PTS sugars did not inhibit the efflux of the non-PTS sugars. These and other results indicate that inhibition did not result from competition between the PTS and non-PTS sugars for the transport systems, nor to competition for metabolic energy. Inhibition appears to require interaction of the PTS sugar with its membrane-bound Enzyme II complex, but whether concomitant uptake and phosphorylation of trace quantities of the PTS sugars is also required remains to be determined.

Biological Transport, Active↗