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PubMed2005

Identification of a novel conjugate in human urine: bile acid acyl galactosides.

We report a novel conjugate, bile acid acyl galactosides, which exist in the urine of healthy volunteers. To identify the two unknown peaks obtained in urine specimens from healthy subjects, the specimens were subjected to solid phase extraction and then to liquid chromatographic separation. The eluate corresponding to the unknown peaks on the chromatogram was collected. Following alkaline hydrolysis and liquid chromatography (LC)/electrospray ionization (ESI)-mass spectrometric (MS) analysis, cholic acid (CA) and deoxycholic acid (DCA) were identified as liberated bile acids. When a portion of the alkaline hydrolyzate was subjected to a derivatization reaction with 1-phenyl-3-methyl-5-pyrazolone, a derivative of galactose was detected by LC/ESI-MS. Finally, the liquid chromatographic and mass spectrometric properties of these unknown compounds in urine specimens were compared to those of authentic specimens and the structures were confirmed as CA 24-galactoside and DCA 24-galactoside. These results strongly imply that bile acid 24-galactosides, a novel conjugate, were synthesized in the human body.

Adult↗
PubMed1991

Localization of endogenous beta-galactoside-specific lectins by neoglycoproteins, lectin-binding tissue glycoproteins and antibodies and of accessible lectin-specific ligands by mammalian lectin in human breast carcinomas.

Protein-carbohydrate interactions constitute a system of molecular interaction with relevance to pathologic conditions. Carrier-immobilized carbohydrate structures enable the histochemical investigation of the protein part of this recognitive system. However, thorough systematic studies are inevitably required for standardized application of this relatively novel class of markers. Consequently, serial sections of 21 cases of malignant breast lesion were comparatively analyzed with three different types of probe, specific for beta-galactoside-binding lectins. In addition to the chemically lactosylated neoglycoprotein, human lectin-binding glycoproteins, purified by affinity chromatography on resins with an immobilized beta-galactoside-specific lectin, and a lectin-specific antibody were employed to answer the question whether differences occur in their capacity for lectin localization. The patterns of staining were qualitatively similar, the lectin-binding glycoproteins yielding the most intense reaction. Having assured the reliable applicability of the neoglycoprotein, structural alterations of the subterminal carbohydrate residue on the labelled carrier addressed the issue, whether selectivity of binding can be inferred histochemically, allowing rational synthetic tailoring. An N-acetylglucosamine residue in beta-1,3-linkage proved to be a less favorable extension than this type of sugar in beta-1,4-linkage or an N-acetylgalactosamine moiety in beta-1,3-linkage. Binding was clearly reduced in cells of normal breast tissue with this probe. In order to gain evidence on the expression of potential carbohydrate ligands for the glyco- and immunohistochemically localized binding activity, a labelled mammalian beta-galactoside-specific lectin was similarly used as histochemical tool. It effectively bound to accessible sites in the sections. The binding pattern was different to that of plant lectins with specificity to beta-galactosides. This result underscores that caution is necessary in the functional interpretation of results of studies with plant, not mammalian lectins.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies↗
PubMed2002

Biological activity of alpha-galactoside preparations from Lupinus angustifolius L. and Pisum sativum L. seeds.

Biological activity tests were performed on alpha-galactoside preparations obtained from Lupinus angustifolius L. cv. Mirela (alkaloid-rich) and Pisum sativum L. cv. Opal seeds. The studies included the following tests: acute toxicity, cytotoxic test, delayed type hypersensitivity (DTH), plaque-forming cell number (IgM-PFC), and influence on the growth of bifidobacteria and coliform presence in rat colon. Results of these studies showed that alpha-galactosides from lupin and pea seeds were essentially nontoxic. Their acute toxicity (LD(50)) in mice was >4000 mg kg(-1) of body weight. alpha-galactoside preparations were not cytotoxic for mouse thymocytes in vitro. The in vitro test shows that oligosaccharides from lupin and pea are utilized by selected beneficial colon bacterium strains. The in vivo experiment demonstrated that alpha-galactosides from legume significantly influenced the growth of bifidobacteria in rats colon. Simultaneously, the decrease of the coliform presence was observed. The chemical composition of the tested preparations had no significant effect on their biological activity.

Animals↗
PubMed1981

Mitogenicity and binding properties of beta-galactoside-binding lectin from chick-embryo kidney.

THe beta-galactoside-binding lectin binds to glucosamine, mannosamine and galactosamine in addition to beta-galactoside, as determined by the inhibition of haemagglutination. Haemagglutination is further extended to examine the interaction of the binding sites for hexosamines and beta-galactosides, indicating that the binding of hexosamine and beta-galactoside is competitive. The lectin also shows strong mitogenic activity toward lymphocytes from mouse lymph node, as determined by the stimulation of thymidine incorporation.

Animals↗
PubMed1981

The kinetics of the beta-galactoside-proton symport of Escherichia coli.

beta-Galactoside transport by Escherichia coli occurs with the concomitant uptake of a proton. The kinetics of beta-galactoside uptake at various values of external pH are interpreted in terms of a model in which both the galactoside and the proton are substrates of the transport reaction. The values of some of the kinetic constants for this two-substrate reaction were determined. The observed effects of the protonmotive force on the apparent Michaelis constant for galactoside can be explained in terms of the proton being a substrate of the transport reaction.

Biological Transport↗
PubMed1995

Elevated expression of H type GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase is associated with human colon adenocarcinoma progression.

GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase (EC 2.4.1.69) is a key enzyme in the biosynthesis of fucosylated type 1 and 2 lactoseries structures, such as Lewis b and the H type 2 and Lewis Y, respectively, that are accumulated in colon adenocarcinoma. Analysis of the mRNA transcript level for the human H gene-encoded beta-D-galactoside alpha-2-L-fucosyltransferase revealed 40- and 340-fold increases in the mRNA levels in all adenocarcinomas and tumor cell lines, respectively, compared to normal colon mucosa where a low level of mRNA transcript was detected. A variable increase in mRNA transcript levels was observed in 50% of adenomatous polyps. Nucleotide sequence analysis of the protein coding region of the cDNAs derived from normal colon, adenoma, and colon adenocarcinoma revealed 100% homology, suggesting that there are no tumor-associated allelic variations within the H beta-D-galactoside alpha-2-L-fucosyltransferase cDNA. These results suggest that beta-D-galactoside alpha-2-L-fucosyltransferase expression highly correlates with malignant progression of colon adenocarcinoma.

Adenocarcinoma↗
PubMed1980

Rat hepatocytes bind to synthetic galactoside surfaces via a patch of asialoglycoprotein receptors.

The binding of rat hepatocytes to flat polyacrylamide surfaces containing galactose is sugar-specific, requires Ca+2, and occurs only above a critical concentration of sugar in the substratum [Weigel et al., 1979, J. Biol. Chem., 254, 10,830). Binding is completely inhibited by asialo-orosomucoid but not by orosomucoid or asialo-agalacto-orosomucoid, suggesting that cell binding is mediated by asialoglycoprotein receptors. Asialo-orosomucoid was labeled with fluorescein isothiocyanate and used as a direct fluorescent probe to monitor the distribution of cell surface asialoglycoprotein receptors before and after hepatocyte binding to galactoside or control substrata. Cells bound at 37 degrees C were de-adhered at 4 degrees C using the Ca+2 chelator EGTA. The released cells were then stained with fluorescein-asialo-orosomucoid, fixed, washed, and examined by fluorescence microscopy. On freshly isolated cells before binding, the distribution of asialoglycoprotein receptors appears diffuse and nonclustered. However, more than half of the cells released intact from a galactoside surface had a single large (4 micrometer2) fluorescent patch. The receptor patch cannot be detected on cells while they are bound to a galactoside surface but rather only on released cells, indicating that the cell-substratum junction is the site of the receptor patch. No asialoglycoprotein receptor patches (less than or equal to 1%) were observed on cells that were incubated on, but did not bind to, an underivatized polyacrylamide surface or to a surface with a galactose concentration below the critical concentration for binding. Furthermore, no receptor patches were present on cells that had bound to and were subsequently released from substrata that did not contain galactose, including glass, tissue culture plastic, nontissue culture plastic, and collagen. The distribution of asialoglycoprotein receptors is preserved at 4 degrees C because at 37 degrees C the patches disappear with a half-life of approximately 2.6 min. The results directly demonstrate that a large cluster of asialoglycoprotein receptors mediates the binding of rat hepatocytes to a galactoside surface.

Animals↗
PubMed1984

Purification of the lactose:H+ carrier of Escherichia coli and characterization of galactoside binding and transport.

The lactose carrier, a galactoside:H+ symporter in Escherichia coli, has been purified from cytoplasmic membranes by pre-extraction of the membranes with 5-sulfosalicylate, solubilization in dodecyl-O-beta-D-maltoside, Ecteola-column chromatography, and removal of residual impurities by anti-impurity antibodies. Subsequently, the purified carrier was reincorporated into E. coli phospholipid vesicles. Purification was monitored by tracer N-[3H]ethylmaleimide-labeled carrier and by binding of the substrate p-nitrophenyl-alpha-D-galactopyranoside. All purified carrier molecules were active in substrate binding and the purified protein was at least 95% pure by several criteria. Substrate binding to the purified carrier in detergent micelles and in reconstituted proteoliposomes yielded a stoichiometry close to one molecule substrate bound per polypeptide chain. Large unilamellar proteoliposomes (1-5-micron diameter) were prepared from initially small reconstituted vesicles by freeze-thaw cycles and low-speed centrifugation. These proteoliposomes catalyzed facilitated diffusion and active transport in response to artificially imposed electrochemical proton gradients (delta mu H+) or one of its components (delta psi or delta pH). Comparison of the steady-state level of galactoside accumulation and the nominal value of the driving gradients yielded cotransport stoichiometries up to 0.7 proton/galactoside, suggesting that the carrier protein is the only component required for active galactoside transport. The half-saturation constants for active uptake of lactose (KT = 200 microM) or beta-D-galactosyl-1-thio-beta-D-galactoside (KT = 50-80 microM) by the purified carrier were found to be similar to be similar to those measured in cells or cytoplasmic membrane vesicles. The maximum rate for active transport expressed as a turnover number was similar in proteoliposomes and cytoplasmic membrane vesicles (kcat = 3-4 s-1 for lactose) but considerably smaller than in cells (kcat = 40-60 s-1). Possible reasons for this discrepancy are discussed.

Bacterial Proteins↗
PubMed1992

Increased expression of the negative growth factor, galactoside-binding protein, gene in transformed thyroid cells and in human thyroid carcinomas.

Murine beta-galactoside-binding protein has been shown to be a cell growth regulatory molecule and a cytostatic factor. We analysed the beta-galactoside-binding protein gene expression in a thyroid cell system including two normal cell lines (FRTL-5 and PC Cl 3) and the same cells transfected by several oncogenes that induce different degrees of malignancy and differentiation. We show that beta-galactoside-binding protein mRNA levels correlate with the expression of the malignant phenotype. Run-on experiments suggest that a transcriptional effect accounts at least in part for such a difference. We also show that the beta-galactoside-binding protein gene expression is increased in most human papillary thyroid carcinomas compared with normal thyroid.

Adenovirus E1A Proteins↗
PubMed1990

The mechanism of initiation of chondroitin sulphate synthesis by beta-D-galactosides.

Embryonic chicken cartilage was incubated in vitro with phenyl-beta-[6-3H]galactoside and cycloheximide. Free chondroitin sulphate chains initiated by galactoside were isolated and degraded to yield 3-O-beta-D-glucuronosyl D-galactose (GlcA-Gal) derived from the sequence, GlcA-Gal-Gal-Xyl-Ser, which links the polysaccharide to protein. This enabled the distribution of 3H into specific galactose residues within the linkage oligosaccharide to be determined. Most of the 3H label (65%) was released as free galactose although 35% was recovered as GlcA-Gal. Similar experiments performed with unlabelled phenyl-beta-galactoside and [14C]galactose yielded 14C-labelled GlcA-Gal as a major product. We conclude that beta-galactosides initiate chondroitin sulphate synthesis primarily by serving as substrates for galactosyl transferase II.

Animals↗
PubMed1990

Binding characteristics of galactoside-binding lectin (galaptin) from human spleen.

Binding characteristics of human spleen soluble galactoside-binding protein (galaptin) were studied using simple galactosides, galactose-terminated disaccharides, cluster glycosides containing up to 6 terminal lactosyl residues, bovine serum albumin derivatives containing 7 to 40 lactosyl residues, desialylated serum glycoproteins, and glycopeptides derived thereof as inhibitors in a newly developed binding assay. In this assay, aminohexyl lactoside was attached to divinyl sulfone-activated Sepharose, which was then used to bind 125I-galaptin. Similarly derivatized Sepharose containing mannoside served as a control. The assay is sensitive, maintains linearity in the concentration range of 125I-galaptin tested, and has very low nonspecific binding. The following new findings were made. 1) All the alpha-D-galactopyranosides with non-sugar aglycon were better inhibitors than the corresponding beta-D-galactopyranoside. 2) The S-galactosides were better inhibitors than the corresponding O-galactosides, regardless of the anomeric configuration. 3) Many Gal beta 1-4- and Gal beta 1-3-linked disaccharides were tested. Although the galaptin did not appear to recognize N-acetylglucosamine as a monosaccharide, the presence of this sugar penultimate to galactose increased the binding affinity by as much as 500-fold, as was the case for N-acetyllactosamine. Of a particular importance is the presence of an equatorial 3-OH group on this sugar. We synthesized the 3-deoxy derivative of N-acetyllactosamine and found that it had 50-fold lower binding affinity compared to N-acetyllactosamine. 4) The binding sites of this lectin do not seem to be operating in a cooperative fashion, since synthetic lactose-containing divalent ligands with various inter-galactose distances did not increase the binding affinity significantly.

Binding Sites↗
PubMed1982

The subcellular localization of the beta-galactoside-binding protein of rat lung.

The subcellular localization of the beta-galactoside-binding protein, or lectin, from rat lung was investigated by the specific binding of anti-lectin immunoglobulin G to subcellular fractions. We used both adult and immature (12-day-old) rats; the immature rat lungs have an 8-10-fold greater concentration than adult rat lungs [Powell & Whitney (1980) Biochem. J. 188, 1-8]. In both groups of animals we observed greater specific binding of anti-lectin immunoglobulin G to intracellular membrane (mitochondrial and microsomal fractions) than to plasma membranes. Pre-incubation of membrane fractions with lactose resulted in a marked diminution of anti-lectin immunoglobulin G binding. In the adult rat lung most (approx. 80%) of the lectin activity was membrane-associated. In the immature rat lung only approx. 30% of the lectin activity was membrane associated and most of the beta-galactoside-binding protein appeared to be a soluble cytoplasmic component. The rat lung beta-galactoside-binding protein appeared to have a broad but predominantly intracellular location, being associated with membranes through one of its galactoside-binding sites.

Age Factors↗
PubMed1987

Biosynthesis of polylactosaminoglycans. Novikoff ascites tumor cells contain two UDP-GlcNAc:beta-galactoside beta 1----6-N-acetylglucosaminyltransferase activities.

Novikoff ascites tumor cells contain a UDP-GlcNAc:beta-galactoside beta 1----6-N-acetylglucosaminyltransferase (beta 6-GlcNAc-transferase B) that acts on galactosides and N-acetylgalactosaminides in which the accepting sugar is beta 1----3 substituted by a Gal or GlcNAc residue. Characterization of enzyme products by 1H-NMR and methylation analysis indicates that an R beta 1----3(GlcNAc beta 1----6)Gal- branching point is formed such as occurs in blood-group-I-active substances. The enzyme does not show an absolute divalent cation requirement and 20 mM EDTA is not inhibitory. The activity is strongly inhibited by Triton X-100 at concentrations of greater than or equal to 0.2%. Competition studies suggest that a single enzyme acts on Gal beta 1----3Gal beta 1----4Glc, GlcNAc beta 1----3Gal beta 1----4GlcNAc and GlcNAc beta 1----3GalNAc alpha-O-benzyl (Km values 0.71, 0.83 and 0.53 mM, respectively). Gal beta----3Gal beta 1----4Glc as an acceptor substrate for beta 6-GlcNAc-transferase B does not inhibit the incorporation of GlcNAc in beta 1----6 linkage to the terminal Gal residues of asialo-alpha 1-acid glycoprotein catalyzed by a beta-galactoside beta 1----6-N-acetylglucosaminyltransferase (beta 6-GlcNAc-transferase A) previously described in Novikoff ascites tumor cells [D. H. Van den Eijnden, H. Winterwerp, P. Smeeman & W.E.C.M. Schiphorst (1983) J. Biol. Chem. 258, 3435-3437]. Neither is Triton X-100 at a concentration of 0.8% inhibitory for the activity of beta 6-GlcNAc-transferase A. This activity is absent from hog gastric mucosa microsomes, which has been described to contain high levels of beta 6-GlcNAc-transferase B. [F. Piller, J. P. Cartron, A. Maranduba, A. Veyrières, Y. Leroy & B. Fournet (1984) J. Biol. Chem. 259, 13,385-13,390]. Our results show that Novikoff tumor cells contain two beta-galactoside beta 6-GlcNAc-transferases, which differ in acceptor specificity and tolerance towards Triton X-100. A role for these enzymes in the synthesis of branched polylactosaminoglycans and of O-linked oligosaccharide core structures having blood-group I activity is proposed.

Animals↗
PubMed1997

Coregulation of beta-galactoside uptake and hydrolysis by the hyperthermophilic bacterium Thermotoga neapolitana

Regulation of the beta-galactoside transport system in response to growth substrates in the extremely thermophilic anaerobic bacterium Thermotoga neapolitana was studied with the nonmetabolizable analog methyl-beta-D-thiogalactopyranoside (TMG) as the transport substrate. T. neapolitana cells grown on galactose or lactose accumulated TMG against a concentration gradient in an intracellular free sugar pool that was exchangeable with external galactose or lactose and showed induced levels of beta-galactosidase. Cells grown on glucose, maltose, or galactose plus glucose showed no capacity to accumulate TMG, though these cells carried out active transport of the nonmetabolizable glucose analog 2-deoxy-D-glucose. Glucose neither inhibited TMG uptake nor caused efflux of preaccumulated TMG; rather, glucose promoted TMG uptake by supplying metabolic energy. These data show that beta-D-galactosides are taken up by T. neapolitana via an active transport system that can be induced by galactose or lactose and repressed by glucose but which is not inhibited by glucose. Thus, the phenomenon of catabolite repression is present in T. neapolitana with respect to systems catalyzing both the transport and hydrolysis of beta-D-galactosides, but inducer exclusion and inducer expulsion, mechanisms that regulate permease activity, are not present. Regulation is manifest at the level of synthesis of the beta-galactoside transport system but not in the activity of the system.

Journal Article↗
PubMed1969

Energy coupling in the transport of beta-galactosides by Escherichia coli: effect of proton conductors.

Escherichia coli accumulates thiomethyl-beta-d-galactoside against a concentration gradient under anaerobic conditions. The accumulation was abolished by carbonylcyanide m-chlorophenylhydrazone, tetrachlorosalicylanilide, 2,4 dinitrophenol, and other uncouplers of oxidative phosphorylation even though oxidative phosphorylation would not be expected to occur anaerobically. In the presence of the uncouplers, the beta-galactoside carrier remained functional and catalyzed equilibration of thiomethylgalactoside across the membrane. The uncouplers did not inhibit the generation of adenosine triphosphate or protein turnover, or the accumulation of alpha-methylglucoside and glycerol by phosphorylation. We conclude that, at least anaerobically, uncouplers of oxidative phosphorylation do not interfere with energy metabolism in general, but prevent the utilization of metabolic energy for the active transport of galactosides. The uncouplers also facilitate passage of protons across the membrane. Various hypotheses are considered to explain why a proton-impermeable membrane may be required for active transport of galactosides and other substrates.

Adenosine Triphosphate↗
PubMed1970

Gargoylism: hydrolysis of beta-galactosides and tissure accumulation of galactose- and mannose-containing compounds.

The sugars present in hydrolyzed extracts of human liver and brain were analyzed by gasliquid chromatography after conversion to their alditol acetates. The samples analyzed were obtained from control subjects, patients with gargoylism, and patients with a few other kinds of storage disorders. Accumulation of galactose was demonstrated in the liver and the brain of two patients with gargoylism, and in the liver samples, high levels of mannose were found too. We also studied the hydrolysis of a number of galactosides by homogenates from different tissues in the control subjects and in the patients. Separation methods and kinetic studies demonstrated the presence in normal human tissues of two different beta-galactosidases, which we call enzyme A and enzyme B, respectively. Enzyme A hydrolyzed all the beta-galactosides tested. Enzyme B hydrolyzed the synthetic substrates tested (4-methylumbelliferyl-, p-nitrophenyl-, o-nitrophenyl-, and phenyl-beta-galactoside) but not the natural substrates tested (ceramide-beta-galactoside, ceramide lactoside, transferrin glycopeptide, and keratan sulfate). Enzyme B also exerted beta-glucosidase activity. In various tissues from patients with gargoylism, deficiency of beta-galactosidase A could be demonstrated. It is suggested that the high level of galactose found in the hydrolyzed extracts of tissues from gargoylism patients is due to storage of galactose-rich glycosaminoglycans and glycopeptides, and that this storage is a result of the deficiency of beta-galactosidase A. The high level of mannose in the liver from gargoylism patients seems to indicate storage of glycopeptide, adding a new group of substances to those known to be stored in gargoylism.

Brain↗
PubMed1975

Energy-dependent binding of dansylgalactosides to the beta-galactoside carrier protein.

Fluorescent beta-galactosides (1-(N-dansyl)amino-beta-D-galactopyranoside (DG0), 2'-(N-dansyl)aminoethyl-beta-D-thiogalactopyranoside (DG2), 2'-(N-dansyl)aminoethyl-beta-D-galactopyranoside (oxy-DG2), and 6'-(N-dansyl)aminohexyl-beta-D-thiogalactopyranoside (DG6)) competitively inhibit lactose transport by membrane vesicles from Escherichia coli ML 309-225, but are not actively transported. An increase in the fluorescence of these dansylgalactosides is observed upon addition of D-lactate, imposition of a membrane diffusion potential (positive outside), or dilution-induced, carrier-mediated lactose efflux. The increase is not observed with 2'-(N-dansyl)aminoethyl-beta-D-thioglucopyranoside nor with membrane vesicles lacking the beta-galactoside transport system. Moreover, the D-lactate-induced fluorescence increase is blocked or rapidly reversed by addition of beta-galactosides, sulfhydryl reagents, inhibitors of D-lactate oxidation, or uncoupling agents. The fluorescence increase exhibits an emission maximum at 500 nm and excitation maxima at 345 nm and at 292 nm. The latter excitation maximum is absent unless D-lactate is added, indicating that the bound dansylgalactoside molecules are excited by energy transfer from the membrane proteins. Titration of vesicles with dansylgalactosides in the presence of D-lactate demonstrates that the lac carrier protein constitutes 3 to 4% oof the total membrane protein, and that the affinity of the carrier for substrate is directly related to the length of the alkyl chain between the galactosidic and the dansyl moieties of the dansylgalactosides. In addition, there is excellent agreement between the affinity constants of the various dansylgalactosides as determined by fluorimetric titration and their apparent Kis for lactose transport (KDs and/or apparent Kis are approximately 550, 3o, 40, and 5 muM FOR DG0, DG2, oxy-DG2, and DG6, respectively). Polarization of fluorescence measurements with DG2 and DG6 demonstrate a dramatic increase in polarization on addition of D-lactate which is reversed by addition of lactose or anaerobiosis. These findings provide strong evidence for the contention that the fluorescence changes observed on "energization" of the membrane are due to binding of the dansylgalactosides per se, rather than binding followed by transfer into the hydrophobic interior of the membrane

Bacterial Proteins↗
PubMed1978

The protonmotive force and beta-galactoside transport in Bacillus acidocaldarius.

The acidophilic and thermophilic bacterium, Bacillus acidocaldarius maintains a cytoplasmic pH between 5.85 and 6.31 over a range of external pH from 2.0 to 4.5. Consistently, the pH optimum of beta-galactosidase, as assayed in cell extracts, is between pH 6.0 and 6.5. An electrical potential (delta-psi), interior positive, is also maintained across the membrane. A delta-psi of approximately 34 mV was calculated from determinations of thiocyanate uptake by cells at pH 3.5. Addition of the proton conductor carbonyl cyanide m-chlorophenylhydrazone increased the delta-psi. Treatment of cells with valinomycin (in the absence of external potassium ions) or high concentrations of thiocyanate, to abolish the delta psi, resulted in collapse of the transmembrane proton gradient (delta pH). Active transport of methylthio-beta, D-galactoside occurred optimally at pH 3.5. Transport of the galactoside was inhibited by various compounds which could dissipate the transmembrane delta pH and by respiratory inhibitors. A decrease in the delta pH and an increase in the delta psi occurred upon addition of methylthio-beta, D-galactoside to cells of B. acidocaldarius. Thus the transport of this solute appears to involve an electrogenic symport with protons. The transport system is most active at 50 degrees C and shows little activity at 25 degrees C, although the delta pH is the same at the two temperatures. Gramicidin inhibits methylthio-beta, D-galactoside transport equally effectively at 50 degrees C and 25 degrees C, while nigericin inhibits only after a lag at 25 degrees C.

Bacillus↗