Associative properties of the Escherichiacoli galactose binding protein and maltose binding protein

The periplasmic galactose binding protein and maltose binding protein of $\text{Escherichia}\text{coli}$ are recovered mostly in dimeric form when purified, from osmotically-shocked bacteria, in the presence of protease inhibitors and 2-mercaptoethanol without dialysis and concentration of the shock fluid. The specific ligands, galactose (but not glucose) for galactose binding protein, and maltose for maltose binding protein, provoque the monomerisation of the dimeric native forms. These results are discussed in relation to the function of both binding proteins in transport and chemotaxis.     

Generation of small plasmids from colicin E1 factor carrying genes for galactose utilization and ampicillin resistance,.

Ampicillin-resistant colonies that did not utilize galactose appeared sporadically in cultures of galactose genedeleted $\text{Escherichia coli}$ K-12 cells containing colicin E1 factor carrying genes for galactose utilization and ampicillin resistance. Most of these colonies contained small plasmid DNAs. These plasmids existed as monomer DNAs within $\text{E. coli}$ K-12 cells and formed a series of covalently closed circular DNA molecules ranging in size from 6.3 × 10⁶ to 15.1 × 10⁶ daltons. The use of these plasmid DNAs was discussed.     

Mitochondrial mutants of the yeast Saccharomyces cerevisiae showing resistance in vitro to chloramphenicol inhibition of mitochondrial protein synthesis

Two cytoplasmic genetic mutants of yeast, genetically separable by recombination, displaying high levels of chloramphenicol resistance have been isolated. Protein synthesis in isolated mitochondria of mutant [$\text{cap 2-r}$] is almost completely resistant to chloramphenicol inhibition while that in mitochondria of mutant [$\text{cap 1-r}$] is partially resistant. Biochemical differences between the two mutants were confirmed by studies of chloramphenicol inhibition of aerobic adaptation of anaerobically grown cells. The mutants appear to contain altered mitochondrial ribosomes.     

Glutamine-requiring mutants of Bacillus subtilis.

Two glutamine-requiring (Gln^?) mutants of $\text{Bacillus subtilis}$ SMY were deficient in glutamine synthetase activity $\text{in vitro}$. The Gln^? mutants sporulated poorly unless glutamine was provided at high concentrations. The differential rate of histidase synthesis following induction was 4- to 6-fold higher in the Gln^? mutants than in wild-type cells. In addition, glucose repression of utilization of alternative carbohydrates appeared to be partially relieved in the Gln^? mutants.     

Steric factors involved in the action of glycosidases and galactose oxidase

α-(1→2)-$\text{L}\text{=}$-Fucosidase, β-$\text{D}\text{=}$-galactosidase and galactose oxidase are sterically hindered by certain types of branching in the oligosaccharide chains. 1) β-$\text{D}\text{=}$-Galactosidase will not cleave galactose when the penultimate sugar carries a sialic acid residue as in I. 2) Galactose Oxidase will not oxidize the galactose residue in trisaccharide I but will in II. Moreover, neither galactose nor $\text{N}$-acetylgalactosamine, glycosidically bound as in III, is susceptible to oxidation with galactose oxidase until the α-(1→2) linkage between them is cleaved by $\text{α-}\text{N}\text{-acetylgalactosaminidase}$. 3) α-(1→2)-$\text{L}\text{=}$-Fucosidase action is inhibited by $\text{α-(1→3)-}\text{N}\text{-acetylgalactosaminyl}$ or galactosyl residue, as in III and IV. Removal of the terminal sugars makes the fucosyl residue susceptible to fucosidase action.

     

Glycoprotein characteristics of the sodium channel saxitoxin-binding component from mammalian sarcolemma

The saxitoxin-binding component of the excitable membrane sodium channel exhibits glycoprotein characteristics as evidenced by its specific interaction with various agarose-immobilized lectins. The detergent-solubilized saxitoxin-binding component interacts quantitatively with immobilized wheat germ agglutinin and concanavalin A and fractionally with immobilized Lens culinaris hemagglutinin and Ricinus communis agglutinin. These lectins preferentially bind $\text{N-}\text{acetylglucosamine}$ and sialic acid (wheat germ agglutinin), mannose (concanavalin A and Lens cunilaris and galactose (Ricinus communis). Removal of terminal sialic acid residues by neuraminidase markedly decreases binding to immobilized wheat germ agglutinin but uncovers sites capable of interacting with lectins specific for galactose and $\text{N-}\text{acetylgalactosamine}$. $\text{β-N-}\text{acetylglucosaminidase}$, an exoglycosidase has no effect on the binding of the channel protein to wheat germ agglutinin. Similarly, phospholipase C has no effect on binding of the solubilized toxin binding component to this lectin. Neither wheat germ agglutinin nor concanavalin A free in solution alters the number of toxin binding sites or their affinity for toxin. The sodium channel saxitoxin-binding component appears to be a glycoprotein containing terminal sialic acid residues and internal mannose, galactose, $\text{N-}\text{acetylglucosamine}$, and $\text{N-}\text{acetylgalactosamine}$ residues. The toxin binding site is spatially separated from the binding sites for the lectins studied. The effect of these sugar moieties must be considered when evaluating the biophysical parameters of the sodium channel.     

Enxymology of human colon tumors

The biochemical strategy of human colon adenocarcinoma was studied by elucidating the enzymic programs of pyrimidine biosynthesis and degradation, glycolysis, pentose phosphate production, and galactose metabolism in normal colon mucosa and in 9 cases of primary colon adenocarcinoma. Enzymic activities were determined in the 100,000 X $\text{g}$ supernatant fluid with spectrophotometric or isotopic assays under optimum conditions yielding linear kinetics. In the human colon tumors the activities of enzymes of the $\text{de}$$\text{novo}$ pyrimidine biosynthesis, CTP synthetase, OMP decarboxylase, and orotate phosphoribosyltransferase, were increased to 348, 183, and 201% of those of normal human colon mucosa. The activities of the salvage pathway enzymes, thymidine kinase, uracil phosphoribosyltransferase and uridine kinase, were increased to 331, 254 and 281%. By contrast, the activity of the catabolic enzyme, uridine phosphorylase, was decreased to 69%. The ratio of activities of uridine kinase/ uridine phosphorylase was elevated to 564%. The activities of the key glycolytic enzymes, hexokinase and pyruvate kinase, and those of pentose phosphate production, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and transaldolase, increased to 348, 209, 262, 156, and 180% respectively. The activity of the first committed enzyme of galactose utilization, galactokinase, was increased to 315%. The enzymic program of human primary colonic adenocarcinoma was similar in most respects to that which we observed in chemically-induced, transplantable adenocarcinomas of the colon in mouse and in rat (4). The reprogramming of gene expression in human colon tumor provides an increased capacity for biosynthesis of pyrimidines and ribose 5-phosphate, and for utilization of the glycolytic pathway and of galactose. These alterations in gene expression should confer selective advantages to the human colon tumor cells. The marked elevations in the activities of the salvage enzymes, uridine-cytidine kinase and thymidine kinase, explain in part the failure to obtain good therapeutic results with inhibitors of the $\text{de}$$\text{novo}$ pathway and account, in part at least, for the clinical difficulties encountered in the treatment of colon tumors. The elevated activities of CTP synthetase, OMP decarboxylase, uridine-cytidine kinase and thymidine kinase mark out these enzymes as targets for combination chemotherapy. Through such enzyme-pattern-targeted chemotherapy the drug treatment of human colon tumors should be improved.     

Metabolic effects of glucose deprivation and of various sugars in normal and transformed fibrobalst cell lines.

The sugar composition of the growth medium influenced the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio, pyruvate and lactate production, and ATP levels in both normal and transformed fibroblast cell lines growing in tissue culture. Removal of glucose led to a rapid three- to fourfold rise in the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio, followed by a slower decline in the content of ATP. However, there was no change in the adenylate energy charge [$\text{(}\text{ATP}\text{+}\text{1}\text{2}\text{ADP}\text{)/(}\text{ATP + ADP + AMP}\text{)}$] over a 2-h period. The $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio was restored to the original level within 10 s of glucose readdition. The $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ratios in cell lines growing on galactose were as high as for those incubated without sugars; growth on mannose or fructose produced intermediate ratios. There was an inverse relationship between the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio and pyruvate-lactate production for glucose, fructose and galactose. Thus, all cell lines had a high production of pyruvate and lactate but a low $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio when grown on glucose. In contrast, when galactose served as the sugar source, acid production was low, while the ratio was high. All cell lines had comparable hexokinase activity, and glucose was the best substrate, mannose intermediate and fructose poorest. Hexokinase activity did not correlate with the relative degree of utilization of the sugars. These results suggest that the sugar composition of the growth medium affects the metabolic pattern of a cell line, including the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio, the ATP content and the production of pyruvate and lactate.     

Structure of the "keratosulfate-like" material in liver from a patient with G M1 -gangliosidosis ( -D-galactosidase deficiency)

Large amounts of a glycopeptide containing galactose, $\text{N}$-acetylglucosamine, $\text{N}$-acetylgalactosamine and threonine in the ratio 4:3:1:1, together with smaller amounts of mannose, fucose, sialic acid, sulfate, serine, and other amino acids were isolated from the liver of a patient with G_M1-gangliosidosis. Treatment with mild alkali and sodium borohydride indicated an $\text{O}$-glycosidic linkage between $\text{N}$-acetylgalactosamine and threonine. All the hexosamine residues were resistant to sodium metaperiodate whereas 2 out of 4 D-galactose residues were destroyed. Further studies indicated that one of the galactose residues was 1→3 linked to $\text{N}$-acetylgalactosamine (as in G_M1) and the other 1→4 linked to $\text{N}$-acetylglucosamine as found in skeletal keratosulfate.     

Isolation and partial characterization of a novel disulfoglycosphingolipid from rat kidney

A novel sulfoglycosphingolipid containing two sulfate ester groups was isolated from the lipid extract of rat kidney by a procedure involving mild alkaline methanolysis and column chromatographies on DEAE-Sephacel and silicic acid. The component carbohydrates were galactose, glucose and $\text{N}$-acetylgalactosamine in equimolar amounts. Infrared spectroscopy, permethylation study, periodate oxidation and solvolysis suggested that the sulfoglycolipid was GalNAc1-4Gal1-4GlcCer sulfated at the C3 hydroxyls of both galactose and $\text{N}$-acetylgalactosamine. The yield of this sulfoglycolipid was 11.2 nmol/g tissue.     

Anti-glycosyl antibodies: Preparation and characterization of rabbit anti-galactose and anti-lactose antibodies

Anti-galactose and anti-lactose antibodies have been isolated from the antisera of rabbits immunized with non-viable cells of $\text{Streptococcus}$$\text{faecalis}$, strain N containing an antigenic diheteroglycan of glucose and galactose in the cell wall. The anti-galactose antibodies are specific for the galactosyl moiety while the anti-lactose antibodies are specific for the lactosyl moiety of the diheteroglycan. Hapten inhibitions with galactose and lactose, the sedimentation constant, the immunoglobulin type, the carbohydrate content, the electrophoretic mobility and the amino acid composition have been determined for the two new types of anti-glycosyl antibodies.     

Impairment by hexoses of the utilization of maltose by Saccharomyces cerevisiae1

The effect of hexoses with different transport and phosphorylation systems on the utilization of maltose by a galactose constitutive mutant of Saccharomyces cerevisiae has been studied. Galactose, mannose and fructose inhibit both the entrance of maltose in the cells and the phosphorylation of the glucose generated by intracellular hydrolysis of maltose. Transport of maltose is less affected than glucose phosphorylation and, once inside the cell, maltose is hydrolysed and the sparing glucose subsequently excreted. In addition to the well known inactivating effect of glucose, we have found that galactose inactivates the maltose transporter and that this inactivation is enhanced by maltose, which fails to inactivate the system by itself. As reported for glucose, inactivation by galactose involves proteolysis. Other strains of yeast with inducible pathways for both galactose and maltose behave similarly to the galactose constitutive mutant, with some minor changes. The use of maltose as a source of intracellular glucose has allowed to find the existence of mutual interferences in the utilization of hexoses by yeast at the phosphorylation step, that otherwise would have remained unnoticed.     

Use of lac operon fusions to isolate Escherichia coli mutants with altered expression of the fumarate reductase system in response to substrate and respiratory controls.

Strains of $\text{E}\text{.}\text{coli}$ with fusions between the $\text{lac}$ structural genes and the promoter region of the fumarate reductase system were constructed from a parental strain deleted in the native $\text{lac}$ operon. Like fumarate reductase in wild-type cells, β-galactosidase in these fusion strains is inducible by fumarate, but only under anaerobic conditions. From one of these strains, three classes of mutants altered in the expression of the hybrid operon were isolated. By anaerobic selection for growth on lactose in the absence of fumarate, mutants that synthesize β-galactosidase constitutively both aerobically and anaerobically were obtained. By aerobic selection for growth on lactose in the presence of fumarate, mutants that are inducible in the enzyme both aerobically and anaerobically and mutants that are inducible in the enzyme only aerobically were obtained. The regulatory behaviors of the mutants studied suggest that substrate and respiratory control of the expression of the fumarate reductase complex are mechanistically connected.     

Porphyrin mutants of Saccharomyces cerevisiae: Correlated lesions in sterol and fatty acid biosynthesis

The $\text{ole2}$, $\text{3}$ and $\text{4}$ mutants of yeast require an unsaturated fatty acid and methionine for growth and do not synthesise ergosterol. They have very similar sterol compositions and all accumulate lanosterol. The mutants lack cytochrome pigments and have negligible respiratory activity. Porphyrin intermediates alleviate the lipid requirement of $\text{ole2}$ and $\text{ole3}$ and restore respiratory competence. It is concluded that the primary defects in these mutants are lesions in porphyrin biosynthesis.     

Influence of steady-state and fluctuating salinities on the oxygen consumption and activity of some brackish water shrimps and fishes

Oxygen consumption, locomotory activity and, in some cases, osmoregulatory responses of different populations of Palaemon adspersus (Rathke) and Pomatoschistus microps (Krøyer) from the Isefjord ($\text{S 19‰}$) and Karrebaek Fjord ($\text{S 12‰}$) in Denmark and the Barther Bodden ($\text{S 6‰}$) in the G.D.R. to short-term salinity fluctuations, and after long-term adaptation, were tested. The same tests were performed on populations of Gasterosteus aculeatus (L.), Palaemonetes varions (Leach) (both from Barther Bodden, G.D.R.) and Palaemon elegans (Rathke) (Black Sea, Bulgaria, $\text{S 18‰}$). The steady-state experiments showed that the standard metabolic rates of P. adspersus and Pomatoschistus microps reach their lowest levels at mean biotope salinities at both 10 and 20°C. In contrast, the routine metabolic rates of both species are independent of salinity in the ecological salinity range.All Palaemon adspersus and Pomatoschistus microps populations responded to sudden changes in salinity with increased locomotory activity and respiration regardless of the direction of stressing. Metabolic adaptation in these euryhaline species, which is not synchronous with osmotic readjustment, takes from 5 to 12 h, depending on the salinity gradient.The polystenohaline Palaemon elegans from the Black Sea and the holeuryhaline Palaemonetes varians from the Barther Bodden exhibit similar short adaptation times (≈ 2 h) to identical salinity gradients but in different salinity zones.     

Metabolic control of lactose entry in Escherichia coli

A general method has been developed for determining the rate of entry of lactose into cells of Escherichia coli that contain β-galactosidase. Lactose entry is measured by either the glucose or galactose released after lactose hydrolysis. Since lactose is hydrolyzed by β-galactosidase as soon as it enters the cell, this assay measures the activity of the lactose transport system with respect to the translocation step. Using assays of glucose release, lactose entry was studied in strain GN2, which does not phosphorylate glucose. Lactose entry was stimulated 3-fold when cells were also presented with readily metabolizable substrates. Entry of $\text{o-}\text{nitrophenyl-β-}\text{d}\text{-galactopyranoside}$ (ONPG) was only slightly elevated (1.5-fold) under the same conditions. The effects of arsenate treatment and anaerobiosis suggest that lactose entry may be limited by the need for reextrusion of protons which enter during H⁺/sugar cotransport. Entry of $\text{o-}\text{nitrophenyl-β-}\text{d}\text{-galactopyranoside}$ is less dependent on the need for proton reextrusion, probably because the stoichiometry of H⁺/substrate cotransport is greater for lactose than for ONPG.     

Microvillus membrane vesicles from pig small intestine Purity and lipid composition

Microvillus membrane vesicles from pig small intestine were isolated by a method based on hypotonic lysis, Mg²⁺ aggregation of contaminants and differential centrifugation. The purity of the membrane vesicles were established by measuring the activity of marker enzymes and the RNA and DNA content. The membranes were found free of contamination by other subcellular membrane fragments, except for a minor contamination with basolateral plasma membranes. The lipid composition was established and, based on weight percentage, the membrane contained neutral lipids, phospholipids, neutral glycolipids and gangliosides in the weight ratio of 18:50:29:2%. The amount of individual phospholipids and glycolipids were quantitated. Phosphatidylethanolamine, -choline, -serine, -inositol and sphingomyelin made up 17,17,6,5 and 5%, respectively of the total lipid. The major glycolipids were two monohexosylceramides containing glucose and galactose as the carbohydrate component, a dihexosylceramide containing galactose as the only carbohydrate component and two pentahexosylceramides containing fucose, galactose, glucose and hexosamine (either $\text{N-}\text{acetylglucosamine}$ or $\text{N-}\text{acetylgalactosamine}$) in the molar ratio of 1:2:1:1.     

Chromatographic detection of the acetohydroxy acid synthase isoenzymes of Escherichia coli K-12.

Two valine-sensitive acetohydroxy acid synthase activities were separable from $\text{Escherichia}\text{coli}$ K-12 cells by virtue of their different affinities for DEAE-cellulose eluted with a KC1 gradient. These activities appeared to be independent from a valine-resistant cryptic component expressed only in $\text{ilvO}$ regulatory mutants. The properties of the first and second activity were coincident to those of extracts of $\text{ilvB}$ and $\text{ilvHI}$ mutants, respectively. These data prove that the $\text{ilvB}$ and $\text{ilvHI}$ gene products exist in the cell as physically distinct acetohydroxy acid synthase isoenzymes.     

Regulation of the Escherichiacoli tryptophan operon by readthrough of UGA termination codons

The regulation of the synthesis of $\text{trp}$ operon enzymes was studied in streptomycin-resistant $\text{Escherichia}\text{coli}$ mutants temperature-sensitive for UGA suppression by normal tRNA^Trp. Our mutants carry a $\text{trp}\text{R}{}^{\mathrm{+}}$ allele that when transferred to a different genetic background causes repression of trp operon enzyme synthesis at both low (35°C) and high (42°C) temperatures; however, in our mutants with an excess of tryptophan and at increased temperatures $\text{trp}$ enzyme synthesis is derepressed. Based on our results and the sequence data of the $\text{trp}$R gene [Singleton et al. (1980) Nucleic Acids Res., 8, 1551–1560], we offer a model for the involvement of the limited misreading of UGA codons by normal charged tRNA^Trp in the autogenous regulation of the $\text{trp}$R gene expression. The UGA readthrough process may be a regulatory amplifier of the effect of tryptophan starvation.