The structure of the O-specific polysaccharide chain of the lipopolysaccharide of Salmonella arizonae O61

The O-specific polysaccharide was obtained by mild degradation of the Salmonella arizonae O61 lipopolysaccharide with acid. It contained 2-acetamido-2-deoxy-D-glucose, 2-acetamidino-2,6-dideoxy-L-galactose (FucAm), and 7-acetamido-3,5,7,9-tetradeoxy-5-[(R)-3-hydroxybutyramido]-D- glycero-L-galacto-nonulosonic acid (Sug). On the basis of partial acid hydrolysis with 0.1 M HCl, solvolysis with anhydrous HF in methanol, and 1H- and 13C-NMR analysis (including 1H/13C inversely correlated spectroscopy for localisation of N-acyl substituents), it was concluded that the O-specific polysaccharide had the following structure. ----3)-alpha-L-FucAm-(1----3)-alpha-D-GlcNAc-(1----8)-beta-Sug+ ++-(2---- The O-antigen of S. arizonae O61 is structurally related to that of Pseudomonas aeruginosa O12, thus explaining the known serological cross-reactivity between these micro-organisms.

The role of the O antigen in adjuvant activity of lipopolysaccharide

Adjuvant activities of isogenic Salmonella enterica, serovar Typhimurium, O-6,7 and O-4,5,12 lipopolysaccharide (LPS), lipid A and Bordetella pertussis LPS were compared by immunizing groups of mice subcutaneously with diphtheria and tetanus toxoid vaccine alone or mixed with one of the LPS derivatives. Five weeks later the mice were bled and the tetanus and diphtheria antibodies in the sera were measured. All the LPS derivatives efficiently increased the antibody responses when compared to the vaccine alone, but the mannose-rich O-6,7 LPS and lipid A were significantly more potent than O-4,5,12 LPS and B. pertussis LPS. We conclude that the quality of the O antigen influences the adjuvant activity of LPS.

Topography of initiation of N-glycosylation reactions

Previous studies on the topography of the reactions leading to the formation of dolichol-P-P-Glc-NAc2Man9Glc3 have shown that these occur on both sides of the endoplasmic reticulum membrane (Hirschberg, C. B., and Snider, M. D. (1987) Annu. Rev. Biochem. 56, 63-87). Dolichol-P-P-GlcNAc2Man5 has been detected on the cytoplasmic side of the endoplasmic reticulum membrane while the subsequent dolichol-oligosaccharide intermediates face the lumen. Less clear is the side of the membrane where dolichol-P-P-GlcNAc2 is assembled. We now present evidence strongly suggesting that the active sites of the enzymes catalyzing the synthesis of this latter intermediate are on the cytoplasmic side of the endoplasmic reticulum membrane. In addition, dolichol-P-P-GlcNAc2 has also been detected on this side. Incubations of sealed, "right side out" rat liver endoplasmic reticulum-derived vesicles with [beta-32P] UDP-GlcNAc in the presence of 5-Br-UMP resulted in the formation of radiolabeled dolichol-P-P-GlcNAc and dolichol-P-P-GlcNAc2 under conditions where there was complete inhibition of transport of the nucleotide sugar. In other experiments with the above radiolabeled nucleotide sugar and sealed vesicles, it was demonstrated that EDTA (a membrane-impermeable reagent) inhibited the N-acetylglucosamine-1-phosphate transferase under conditions where transport of the nucleotide sugar into the lumen was unaffected. Finally, sealed vesicles were first incubated with [32P]UDP-GlcNAc and subsequently with UDP-Gal and soluble galactosyltransferase. This resulted in galactosylation of dolichol-P-P-GlcNAc2. The above results, together with the previous observations, strongly suggest that all reactions leading to this latter dolichol intermediate occur on the cytosolic side of the endoplasmic reticulum membrane.

A Chinese hamster ovary cell mutant F2A8 utilizes polyprenol rather than dolichol for its lipid-dependent asparagine-linked glycosylation reactions

Previous results suggested that F2A8, a glycosylation mutant of Chinese hamster ovary cells, had a lower amount of dolichyl phosphate available for asparagine-linked glycosylation reactions relative to parental cells. The steady-state amounts and identities of polyisoprenoid lipids were determined by incubating F2A8, its parental cell line B4-2-1, and wild-type Chinese hamster ovary cells for 24 h with [2-3H]mevalonate. The neutral lipids, ubiquinone, cholesterol, and cholesteryl esters, which were the most highly labeled from [3H]mevalonate, were labeled equally in all three cell types. In wild-type and B4-2-1 cells, mevalonate incorporation into the anionic glycosylated and phosphorylated derivatives of dolichol was 10-fold higher than into the neutral free dolichol and dolichyl esters. In contrast, in F2A8 cells, label accumulated in neutral polyisoprenol lipids, so that the ratio of neutral to anionic lipids was 1:1 rather than 1:10. In wild-type and B4-2-1 cells, the polyisoprenoid found as free alcohol and in phosphorylated and glycosylated forms was shown by high pressure liquid chromatography using a silica column to be primarily dolichol, a polyisoprenol that has a saturated terminal isoprene unit. In contrast, in F2A8 cells the polyisoprenoid found primarily as the free alcohol and in phosphorylated and glycosylated forms appeared to be completely unsaturated polyprenol. The distribution of chain lengths of the labeled polyisoprenols of F2A8, B4-2-1, and wild-type cells was the same as determined by high pressure liquid chromatography using a reverse-phase column, with the predominant chain length being 19 isoprene units. These results combined with our previous studies on the phenotype of the F2A8 mutant indicate that the unsaturated polyprenyl phosphate derivatives do not function as well as dolichyl phosphate derivatives in cellular glycosylation reactions.

Recovery of dolichyl diphosphate oligosaccharide in methanolic aqueous phase prepared from rat liver microsomal fractions

The synthesis of dolichyl diphosphate oligosaccharide was studied by incubating rat liver microsomes (microsomal fractions) with GDP-[14C]mannose, UDP-glucose, UDP-N-acetylglucosamine and [3H]dolichol phosphate. The labelled products obtained by the first step of extraction of the microsomes in methanolic aqueous phase (MAP fraction in chloroform/methanol/water; 3:2:1, by vol.) and in CMW fraction (chloroform/methanol/water; 10:10:3, by vol.) obtained by extraction of the interphase after the first step of extraction were analysed on a DEAE-cellulose column. With the progress of incubation, the radioactivity in unchanged GDP-mannose decreased, whereas the labelled dol-P-P-oligo in the MAP fraction increased about 5-6-fold. The lipid oligosaccharide in this fraction accounted for about 50-60% of the GDP-mannose used, whereas the recovery of the labelled lipid oligosaccharide in the CMW fraction was about 10%. The lipid oligosaccharide from both reactions after mild acid hydrolysis were analysed by gel filtration on Bio-Gel P-4. The oligosaccharide from the MAP fraction gave a peak of higher Mr distinctly separate from the lower-Mr peak obtained from the CMW fraction. Microsomes incubated with labelled lipid oligosaccharide from the MAP fraction showed incorporation of the label into endogenous protein.

Separation of dolichol monophosphate mannose and dolichol monophosphate glucose by thin-layer chromatography

Dolichol monophosphate mannose and dolichol monophosphate glucose from mammalian or mold cells were separated by thin-layer chromatography. This separation was not due to a difference in the size of the lipid moieties. It was found that the lipid moieties of dolichol monophosphate mannose and dolichol monophosphate glucose are the same size when synthesized by the same cell. The thin-layer chromatographic separation appeared to be due, therefore, to the saccharide part of the molecules.

Glucosyldiphosphoundecaprenol, the mannose acceptor in the synthesis of the O9 antigen of Escherichia coli. Biosynthesis and characterization

We describe the biosynthesis in vitro of the mannose acceptor of the O9 mannan synthesis by Escherichia coli membranes and its analysis with chemical, enzymatic and physical means. Membranes from E. coli 1357 (O9:K29-:H-his,pmi,rfe) were incubated with 10 mM UDP-glucose and 20 mM magnesium chloride in large scale. The incubation mixtures were extracted with butan-1-ol and the extract was fractionated by ion-exchange chromatography on DEAE-cellulose. The presence of the mannose acceptor was detected in the column effluent by using aliquots of the fractions in membrane-reconstitution experiments. The purified mannose acceptor was hydrolyzed for 10 min in 0.1 M hydrochloric acid at 100 degrees C and the hydrolyzate was extracted with light petroleum. Mass spectrometric analysis of the material from the organic phase showed it to be undecaprenol. The aqueous phase contained phosphate and glucose (as determined with glucose oxidase peroxidase) in the ratio of 1.9, alpha-Galactosyldiphosphoundecaprenol and beta-glucosylphosphoundecaprenol were prepared for comparison in these experiments. The results obtained showed that the mannose acceptor in the synthesis of the O9 mannan of E. coli is alpha-glucosyldiphosphoundecaprenol.

Characterization of a mannosyl-lipid compound of microsomal fractions of rat pancreas and influence of diet

1. High-starch diet induces an activation of rat pancreatic microsomal mannosyl-transferase activity as compared with a standard diet or a high-fat diet. 2. This increase is found in a mannose-containing lipid which is identified as a dolichyl-phosphoryl-mannose on the criteria of DEAE-cellulose chromatography, alkaline and acid hydrolysis, thin-layer chromatography and identity of this endogenous product with the [14C]mannose-containing product synthesized in presence of exogenous dolichyl-monophosphate added to the incubation medium. 3. Kinetic parameters (Km and Vmax) of the enzyme versus polyprenic acceptor are not modified by the diet. 4. The results indicate that the activation of the mannose transfer is principally due to an increase of the polyprenic endogenous acceptor by the high-starch diet.

A novel N-acetylglucosaminyl polyprene in hen oviduct

Incubation of hen oviduct membranes with UDP-[14C]N-acetylglucosamine (GlcNAc) leads to the formation of four endogenously labeled lipids. One of these lipids has not previously been characterized. Based on its chromatographic behavior on SG-81 paper and DEAE-cellulose, it is a monophosphate diester. The oviduct lipid is extremely sensitive to mild acid hydrolysis and, based on a comparison with alpha-GlcNAc-phosphoryl-undecaprenol from Bacillus cereus, the oviduct lipid contains GlcNAc linked to a polyisoprene as the beta anomer, the polyisoprene containing an alpha-unsaturated isoprene unit. Molecular sieve chromatography indicates that the molecular weight of the lipid is on the order of mannosyl-phosphoryl-dolichol and larger than alpha-GlcNAc-phosphoryl-undecaprenol. Formation of the GlcNAc-lipid is insensitive to tunicamycin. Dolichyl phosphate stimulates formation of a GlcNAc-lipid with similar chromatographic properties.

Identification and characterization of mannosyl retinyl phosphate occurring in rat liver and intestine invivo

A study was conducted to determine whether mannosyl retinyl phosphate occurred in rat liver and intestine in vivo, and, if so, to partially purify it and investigate its properties. After injection of [(3)H]retinol and [(14)C]mannose, a chloroform-methanol 2:1 extract of rat liver and small intestinal mucosa yielded two (3)H/(14)C-labeled peaks on DEAE-cellulose column chromatography: peak I eluted with 10 mM and peak II eluted with 29 mM ammonium acetate. Peak II, subjected to silicic acid column chromatography, gave principally two (3)H/(14)C-labeled fractions, one eluted with chloroform-methanol 2:1 and the other with chloroform-methanol 1:1. The latter showed, on thin-layer chromatography in a chloroform-methanol-water 60:25:4 system, an R(f) of 0.25 (with coincidence of the (3)H and (14)C radioactivity), which is identical to the R(f) of authentic mannosyl retinyl phosphate. The chloroform-methanol 1:1 peak, on mild acid hydrolysis, yielded [(3)H]retinol (identified by two thin-layer chromatography systems), [(14)C]mannose, and [(14)C]-mannose phosphate (identified by paper chromatography). On mild alkali hydrolysis, the peak yielded [(3)H]retinol and [(14)C]mannose phosphate. The substance eluted in the chloroform-methanol 1:1 peak from silicic acid was therefore concluded to be mannosyl retinyl phosphate. When chromatographed on silicic acid, peak I from the DEAE-cellulose column primarily showed a fraction eluted with chloroform-methanol 2:1. When chromatographed on thin-layer plates in the above solvent, this fraction showed an R(f) of 0.3, with coincidence of (3)H and (14)C radioactivity; it was resistant to mild acid hydrolysis, mild and strong alkali hydrolysis, and glucuronidase action. Mannosyl retinyl phosphate occurs, therefore, in vivo in liver and intestinal mucosa, and it is accompanied by a closely similar, though slightly less polar, compound that remains unidentified.