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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lipid A, the component of lipopolysaccharide that provides the membrane anchor of the core and O-antigen sugars, is known to contain characteristic R-3-hydroxy fatty acids bound to the 2,2' (N-linked) and 3,3' (O-linked) positions of the glucosamine disaccharide in different gram-negative bacteria. The studies reported here show that it is the acyl-acyl carrier protein specificities of the enzymes UDP-GlcNAc-O-acyltransferase and UDP-3-O-[(R)-3-hydroxyacyl]-GlcN-N-acyltransferase that determine the nature of these fatty acids.
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PMID:Acyl-acyl carrier protein specificity of UDP-GlcNAc acyltransferases from gram-negative bacteria: relationship to lipid A structure. 190 41

The O-specific polysaccharide from the lipopolysaccharide of Pseudomonas aeruginosa NCTC 8505 (IATS serotype O:3) consists of a tetrasaccharide repeating unit comprising L-rhamnose, N-acetyl-D-glucosamine (GlcNAc), bacillosamine, and N-acetyl-L-galactosaminuronic acid (L-GalNAcA) (Y. Tahara and S. G. Wilkinson, Eur. J. Biochem. 134:299-304, 1983). Incubation of GlcN or UDP-GlcNAc with cell extracts or EDTA-treated cells of P. aeruginosa NCTC 8505 yielded a mixture of UDP-ManNAc, UDP-GalNAc, UDP-GlcNAcA, UDP-ManNAcA, UDP-L-GalNAc, and UDP-L-GalNAcA. The last two compounds, here identified for the first time, may be intermediates in the synthesis of the L-GalNAcA moiety of the O-specific portion of the lipopolysaccharide of P. aeruginosa.
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PMID:Formation of UDP-2-acetamido-2-deoxy-L-galactose and UDP-2-acetamido-2-deoxy-L-galacturonic acid by Pseudomonas aeruginosa. 215 5

Cell envelopes of Salmonella typhimurium and Escherichia coli were disrupted in a French pressure cell and fractionated by successive cycles of sedimentation and floatation density gradient centrifugation. This permitted the identification and isolation of several membrane fractions in addition to the major inner membrane and murein-outer membrane fractions. One of these fractions (fraction OML) accounted for about 10% of the total cell envelope protein, and is likely to include the murein-membrane adhesion zones that are seen in electron micrographs of plasmolyzed cells. Fraction OML contained inner membrane, murein, and outer membrane in an apparently normal configuration, was capable of synthesizing murein from UDP-[3H]N-acetylglucosamine and UDP-N-acetylmuramylpentapeptide and covalently linking it to the endogenous murein of the preparation, and showed a labeling pattern in [3H]galactose pulse-chase experiments that was consistent with its acting as an intermediate in the movement of newly synthesized lipopolysaccharide from inner membrane to outer membrane. The fractionation procedure also identified two new minor membrane fractions, with characteristic protein patterns, that are usually included in the region of the major inner membrane peak in other fractionation procedures but can be separated from the major inner membrane fraction and from contaminating flagellar fragments by the subsequent floatation centrifugation steps.
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PMID:Isolation of differentiated membrane domains from Escherichia coli and Salmonella typhimurium, including a fraction containing attachment sites between the inner and outer membranes and the murein skeleton of the cell envelope. 351 Feb 2

Preliminary studies from our laboratory have suggested the existence of a novel set of fatty acyltransferases in extracts of Escherichia coli that attach two R-3-hydroxymyristoyl moieties to UDP-GlcNAc (Anderson, M.S., Bulawa, C.E., and Raetz, C.R.H. (1985) J. Biol. Chem. 260, 15536-15541). The resulting "glucosamine-derived" phospholipids appear to be crucial precursors for the biosynthesis of the lipid A component of lipopolysaccharide. We now describe an assay and a 1000-fold purification of the first enzyme in this pathway, which catalyzes the reaction: UDP-GlcNAc + R-3-hydroxymyristoyl-acyl carrier protein----UDP-3-O-(R-3-hydroxymyristoyl)-GlcNAc + acyl carrier protein. The covalent structure of the monoacylated UDP-GlcNAc product was established by fast atom bombardment mass spectrometry and 1H-NMR spectroscopy. The UDP-GlcNAc acyltransferase has a strict requirement for R-3-hydroxymyristoyl-acyl carrier protein, since R-3-hydroxymyristoyl coenzyme A and myristoyl-acyl carrier protein are not substrates. Of various NDP-GlcNAc preparations examined, only the uridine and thymidine derivatives were utilized to a significant extent. When the product of the reaction (UDP-3-O-(R-3-hydroxymyristoyl)-GlcNAc) was isolated and reincubated with crude E. coli extracts, it was rapidly converted to more hydrophobic products in the presence of R-3-hydroxymyristoyl-acyl carrier protein. We propose that the addition of an R-3-hydroxymyristoyl residue to the 3 position of the GlcNAc moiety of UDP-GlcNAc is the first committed step in lipid A biosynthesis and that UDP-GlcNAc is situated at a biosynthetic branchpoint in E. coli leading either to lipid A or to peptidoglycan.
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PMID:Biosynthesis of lipid A precursors in Escherichia coli. A cytoplasmic acyltransferase that converts UDP-N-acetylglucosamine to UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine. 354 16

Injection of D-galactosamine sensitizes mice many thousand-fold to the lethal action of endotoxin (lipopolysaccharide [LPS]). Comparable sensitization was practically absent in LPS-resistant C3H/HeJ mice, which after D-galactosamine treatment were about 500,000 times less sensitive to LPS lethality than histocompatible LPS-sensitive C3H/HeN mice. D-Galactosamine induces changes in the hepatocytes of treated animals, such as depletion of UTP and alterations in the pattern of UDP sugars. These early biochemical changes, which are necessary for development of sensitization, were similar in both mouse strains which we examined. High sensitivity to the lethal effects of LPS was achieved in C3H/HeJ mice after D-galactosamine treatment by transfer of C3H/HeN macrophages obtained in culture from bone marrow precursor cells.
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PMID:Requirement for lipopolysaccharide-responsive macrophages in galactosamine-induced sensitization to endotoxin. 394 85

Extraction of the cell envelope of E. coli with 1% sodium dodecyl sulfate yielded a lipopolysaccharide protein that was purified to homogeneity by conventional techniques. Analysis of the pure protein indicated that it is a complex lipopolysaccharide protein with the following molar ratios of constitutents: 3-deoxyoctulosonate, 1.0; glucosamine, 1.3; neutral sugar (glucose + heptose), 1.0; organic phosphate, 2.3; and amino acid, 21. On a quantitative basis, all of the 3-deoxyoctulosonate present in the cell envelope preparation was solubilized in hot sodium dodecyl sulfate and subsequently accounted for in its entirely in the isolated protein component. After incubation of the cell-wall particulate fraction of cells grown on [(3)H]glucosamine with UDP-[(14)C]galactose under conditions designed to measure galactosyl transferase activity, the isolated lipopolysaccharide protein contained all of the [(14)C]galactose that was incorporated during the incubation. We concluded that the lipopolysaccharide of this organism occurs in the outer cellenvelope membrane exclusively in the form of lipopolysaccharide protein.
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PMID:Isolation and characterization of lipopolysaccharide protein from Escherichia coli. 458 89

The 6.6-kb rfb gene cluster from Klebsiella pneumoniae serotype O1 (rfbKpO1) contains six genes whose products are required for the biosynthesis of a lipopolysaccharide O antigen with the following repeating unit structure: -->3-beta-D-Galf-1-->3-alpha-D-Galp-1-->(D-galactan I). rfbFKpO1 is the last gene in the cluster, and its gene product is required for the initiation of D-galactan I synthesis. Escherichia coli K-12 strains expressing the RfbFKpO1 polypeptide contain dual galactopyranosyl and galactofuranosyl transferase activity. This activity modifies the host lipopolysaccharide core by adding the disaccharide beta-D-Galf-1-->3-alpha-D-Galp, representing a single repeating unit of D-galactan I. The formation of the lipopolysaccharide substituted either with the disaccharide or with authentic polymeric D-galactan I is dependent on the activity of the Rfe enzyme. Rfe (UDP-GlcpNAc::undecaprenylphosphate GlcpNAc-1-phosphate transferase) catalyzes the formation of the lipid-linked biosynthetic intermediate to which galactosyl residues are transferred during the initial steps of D-galactan I synthesis. The rfbFKpO1 gene comprises 1,131 nucleotides, and the predicted polypeptide consists of 373 amino acid residues with a predicted M(r) of 42,600. A polypeptide with an M(r) of 42,000 was evident in sodium dodecyl sulfate-polyacrylamide gels when rfbKpO1 was expressed behind the T7 promoter. The carboxy-terminal region of RfbFKpO1 shares similarity with the carboxy terminus of RfpB, a galactopyranosyl transferase which is involved in the synthesis of the type 1 O antigen of Shigella dysenteriae.
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PMID:Role of Rfe and RfbF in the initiation of biosynthesis of D-galactan I, the lipopolysaccharide O antigen from Klebsiella pneumoniae serotype O1. 755 23

A Drosophila UDP-glucose:glycoprotein glucosyltransferase was isolated, cloned and characterized. Its 1548 amino acid sequence begins with a signal peptide, lacks any putative transmembrane domains and terminates in a potential endoplasmic reticulum retrieval signal, HGEL. The soluble, 170 kDa glycoprotein occurs throughout Drosophila embryos, in microsomes of highly secretory Drosophila Kc cells and in small amounts in cell culture media. The isolated enzyme transfers [14C]glucose from UDP-[14C]Glc to several purified extracellular matrix glycoproteins (laminin, peroxidasin and glutactin) made by these cells, and to bovine thyroglobulin. These proteins must be denatured to accept glucose, which is bound at endoglycosidase H-sensitive sites. The unusual ability to discriminate between malfolded and native glycoproteins is shared by the rat liver homologue, previously described by A.J. Parodi and coworkers. The amino acid sequence presented differs from most glycosyltransferases. There is weak, though significant, similarity with a few bacterial lipopolysaccharide glycotransferases and a yeast protein Kre5p. In contrast, the 56-68% amino acid identities with partial sequences from genome projects of Caenorhabditis elegans, rice and Arabidopsis suggest widespread homologues of the enzyme. This glucosyltransferase fits previously proposed hypotheses for an endoplasmic reticular sensor of the state of folding of newly made glycoproteins.
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PMID:Drosophila UDP-glucose:glycoprotein glucosyltransferase: sequence and characterization of an enzyme that distinguishes between denatured and native proteins. 772 8

Serum resistance of gonococci in most patients is due to sialylation of a Gal beta 1-4GlcNAc group on a conserved 4.5 kDa lipopolysaccharide (LPS) component by host cytidine 5'-monophospho-N-acetyl neuraminic acid (CMP-NANA) catalysed by a gonococcal sialyl transferase. This sialylation is enhanced by a low M(r) factor(s) which, like CMP-NANA, is released in diffusates from high M(r) fractions obtained from sonicates dialysed at 4 degrees C. Also, as shown here, this factor(s) is released when the sonicates are dialysed at 18-20 degrees C. The enhancement of sialylation, first demonstrated using enzymes in gonococcal extracts, has been shown to occur in live gonococci and hence probably to have a role in pathogenicity. Gonococci, emerging from lag phase and incubated for 2 h with CMP-14CNANA fixed up to 90% more radiolabel than controls when the second factor(s) was present; their LPS separated by SDS-PAGE contained more radiolabel than control samples and label was not detected in any other component. Fractions with enhancing activity absorbed maximally at about 260 nm but a mixture of UDP-galactose (UDP-Gal), UDP-N-Acetyl galactosamine (UDP-GalNAc), UDP-glucose (UDP-Glc) and UDP-N-Acetyl glucosamine (UDP-GlcNAc) showed no significant enhancing activity. The enhancing action of the low M(r) fractions was unaffected by incubation with beta-galactosidase.
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PMID:Sialylation of lipopolysaccharide by CMP-NANA in viable gonococci is enhanced by low Mr material released from blood cell extracts but not by some UDP sugars. 783 May 28

The glmU gene product of Escherichia coli was recently identified as the N-acetylglucosamine-1-phosphate uridyltransferase activity which catalyzes the formation of UDP-N-acetylglucosamine, an essential precursor for cell wall peptidoglycan and lipopolysaccharide biosyntheses (D. Mengin-Lecreulx and J. van Heijenoort, J. Bacteriol. 175:6150-6157, 1993). Evidence that the purified GlmU protein is in fact a bifunctional enzyme which also catalyzes acetylation of glucosamine-1-phosphate, the preceding step in the same pathway, is now provided. Kinetic parameters of both reactions were investigated, indicating in particular that the acetyltransferase activity of the enzyme is fivefold higher than its uridyltransferase activity. In contrast to the uridyltransferase activity, which is quite stable and insensitive to thiol reagents, the acetyltransferase activity was rapidly lost when the enzyme was stored in the absence of reducing thiols or acetyl coenzyme A or was treated with thiol-alkylating agents, suggesting the presence of at least one essential cysteine residue in or near the active site. The acetyltransferase activity is greatly inhibited by its reaction product N-acetylglucosamine-1-phosphate and, interestingly, also by UDP-N-acetylmuramic acid, which is one of the first precursors specific for the peptidoglycan pathway. The detection in crude cell extracts of a phosphoglucosamine mutase activity finally confirms that the route from glucosamine-6-phosphate to UDP-N-acetylglucosamine occurs via glucosamine-1-phosphate in bacteria.
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PMID:Copurification of glucosamine-1-phosphate acetyltransferase and N-acetylglucosamine-1-phosphate uridyltransferase activities of Escherichia coli: characterization of the glmU gene product as a bifunctional enzyme catalyzing two subsequent steps in the pathway for UDP-N-acetylglucosamine synthesis. 808 70


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