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

Heat-stable enterotoxin (ST) produced by porcine strains of enterotoxigenic (ENT+) Escherichia coli has been purified to apparent homogeneity by sequential ultrafiltration, acetone fractionation, preparative gel electrophoresis, diethylaminoethyl Bio-Gel A ion-exchange chromatography, and Bio-Gel P-10 gel filtration. The enterotoxin, purified more than 1,500-fold, exhibited a molecular weight of 4,400, as determined by both sodium dodecyl sulfate-gel electrophoresis and gel filtration. A molecular weight of 5,100, representing 47 residues, was calculated from amino acid analysis data. The amino acid content was distinctive, with an unusually high proportion of cystines and few hydrophobic amino acids. A single amino-terminal residue, glycine, was observed. Purified ST was stable to heating (100 degrees C, 30 min) and did not lose biological activity after treatment with Pronase, trypsin, proteinase K, deoxyribonuclease, ribonuclease, and phospholipase C. Periodic acid oxidation and several organic solvents (acetone, phenol, chloroform, and methanol) had no effect on the biological activity of ST. Further, purified ST was stable to acid treatment at pH 1.0 but lost biological activity at pH values greater than 9.0. Neither lipopolysaccharide nor lipid contamination was evident in purified preparations. A characteristic absorption spectrum was observed during the course of the purification, which shifted from a maximum at 260 nm in crude preparations to 270 nm for the purified toxin. Antiserum obtained from rabbits immunized with ST or ST coupled to bovine serum albumin neutralized the action of the enterotoxin in suckling mice; however, passive hemagglutination and hemolysis titer assays suggested that ST is a poor antigen.
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PMID:Purification and chemical characterization of the heat-stable enterotoxin produced by porcine strains of enterotoxigenic Escherichia coli. 34 81

The isolation and characterization of two mutants of Escherichia coli K12 with an altered outer membrane protein c is described. The first mutant, strain CE1151, was isolated as a bacteriophage Me1 resistant strain which contains normal levels of protein c. Mutant cells adsorbed the phage with a strongly decreased rate. Complexes of purified nonheat modified wild type protein c and wild type lipopolysaccharide inactivated phage Me1, indicating that these components are required for receptor activity for phage Me1. When wild type protein c was replaced by protein c of strain CE1151, the receptor-complex was far less active, showing that protein c of strain CE1151 is altered. The second mutant produces a protein c with a decreased electrophoretic mobility, designated as protein c. An altered apparent molecular weight was also observed for one or more fragments obtained after fragmentation of the mutant protein with cyanogen bromide, trypsin and chymotrypsin. Alteration of protein c was not accompanied by a detectable alteration in protein b or its fragments. Both mutations are located at minute 48 of the Escherichia coli K12 linkage map. The results strongly suggest that meoA is the structural gene for protein c.
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PMID:meoA is the structural gene for outer membrane protein c of Escherichia coli K12. 37 4

Escherichia coli ompA mutants are tolerant to colicin L-JF246. This tolerance can be overcome by a variety of treatments that have as their target the outer membrane or the peptidoglycan layers of the cell envelope. Thus, increasing the concentration of colicin L, releasing lipopolysaccharide from the outer membrane by treatment of intact cells with ethylenediaminetetracetic acid (EDTA), converting cells to spheroplasts by treatment with lysozyme-EDTA or penicillin, or trypsin, treatment of intact cells will result in an increased colicin sensitivity. These treatments alter the outer membrane of ompA mutants and suggest that the altered outer membrane may allow the penetration of at least a portion of the colicin L molecule to a site of action located within this barrier. To substantiate this, we have demonstrated that membrane vesicles prepared from ompA mutants are sensitive to colicin L and that 14C-labeled colicin L binds rapidly to both the outer and inner membrane fractions of the cell.
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PMID:Defeat of colicin tolerance in Escherichia coli ompA mutants: evidence for interaction between colicin L-JF246 and the cytoplasmic membrane. 41 31

Ribosomal preparations from Neisseria gonorrhoeae types 1 and 4 were examined for their in vitro stimulation of mouse splenocytes to determine the ribosomal moiety or contaminant responsible for the immunoproliferative activity. In immunodiffusion tests with homologous rabbit antiserum, crude 70S ribosomes formed four precipitin bands while the purified 30S and 50S subunits showed one major line. The same antiserum reacted with lysed N. gonorrhoeae and Neisseria meningitidis A cells but no precipitation occurred with Escherichia coli cells purified N. gonorrhoeae lipopolysaccharide (LPS). No membrane or LPS contaminant was detected in the purified 30S and 50S preparations. All the ribosomal preparations from virulent and non-virulent N. gonorrhoeae consistently stimulated the murine splenocytes. The mitogenic activity of the 30S and 50S ribosomal preparation was destroyed by treatment with trypsin but only slightly decreased by ribonuclease. It is suggested that the lymphoproliferative response elicited by gonococcal ribosomes is triggered by the protein moiety of the 30S or 50S subunits.
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PMID:Characterization of the mitogenic activity elicited by Neisseria gonorrhoeae ribosomal fractions. 41 60

Trypsin, a neutral protease, enhanced the direct plaque response of T cell-suffiecient mouse spleen cell cultures to sheep erythrocytes (SRBC) and significantly increased the number of spontaneous PFC against SRBC in cultures without antigen. Moreover, trypsin proved to be able to substitute for T cells in nu/nu spleen cell cultures stimulated with SRBC. Its restorative capacity in this type of response was comparable to the one of lipopolysaccharide. Restoration of antibody synthesis in T cell-deprived cultures could not be explained by enzymatic alteration of SRBC. The data are discussed in terms of a possible role of hydrolytic enzymes released by accessory cells during the induction of an antibody response.
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PMID:Trypsin increases in vitro antibody synthesis and substitutes for helper T cells. 77 82

Labelling of cell walls or outer membranes from Salmonella typhimurium with ferritin-conjugated antibodies directed against the polysaccharide moiety of the lipopolysaccharide gave the following results: 1. Cell walls or outer membranes from which the mucopeptide had been removed by lysozyme digestion at 0 degrees C carried the label on the outer face of the membrane. 2. When the murein layer was removed by either lysozyme or trypsin at physiological temperature (25-37 degrees C) subsequent labelling showed the lipopolysaccharide to be present on both membrane faces. 3. This reorientation could be achieved by a 1-min treatment of the membranes at 37 degrees C. 4. Glutaraldehyde fixation of the outer membranes did not entirely prevent but somewhat inhibited the temperature-induced reorientation process. 5. The same reorientation phenomenon was observed in lysozyme spheroplasts, which were prepared at 37 degrees C and were subsequently lysed in hypotonic medium at 0 degrees C. These observations are discussed as evidence for a transmembrane movement of lipopolysaccharide, which only takes place in areas where the mucopeptide layer is defective, and only when the temperature is sufficiently high to allow such movement.
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PMID:Asymmetrical distribution and artifactual reorientation of lipopolysaccharide in the outer membrane bilayer of Salmonella typhimurium. 80 74

This paper reports that B cells undergoing translatory motion spontaneously segregate their surface Ig to one portion of their plasma membrane. The spontaneous redistribution of surface Ig was found to be: (a) selective, concanavalin A-dependent on translatory motion and energy metabolism. Abundant B cells undergoing motility were found after cultures in lipopolysaccharide or trypsin, or after brief exposure to cholinergic drugs.
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PMID:Spontaneous redistribution of surface immunoglobulin in the motile B lymphocyte. 108 28

Recently we reported that rapid killing of Escherichia coli by granulocytes or granulocyte fractions is accompanied by an equally rapid and discrete increase in permeability of the microbial envelope (Beckerdite, Mooney, Weiss, Franson, and Elsbach. 1974. J. Exp. Med. 140: 396-409). Most of this permeability-increasing activity (PI) is found in a crude granule preparation. PI is quantitatively recovered in a 23,000-g supernatant fraction (Sup II) after sulfuric acid extraction of granulocyte homogenates prepared in water. PI is nondialyzable, destroyed by pronase and trypsin, stable at 4degreesC for at least 2 mo, and destroyed by heating at 94degreesC. Anionic substances, such as heparin sulfate and isolated E. coli lipopolysaccharide, bind to and inhibit PI. PI has been purified up to 1,000-fold from homogenate in a yield of 50percent by acid extraction and carboxymethyl-Sephadex chromatography. Such purified fractions have bactericidal activity that equals that of disrupted granulocytes and Sup II, are similarly enriched with respect to granule-associated phospholipase, and protease activities. Whereas E. coli, sensitive to PI, binds or inactivates solubilized PI, a resistant strain of Serratia marcescens does not. Binding of PI to sensitive microorganisms seems to be necessary for expression of its biological activity since both the apparent binding to and the biological effect of PI on E. coli are completely blocked by 10-20 mM Mg2+ or Ca2+. Mg2+ or Ca2+ can reverse the effect on E. coli permeability produced by Sup II or the carboxymethyl-Sephadex fraction but not that produced by granulocyte homogenate. The close association of bactericidal, phospholipase A2, and permeability-increasing activities towards several gram-negative bacterial species suggests that they may be related.
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PMID:Partial characterization and purification of a rabbit granulocyte factor that increases permeability of Escherichia coli. 108 9

In Escherichia coli and Salmonella typhimurium, the cell wall that contains both the outer membrane layer and the peptidoglycan layer acts as a barrier of the molecular sieve type for the penetration of uncharged saccharides (G. Decad, T. Nakae, and H. Nikaido (1974) Fed. Proc. 33, 1240). Here we examined which of the layers of the cell wall limited the size of the penetrating molecules, by studying the penetration of saccharides into (a) cells whose peptidoglycan layer had been destroyed by lysozyme treatment or growth in the presence of penicillin and (b) isolated outer membrane vesicles. We found that peptidoglycan-defective cells were similar to intact, plasmolyzed cells in that they allowed a partial penetration of stachyose (molecular weight 666), but essentially excluded saccharides with molecular weights higher than 900 to 1000. We also found that the isolated outer membrane acted as a penetration barrier for saccharides. These observations led us to conclude that the outer membrane, rather than peptidoglycan, sets the size limit for the penetration of uncharged, hydrophilic molecules through the E. coli or S. typhimurium cell wall. The isolated outer membrane, however, had an exclusion limit much higher than that found in intact cells. This "leakiness" could be decreased either by the use of mutants producing extremely deficient lipopolysaccharide, or by trypsin treatment of the isolated membrane followed by heating and slow cooling in the presence of Mg2+. We feel that these observations are consistent with the hypothesis that the resealing of the ruptured outer membrane during the isolation procedure is often incomplete, and that cracks and holes thus generated are responsible for the "leakiness" of the isolated membrane vesicles.
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PMID:Outer membrane as a diffusion barrier in Salmonella typhimurium. Penetration of oligo- and polysaccharides into isolated outer membrane vesicles and cells with degraded peptidoglycan layer. 110 Jun 25

The influence of aging on neutrophil chemotaxis, chemokinesis, and superoxide production was investigated in rats. Animals of two age groups, 3 to 4 months and 20 to 21 months, were used. Equivalent neutrophil chemotactic responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), leukotriene B4 (LTB4), and bacterial lipopolysaccharide (LPS)-activated plasma were observed in both groups of animals, with cells suspended in Hanks' balanced salt solution (HBSS). However, cross-incubation studies in which cells from young adult rats were exposed to plasma from aged donors, then resuspended in HBSS for testing, showed marked changes in the ability of the cells to respond to the chemoattractants. The response to LPS-activated plasma was reduced, whereas responses to fMLP and LTB4 remained unaltered. Previous incubation of the cells with homologous plasma from young donors produced no effect. The inhibitory activity developing with advancing age affected not only chemotaxis but also random movement stimulated by LPS-activated plasma. The inhibitory activity of chemotaxis and chemokinesis in plasma of aged animals was heat labile (56 degrees C), vanished in the presence of a proteolytic enzyme like trypsin, and was maintained after dialysis with 12,000-Mr retention dialysis tubing. The material did not influence superoxide production by stimulated neutrophils. It is suggested that inhibition of neutrophil locomotion with advancing age is associated with a plasma protein capable of interacting with neutrophil receptors for complement-derived chemoattractants. The inhibitory substance might influence neutrophil responses to infection and inflammation in the elderly.
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PMID:Inhibition of neutrophil chemotaxis and chemokinesis associated with a plasma protein in aging rats: selective depression of cell responses mediated by complement-derived chemoattractants. 131 Oct 13


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