Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endotoxins may interfere with platelet aggregation by interacting with the platelet membrane. The aim of this study was to evaluate the effects of tetanus toxin, Salmonella typhimurium porin, and bacterial lipopolysaccharide (LPS) on platelet aggregation induced by ADP and thrombin in vitro. Spontaneous platelet aggregation and platelet aggregation induced by ADP and thrombin were measured. Our results show that Salmonella typhimurium porin and bacterial LPS enhanced human and rabbit platelet aggregation induced by ADP and thrombin. Tetanus toxin did not affect platelet aggregation.
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PMID:Effects of tetanus toxin, Salmonella typhimurium porin, and bacterial lipopolysaccharide on platelet aggregation. 133 19

The ability of Bdellovibrio bacteriovorus to relocalize the OmpF major outer membrane porins from its Escherichia coli prey to its own outer membranes is diminished in prey expressing smooth lipopolysaccharide (S-LPS). Since porins exist in the membrane complexed with LPS, we examined the LPS associated with relocalized porin to determine whether it had been acquired intact, mixed or replaced with Bdellovibrio LPS, or derivatized by the bdellovibrios. The relocalized trimers were found associated with the same LPS originally bound to them in the E. coli. The bulk-phase LPS from bdellovibrios grown on various chemotypes of rough prey was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to determine whether more than the trimer-bound LPS was acquired by the bdellovibrios. This analysis revealed bands of Bdellovibrio LPS matching the LPS chemotype of the prey. One or two other bands were identical in migration to the LPS of prey-independent mutants of B. bacteriovorus and represented bdellovibrio-synthesized LPS. The LPS of bdellovibrios grown on prey with radiolabeled lipid A showed radioactivity only in gel band positions identical with those of the prey's LPS. The amount of this prey-derived LPS was shown by enzyme-linked immunosorbent assay to reach a constant value during the purification of the bdellovibrios, and it represented approximately 25% of the total Bdellovibrio LPS. Immunoelectron microscopy confirmed the presence of prey-derived LPS on the cell surface of bdellovibrios, and no evidence could be found for bdellovibrio-induced modifications of the relocalized prey LPS.
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PMID:Acquisition of apparently intact and unmodified lipopolysaccharides from Escherichia coli by Bdellovibrio bacteriovorus. 137 16

The OmpF protein is the major outer membrane trimeric porin of Escherichia coli B. The exposure of several cell-surface-exposed epitopes, that are recognized by various monoclonal antibodies directed against the protein, is investigated. Kinetic analyses show that two epitopes (E18 and E19) appear early during the in-vivo assembly on the folded monomer, just after the removal of the signal peptide, and are conserved in the native trimer. The trimerization that immediately follows or occurs in conjunction with the folding of monomers exposes another antigenic site (E21) at the surface of metastable forms. The binding of nascent lipopolysaccharide promotes the conversion of the heat-modifiable intermediate to a stable trimer and ensures the exposure of E20, E1, E3, E4 and E7. Late epitopes, E1, E3, E4 and E7 are only detected in the outer membrane fraction. These results suggest that different steps induce the sequential exposure of native antigenic sites. The detection of these epitopes depends on conformational changes occurring during the OmpF insertion into the outer membrane.
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PMID:Dynamics of the exposure of epitopes on OmpF, an outer membrane protein of Escherichia coli. 137 55

An enoxacin-resistant Pseudomonas aeruginosa mutant (G49) isolated during patient therapy was characterized in detail. The G49 mutant was cross resistant to several classes of antibiotics including quinolones, beta-lactams, chloramphenicol, and tetracycline, but not imipenem or aminoglycosides. Compared with its paired pretherapy isolate G48, this mutant had several alterations in outer membrane proteins including a complete loss of the major porin protein OprF and a substantially altered lipopolysaccharide profile. Revertants were selected at a frequency of approximately 1% after enrichment for OprF+ cells on low-salt proteose peptone no. 2 medium. Ninety-seven of these OprF+ revertants were as susceptible to carbenicillin and norfloxacin as the pretherapy isolate. One of these revertants was characterized in more detail and shown to be indistinguishable in all properties from the pretherapy isolate. It is proposed that the multiple-antibiotic-resistance (Mar) phenotype of this mutant resulted from a single pleiotropic mutation.
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PMID:A pleiotropic, posttherapy, enoxacin-resistant mutant of Pseudomonas aeruginosa. 151 Mar 93

Protein carriers vary in their ability to increase the immunogenicity of poorly immunogenic or T-lymphocyte-independent antigens. We examined one such carrier, the outer membrane protein complex derived from Neisseria meningitidis serogroup B strain B11, in an attempt to determine why this outer membrane protein complex was more immunogenic in young infants and in relevant animal models than two other carriers used in conjugates made with Haemophilus influenzae type b polysaccharide, a T-cell-independent antigen. A single protein of the outer membrane protein complex, the class 2 porin protein, was purified and shown to function as a T-helper lymphocyte carrier protein. Unexpectedly, it was also found to have mitogenic activity for lymphocytes that was not due to lipopolysaccharide. This mitogenic activity appears to date to be unique to this carrier protein of the carrier proteins tested and may contribute to the ability of the H. influenzae type b conjugate vaccine made with the outer membrane protein complex to generate IgG anti-polysaccharide antibody responses in mice and infant monkeys and protective immune responses in infants less than 6 months of age.
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PMID:A vaccine carrier derived from Neisseria meningitidis with mitogenic activity for lymphocytes. 153 34

The mechanism of uptake of aminoglycosides across the outer membrane of Escherichia coli was reevaluated. Porin-deficient mutants showed no alteration in gentamicin or kanamycin susceptibility. Furthermore, the influence of kanamycin on intrinsic tryptophan fluorescence of porin OmpF (Y. Kobayashi, and T. Nakae, Eur. J. Biochem. 151:231-236, 1985) was shown to be strongly influenced by protein concentration and EDTA. This led to the hypothesis that aminoglycoside-mediated increases and decreases in intrinsic tryptophan fluorescence were due to aggregation-disaggregation of OmpF mediated by interaction at a divalent cation binding site on OmpF. Gentamicin, kanamycin, and polymyxin B increased E. coli outer membrane permeability to the hydrophobic fluorescent compound 1-N-phenyl-naphthylamine (NPN) and the peptidoglycan-degrading enzyme lysozyme. Addition of Mg2+ blocked these permeabilizing activities. Furthermore, gentamicin and polymyxin B bound to Mg(2+)-binding sites on E. coli lipopolysaccharide, as determined in dansyl polymyxin displacement experiments. A polymyxin-resistant, lipopolysaccharide-altered pmr mutant of E. coli had a fourfold-lower MIC of gentamicin and kanamycin and was more poorly permeabilized to 1-N-phenylnaphthylamine than was its parent strain. These data were consistent with uptake of aminoglycosides across the E. coli outer membrane by the self-promoted uptake mechanism.
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PMID:Interaction of aminoglycosides with the outer membranes and purified lipopolysaccharide and OmpF porin of Escherichia coli. 165 59

Routes of quinolone permeation in Pseudomonas aeruginosa were investigated by using sparfloxacin as a prototype compound. [14C]sparfloxacin cell labeling was 13 to 28% lower in three protein D2-deficient mutants resistant to imipenem than in their imipenem-susceptible counterparts. In four impermeability-type quinolone-resistant strains isolated from pefloxacin-treated animals, we observed two- to fourfold-greater resistance to imipenem, reduced protein D2 expression in the outer membrane according to Western blotting (immunoblotting), and 25 to 29% decreased cell labeling with imipenem. In a protein D2-producing strain but not in its protein D2-deficient isogenic mutant, uptake of [14C]sparfloxacin was strongly inhibited by L-lysine and imipenem, which act as substrates for protein D2. Conversely, binding of [14C]imipenem in a porin D2-positive strain was reduced by sparfloxacin but not by the nonamphoteric quinolone nalidixic acid. Sparfloxacin, imipenem, and lysine possess a carboxyl group and a potentially protonated nitrogen separated from each other by 0.64 to 1.07 nm as calculated by computer. Hence, protein D2 may catalyze facilitated diffusion for sparfloxacin, as it does for imipenem. In addition, pefloxacin-selected isolates contained 41 to 113% more 3-deoxy-D-mannooctulosonic acid than their quinolone-susceptible counterparts, with MIC increases of 2- to 4-fold for WIN-57273 (n-octanol-phosphate buffer partition coefficient, 13.139), 4- to 8-fold for difloxacin (partition coefficient, 3.093) and sparfloxacin (partition coefficient, 0.431), and 8- to 16-fold for norfloxacin (partition coefficient, 0.059) and ciprofloxacin (partition coefficient, 0.056). Thus, we hypothetize that in quinolone-selected strains, increased amounts of lipopolysaccharide form a permeability barrier that acts preferentially against hydrophilic quinolones.
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PMID:Role of protein D2 and lipopolysaccharide in diffusion of quinolones through the outer membrane of Pseudomonas aeruginosa. 166 23

The structure of PhoE porin in projection normal to the membrane plane has been determined to a resolution of about 3.5 A by electron crystallographic techniques. The purified protein was reconstituted with lipid to form two-dimensional crystals. High resolution images and electron diffraction patterns of these specimens embedded in trehalose were recorded to obtain respectively the structure factor phase information and the more accurate values of the amplitude. The projection map shows interesting features that are not seen in the earlier map at 6.5 A. Details of the trimeric ring-like structures in our earlier map are now resolved. Each ring-like structure consists of "beads" with interbead spacings of about 4-6 A. These beads are interpreted as the projections of beta-strands along the strands' axes. At the center of the trimeric structure, there is a low density region that we proposed previously to be the location of lipopolysaccharide. Within each ring-like structure, there are complicated features which may play an important role in the size, selectivity, and stability of the channel.
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PMID:Structure of PhoE porin in projection at 3.5 A resolution. 169 59

A panel of monoclonal antibodies (MAbs) to seven Brucella outer membrane proteins were characterized. These antibodies were obtained by immunizing mice with sodium dodecyl sulfate-insoluble (SDS-I) fractions, cell walls, or whole bacterial cells of Brucella abortus or B. melitensis. Enzyme-linked immunosorbent assays were used to screen the hybridoma supernatants and to determine their binding at the surface of rough and smooth B. abortus and B. melitensis cells. The outer membrane proteins (OMPs) recognized by these antibodies were the proteins with molecular masses of 25 to 27 kDa and 36 to 38 kDa (porin) (major proteins) and the proteins with molecular masses of 10, 16.5, 19, 31 to 34, and 89 kDa (minor proteins). Surface exposure of these OMPs was visualized by electron microscopy by using the MAbs and immunogold labeling. Binding of the MAbs on whole rough bacterial cells indicates that the 10-, 16.5-, 19-, 25- to 27-, 31- to 34-, 36- to 38-, and 89-kDa OMPs are exposed at the cell surface. However, enzyme-linked immunosorbent assay results indicate a much better binding of the anti-OMP MAbs on rough strains than on the corresponding smooth strains except for the anti-19-kDa MAb. Immunoelectron microscopy showed that on smooth B. abortus cells only the 89- and 31- to 34-kDa OMPs were not accessible to the MAbs tested. Binding of the anti-31- to 34-kDa MAb at the cell surface was observed for the rough B. abortus cells and for the rough and smooth B. melitensis cells. These results indicate the importance of steric hindrance due to the presence of the long lipopolysaccharide O side chains in the accessibility of OMPs on smooth Brucella strains and should be considered when undertaking vaccine development.
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PMID:Identification of seven surface-exposed Brucella outer membrane proteins by use of monoclonal antibodies: immunogold labeling for electron microscopy and enzyme-linked immunosorbent assay. 170 17

The major outer membrane protein (Omp34) of Acidovorax delafieldii (formerly Pseudomonas delafieldii) was purified to homogeneity and was characterized biochemically and functionally. The polypeptide has an apparent molecular weight (Mr) of 34,000, and it forms stable oligomers at pH 9.0 in the presence of 10% octylpolyoxyethylene or 2% lithium dodecyl sulfate below 70 degrees C. The intact protein has a characteristic secondary structure composition, as revealed by Fourier transforming infrared spectroscopy (about 60% beta sheet). These features and the amino acid composition are typical for porins. The purified Omp34 is associated with 1 to 2 mol of lipopolysaccharide per mol of the monomer. Pore-forming activity was demonstrated with lipid bilayer experiments. Single-channel and selectivity measurements showed that the protein forms highly anion-selective channels. The unusual dependence of the single-channel conductance on salt concentration suggests that the porin complexes bear positive surface charges, accumulating negatively charged counterions at the pore mouth.
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PMID:The major outer membrane protein of Acidovorax delafieldii is an anion-selective porin. 171 13


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