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

Lipoprotein I (OprI) is one of the major proteins of the outer membrane of Pseudomonas aeruginosa. Like porin protein F (OprF), it is a vaccine candidate because it antigenically cross-reacts with all serotype strains of the International Antigenic Typing Scheme. Since lipoprotein I was expressed in Escherichia coli under the control of its own promoter, we were able to isolate the gene by screening a lambda EMBL3 phage library with a mouse monoclonal antibody directed against lipoprotein I. The monocistronic OprI mRNA encodes a precursor protein of 83 amino acid residues including a signal peptide of 19 residues. The mature protein has a molecular weight of 6,950, not including bound glycerol and lipid. Although the amino acid sequences of protein I of P. aeruginosa and Braun's lipoprotein of E. coli differ considerably (only 30.1% identical amino acid residues), peptidoglycan in E. coli, are identical. Using lipoprotein I expressed in E. coli, it can now be tested whether this protein alone, without P. aeruginosa lipopolysaccharide contaminations, has a protective effect against P. aeruginosa infections.
 ...
PMID:Pseudomonas aeruginosa outer membrane lipoprotein I gene: molecular cloning, sequence, and expression in Escherichia coli. 250 33

The three-dimensional structure of PhoE porin from Escherichia coli, negatively stained with uranyl acetate, has been determined by electron crystallographic techniques to a resolution of about 18 A. The structure shows that PhoE porin consists of trimeric stain-filled channels as the basic unit. The trimeric channels converge as they transverse the membrane but they do not merge. Our three-dimensional structure of PhoE porin indicates that there is a short, narrower segment of channel, which extends beyond the visible strain-filled portion of the channel. The map of glucose-embedded PhoE porin in projection normal to the membrane has also been determined to a resolution of 6.5 A. The projected map shows trimeric ring-like structures, which are presumably cylindrical domains of beta-sheet. At the 3-fold symmetry axis of the trimer, there is a low density region, which is suggested to be a site of lipopolysaccharide that is required for channel and bacteriophage receptor activities. The structural model of the PhoE monomer consists of a flattened cylinder with a large water-filled vestibule about 35 A long with an elliptically shaped opening that is 27 A along the major axis and 18 A along the minor axis. The vestibule has a narrower extension about 10 A long with an average diameter of about 10 A. The vestibule wall is formed by beta-sheet, which may have a large fraction of the beta-strands oriented normal to membrane. Our structural model provides a clue as to how the surface charges on the outer membrane may regulate the permeation of ionic solutes through the channel.
 ...
PMID:Molecular design of PhoE porin and its functional consequences. 253 27

A gentle and rapid isolation procedure is described yielding fractions containing better than 95% pure OmpF porin of Escherichia coli BE with different amounts of bound lipopolysaccharide (LPS). The procedure employs continuous free-flow electrophoresis (FFE) in the presence of detergent above its critical micelle concentration. Total yields of around 45% were typically obtained when porin-enriched membrane extracts were processed. By use of analytical ultracentrifugation a molecular mass of 114,000 and a sedimentation coefficient S20,w of 5.0 S were determined for porin trimers containing approximately 1 mol of tightly bound LPS. This porin readily formed 3D crystals suitable for high-resolution X-ray diffraction analysis. Three other porin-LPS isoforms isolated by FFE revealed molecular masses of 120,000, 124,000, and 151,000, suggesting that, in addition to the tightly bound LPS, 1, 2, and 8 mol of loosely bound LPS were present per mole of porin trimer. Each of the four different isoforms was suitable for reconstitution into highly ordered protein-lipid membrane arrays. The membrane crystals obtained with the 151-kDa isoform exhibited a unit cell polymorphism similar to that previously reported.
 ...
PMID:Rapid isolation of OmpF porin-LPS complexes suitable for structure-function studies. 254 70

Porin, a major outer membrane protein was purified from Salmonella typhimurium and its immune potential was studied in mice. Active immunization with porin induced about 45 per cent protection to an intravenous challenge with 10LD50 of S. typhimurium. Further, in porin immunized mice significant level of anti-porin antibodies and DTH reaction were detected. Attempts were also made to improve the immune potential of porin. Freund's complete adjuvant when mixed with immunogenic doses of porin enhanced the anti-porin antibody titre. However, it could not improve the protective ability of porin. On the other hand, porin when injected along with lipopolysaccharide (LPS) induced a higher level (55% survival with 50LD50) of protection than porin or LPS alone. This finding was also substantiated by the significantly reduced in vivo growth of challenge organisms in mice immunized with porin plus LPS. These results indicate that porin is a protective antigen and LPS significantly enhances the protective ability of porin.
 ...
PMID:Protective immunity induced by porin against Salmonella infection in mice. 255 Mar 63

Amifloxacin showed potent inhibitory activity against DNA gyrase of Escherichia coli. The difference in the susceptibilities of lipopolysaccharide-deficient Salmonella typhimurium mutants and their parent strain was less than twofold, and the difference in the susceptibilities of porin-deficient E. coli mutants and their parent strain was less than twofold. There was cross resistance among the quinolone group of agents; however, the decrease in MIC for norB mutants was slightly lower than that of other fluoroquinolones. Cell lysis was induced with combined treatment of amifloxacin and sodium dodecyl sulfate in E. coli. The frequency of mutants spontaneously resistant to amifloxacin was extremely low in all species tested.
 ...
PMID:In vitro activity of amifloxacin against outer membrane mutants of the family Enterobacteriaceae and frequency of spontaneous resistance. 255 11

We have examined the effects of acidic pH, in the range of those prevailing within phagosomes and lysosomes, on the growth and the susceptibility to different antibiotics of several strains of Salmonella spp. The minimal inhibitory concentration and the minimal bactericidal concentration of several beta-lactams were increased considerably during culture at pH 5.2. The extent of the increase was a function of: (1) the beta-lactam structure and, more particularly, the hydrophobicity of the side-chain of the molecule; and (2) the bacterial serotype. This phenotypic resistance at acid pH was not due to beta-lactamase activity or to a lower growth rate. In contrast, rifamycin SV was more active at acidic pH than at neutral pH and chloramphenicol, another highly hydrophobic drug, was equally efficacious at both pH values. Membrane lipopolysaccharide mutants, but not porin mutants, cultivated at an acidic pH were inhibited by lower concentrations of the beta-lactams. This suggests that the increased resistance to beta-lactams, and the increased susceptibility to rifamycin SV, at acidic pH, could have resulted from modified permeability of the outer membrane to antibiotics.
 ...
PMID:Antibiotic susceptibility of Salmonella spp. at different pH values. 255 49

The 39 kDa porin from Enterobacter cloacae 908S was isolated in a lipopolysaccharide-free form using the non-ionic detergent, octylpentaoxyethylene, and reconstituted into vesicles of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC), respectively. Porin activity, measured by the rate of hydrolysis of the lipid-impermeant beta-lactam cephazoline by entrapped lactamase, could be demonstrated for porin-DMPC but not for porin-DOPC vesicles, and for the former was significantly lower in the gel than in the liquid-crystalline phase. The fluorescence changes are thought to arise from lipid phase-induced structural/dynamic changes of the porin structure.
 ...
PMID:Effect of lipid fluidity upon the activity and structure of the 39 kDa porin from Enterobacter cloacae 908S. 282 Jul 92

Porins were prepared from the outer membrane of Salmonella typhimurium and consisted of three polypeptides with similar molecular ratios around 40 kDa, and isoelectric points around 4.7. They constituted potent polyclonal activators for murine B lymphocytes. The compounds were mitogenic towards splenic lymphocytes of lipopolysaccharide responder Balb/c, non-responder (C3H/HeJ), and athymic (Balb/c nu/nu) mouse inbred strains, as measured by 3H-thymidine incorporation into DNA. Furthermore, porin-activated B cells differentiated into immunoglobulin-secreting cells, as was measured by an ELISA test. The porins will be valuable in elucidating the molecular mechanism of lymphocyte activation in bacterial infections.
 ...
PMID:Polyclonal activation of murine B lymphocytes in vitro by Salmonella typhimurium porins. 282 46

We studied the reactivity of 66 anti-Escherichia coli B/r porin monoclonal antibodies (MAbs) with several E. coli and Salmonella typhimurium strains. Western immunoblots showed complete immunological cross-reactivity between E. coli B/r and K-12; among 34 MAbs which recognized porin in immunoblots of denatured outer membranes of E. coli B/r, all reacted with OmpF in denatured outer membranes of E. coli K-12. Extensive reactivity, although less than that for strain B/r (31 of 34 MAbs), occurred for porin from a wild-type isolate, E. coli O8:K27. Only one of the MAbs reacted with porin in denatured outer membranes of S. typhimurium. Even with immunochemical amplification of the Western immunoblot technique, only six MAbs recognized S. typhimurium porin (OmpD), demonstrating that there is significant immunological divergence between the porins of these species. Antibody binding to the bacterial surface, which was analyzed by cytofluorimetry, was strongly influenced by lipopolysaccharide (LPS) structure. An intact O antigen, as in E. coli O8:K27, blocked adsorption of all 20 MAbs in the test panel. rfa+ E. coli K-12, without an O antigen but with an intact LPS core, bound seven MAbs. When assayed against a series of rfa E. coli K-12 mutants, the number of MAbs that recognized porin surface epitopes increased sequentially as the LPS core became shorter. A total of 17 MAbs bound porin in a deep rough rfaD strain. Similar results were obtained with S. typhimurium. None of the anti-E. coli B/r porin MAbs adsorbed to a smooth strain, but three antibodies recognized porin on deep rough (rfaF, rfaE) mutants. These data define six distinct porin surface epitopes that are shielded by LPS from reaction with antibodies.
 ...
PMID:Effect of lipopolysaccharide structure on reactivity of antiporin monoclonal antibodies with the bacterial cell surface. 283 Feb 27

From Fusobacterium nucleatum ATCC 10953 cell envelope fraction whose inner membranes had been removed by treatment with sodium N-lauroyl sarcosinate, an outer membrane protein (37,000 Mr in a native state) was prepared by extraction with lithium dodecyl sulfate. The protein thus obtained showed distinct porin activity, namely, the ability to form hydrophilic diffusion pores by incorporation into the artificial liposome membrane. The porin fraction exhibited strong immunobiological activities in the in vitro assays: B-cell mitogenicity and polyclonal B-cell activation on murine splenocytes, stimulatory effects on guinea pig peritoneal macrophages, and enhancement of the migration of human blood monocytes. The porin fraction also exhibited immunoadjuvant activity to increase the antibody production against sheep erythrocytes in the spleen of mice that were immunized by sheep erythrocytes with porin. Although chemical analyses revealed that the test porin fraction contained a considerable amount of lipopolysaccharide (LPS) (around 12% of the fraction), the studies with LPS-nonresponding C3H/HeJ mice and on the inhibitory effects of polymyxin B strongly suggest that most of the above bioactivities are due to porin protein itself, not to coexistent LPS in the porin fraction.
 ...
PMID:Immunobiological activities of a porin fraction isolated from Fusobacterium nucleatum ATCC 10953. 283 Nov 55


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>