UNIPROT:P50583 - FACTA Search

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Query: UNIPROT:P50583 (asymmetrical)
12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The majority of Pseudomonas aeruginosa strains synthesize two antigenically distinct types of lipopolysaccharide (LPS), namely, a serotype-specific B-band LPS and a common antigen A-band LPS. A-band LPS consists of uncharged poly-D-rhamnan, which does not bind uranyl ions and is difficult to stain for electron microscopy; the highly charged B-band LPS is more easily visualized. We selected two wild-type strains, PAO1 (serotype O5) and IATS O6 (serotype O6), generated isogenic mutants from them, and examined the distribution of LPS on the surface of these organisms by freeze-substitution and electron microscopy. On PAO1 cells, which express both A-band and B-band LPSs, a 31- to 36-nm-wide fringe extending perpendicularly from the outer membrane was observed. A fine fibrous material was also observed on the surface of serotype O6 (A+ B+) cells, although this material did not form a uniform layer. When the LPS-deficient mutants, strains AK1401 (A+ B-), AK 1012 (A- B-), rd7513 (A- B-), and R5 (an IATS O6-derived rough mutant; A- B-), were examined, no extraneous material was apparent above the bilayer. However, an asymmetrical staining pattern was observed on the outer leaflet of the outer membrane of each of these mutants, presumably conforming to the anionic charge distribution of the core region of the rough LPS. In all cases, expression of the LPS types was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining. When optical densitometry on electron microscopy negatives was used to analyze the outer membrane staining profiles, subtle differences in the degrees of core deficiency among rough mutants were detectable. This is the first time an electron microscopy technique has preserved the infrastructure produced in the outer membrane by its constituent macromolecules. We conclude that freeze-substitution electron microscopy is effective in the visualization of LPS morphotypes.
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PMID:Ultrastructural examination of the lipopolysaccharides of Pseudomonas aeruginosa strains and their isogenic rough mutants by freeze-substitution. 142 38

Phospholipids are the principal constituents of biological membranes. In Escherichia coli, phospholipids are involved in the metabolism of other envelope constituents such as lipoprotein, lipopolysaccharide, certain envelope proteins and peptidoglycan. They are also involved in the regulation of the cell cycle. DNAA, the key protein in the initiation of chromosome replication, is activated by acidic phospholipids only when these are in fluid bilayers, whilst interruptions of phospholipid synthesis inhibit both the initiation of chromosome replication and cell division. The transmembrane movement or flip-flop of phospholipids from one monolayer to the other requires the passage of the polar head group through the hydrophobic core of the bilayer. Hence, in many systems, flip-flop is a slow process with half-time of days. Flip-flop accompanies the formation of non-bilayer structure. Such structures form under certain conditions of packing density and composition and have been observed both in vitro and in vivo. In bacteria, flip-flop appears to be extremely rapid, with half-times as fast as 3 min being observed. However, such rapid flip-flop may not be characteristic of all phospholipids. The asymmetrical distribution of phosphatidylethanolamine in the plasma membrane of Bacillus megaterium has been attributed to the existence of two classes of this phospholipid. In E. coli, studies of the metabolic turnover of phosphatidylserine, phosphatidylglycerol and phosphatidic acid also reveal the existence of distinct classes of these phospholipids. In this article I propose that, in E. coli, a class of phospholipids does indeed escape the rapid flip-flop mechanism; this class probably includes a subpopulation of the acidic phospholipids. Therefore during the cell cycle these phospholipids accumulate in the inner monolayer of the cytoplasmic membrane and so cause an increase in its packing density; at a critical density, phospholipids "flip out" from the inner to the outer monolayer. This flip-out occurs once per cycle and initiates cell cycle events.
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PMID:Phospholipid flip-out controls the cell cycle of Escherichia coli. 268 87

The cerebral neocortex has been shown to modulate the immune system in an asymmetrical way. In mice, ablation of the left cortex decreases whereas a symmetrical right lesion enhances B and T cell-mediated responses measured at 6-8 weeks after lesioning. In order to study the possibility of neuronal reorganisation during the post-operative period, immunological parameters were determined as early as 2 weeks after right or left cortical ablation. Right lesions depressed lymphocyte DNA synthesis induced by concanavalin A (ConA) and phytohemagglutinin whereas left lesions only depressed ConA-induced blastogenesis. Right or left lesions had no effect on lipopolysaccharide-induced proliferation of B lymphocytes as well as on serum antibody levels. Comparisons between early and late effects of right or left cortical ablation on the immune system showed that each hemicortex differentially modulates lymphocyte subpopulations but also that the neuronal reorganisation following surgery can be different according to the side of cortex lesion.
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PMID:Early effects of right or left cerebral cortex ablation on mitogen-induced spleen lymphocyte DNA synthesis. 341 41

Maltoporin, a protein spanning Escherichia coli outer membranes, modifies electrical conductance of membranes due to its channel-forming properties. This observation was made by conductance measurements across planar bilayers which were derived from unextracted, isolated outer membrane vesicles using a porin-deficient E. coli strain. Alternatively, proteoliposomes reconstituted with detergent-solubilized homogeneous maltoporin and phospholipids were used. With either membrane preparation, channel conductance was observed, although no discrete conductance levels were detected. The presence of lipopolysaccharide, a bacterial glycolipid, was not required, nor did it affect channel activity. In the presence of the water-soluble periplasmic maltose-binding protein, conductance fluctuations occurred in discrete steps, demonstrating opening and closing events of channels. Multiple step sizes (1/3, 2/3 and 1 ns in 1 M KCl) in single channel traces suggest cooperative opening and closing of up to three channels. The action of maltose-binding protein is highly asymmetrical, and its affinity to maltoporin is very high (KD = 1.5 X 10(-7) M). Association of maltose-binding protein to maltoporin shifts, for a given polarity, the equilibrium between open and closed states in favour of closed states. This result matches earlier in vivo studies, and supports the physiological significance of the observations made.
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PMID:The periplasmic maltose-binding protein modifies the channel-forming characteristics of maltoporin. 631 10

The inducible human cationic amino acid transporter hCAT-2B was expressed in Xenopus laevis oocytes, and this system was used to test the effect of several NO synthase (NOS) inhibitors and/or L-arginine analogues on L-arginine transport by this y+ carrier. L-NG-Methyl-L-arginine (L-NMA), asymmetrical L-NG, NG-dimethyl-L-arginine (L-ADMA), L-N5-(1-iminoethyl)-ornithine (L-NIO), L-NG-nitro-L-arginine (L-NNA), and L-NG-nitro-L-arginine methyl ester (L-NAME) all inhibited the inducible NOS II extracted from RAW 264.7 macrophages induced with bacterial lipopolysaccharide. L-NMA, L-ADMA, and L-NIO also competed with L-arginine for transport by hCAT-2B, whereas L-NNA and L-NAME did not. The two L-arginine analogues, symmetrical NG, NG-dimethyl-L-arginine (L-SDMA) and alpha-amino-delta-isothioureidovaleric acid (AITV), as well as L-lysine, did not block enzymatic activity of NOS II, but did compete for L-arginine transport mediated by hCAT-2B. L-Lysine and L-SDMA were transported efficiently by hCAT-2B and exchanged against intracellular L-arginine, resulting in an L-arginine depletion of the cells. AITV was a much poorer substrate of hCAT-2B and had only little effect on intracellular L-arginine concentrations. These data indicate that substrate recognition differs markedly between the inducible L-arginine transporter hCAT-2B and the inducible NOS II, with different L-arginine analogues having affinity to only one or both of these proteins.
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PMID:Interference of L-arginine analogues with L-arginine transport mediated by the y+ carrier hCAT-2B. 970 Oct 46

The brain modulates the immune system in an asymmetrical way, as shown by the association between paw preference and immune response in the mice. The purpose of the present work was to study the relationship between plasma tumor necrosis factor-alpha (TNF-alpha), nitric oxide (NO) and nitric oxide synthase (NOS) and brain lateralization. In the study, paw preference test was used to select right-pawed, left-pawed and ambidextrous mice. Mice were classified as the right-pawed if the right paw entry (RPE) score was equal to or greater than 30 (30-50), as the left-pawed if the score was equal to or less than 20 (0-20), and as the ambidextrous if the score was between 21 and 29. One week after the paw preference testing, the animals were injected intraperitoneally with either sterilized 0.9% saline or lipopolysaccharide (LPS) (5 microg/0.5 ml NS) and were killed 2 h later. Plasma was collected from each mouse. The level of plasma TNF-alpha was measured with ELISA kits provided by ENDOGEN. NO and NOS levels of plasma were detected with kits from Juli Biotechnology Company. The results showed that (1) in the normal mice, ambidextrous mice had higher NO levels compared with left-pawed mice (P<0.05). After the injection of LPS, plasma level of TNF-alpha was lower in left-pawed mice compared with those of the right-pawed and ambidextrous mice; plasma level of NO was higher in ambidextrous mice compared with those of the right- (P<0.01) and left-pawed (P<0.05) ones, and there was no significant difference in the plasma levels of NOS among ambidextrous, right- and left-pawed mice. (2) Immune parameters were correlated with the RPE scores. The shape of the curve describing this relation was similar to a parabola. In general, the levels of TNF-alpha, NO, NOS rose along with the increase of RPE if the scores were in the score range of left-pawed mice.After that, they reached a peak if the scores were in the score range of ambidextrous mice. Then they declined along with the increase of RPE if the scores were in the score range of right-pawed mice. In conclusion, plasma levels of TNF-alpha, NO and NOS were associated with brain lateralization, suggesting that the activities of Mo/Mphi were influenced by brain lateralization, and that the immune parameters were correlated with the RPE scores.
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PMID:[The correlations between plasma TNF-alpha, NO, NOS levels and brain lateralization in mice]. 1250 25

Acute inflammation impairs vascular function. Based on the association between endothelial dysfunction and plasma concentrations of L-arginine and the endogenous nitric oxide synthase inhibitor ADMA (asymmetrical dimethylarginine), we hypothesized that the ratio between L-arginine and ADMA could be affected by experimental inflammation. Plasma concentrations of L-arginine, ADMA and SDMA (symmetrical dimethylarginine) were studied at baseline and 3.5 h after intravenous administration of Escherichia coli endotoxin [LPS (lipopolysaccharide), 20 units/kg of body mass; n =8] or placebo ( n =9) in healthy males. L-Arginine and dimethylarginines were quantified after solid-phase extraction by reversed-phase HPLC. Body temperature, heart rate and leucocyte count increased after LPS administration ( P <0.01 for all). LPS administration decreased plasma concentrations of L-arginine from 66 micromol/l [95% CI (confidence interval): 56, 88] at baseline to 48 micromol/l (CI: 40, 60) after 3.5 h ( P <0.02), but did not affect ADMA and SDMA concentrations. Consequently, the L-arginine/ADMA ratio declined significantly from a median of 159 (CI: 137, 193) to 135 (CI: 103, 146); a decrease of 25 (CI: -68, -13; P <0.02). L-Arginine, ADMA, SDMA and the L-arginine/ADMA ratio remained constant over time in controls. Acute inflammation reduces the L-arginine/ADMA ratio which could contribute to impaired vascular function.
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PMID:Acute Escherichia coli endotoxaemia decreases the plasma l-arginine/asymmetrical dimethylarginine ratio in humans. 1474 Oct 43

The present study was undertaken to explore involvement of nitric oxide (NO) in the experimental models of Parkinson's disease. Neurodegeneration was induced by unilateral injections of 6-hydroxydopamine (6-OHDA) or lipopolysaccharide (LPS) in the right striatum. Lesions were functionally evaluated by amphetamine-induced asymmetrical behaviour and by decrease in the tyrosine hydroxylase (TH) immunostaining. An induction in the expression of iNOS and augmentation in nitrite content was observed in both the models. The extent of increase in iNOS expression was, however, different but the elevation in the nitrite content was comparable in both the models. The increase in iNOS expression inversely correlated with the tyrosine hydroxylase (TH) immunolabeling. Animals pretreated with a NOS inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), exhibited complete protection against amphetamine induced rotations in both the models. Thus, augmented NO availability subsequent to iNOS induction seems to play an important role in the initial phase of neurodegeneration.
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PMID:Involvement of nitric oxide in neurodegeneration: a study on the experimental models of Parkinson's disease. 1594 31

Similar to most Gram-negative bacteria, the outer leaflet of the outer membrane of Vibrio cholerae is comprised of lipopolysaccharide. Previous reports have proposed that V. cholerae serogroups O1 and O139 synthesize structurally different lipid A domains, which anchor lipopolysaccharide within the outer membrane. In the current study, intact lipid A species of V. cholerae O1 and O139 were analysed by mass spectrometry. We demonstrate that V. cholerae serogroups associated with human disease synthesize a similar asymmetrical hexa-acylated lipid A species, bearing a myristate (C14:0) and 3-hydroxylaurate (3-OH C12:0) at the 2'- and 3'-positions respectively. A previous report from our laboratory characterized the V. cholerae LpxL homologue Vc0213, which transfers a C14:0 to the 2'-position of the glucosamine disaccharide. Our current findings identify V. cholerae Vc0212 as a novel lipid A secondary hydroxy-acyltransferase, termed LpxN, responsible for transferring the 3-hydroxylaurate (3-OH C12:0) to the V. cholerae lipid A domain. Importantly, the presence of a 3-hydroxyl group on the 3'-linked secondary acyl chain was found to promote antimicrobial peptide resistance in V. cholerae; however, this functional group was not required for activation of the innate immune response.
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PMID:Elucidation of a novel Vibrio cholerae lipid A secondary hydroxy-acyltransferase and its role in innate immune recognition. 2175 9

Bacteria of the phylum Planctomycetes are of special interest for the study of compartmental cellular organization. Members of this phylum share a very unusual prokaryotic cell plan, featuring several membrane-bound compartments. Recently, it was shown that this cellular organization might extend to certain members of the phylum Verrucomicrobia. The Planctomycete cell plan has been defined as featuring a proteinaceous cell wall, a cytoplasmic membrane surrounding the paryphoplasm, and an intracytoplasmic membrane defining the riboplasm. So far it was presumed that Planctomycetes did not have an asymmetric bilayer outer membrane as observed in Gram-negative bacteria. However, recent work on outer membrane biogenesis has provided several marker genes in the outer membrane protein (OMP) assembly and the lipopolysaccharide (LPS) insertion complexes. Additionally, advances in computational prediction of OMPs provided new tools to perform more accurate genomic screening for such proteins. Here we searched all 22 Planctomycetes and Verrucomicrobia genomes available in GenBank, plus the recently published genome of "Candidatus Scalindua profunda," for markers of outer membrane biogenesis and OMPs. We were able to identify the key components of LPS insertion, OMP assembly and at least eight OMPs in all genomes tested. Additionally, we have analyzed the transcriptome and proteome data of the Planctomycetes "Candidatus Kuenenia stuttgartiensis" and "Ca. S. profunda" and could confirm high expression of several predicted OMPs, including the biomarkers of outer membrane biogenesis. These analyses provide a strong indication that an asymmetrical outer membrane may be present in bacteria of both phyla. However, previous experiments have made obvious that the cell envelope of Planctomycetes is clearly divergent from both the Gram-negative and Gram-positive cell types. Thus, the functional implications of the presence of an outer membrane for the Planctomycete cell plan and compartmentalization are discussed and a revised model including an outer membrane is proposed. Although this model agrees with most experimental data, we do note that the presence, location, and role of an outer membrane within the Planctomycetes and Verrucomicrobia awaits further experimental validation.
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PMID:Genomic analysis indicates the presence of an asymmetric bilayer outer membrane in planctomycetes and verrucomicrobia. 2293 92

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