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)

The rfaD gene encodes ADP-L-glycero-D-mannoheptose-6-epimerase, an enzyme required for the biosynthesis of the lipopolysaccharide precursor ADP-L-glycerol-D-mannoheptose. The precise localization of the rfaD gene on a 1.3-kilobase SspI-HpaI fragment is reported. The rfaD gene and the flanking regions were completely sequenced. The location of the rfaD gene on the physical map of the Escherichia coli chromosome was determined. Primer extension studies were used to define the regulatory region of the rfaD gene. The cloned rfaD gene directed the synthesis of a 37,000-dalton polypeptide in several in vivo and in vitro expression systems. N-terminal analysis of purified ADP-L-glycero-D-mannoheptose-6-epimerase confirmed the first 34-amino-acid sequence deduced from the nucleotide sequence of the rfaD gene coding region. The primary structure of the rfaD protein contains the sequence fingerprint for the ADP-binding beta alpha beta fold at the N terminus.
 ...
PMID:Cloning, expression, and characterization of the Escherichia coli K-12 rfaD gene. 219 71

L-Arginine is required for expression of the activated macrophage cytotoxic effector mechanism that causes inhibition of mitochondrial respiration, aconitase activity, and DNA synthesis in tumor target cells. This effector mechanism is active in the presence of L-arginine even when the cocultivation medium lacks all other amino acids and serum. Cytotoxic activated macrophage-induced inhibition of mitochondrial respiration in target cells is proportional to the concentration of L-arginine in the medium. L-Arginine must be present during the cocultivation period. Pretreatment of cytotoxic activated macrophages with L-arginine or posttreatment of the target cells after cocultivation is not effective. D-Arginine does not substitute for L-arginine and at high concentrations is a competitive inhibitor of the L-arginine-dependent effector mechanism. Other analogues that could not replace L-arginine include agmatine, argininic acid, arginine hydroxamate, and tosyl-L-arginine methyl ester. L-homoarginine, however, can effectively substitute for L-arginine. NG-monomethyl-L-arginine is a potent competitive inhibitor of this effector mechanism. High concentrations of lipopolysaccharide do not reverse inhibition of the L-arginine-dependent effector mechanism by NG-monomethyl-L-arginine. However, inhibition of the effector mechanism by NG-monomethyl-L-arginine can be overridden by increasing the concentration of L-arginine in the culture medium. We compared NGNG-dimethyl-L-arginine and NGN1G-dimethyl-L-arginine with NG-monomethyl-L-arginine as inhibitors of the L-arginine-dependent effector mechanism. The results show that the inhibitory effect of these guanidino methylated derivatives of L-arginine is highly determined by structure. Guanidine is a weak competitive inhibitor of the L-arginine-dependent effector mechanism. The requirement for L-arginine does not appear to be for protein synthesis, creatine biosynthesis, polyamine biosynthesis, or ADP ribosylation reactions. Bacterial lipopolysaccharide is effective as a second signal only when the cocultivation medium contains L-arginine, and this strict L-arginine dependency is not overridden by increasing the concentration of lipopolysaccharide. Bovine liver arginase, by competing for L-arginine in the cocultivation medium, inhibits the L-arginine-dependent activated macrophage cytotoxic effector mechanism.
 ...
PMID:L-arginine is required for expression of the activated macrophage effector mechanism causing selective metabolic inhibition in target cells. 243 29

Botulinum toxins are potent neurotoxins which block the release of neurotransmitters. The effects of these toxins on hematopoietic cells, however, are unknown. Monocytes secrete a variety of polypeptide growth factors, including tumor necrosis factor (TNF). In the study reported here, the effects of botulinum toxin type D on the secretion of TNF from human monocytes were examined. The results demonstrate that botulinum toxin type D inhibits the release of TNF from monocytes activated by lipopolysaccharide (LPS) but not by 12-O-tetradecanoylphorbol-13-acetate. Botulinum toxin type D had no detectable effect on intracellular TNF levels in LPS-treated monocytes, indicating that the effects of this toxin involve the secretory process. This inhibitory effect of botulinum toxin type D on TNF secretion from LPS-treated monocytes was partially reversed by treatment with 12-O-tetradecanoylphorbol-13-acetate or introduction of guanosine 5'-[gamma-thio]triphosphate into these cells. The results demonstrate that TNF secretion is regulated by at least two distinct guanine nucleotide-binding proteins, one responsible for the activation of phospholipase C and another which acts as a substrate for botulinum toxin type D. ADP-ribosylation of monocyte membranes by botulinum toxin type D demonstrated the presence of three substrates with Mrs of 45,000, 21,000, and 17,000. While the role of these substrates in exocytosis is unknown, the results suggest that the Mr 21,000 substrate is involved in a process other than TNF secretion.
 ...
PMID:Effects of botulinum toxin type D on secretion of tumor necrosis factor from human monocytes. 250 64

Phorbol esters induce the differentiation of the human promonocytic cell line U937 to a monocyte/macrophage. This process is associated with the induction of interleukin 1 beta (IL-1 beta) gene expression (Strulovici, B., Daniel-Issakani, S., Oto, E., Nestor, J., Jr., Chan, H., and Ping-Tsou, A. (1989) Biochemistry 28, 3569-3576). Here we describe the induction by phorbol esters of lipopolysaccharide (LPS) responsiveness in U937 cells. Preincubation with phorbol myristate acetate (TPA, 5 x 10(-8) M) for at least 4-6 h and up to 12 h followed by 3 h of LPS treatment induced a 4-fold enhancement in the accumulation of IL-1 beta transcripts compared to treatment with TPA alone. This "priming" effect was specific for protein kinase C agonists and required de novo protein synthesis. Exposure of [35S]methionine-labeled U937 cells to phorbol esters induced the de novo synthesis of a protein which migrated with a 40-kDa molecular mass in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, had an isoelectric point of 5.7 (p 40/5.7), and was recognized by a specific antibody to the pertussis toxin (PT)-sensitive Gi2. The time course for the appearance of Gi2 correlated with that for the induction of LPS responsiveness by TPA. Moreover, the LPS response was PT-sensitive. In cells treated with LPS for 5 min, Gi2 showed diminished ADP-ribosylation by PT. Treatment of U937 cells with LPS for 30 min induced phosphorylation of Gi2 and enhanced PT labeling. In a cell-free assay, phosphorylation of Gi2 by protein kinase C type III, rendered it a better PT substrate. The present findings thus suggest: 1) that TPA induces LPS responsiveness in U937 cells via de novo synthesis of Gi2; 2) that the LPS response (enhanced IL-1 production) is linked to a pertussis toxin-sensitive G protein which we identified as Gi2; and 3) that LPS leads to phosphorylation of Gi2.
 ...
PMID:Lipopolysaccharide response is linked to the GTP binding protein, Gi2, in the promonocytic cell line U937. 251 Dec

Selective inhibition by pertussis toxin (PT) of mitogenic activation of mouse B lymphocytes by bacterial mitogens (peptidoglycan and lipopolysaccharide) and muramyl dipeptide (a synthetic analog of peptidoglycan fragment) was demonstrated. Mitogenic activation of B cells by protein kinase C activators and ionomycin was insensitive to PT. Also PT did not inhibit peptidoglycan- and lipopolysaccharide-induced differentiation of B cells into Ig-secreting cells, when it was added to the cultures after the proliferative stage of the response. B lymphocyte membranes contained two major PT substrates (40 and 41 kDa). The extent of PT-mediated ADP ribosylation of these substrates correlated with the degree of PT-mediated inhibition of mitogenic stimulation of B cells. B cell stimulation by all mitogens tested was not inhibited by cholera toxin at nontoxic concentrations that are known to cause maximal increase in cAMP in B cells. Since the only known substrates for PT-mediated ADP ribosylation in mammalian cells are the alpha subunits of some G proteins, our data suggest that G proteins are present in B cell membranes and that they are involved in B cell activation induced by bacterial mitogens.
 ...
PMID:Correlation between ribosylation of pertussis toxin substrates and inhibition of peptidoglycan-, muramyl dipeptide- and lipopolysaccharide-induced mitogenic stimulation in B lymphocytes. 253 32

Genotoxic activities of a series of commercially purchased 1,N6-ethenoadenosine (epsilon-Ado) and epsilon-deoxyadenosine (epsilon-dAdo) derivatives were assessed using the sister chromatid exchange (SCE) assay in murine spleen lymphocytes in vitro. Of the epsilon-Ado adducts evaluated for SCE induction epsilon-ATP and epsilon-dATP were highly active (5x baseline) SCE inducers over a concentration range of 50-150 microM. Moderate SCE-inducing activities were seen with epsilon-dAdo, epsilon-A, and epsilon-AMP. epsilon-A was of particular interest in that spleen lymphocytes from a single mouse were highly sensitive to SCE (greater than 50 SCE/cell at 75 microM). epsilon-Ado was weakly effective and epsilon-ADP and epsilon-dAMP did not produce significantly elevated SCEs. Cocanavalin A-stimulated T-lymphocytes and lipopolysaccharide-stimulated B-lymphocytes exhibited comparable SCE responses to epsilon-A, epsilon-AMP, and epsilon-dATP. However, B-lymphocytes were considerably less sensitive than T-lymphocytes to epsilon-dAdo and epsilon-ATP. Evaluation of the purities of specific epsilon-Ado derivatives, as performed by high-performance liquid chromatography and thin layer chromatography, failed to detect potential contaminants as cytogenetically active agents. However, a difference (about threefold) in cytogenetic activities of two lot numbers of epsilon-ATP paralleled the difference in UV absorbance of quivalent concentrations (mg/ml), prepared according to the manufacturers stated purity. Any impurities likely to be present were consistent with inactive nonchromophoric compounds such as buffer salts. Because of the direct genotoxic activity of epsilon-A in intact mammalian cells, we suggest that intracellular adenylate pools, including the prominent ubiquitous nucleotide ATP, are non-DNA targets for epsilon-modification by active metabolites and the resulting epsilon-adducts are likely to be active moieties in SCE induction and in neoplastic transformation produced by ethyl carbamate.
 ...
PMID:Sister chromatid exchange induced by etheno-ATP derivatives in vitro. 273 26

Many bacterial toxins are proteins, encoded by the bacterial chromosomal genes, plasmids or phages. Lysogenic phages form part of the chromosome. The toxins are usually liberated from the organism by lysis, but some are shed with outer membrane proteins in outer membrane vesicles. An important non-protein toxin is lipopolysaccharide or endotoxin, which is a constituent of the cell wall of gram negative bacteria. Toxins may damage the eukaryotic cell membrane by combining with some structural component, or otherwise alter its function. Many toxins combine with specific receptors on the surface membrane, frequently glycoproteins or gangliosides, and penetrate the cell to reach their intracellular target. A common mechanism of entry is absorptive endocytosis. Many protein toxins have an A-B structure, B being a polypeptide which binds to the receptor and A being an enzyme. Many toxins are activated, either when produced by the bacterium or when bound to the membrane receptor, by proteases (nicking). An enzymatic process common to many toxins is adenosine diphosphate (ADP)-ribosylation of the adenylate cyclase regulatory proteins, leading to an increase in intracellular cyclic adenosine monophosphate (cAMP). This is the mechanism of action of cholera toxin. Diphtheria toxin catalyzes the transfer of ADP-ribose to elongation factor-2, inhibiting protein synthesis. Most toxins act on the target cells to which they bind, but tetanus toxin, and, to a lesser degree, botulinum toxin, ascend axons and affect more distant structures. Although many toxin effects caused by bacteria have been described, only a few toxins have been identified, characterized, and their mode of action determined at the molecular level. The best known of these are discussed.
 ...
PMID:Bacterial toxins. 328 62

Peritoneal cells from thioglycollate-stimulated mice were allowed to adhere to coverglasses for 2 h to give a dense monolayer of adherent cells greater than 95% of which were macrophages. After incubation with the tetra-acetoxymethyl ester of quin2, coverglasses were rinsed with Ca2+-free saline, oriented at a 45 degree angle in square cuvettes containing a magnetically driven stir bar, and analyzed for changes in quin2 fluorescence in a spectrofluorimeter. Such fluorescence, taken as an indication of intracellular calcium ion concentration ([Ca2+]i), increased as exogenous calcium ion concentration ([Ca2+]o) was raised to 1 mM. At [Ca2+]o approximately equal to 10 microM, [Ca2+]i = 72 +/- 14 nM (n = 26); at [Ca2+]o = 1 mM, [Ca2+]i = 140-220 nM, levels not increased by N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine, a membrane-permeant chelator of heavy metals than can quench quin2. Addition of mouse alpha + beta fibroblast interferon, lipopolysaccharide, thrombin, collagen, vasopressin, ADP, compound 48/80, or U46619 did not change [Ca2+]i. However, addition of platelet activating factor (PAF) (2-20 ng/ml) raised [Ca2+]i by 480 nM within 1 min if [Ca2+]o = 1 mM. In the presence of 5 mM EGTA, PAF raised [Ca2+]i by 25 nM. This suggests that PAF causes influx of exogenous Ca2+, as well as releasing some Ca2+ from intracellular stores. Consistent with these results, when PAF was added to 1 mM Ca2+ in the presence of 100 microM Cd2+ or Mn2+ to block Ca2+ influx, [Ca2+]i increased by only intermediate amounts; at the times of such dampened peak response, [Ca2+]i could be raised within 1 min to normal PAF-stimulated levels by chelation of the exogenous heavy metals with diethylenetriaminepentaacetic acid. Normal PAF responses were observed in the presence of indomethacin. The lowest dose of PAF observed to raise [Ca2+]i was 0.1 ng/ml. Response of [Ca2+]i to 2-20 ng/ml PAF was transient, and second applications had no effect. The PAF response also was seen in cell suspensions. These results suggest that an increase in [Ca2+]i may be an early event in PAF activation of macrophages.
 ...
PMID:Platelet activating factor raises intracellular calcium ion concentration in macrophages. 373 74

The mechanism through which human blood platelets interact with gram-negative bacteria with well-defined structural variations in endotoxic lipopolysaccharide was studied. Secretion of 14C-serotonin and aggregation of platelets separated from plasma proteins were observed on challenge with rough mutant Re595 of Salmonella minnesota possessing a glycolipid outer layer composed of Lipid A and 2-keto-3-deoxyoctonate (KDO) but lacking heptose phosphate in the core and O-polysaccharide in its outer portion. Both 14C-serotonin secretion and platelet aggregation were concentration-dependent, with a half-maximum response at the ratio of one bacterial colony-forming unit (CFU) to two platelets. The aggregation of human platelets induced by mutant Re595 was divalent cation-dependent and required secretion of ADP and fibrinogen from platelet storage granules because it was inhibited by chelators, by the ADP-splitting enzyme apyrase, and by monospecific antifibrinogen Fab fragments. The synthetic peptide analog of the platelet receptor recognition site on the gamma chain of fibrinogen, gamma 400-411, inhibited platelet aggregation induced by mutant Re595 (IC50 160 mumol/L), whereas serotonin secretion was unaffected. Tetrapeptide, RGDS, analogous to human fibrinogen alpha chain (alpha 572-575) and to the cell adhesion site of fibronectin, also inhibited aggregation induced by mutant Re595 (IC50 60 mumol/L). Secretion of 14C-serotonin was preceded by a very rapid phosphorylation of a platelet protein of mol wt 47,000, which is associated with protein kinase C activation. Myosin light chain (mol wt 20,000) was also phosphorylated. Both phosphoproteins were dephosphorylated while secretion was reaching maximum. Furthermore, release of 3H-arachidonic acid from platelet phospholipids and generation of thromboxane B2 via the cyclooxygenase pathway were observed. Inhibition of this pathway with acetylsalicylic acid (10(-4) mol/L) or indomethacin (5 X 10(-4) mol/L) reduced 14C-serotonin secretion and platelet aggregation. The role of Lipid A in the interaction of mutant Re595 with human platelets was deduced from the inhibitory effect of the Lipid A-binding protein present in Limulus amebocyte lysate. Likewise, polymyxin B, known to complex with Lipid A, was inhibitory. The reactivity of mutant Re595 toward platelets was attenuated by mild acid hydrolysis, during which KDO was dissociated from the glycolipid, and by alkaline hydrolysis, which breaks ester-linked fatty acids in Lipid A. In contrast to mutant Re595, strain S218 of S minnesota bearing "complete" endotoxic lipopolysaccharide did not induce secretion and aggregation of human platelets.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Mechanism of human platelet activation by endotoxic glycolipid-bearing mutant Re595 of Salmonella minnesota. 376 28

Early changes in hepatic carbohydrate metabolism without apparent hepatocyte dysfunction were reported previously in mice infected with Listeria monocytogenes. This study was undertaken to examine possible imbalance in host regulatory mechanisms which might be responsible for these changes. Female CD-1 mice fasted 12 hr prior to the experiments were injected intraperitoneally with 10(5), 10(6), or 10(7)Listeria. Control mice received either 10(9) heat-killed Listeria or 150 mug of Salmonella typhimurium lipopolysaccharide. Hepatic glycogen, adenosine triphosphate (ATP), adenosine diphosphate (ADP), and nicotinamide adenine dinucleotide (NAD) (NAD(+), NADH, NADP(+), and NADPH) levels were assayed periodically. Activities of ATP hydrolyzing enzyme and NAD glycohydrolase were measured at various intervals after infection. Decreases in glycogen occurred as early as 10 hr after infection. Responses in the controls differed from those in infected mice. Hepatic ATP levels decreased as early as 10 hr after infection, with concomitant increases noted in ADP. Hepatic ATP hydrolyzing enzyme activity increased as the infection progressed. Decreases were noted in hepatic NAD levels, with the greatest reduction in the reduced form of NAD. Slight changes were observed after 10 hr, and greater differences were noted 20 hr after infection. The magnitude of these biochemical changes appeared to be dose-dependent. Significant increases in hepatic NAD glycohydrolase activity were noted as the infection progressed. Small but significant increases in serum inorganic phosphate were noted 10 and 20 hr after infection, with a larger increase observed 30 hr after infection. The results indicate impairment of host energy metabolism early in the course of experimental listeriosis.
 ...
PMID:Mechanisms of pathogenesis in Listeria monocytogenes infection. V. Early imbalance in host energy metabolism during experimental listeriosis. 434 93


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