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

Spleen cells from mice inoculated with partially purified preparations of interferon (Sp. Act. 1 X 10(7) i.u./mg protein, 0.2 ml i. v./mouse) were stimulated in vitro with phytohemagglutinin, concanavalin A or lipopolysaccharide. After 2 days of stimulation, the incorporation of 3H-thymidine into TCA-insoluble radioactivity was inhibited 50-90% when compared with cells from animals inoculated with mock interferon. Maximal inhibition, with optimal doses of lectins was obtained when interferon was;inoculated 18 hours before. This effect of interferon on DNA synthesis was preceeded by inhibition of the incorporation of 3H-uridine into TCA-insoluble material. When cells were pretreated in vitro with interferon for 24 hours and subsequently stimulated with PHA, RNA synthesis was inhibited by 30-40%, whatever was the dose of the mitogen. The synthesis of 4S tRNA, 18S and 28S ribosomal RNAs were inhibited to the same degree by interferon. The incorporation of methyl groups into cytoplasmic sRNA was unaltered.
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PMID:Inhibitory effect of interferon on DNA and RNA synthesis in murine spleen cells stimulated by lectins. 93 1

It has been found that the bacterial endotoxins (lipopolysaccharides, LPSs) contain some amino acids and glycine is the most abundant amino acid in the polysaccharide core preparations of LPSs of gram-negative bacteria. Until now nothing was known about the mechanism of amino acid incorporation into the lipopolysaccharide core. We found that one out of three glycyl-tRNAs(Gly) from Escherichia coli is the donor of amino acid and is the substrate for a putative aminoacyl-tRNA:LPS transferase. We have isolated, purified this tRNA and determined its nucleotide sequence to be major E.coli tRNA(3Gly). This tRNA(Gly) (anticodon GCC) conserved the tRNA structural features. The assay for determination of the specific incorporation of glycine into the lipopolysaccharide was also invented and described.
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PMID:Specific incorporation of glycine into bacterial lipopolysaccharide. Novel function of specific transfer ribonucleic acids. 171 87

The biosynthesis of pyrophosphoethanolamine residues linked to the core oligosaccharide region of the lipopolysaccharide of Escherichia coli K2 strain BB 26-36 has been investigated by means of isotope tracer experiments in living cells. Phosphoethanolamine was isolated from the pyrophosphoethanolamine residues after hydrolysis in 1 N HCl at 100 degrees C. The kinetics of labeling of the phosphoethanolamine from [3H]serine or sn-glycero-3-32P during pulse-chase experiments revealed that the biosynthetic precursor of the phosphoethanolamine must be a large, relatively stable pool, and not a small, rapidly metabolized pool such as that of free serine, or seryl-tRNA. Labeling of the pyrophosphoethanolamine residues of the lipopolysaccharide from the two isotopes was closely parallel, and the isotope ratio 3H/32P was closely similar to that in phosphatidylethanolamine at the same time intervals. These experiments offer strong evidence that phosphatidylethanolamine functions in the biosynthesis of pyrophosphoethanolamine residues in lipopolysaccharide in a reaction in which the phosphoethanolamine head-group of the phospholipid is transferred as a unit to a lipopolysaccharide acceptor.
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PMID:Role of phosphatidylethanolamine in the biosynthesis of pyrophosphoethanolamine residues in the lipopolysaccharide of Escherichia coli. 675 35

The O antigen of the Shigella flexneri lipopolysaccharide (LPS) is an important virulence determinant and immunogen. We have isolated S. flexneri mutants which produce a semi-rough LPS by using an O-antigen-specific phage, Sf6c. Western immunoblotting was used to show that the LPS produced by the semi-rough mutants contained only one O-antigen repeat unit. Thus, the mutants are deficient in production of the O-antigen polymerase and were termed rfc mutants. Complementation experiments were used to locate the rfc adjacent to the rfb genes on plasmid clones previously isolated and containing this region (D. F. Macpherson, R. Morona, D. W. Beger, K.-C. Cheah, and P. A. Manning, Mol. Microbiol 5:1491-1499, 1991). A combination of deletions and subcloning analysis located the rfc gene as spanning a 2-kb region. Insertion of a kanamycin resistance cartridge into a SalI site in this region inactivated the rfc gene. The DNA sequence of the rfc region was determined. An open reading frame spanning the SalI site was identified and encodes a protein with a predicted molecular mass of 43.7 kDa. The predicted protein is highly hydrophobic and showed little sequence homology with any other protein. Comparison of its hydropathy plot with that of other Rfc proteins from Salmonella enterica (typhimurium) and Salmonella enterica (muenchen) revealed that the profiles were similar and that the proteins have 12 or more potential membrane-spanning segments. A comparison of the S. flexneri rfc gene and protein product with other rfc and rfc-like proteins revealed that they have a similarly low percentage of G + C content and have similar codon usage, and all have a high percentage of rare codons. An attempt to identify the S. flexneri Rfc protein was unsuccessful, although proteins encoded upstream and downstream of the rfc gene could be identified. Examination of the distribution of rare or minor codons in the rfc gene revealed that it has several minor codons within the first 25 amino acids. This is in contrast to the upstream gene rfbG, which also has a high percentage of rare codons but whose gene product could be detected. The positioning of the rare codons in the rfc gene may restrict translation and suggests that minor isoaccepting tRNA species may be involved in translational regulation of rfc expression. The low percentage of G + C content of rfc genes may be a consequence of the selection pressure to maintain this form of control.
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PMID:Characterization of the rfc region of Shigella flexneri. 750 20

The sequence of a 281-kbp contig from the crenarchaeote Sulfolobus solfataricus P2 was determined and analysed. Notable features in this region include 29 ribosomal protein genes, 12 tRNA genes (four of which contain archaeal-type introns), operons encoding enzymes of histidine biosynthesis, pyrimidine biosynthesis, and arginine biosynthesis, an ATPase operon, numerous genes for enzymes of lipopolysaccharide biosynthesis, and six insertion sequences. The content and organization of this contig are compared with sequences from crenarchaeotes, euryarchaeotes, bacteria, and eukaryotes.
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PMID:Gene content and organization of a 281-kbp contig from the genome of the extremely thermophilic archaeon, Sulfolobus solfataricus P2. 1070 Nov 21

Characterization of nine transposon-induced mutants of Rhizobium tropici with decreased salt tolerance (DST) allowed the identification of eight gene loci required for adaptation to high external NaCl. Most of the genes also were involved in adaptation to hyperosmotic media and were required to overcome the toxicity of LiCl. According to their possible functions, genes identified could be classified into three groups. The first group included two genes involved in regulation of gene expression, such as ntrY, the sensor element of the bacterial ntrY/ntrX two-component regulatory system involved in regulation of nitrogen metabolism, and greA, which encodes a transcription elongation factor. The second group included genes related to synthesis, assembly, or maturation of proteins, such as alaS coding for alanine-tRNA synthetase, dnaJ, which encodes a molecular chaperone, and a nifS homolog probably encoding a cysteine desulfurase involved in the maturation of Fe-S proteins. Genes related with cellular build-up and maintenance were in the third group, such as a noeJ-homolog, encoding a mannose-1-phosphate guanylyltransferase likely involved in lipopolysaccharide biosynthesis, and kup, specifying an inner-membrane protein involved in potassium uptake. Another gene was identified that had no homology to known genes but that could be conserved in other rhizobia. When inoculated on Phaseolus vulgaris growing under nonsaline conditions, all DST mutants displayed severe symbiotic defects: ntrY and noeJ mutants were impaired in nodulation, and the remaining mutants formed symbiosis with very reduced nitrogenase activity. The results suggest that bacterial ability to adapt to hyperosmotic and salt stress is important for the bacteroid nitrogen-fixing function inside the legume nodule and provide genetic evidence supporting the suggestion that rhizobia face severe environmental changes after their release into plant cells.
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PMID:Rhizobium tropici genes involved in free-living salt tolerance are required for the establishment of efficient nitrogen-fixing symbiosis with Phaseolus vulgaris. 1195 25

Burkholderia thailandensis is a nonpathogenic gram-negative bacillus that is closely related to Burkholderia mallei and Burkholderia pseudomallei. We found that B. thailandensis E125 spontaneously produced a bacteriophage, termed phiE125, which formed turbid plaques in top agar containing B. mallei ATCC 23344. We examined the host range of phiE125 and found that it formed plaques on B. mallei but not on any other bacterial species tested, including B. thailandensis and B. pseudomallei. Examination of the bacteriophage by transmission electron microscopy revealed an isometric head and a long noncontractile tail. B. mallei NCTC 120 and B. mallei DB110795 were resistant to infection with phiE125 and did not produce lipopolysaccharide (LPS) O antigen due to IS407A insertions in wbiE and wbiG, respectively. wbiE was provided in trans on a broad-host-range plasmid to B. mallei NCTC 120, and it restored LPS O-antigen production and susceptibility to phiE125. The 53,373-bp phiE125 genome contained 70 genes, an IS3 family insertion sequence (ISBt3), and an attachment site (attP) encompassing the 3' end of a proline tRNA (UGG) gene. While the overall genetic organization of the phiE125 genome was similar to lambda-like bacteriophages and prophages, it also possessed a novel cluster of putative replication and lysogeny genes. The phiE125 genome encoded an adenine and a cytosine methyltransferase, and purified bacteriophage DNA contained both N6-methyladenine and N4-methylcytosine. The results presented here demonstrate that phiE125 is a new member of the lambda supergroup of Siphoviridae that may be useful as a diagnostic tool for B. mallei.
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PMID:Burkholderia thailandensis E125 harbors a temperate bacteriophage specific for Burkholderia mallei. 1208 73

In the present study, differential responses of regulatory proteins involved in translation initiation in skeletal muscle and liver during sepsis were studied in neonatal pigs treated with lipopolysaccharide (LPS). LPS did not alter eukaryotic initiation factor (eIF) 2B activity in either tissue. In contrast, binding of eIF4G to eIF4E to form the active mRNA-binding complex was repressed in muscle and enhanced in liver. Phosphorylation of eIF4E-binding protein, 4E-BP1, and ribosomal protein S6 kinase, S6K1, was reduced in muscle during sepsis but increased in liver. Finally, changes in 4E-BP1 and S6K1 phosphorylation were associated with altered phosphorylation of the protein kinase mammalian target of rapamycin (mTOR). Overall, the results suggest that translation initiation in both skeletal muscle and liver is altered during neonatal sepsis by modulation of the mRNA-binding step through changes in mTOR activation. Moreover, the LPS-induced changes in factors that regulate translation initiation are more profound than previously reported changes in global rates of protein synthesis in the neonate. This finding suggests that the initiator methionyl-tRNA-rather than the mRNA-binding step in translation initiation may play a more critical role in maintaining protein synthesis rates in the neonate during sepsis.
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PMID:Endotoxin induces differential regulation of mTOR-dependent signaling in skeletal muscle and liver of neonatal pigs. 1277 8

In adults, protein synthesis in skeletal muscle is reduced by as much as 50% after a septic challenge, and is associated with repression of translation initiation. Neonates are highly anabolic and their muscle protein synthesis rates are elevated and uniquely sensitive to amino acid and insulin stimulation. In the present study, neonatal piglets were infused with Endotoxin (lipopolysaccharide, LPS) for 20 h at 0 (n = 6) and 13 microg/kg*h (n = 8). During the last 2 h, dextrose and an amino acid mixture were infused to attain fed plasma concentrations of amino acids, glucose, and insulin. Fractional protein synthesis rates and translational control mechanisms were examined. LPS reduced protein synthesis in glycolytic muscles by only 13% and had no significant effect in oxidative muscles. This depression was associated with reductions in the phosphorylation of 4E-BP1 (-31%) and S6 K1 (-78%), and a decrease in eIF4G binding to eIF4E (-62%), an event required for formation of the active mRNA binding complex. By comparison, LPS increased protein synthesis in the liver (+29%), spleen (+32%), and kidney (+27%), and in the liver, this increase was associated with augmented eIF4G to eIF4E binding (+88%). In muscle and liver, LPS did not alter eIF2B activity, an event that regulates initiator met-tRNA(i) binding to the 40S ribosomal complex. These findings suggest that during sustained endotoxemia, the high rate of neonatal muscle protein synthesis is largely maintained in the presence of substrate supply, despite profound changes in translation initiation factors that modulate the mRNA binding step in translation initiation.
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PMID:Regulation of muscle protein synthesis in neonatal pigs during prolonged endotoxemia. 1468 94

A lambda clone containing a rainbow trout IL-1beta1 gene was isolated by a PCR screening strategy from a genomic library cloned in lambda GEM-11, and an EcoRI fragment from this clone was fully sequenced, and contained 1680 bp 5'-flanking sequence, the whole IL-1beta1 gene open reading frame, and the 3'-flanking region with two potential poly A signals and poly A sites. This clone encoded a protein that shared 99.8% identity to the previously published trout IL-1beta1 cDNA sequence, with only three base substitutions. The main difference was that this clone had an additional complete HpaI SINE insertion in the 3rd intron making intron III 211 bp larger (834 bp via 623 bp). Thus this sequence was designated as allele B (Big intron III) of IL-1beta1 and the previously reported sequence as allele S (Short intron III). Three lines of evidence (allele specific PCR, cloning and sequencing, and direct sequencing of PCR products) revealed that allele B was constitutively expressed and could respond to stimulation with lipopolysaccharide or trout recombinant IL-1beta. Searching of the GenBank database with the HpaI SINE sequence resulted in three additional HpaI loci being identified in rainbow trout. Another SINE retroposition was also identified in the same intron of both alleles of IL-1beta1 by comparison with the trout IL-1beta2 gene. This novel SINE sequence, sharing high homology with the HpaI SINE at the 3'-end region, is present in EST databases of several species including human, mouse and fish. The consensus of this novel SINE shares 57 to 61% identities to tRNA-Leu from different species. Another older retroposition event in the same intron of IL-1beta1 has also been hypothesised, recognised as six adenines, that may function as a RNA polIII terminator. A model for the IL-1beta1 allele formation is proposed. Following the earliest retroposition into one of the two IL-1beta genes that resulted from a genome duplication in salmonids, the proper environment for successive PV SINE retroposition was created. A recent retroposition of the HpaI SINE in IL-1beta1 resulted in the formation of the two alleles of IL-1beta1. Examination of the SINEs insertion and their host gene microenvironments revealed that the SINE retroposition does not appear random, both in the site selection and the direction of insertion. The mechanism governing this outcome is discussed.
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PMID:Sequencing and expression of the second allele of the interleukin-1beta1 gene in rainbow trout (Oncorhynchus mykiss): identification of a novel SINE in the third intron. 1512 2


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