(1/2042) Inhibition of Echovirus-12 multiplication by N-carbobenzoxy-D-glucosamine.
The glucosamine derivative, N-carbobenzoxy-D-glucosamine (NCBZG) inhibits the multiplication of Echovirus-12 and the synthesis of both virus RNA and protein at a stage in the virus growth cycle after attachment and penetration. However, the compound does not inhibit virus multiplication after the appearance of progeny virus nor after virus RNA has accumulated. Incorporation of radioactive glucosamine and choline into infected and uninfected cultures is inhibited by NCBZG as is the virus-induced increase in choline incorporation. The compound also prevents the appearance of radioactive choline in isolated membranous structures. The compound did not alter significantly the cellular RNA or protein synthesis, plating efficiency of the cells, their growth over a period of several days, nor the virus-directed inhibition of cellular RNA and protein. These findings suggest that the compound inhibits virus multiplication by its effect on the initiation of biosynthesis which appears to require membrane synthesis. (+info)
(2/2042) Binding partners for the myelin-associated glycoprotein of N2A neuroblastoma cells.
The myelin-associated glycoprotein (MAG) has been proposed to be important for the integrity of myelinated axons. For a better understanding of the interactions involved in the binding of MAG to neuronal axons, we performed this study to identify the binding partners for MAG on neuronal cells. Experiments with glycosylation inhibitors revealed that sialylated N-glycans of glycoproteins represent the major binding sites for MAG on the neuroblastoma cell line N2A. From extracts of [3H]glucosamine-labelled N2A cells several glycoproteins with molecular weights between 20 and 230 kDa were affinity-precipitated using immobilised MAG. The interactions of these proteins with MAG were sialic acid-dependent and specific for MAG. (+info)
(3/2042) Evidence for an adenovirus type 2-coded early glycoprotein.
We have identified an adenovirus type 2 (Ad2)-induced early glycopolypeptide with an apparent molecular weight of 20,000 to 21,000 (20/21K), as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 20/21K polypeptide could be labeled in vivo with [(3)H]glucosamine. [(35)S]methionine- and [(3)H]-glucosamine-labeled 20/21K polypeptides bound to concanavalin A-Sepharose columns and were eluted with 0.2 M methyl-alpha-d-mannoside. The pulse-labeled polypeptide appeared as a sharp band with an apparent molecular weight of 21K, but after a chase it converted to multiple bands with an average molecular weight of 20K. This variability in electrophoretic mobility is consistent with glycosylation or deglycosylation of the 20/21K polypeptide. Analysis of the pulse and pulse-chase-labeled forms by using partial proteolysis indicated that the polypeptides were highly related chemically, but not identical. Most of the 20/21K polypeptide is localized in the cytoplasm fraction of infected cells lysed by Nonidet P-40. The 20/21K polypeptide and a 44K polypeptide, labeled with [(35)S]methionine or [(3)H]glucosamine in Ad2-infected human cells, were precipitated by a rat antiserum against an Ad2-transformed rat cell line (T2C4), but not by antisera against three other Ad2-transformed rat cell lines, or by serum from nonimmune rats. The partial proteolysis patterns of the 20/21K and the 44K polypeptides were indistinguishable, indicating that the two polypeptides are highly related, and suggesting that the 44K polypeptide might be a dimer of the 20/21K polypeptide. The 20/21K polypeptide was also induced in Ad2-early infected monkey and hamster cells. These results imply that the 20/21K polypeptide is synthesized in Ad2-infected human, monkey, and hamster cells, and in one but not all Ad2-transformed rat cells. Thus, the 20/21K polypeptide is probably viral coded rather than cell coded and viral induced. (+info)
(4/2042) Effects of antibiotics on metabolism of peptidoglycan, protein, and lipids in Bifidobacterium bifidum subsp. pennsylvanicus.
The formation of cell envelope components of Bifidobacterium bifidum subsp. pennsylvanicus was studied by measuring the incorporation of [(3)H]glycine, (14)C-labeled fatty acids, and N-benzoyl-[(14)C]glucosamine into the membrane protein, membrane lipids, and cell wall peptidoglycan, respectively. Inhibition of peptidoglycan synthesis by antibiotics (penicillin G, vancomycin, d-cycloserine, and bacitracin) and by the omission of glucosamine-containing growth factors caused a marked decrease in glycine incorporation into cellular as well as membrane protein, which was accompanied by a considerable enhancement of fatty acid incorporation. The uncoupling of protein and lipid synthesis led to the release of marked amounts of lipids from the cell under these conditions. Arrestment of protein synthesis by antibiotics (chloramphenicol, tetracycline, and actinomycin D) decreased peptidoglycan and lipid synthesis only partially, but did not lead to lipid release. Mg(2+) deficiency of the medium caused about 60% inhibition of growth and lipid synthesis, but protein synthesis and especially peptidoglycan synthesis were much less inhibited. Staphylococcin 1580 arrested the growth and also the synthesis of protein and peptidoglycan. However, the synthesis and turnover of lipids were considerably increased and a release of large amounts of lipids was observed. Peptidoglycan and cellular protein did not show any turnover either during normal growth or after the inhibition of cell wall and protein synthesis. (+info)
(5/2042) Mutations that confer resistance to 2-deoxyglucose reduce the specific activity of hexokinase from Myxococcus xanthus.
The glucose analog 2-deoxyglucose (2dGlc) inhibits the growth and multicellular development of Myxococcus xanthus. Mutants of M. xanthus resistant to 2dGlc, designated hex mutants, arise at a low spontaneous frequency. Expression of the Escherichia coli glk (glucokinase) gene in M. xanthus hex mutants restores 2dGlc sensitivity, suggesting that these mutants arise upon the loss of a soluble hexokinase function that phosphorylates 2dGlc to form the toxic intermediate, 2-deoxyglucose-6-phosphate. Enzyme assays of M. xanthus extracts reveal a soluble hexokinase (ATP:D-hexose-6-phosphotransferase; EC 184.108.40.206) activity but no phosphotransferase system activities. The hex mutants have lower levels of hexokinase activities than the wild type, and the levels of hexokinase activity exhibited by the hex mutants are inversely correlated with the ability of 2dGlc to inhibit their growth and sporulation. Both 2dGlc and N-acetylglucosamine act as inhibitors of glucose turnover by the M. xanthus hexokinase in vitro, consistent with the finding that glucose and N-acetylglucosamine can antagonize the toxic effects of 2dGlc in vivo. (+info)
(6/2042) Quantitative determination of N-acetylglucosamine residues at the non-reducing ends of peptidoglycan chains by enzymic attachment of [14C]-D-galactose.
The ability of human milk galactosyltransferase to attach D-galactose residues quantitatively to the C-4 of N-acetylglucosamine moieties at the ends of oligosaccharides has been utilized for the specific labeling and quantitative determination of the chain length of the glycan moiety of the bacterial cell wall. The average polysaccharide chain length of the soluble, uncrosslinked peptidoglycan secreted by Micrococcus luteus cells on incubation with penicillin G was studied with this technique and found to be approximately 70 hexosamines long. Furthermore, the peptidoglycan chain length of Escherichia coli sacculi of different cell shapes and dimensions was determined both in rod-shaped cells and in filaments induced by temperature shift of a division mutant or by addition of cephalexin or nalidixic acid. The average chain length found in most of these sacculi was between 70 and 100 hexosamines long. Small spherical 'mini' cells had chain lengths similar to those of the isogenic rod-like cells. (+info)
(7/2042) Tunicamycin-resistant mutants and chromosomal locations of mutational sites in Bacillus subtilis.
The types of tunicamycin-resistant mutants of Bacillus subtilis were analyzed, and their mutational sites on the chromosome were mapped. A type 1 mutation that simultaneously expressed hyperproductivity of extracellular alpha-amylase was located close to amy E. Type 2 mutations were near aroI. (+info)
(8/2042) Interactions on 3-deoxy and 6-deoxy derivatives of N-acetyl-D-glucosamine with hen lysozyme.
The interactions of deoxy derivatives of GlcNAc, 6-deoxy-GlcNAc, and 3-deoxy-GlcNAc with hen egg-white lysozyme [EC 220.127.116.11] were studied at various pH's by measuring the changes in the circular dichroic (CD) band at 295 nm. It was shown that 6-deoxy-GlcNAc and 3-deoxy-GlcNAc bind at subsite C of lysozyme and compete with GlcNAc. The pH dependence of the binding constant of 6-deoxy-GlcNAc was the same as that of GlcNAc. On the other hand, the binding constants of 3-deoxy-GlcNAc were 3--10 times smaller than those of GlcNAc in the pH range from 3 to 9. X-ray crystallographic studies show that O(6) and O(3) of GlcNAc at subsite C are hydrogen-bonded to the indole NH's of Trp 62 and Trp 63, respectively, but the above results indicate that Trp 63, not Trp 62, is important for the interaction of GlcNAc with lysozyme. (+info)