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981.
Distinct mechanisms of entry by envelope glycoproteins of Marburg and Ebola (Zaire) viruses 总被引:2,自引:0,他引:2
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Since the Marburg (MBG) and Ebola (EBO) viruses have sequence homology and cause similar diseases, we hypothesized that they associate with target cells by similar mechanisms. Pseudotype viruses prepared with a luciferase-containing human immunodeficiency virus type 1 backbone and packaged by the MBG virus or the Zaire subtype EBO virus glycoproteins (GP) mediated infection of a comparable wide range of mammalian cell types, and both were inhibited by ammonium chloride. In contrast, they exhibited differential sensitivities to treatment of target cells with tunicamycin, endoglycosidase H, or protease (pronase). Therefore, while they exhibit certain functional similarities, the MBG and EBO virus GP interact with target cells by distinct processes. 相似文献
982.
The co-incubation of morin hydrate with either doxorubicin or mitomycin C could minimize the toxicity of these anti-tumor drugs on cardiovascular cells, such as red blood cells, human umbilical vein endothelial cells (ECV304) and primary mouse cardiomyocytes, whereas morin hydrate did not lower the cytotoxicity of the drugs on human hepatocellular carcinoma cells (HepG2). Morin hydrate may not exert its antioxidant effect by enhancing the antioxidant enzymatic activity because it did not cause any induction on the mRNA levels of manganese superoxide dismutase expression in ECV304 cells and HepG2 cells. 相似文献
983.
To relieve lactic acid inhibition, an aqueous two-phase system (ATPS) was used to grow Lactococcus lactis. Its composition was 11% (w/v) PEG 20000/3.5% (w/v) MgSO4 7H2O. In this ATPS medium, the cells were completely partitioned in the bottom phase, and lactic acid had the biggest partition coefficient of the eight ATPS media tested. The cell biomass in this medium was 0.64 mg ml–1, only 60% of that of the control medium, but nisin production (803 IU ml–1) was enhanced by 33%. The increase in nisin was explained as a result of extraction of lactic acid from the bottom phase to the top one. The changes of tie-line length and phase volume ratio for the identical tie line could affect cell growth and nisin accumulation. 相似文献
984.
The Arcanobacterium (Actinomyces) pyogenes Plasmid pAP1 Is a Member of the pIJ101/pJV1 Family of Rolling Circle Replication Plasmids
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The 2.4-kb plasmid pAP1 from Arcanobacterium (Actinomyces) pyogenes had sequence similarity within the putative replication protein and double-stranded origin with the pIJ101/pJV1 family of plasmids. pJGS84, a derivative of pAP1 containing a kanamycin resistance gene, was able to replicate in Escherichia coli and Corynebacterium pseudotuberculosis, as well as in A. pyogenes. Detection of single-stranded DNA intermediates of pJGS84 replication suggested that this plasmid replicates by the rolling circle mechanism. 相似文献
985.
Lack of S-Adenosylmethionine Results in a Cell Division Defect in Escherichia coli 总被引:3,自引:0,他引:3
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E. B. Newman L. I. Budman E. C. Chan R. C. Greene R. T. Lin C. L. Woldringh R. DAri 《Journal of bacteriology》1998,180(14):3614-3619
The enzyme S-adenosylmethionine (SAM) synthetase, the Escherichia coli metK gene product, produces SAM, the cell’s major methyl donor. We show here that SAM synthetase activity is induced by leucine and repressed by Lrp, the leucine-responsive regulatory protein. When SAM synthetase activity falls below a certain critical threshold, the cells produce long filaments with regularly distributed nucleoids. Expression of a plasmid-carried metK gene prevents filamentation and restores normal growth to the metK mutant. This indicates that lack of SAM results in a division defect. 相似文献
986.
Err-Cheng Chan C. Allen Chang Tzong-Zeng Wu Yuh-Ling Lin 《Biotechnology letters》1998,20(11):1053-1056
The normal human epidermal keratinocyte (NHEK) was used to evaluate the cytotoxicity of recombinant lysostaphin. As determined with the Neutral Red (NR) cytotoxicity assay, the midpoint toxicity value (NR50) after 48 h exposure was 16 ± 0.4 g lysostaphin/l. Lysostaphin cytotoxicity effect is much less than the surface active agent, sodium laurate. However, the NR50 value after 48-h exposure was 1.9 ± 0.02 g/l for S. aureus lysate derived from the bacterial lytic action of lysostaphin. A linear increase in interleukin-8 (IL-8) level in NHEK cells from resting levels of 65 ± 3 pg/ml to peak of 760 ± 15 pg/ml during the first 9 hours was noted for the cells treated with 800 mg lysostaphin/l. S. aureus lysate has the same effect on the induction of IL-8 levels. The induced rises in IL-8 were lysostaphin and S. aureus lysate concentration dependence. © Rapid Science Ltd. 1998 相似文献
987.
Stanislava Uhrínová Dušan Uhrín Helen Denton Mark Smith Lindsay Sawyer Paul N. Barlow 《Journal of biomolecular NMR》1998,12(1):89-107
Although -lactoglobulin (-LG) has been studied extensively for more than 50 years, its physical properties in solution are not yet understood fully in terms of its three-dimensional (3D) structure. For example, despite a recent high-resolution crystal structure, it is still not clear why the two common variants of bovine -LG which differ by just two residues have different aggregation properties during milk processing. We have conducted solution-state NMR studies on a recombinant form of the A variant of -LG at low pH conditions where the protein is partially unfolded and exists as a monomer rather than a dimer. Using a13 C,15N-labelled sample, expressed in Pichia pastoris, we have employed the standard combination of 3D heteronuclear NMR techniques to obtain near complete assignments of proton, carbon and nitrogen resonances. Using a novel pulse sequence we were able to obtain additional assignments, in particular those of methyl groups in residues preceding proline within the sequence. From chemical shifts and on the basis of inter-residue NOEs, we have inferred the secondary structure and topology of monomeric -LG A. It includes eight antiparallel -strands arranged in a barrel, flanked by an -helix, which is typical of a member of the lipocalin family. A detailed comparison with the crystal structure of the dimeric form (for a mixture of A and B variants) at pH 6.5 reveals a close resemblance in both secondary structure and overall topology. Both forms have a ninth -strand which, at the higher pH, forms part of the dimer interface. These studies represent the first full NMR assignment of -LG and will form the basis for a complete characterisation of the solution structure and dynamics of this protein and its variants. 相似文献
988.
Nellie Y. Loh Helen J. Ambrose Lisa M. Guay-Woodford Srimita DasGupta Ralph A. Nawrotzki Derek J. Blake Kay E. Davies 《Mammalian genome》1998,9(11):857-862
β-Dystrobrevin, a dystrophin-related protein that is expressed in non-muscle tissues, is highly homologous to α-dystrobrevin,
a member of the dystrophin-associated protein complex (DPC). β-Dystrobrevin associates with Dp71 and syntrophin and is believed
to have a role in non-muscle DPCs. Here we report the characterization and mapping of the mouse β-dystrobrevin gene. The mouse
β-dystrobrevin gene is organized into 21 exons spanning over 130 kb of DNA. We provide evidence that this gene is transcribed
from at least two promoter regions but appears to utilize a common translation initiation site. We show that the similarity
between β-dystrobrevin and α-dystrobrevin is reflected in the conservation of their exon-intron junctions. β-Dystrobrevin
has been localized to proximal mouse Chromosome (Chr) 12 by backcross mapping. A database search revealed that two mouse genetic
diseases involving tissues expressing β-dystrobrevin have been mapped to this region, namely, congenital polycystic kidneys
(cpk) and fatty liver dystrophy (fld). However, refined mapping analysis has excluded β-dystrobrevin as a candidate gene for either disease.
Received: 1 June 1998 / Accepted: 16 July 1998 相似文献
989.
José Manuel Fernández-Ábalos Helen Fox Chris Pitt Brian Wells & John H. Doonan 《Molecular microbiology》1998,27(1):121-130
Green fluorescent protein (GFP) is a useful reporter to follow the in vivo behaviour of proteins, but the wild-type gfp gene does not function in many organisms, including many plants and filamentous fungi. We show that codon-modified forms of gfp , produced for use in plants, function effectively in Aspergillus nidulans both as gene expression reporters and as vital reporters for protein location. To demonstrate the use of these modified gfp s as reporter genes we have used fluorescence to follow ethanol-induced GFP expression from the alcA promoter. Translational fusions with the modified gfp were used to follow protein location in living cells; plant ER-retention signals targeted GFP to the endoplasmic reticulum, whereas fusion to the GAL4 DNA-binding domain targeted it to the nucleus. Nuclear-targeted GFP allowed real-time observation of nuclear movement and division. These modified gfp genes should provide useful markers to follow gene expression, organelle behaviour and protein trafficking in real time. 相似文献
990.